NASA SP-4220 

Wingless Flight 

The Lifting Body Story 

R. Dale Reed 

with Darlene Lister 

Foreword by General Chuck Yeager 

The NASA History Series 

National Aeronautics and Space Administration 

NASA History Office 

Office of Policy and Plans 

Washington, DC 1997 
Library of Congress cataloging-in-PuMi~ation Data 

Reed, R. Dale, 1930 

a'inglrss Fligllt: The I.tfting Bod) Stoq/R. Dale Rrrtl, 

HII~ Ddrlenc C15ter: foreword bg Chuck ledger. 

p. cm.-(SP; 1220. NAS,1 Histot7 Series) 

111rludrs I~ibliographical references (p. ) and index. 

1. Lifting bodies-United States-Design ant1 constructionHistory. 2. NASA Dryden Flight Research Center-History. 

I. Lister, Darlene, 1945- . 11. Title. 111. Series: NASA SP; 4220. 

11: Seri~s: NASA HistoricaI Series. 

TL'ilS.i.R44 IN7 629.133'3-dc21 

For sale by the U.S. Government Printing Office 

Superintendent of Dcrumenh, Mail Stop: SSOP, Washington, DC 20402.9328 

ISBN 0-16-049390-0 

ISBN 0-1 6-049390-0 
DEDICATED TO BRAVERY AND FAITH 

Paul Bikle 

A leader u~ho believed in our cause and put his career at high risk bj hae'ing$~irh in 

us to meet our commitments. 

Milt Thotnpson 

A research test pilot z~~ho nt only put his lge at risk but exhibited complete faith in 

1~1inglessfEi~ht and those of us who made it happen. 
CONTENTS 

Acknowledgment

Foreword 

Introduction

Chapter 1 The Adventure Begins 

Chapter 2 "Flying Bathtub" 

Chapter 3 Commitment to Risk

Chapter 4 On to the Heavyweights 

Chapter 5 Angry Machines 

Chapter 6 Back to the Drawing Board 

Chapter 7 Wingless Flight Matures 

Chapter 8 Lifting-Body Racehorses

Chapter 9 Wingless Flight Lives On

Appendix

Glossary 

Bibliography

About the Author

Index

The NASA History Series 

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WING1,ESS FLIGHT 

Foreword 

When Dale Reed asked me to write the foreword to his book, Wingless Flight: The 

Lifting Body Story, I had to think back a long ways to remember the day that Paul 

Rikle asked me to fly the M2-F1 lifting body. It was a very interesting program that 

would give a space vehicle similar to the present day space shuttle the ability to 

maneuver. During the time that the lifting body program was being flown, space capsules were re-entering the Earth's atmosphere in a ballistic path and had very little 

ability to maneuver. 

The concept behind the lifting body program was to investigate the ability of the pilot 

to land in a horizontal mode which required an excessive angle of attack to flare. I 

enjoyed flying the lifting body and probably found it easier to Ay than most pilots 

because of my experience with the XF-92 airplane which landed with extremely high 

angles of attack similar to those later experienced with lifting bodies. 

Dale's book covers the warm things that go on during the test programs at Edwards Air 

Force Base, California. Dale has emphasized the cooperative effort that must take 

place between the people he calls the Real Stuff (people who create and service the 

flying machines) and the Right Stuff (pilots who fly the machines). Most of the NASA 

lifting body crews (about 90 percent) were made up of ex-military mechanics and 

technicians, mostly Air Force and of excellent caliber. I owe a deep debt of gratitude 

to many an aircraft crew chief in my career. These crew chiefs provided me with aircraft in first-class condition to fly by working themselves and their people long hours 

to stay on schedule. 

Test pilots, on the other hand, were a different story. Dale, being a pilot himself, could 

see the undercurrent that flows in the macho world of test pilots. Competition has 

always existed between pilots. There was a special kind of competition between Air 

Force and NASA test pilots, and Dale has covered it very well in this book. 

The lifting hotly story covers a little known period at Edwards Air Force Base, and it 

fills a gap during the transition from space capsules to maneuvering space vehic-les. 

Chuck Yeager 

B/Gen., USAF, Ret. 
ACKNOWLEDGMENTS 

I uoul(1 like to express my appreciation to the following people for their contributions 

to this book: Dr. J. D. Hutlley, NASA Dryden Historian, who took on the task of 

reviewing my original manuscript to ensure that it was internally consistent, written 

for the proper audience, ant1 historically accurate. Dr. Hunley added footnotes, 

expanded and edited the glossary, and compiled the present bibliography. Dr. Hunley 

also enlisted Dr. Darlene 1,ister to reorganize the original manuscript for a smooth presentation to the reading audience. To Richard P. Hallion, who is probablj this country's best aviation historian, for his generous offer to allow information from his hooks 

and documents, including On the Frontier, Test Pilots, and The Hypersonic 

Ret~oltttion, to be incorporated into this hook. His attention to detail on facts, dates, 

and management of early aircraft development programs made it easier to correlate my 

own personal story of the lifting-body program with other activities of the time. 

Also, I would like to thank Robert Kempel and Wen Painter for their generous offer to 

allow me to use portions of their personal story of the HI,-10 Lifting Body entitled 

Developing and Flight Testing the HL-10 Lifting Body: A Precursor to the 

Spare Shuttle, a NASA Reference Publication published in April 1994, to be used 

in this book. 

For their contributions to the book's technical accuracy, I \rouId like to thank the following people who reat1 the original nlanuscript and in some cases, the reorganized 

version, and providecl technical corrections where appropriate: Bill Dana, Chuck 

Yeager, John Manke, and Bruce Peterson, lifting body pilots; and Robert Hoey, Bob 

Kempel, Wen Painter, Ed Saltzman, and Joe Wilson, lifting body engineers. 

Thanks also to Betty Love, aeronautical research technician, for contril~uting both 

recorcled and unrecorded flight records on original M2-F1 flights and for her comments on the reorganized version of the manuscript; John Muratore, X-38 program 

manager at NASA's Johnson Space Center, for reviewing the portion of the last chapter on the X-38 program; David Urie, from Lockheed, and Steve Ishmael, from NASA, 

for reviewing the portion of the last chapter dealing with the X-33 program; 

the NASA Headquarters Printing and Design office-Vanessa Nugent and Kimberly 

Jenkins for their Design and Editorial work, as well as Stanley Al-tis and Michael 

Crnkovic who saw the 1)ook through the printing process. 

R. Dale Reed, Aerospace Engineer 

NASA Dryclen Flight Research Center 

August 1997 
INTRODUCTION 

Wingbss Flight tells the story of the most unusual flying machines ever flown, 

the lifting bodies. It is my story about my friends and colleagues who con~niittecl a significant part of their lives in the 1960s and 1970s to prove that the concept was a 

viahle one for use in spacecraft of the future. This story, filled with drama and adkenture, is about the twelve-year period from 1963 to 1975 in which eight different lifting-body configurations flew. It is appropriate for me to write the story, since I was the 

engineer who first presented the idea of flight-testing the concept to others at the 

NASA Flight Research Center. Over those twelve years, I experienced the story as it 

unfolded day by day at that remote NASA facility northeast of Los Angeles in the 

bleak Mojave Desert. 

Benefits from this effort immediately influenced the design and operational concepts of the winged NASA Shuttle Orbiter. However, the full benefits would not be 

realized until the 1990s when new spacecraft such as the X-33 and X-38 would fully 

employ the lifting-body concept. 

A lifting body is basically a wingless vehicle that flies due to the lift generated by 

the shape of its fuselage. Although both a lifting reentry vehicle and a ballistic capsule had been considered as options during the early stages of NASA's space program, 

NASA initially opted to go with the capsule. A number of individuals were not content to close the book on the lifting-body concept. Researchers including Alfred 

Eggers at the NASA Ames Research Center conducted early wind-tunnel experiments, finding that half of a rounded nose-cone shape that was flat on top and rounded on the bottom could generate a lift-to-drag ratio of about 1.5 to 1. Eggers' 

preliminary design sketch later resembled the basic M2 lifting-body design. At the 

NASA Langley Research Center, other researchers toyed with their own lifting-body 

shapes. 

Meanwhile, some of us aircraft-oriented researchers at th_e NASA Flight Research 

Center at Edwards Air Force Base (AFB) in California were experiencing our own fascination with the lifting-hody concept. A model-aircraft builder and private pilot on 

my own time, I found tlie lifting-body idea intriguing. I built a model based on Eggrrs' 

design, tested it repeatedly, made modifications in its control and balance characteristics along the way, then eventually presented the concept to others at the Center, 

using a film of its flights that mj wife, Donna and I had made with our 8-mm home 

camera. I recruited the help of fellow engineer Dick Eldredge and research pilot Milt 

Thompson, especially in later selling the idea to others, including Paul Bikle, then the 

director of the NASA Flight Research Center (redesignated in 1976 the Hugh L. 

Dryden Flight Research Center). What followed was history, and telling for the first 

time in print that historic story of the lifting bodies in full and living detail is what this 

1)ook is all about. 
INTRODUCTION 

Dale Reed holding the originalfree-flight model of the M2-FlJilmed in 8 mm movies used to convince Dryden 

and Ames managers to support the program. Thefull-scale M2-Fl jbwn later is in the background. (NASA 

photo EC67 16475) 
WINGLESS FLIGHT 

Between 1963 and 1975, eight lifting-body configurations were flown at the NASA 

Flight Research Center at Edwards AFB. They varied tremendously-from the 

unpowered, bulbous, lightweight plywood M2-F1 to the rocket-powered, extra-sleek, 

all-metal supersonic X-24B. Some configurations, such as the M2-F2, not only pushed 

the limits of both design engineers and test pilots but also were dangerous to fly. Film 

footage of the 1967 crash of the M2-F2, after test pilot Bruce Peterson lost control of 

this particularly "angry machine," was used about two years later as the lead-in to 

weekly episodes of a popular television series, The Six-Million-Dollar Man, which 

ran for about six years. Although the M2-F2 crash was spectacular enough to inspire 

the concept for a popular television series, it was the only serious accident that 

occurred over the slightly more than twelve years of lifting-body flight-testing. 

But danger has always lurked at the edge of flight innovation. All eight of these 

wingless wonders, the lifting bodies, were considered the flying prototypes for future 

spacecraft that could land like an airplane after the searing heat of reentry from outer 

space. The precursors of today's Shuttle and tomorrow's X-33 and X-38, the lifting 

bodies provided the technical and operational engineering data that has shaped the 

space transportation systems of today and tomorrow. 

The Place and the People 

The story of the lifting bodies is not just a story about wingless machines that fly. 

It is a story as much about people and the unique environment of the NASA facility 

at Edwards AFB as it is about airplanes. The driving force behind the lifting-body program was the small contingent of people at the NASA Flight Research Center at 

Edwards AFB in the western Mojave Desert northeast of Los Angeles. 

Brought together originally in 1946 to flight-test the Bell XS-1, this little group of 

strong-minded individuals was also drawn to this remote facility because of their love 

for airplanes and the adventure of flight-testing. Being surrounded by aviation 

history in the making was enough to keep motivation flying high. 

The NASA facility at Edwards-called initially the National Advisory Committee 

for Aeronautics (NACA) Muroc Flight Test Unit-was paradise to these lovers of airplanes. It was a place where people got their hands dirty working on aircraft, a place 

where they had the freedom to kick an airplane tire at any time. It was a place where 

test pilots, engineers, mechanics, and technicians all breathed the same air and 

walked the same halls, shops, and hangar floors. It was a place where they could take 

a few minutes off from tightening a bolt on an aircraft to watch a new airplane design 

making a flyover. The boss probably was also an airplane lover, and more than likely, 

he too had stopped whatever he was doing to watch the same flyover. And it was a 
INTRODUCTION 

place where about the most exciting thing in life was being involved as a volunteer in 

a new program. 

In 1963, the lifting-body program began, circumventing the normal bureaucratic 

process by launching itself as a bottom-up program. It began when an enthusiastic 

engineer drew together a band of engineers, technicians, ant1 pilots-all volunteers, 

of course-and then moved ahead, bypassing the ponderous amount of paperwork and 

delays of months or even years typically involved in officnially initiating approved and 

funded aerospace programs in that era. 

Besides tapping into the volunteer spirit present in the 1960s at the NASA Flight 

Research Center, the unofficial lifting-body program also used creative methods to 

locate funds. Shortly before his death in January 1991, Paul Bikle explained how that 

was done, saying "it was a real shoestring operation. We didn't get any money from 

anybody. We just built it out of money we were supposed to use to maintain the facility."] As the program grew over the years to involve flight-testing eight different configurations, it became more disciplined and organized. Even then, however, it was still 

intlividuals-not organizations-that made things happen. 

The lifting-body concept was a radical departure frorri the aerodynamics of conventional winged aircraft, and it was the operational experience of the NASA and Air 

Force people at Edwards AFB that made the program a reality. Setting the stage for 

the lifting-body program was the long experience of these engineers, technicians, and 

pilots over previous decades in flight-testing experimental, air-launched, and rocketboosted gliders from the XS-1 to the X-15. 

A special kind of camaraderie existed among the otherwise competitive NASA 

and Air Force people and aircraft contractors who worked in the shops and labs of this 

relatikely isolated facility. Often, for example, a mechanic who needed a special tool 

or piece of equipment would go next door on the flight line to a competing contractor 

and borrow what was needed. Flight-testing was difficult, demanding, and time-critical work. By helping each other get through critical times, everyone benefited from the 

unofficial cooperation that was a hallmark of the facility even then. 

An anti-waste mentality M7as another hallmark of Edwards at the time. If an old 

piece of equipment could do the job as well as a new piece of equipment, why spend 

the money and time developing the new piece of equipment when the program could 

be moved along spredily by refurbishing and using the old one? One of the best examples of this recycling was the extensive use made of Thiokol's Reaction Motors 

1. Qtlotrd in Stephan Wilkinson, "Thr I.egacy of the Lifting BucJy," Air & Space (AI)rilhlay l991), 

p. 54. 
WINGLESS FLIGHT 

Division LR-11 (later designated the X1,R-1 I), a rocket engine flown in rocket-powered experimental aircraft at Edwards for nearly 30 years, from 1947 to 1975. 

The most famous use of this engine was to propel Chuck yeager and the Bell 

XS-1 in the world's first supersonic flight in 1947. The Arnly-version 1,R-11 was also 

used to propel later models of the Bell X-1. A virtually identical Navy version called 

the LR-8 was used through 1959 on Douglas D-558-11 rocket-powered aircraft. 

To keep the X-15 program on schedule, despite delays while the Thiokol XLR-99 

rocket engine was being developed, a pair of old TAR-11s was used in the X-15 until 

the bigger engine became availa1)le. During the year that followed until the XLR-99 

was available, the X-15 was flown with the LR-11s and achieved speeds up to Mach 

3.23. Later, many of the old LR-11 engines were donated to various aeronautical 

museums, some installed in the old X-1 or D-558-11 aircraft and some shown as 

separate engine displays. 

Six years afterwards, these engines were removed from the museums, refurbished, 

and recycled into flight-testing in the lifting-body program. Of the eight lifting-body 

configurations developed, four of them were powered by LR-11 rocket engines "borrowed" from museums. The last flight-test of a lifting body using an LR-11 engine 

occurred on 23 September 1975. Afterwards, the LR-11s found their way back to the 

museums, now installed in lifting bodies as well as other historic rocket-powered 

research aircraft. 

The extremely low-cost M2-F1 launched the unofficial lifting-body program in 

1963. Dubbed the "Flying Bathtub," this simple little vehicle was towed aloft by 

either a car or an old R4D, the Navy version of the C-47 aircraft. Except for the Hyper 

111, which was flown by remote control, the lifting-body vehicles were flown with 

research pilots on board. Two of the configurations, the M2-F2 and the first glider version of the HL-10, were marginal to control and later were modified aerodynamically 

to produce good flying aircraft. The original flight versions, which I call the "angry 

machines," tested the limits of research pilots' capabilities. We were very fortunate at 

the time to have a pool of the world's best research pilots to fly these marginally controllable aircraft until we, as engineers, got smart enough to convert them into goocl 

flying machines. Another lifting body, the Air Force X-24A, was converted into the X24B, a totally new form of lifting body that I call a "racehorse" because it led toward 

high hypersonic aerodynamic performance. 

Begun while the X-15 was still being flight-tested, the lifting-body program was 

unique when compared with previous research, in which most aircraft design artivities were conducted by contractors and delivered to the government to meet performance specifications. For instance, the basic X-15 design, except for minor but 

important changes, was tested by expanding the flight envelope to the maximum speed 

and altitude capabilities of the aircraft. In this way, the X-15 program was mainly dri- 
INTRODUCTION 

Drawing showing the evolution of lifting-body flight t-ehicles starting with rhe M2-Fl flown cn 1963-66, 

"angr) mnrhines" ,V2-F2 ancl the original HI,-1Oflou'n in 1966.67; mature "plou*-horse" lifting bodies ,W2- 

F3, ML-10 modiJied, and X-244flolrn in 1968-73; undjinally, the "race-horse" lifting bodies IIyper III arid 

X-2fBflotcn in 1970-75 (original dmwing by Dak Rercl, cligital version by Dryden Grccphics Offire). 

yen by operational and hardware considerations, whereas the lifting body was mainly 

a design engineer's program with NASA and Air Force engineers doing the basic aerodynamics and control-system designs, wind-tunnel testing, and simulation and control 

system analysis. 

All of the NASA lifting-body configurations-the M2-F1, M2-F2, M2-F3, Hyper 

111, HL-10, and modified HL-10-were developed within NASA facilities. The aerodynamic shapes were developed in NASA wind tunnels, and the control-system control laws were developed at the Flight Research Center by NASA engineers and 

research pilots using simulators and other analytical techniques. Northrop, the contractor, then designed and built the hardware to meet these specifications, relying 
WINGLESS FLIGHT 

Paul Bikk-Director of the NASA Flight Research Centerfrom 1959 to 1971 who provided strong support 

for the lifting-body program. (NASA photo E68 19647) 

totally on the work done by the NASA and Air Force engineers. I believe that this was 

an unprecedented arrangement between government and contractor technical people, 

everyone working together as one design team. 

. . . Xlll 
INTRODUCTION 

Paul Bikle 

From what I've described so far, someone might form the impression that the 

NASA Flight Research Center in the 1960s was an organiration of undisc.~plined doas-you-like intli\iduals. Just the opposite was true. Paul Bikle, the director of 

the NASA Flight Research Center at that time, was a strong cfisciplinarian nho came 

to NASA from a military hackgrouncl. A lover of airplanes, he started his career 

designing light planes for Taylor Aircraft Company before worltl VEhr 11. IIe was a 

civilian flight-test engineer at Wright-Patterson Air Force Base, testing B-17s, B-245, 

B-25s, B-29s, P-51s anti other Air Force aircraft of the time. Next, he became the 

civilian director for flight-testing military jet aircraft with the Air Force at Etlwards 

AFB, working closelj with many top Air Force pilots, including Jimmy Doolittle and 

Chuck Yeager. 

After his career with the Air Force, Bikle was recruited to head up the NASA 

Flight Research Center at Ethards, ~hich had just heen assigned to develop a flighttest program for the X-15. His ability to leati a highly disciplined flight-research organization dedicated to achieving timely results hat1 been demonstrated many times in 

his 4ir Force career, making him an ideal choice for thiq jnh. Walt Williams-the 

original director of the NASA Flight Research Center-went on to lead the Mercury 

and Gemini space programs at Johnson Space Center. 

From 1959 to 1969, Paul Bikle organized and conducted the three-aircraft, hypersonic, rocket-powered X-15 program in a highly professional and tfisriplined manner. 

Even though the X-15 program was the major activity at the NASA Flight Research 

Center at the time, Bikle saw the NASA facility as a research center that had to stay 

tuned to the aerospace world, prepared to move ahead when opportunity arose. As a 

result, about half of the staff was comnlitted to X-15 research, the other half available 

to conduct other aeronautical research geared to the future. 

Having worked closely with test pilots for years and being an accomplished pilot 

himself (having set the world's altitude record for sailplanes), Bikle had the uncanny 

ability to gauge accurately the abilities of research pilots. He also knew the abilities 

of most of the roughlj 400 incli\icluals then at the NASA Flight Research Center. 

Almost dail], Bikle wandered through the shops, talking to mechanics and engineers 

in their offices. Besides touring the hangars, shops, ant1 offices, he usually played 

cards during lunch in the radio shop. In these ways, he 5tayed in touch with the pulse 

of the place and the people. He knew more about the daily details of the Center than 

did most of the engineers and project managers. He also hat1 his own style of asking 

questions. He alreadj knew the answers to the questions he was asking, but hati found 

that asking questions was a good way of gauging how much the person knew about 

what was going on. 
WINGLESS FLIGHT 

A small and balding man, Paul Rikle commanded so much respect and authority that when you met him in the hallway, he seemed ten feet tall. years later, after he 

retired, he added radio-controlled model flying to his first lobe, soaring. One day, 

while he and I were flying radio-controlled gliders at the beach, I had the crazy idea 

that, if I had to, I could lick this friendly little guy in a fist fight. It was a crazy idea 

l~ecause never before had I thought of him as anything but a giant you didn't cross 

unless you were stupid. 

Rikle disliked using up people's time ~ith unnecessary meetings. He held one 

weekly meeting to take care of any and all unresolved problems. Usually, he was so 

attuned to daily details within the Center that he knew about a problem before it was 

voiced at a meeting. The meeting soon became known as the "Bikle Barrel," instilling terror in the hearts of any supervisor or project manager who had screwed up that 

week. Not believing that any good could come from reprimands or punishments, Bikle 

found that exposing screw-ups in the weekly meetings was sufficient to keep all of his 

people on their toes afterwards. No one was immune to the Bikle Barrel, and I had my 

turn a few times, too. 

Bikle occasionally used other unorthodox methods to motivate people. For example, he bet several of the lifting-body people that the M2-F2 would not fly before 

1 July 1966. On 8 June, the XB-70 crashed, intensifying the normal safety-of-flight 

worries. Even minor problems in the lifting-hody program began to loom large in the 

aftermath of the XB-70 accident. In the next weekly meeting, Bikle decided that the 

entire lifting-body project would stand down for 30 days, with no attempts made to fly 

until all problems had been fully evaluated. At the end of the meeting, a pile of money 

began accumulating in front of Bikle as those with whom he had bet paid off. He simply smiled, picked up the money, and left the room. The moral: Never bet against 

someone who controls the game. 

His more personable side came out in informal one-on-one sessions. Like most of 

us at the Center in those days, Bikle was in love with airplanes and loved to swap flying stories or talk about new airplane designs. Many of the hig names in aviation were 

his personal friends. I can remember finagling my way into sitting at the same NASA 

cafeteria table with Paul Rikle and Chuck Yeager, just to be able to listen to them 

swap flying stories. In those days, I felt like a child listening to the bigger boys talk, 

often having to work to keep my eyes from bugging out and my mouth from dropping 

open in pure amazement. 

Bikle was also very knowledgeable ahout flight-test and research techniques, 

even doing a professional-level flight program of his own on weekends of many of the 

state-of-the-art sailplanes of the time. He published their gliding perfomlance results 
INTRODUCTION 

in reports still used today by designers of subsonic aircraft requiring very high lift-todrag ratios. 

Innovation is a personality characteristic, Bikle believed, not something that can 

be taught in schools or training programs. He knew that this characteristic might lie 

within any technician in the shop or any engineer in the office. While wandering 

through shops and offices, talking to various individuals, he was able to calibrate 

many personalities and get a feeling for individual skill levels. The door to his office 

was always open to anyone who had an idea that he or she wanted to share with him. 

The Lifting-Bod y Pilots 

Paul Bikle emphasized teamwork, making it clear that each engineer and technician was just as important as each research pilot to the success of the flight project. 

In actuality, however, the work team didn't always see it this way. The research pilots 

were often thought to be like the Greek gods on Mount Olynipus. After all, the success or failure of a project-after long weeks, months, or years of the team's hart1 

work--depended on one pilot doing the job right for the few minutes of that first 

critical flight. 

Many of us involved in the project were also private or amateur pilots imbued with 

tremendous admiration for our fellow team members, the research pilots. Many of us 

envied these pilots, often trying to mentally put ourselves into their minds and boclies 

during flight tests. In the early days, before flights were conducted from control rooms, 

the radio was the primary contact point between the pilots and others on the ground. 

If a pilot chose to say nothing during a flight, we fairly much had to wait for the postflight debriefing to hear how things had gone during the flight. However, we did have 

on-board aircraft data recordings that we could process to verify the accuracy of 

pilot reports. 

Later, when we developed a control room at the Center for the X-15 project, 

research and flight-test engineers could participate in the flight by ~atching data displayed on consoles in various forms--dials, wiggly lines on paper rolls, and pens moving across radar maps to show the position of the aircraft. Sometimes we could 

influence the course of the flight by sending a message to the pilot over the radio 

through a control-room communicator, usually another research pilot. The groundbased communicator, who had the only radio mike in the control room, could filter 

comments by engineers, deciding whether they were important enough to communicate to the airhorne research pilot. 

As engineers, we began to feel that we were a part of the flight once we were able 

to see real-time data coming into the control room by way of telemetered radio signals. 
WING1,ESS FLIGHT 

Nevertheless, the spotlight remained on the research pilot. He was the man of the 

hour, all eyes watching to see that he did his job properly. A11 of the lifting-body pilots, 

with the exception of Chuck Yeager, had college degrees in engineering or physics. 

These "tigers of the air" did not fit any one stereotype, the spread of personality types 

ranging from the "intellectual," as represented by Fred Haise and Einar Enevoldson, 

to the talented "stick-and-rudder men," represented by Chuck Yeager and Joe Engle. 

The flight performance of any pilot on any given day depended not only on his 

experience and skills but also on a number of personal factors, including whether he 

had had a disagreement the night before with his wife. All but one of the lifting-body 

pilots were current or former military fighter pilots, and fighter pilots by nature 

seemed to need sizable egos to be gootl at what they do. The spotlight appealed differently to each pilot's ego, with varying results. 

For example, some of the lifting-body configurations had very poor flying characteristics, which created situations in which pilots could cause oscillations by overcontrolling. This condition is called "pilot-induced oscillation" (PIO), a deviation 

from controlled flight that can happen with the best of pilots if the fljing characteristics of the aircraft are bad enough. However, the pilots with the biggest egos often had 

the most difficulty admitting they were involved in a PI0 situation during a flight. 

The lifting-body pilots also seemed to belong to an unofficial but exclusive clul) 

in the pilots' office. The performance of any pilot could be judged only by his fellow 

pilots or by his boss, Paul Bikle for the NASA pilots and various Air Force commanders for the Air Force pilots. It was not considered proper for flight-test or research 

engineers to suggest that a pilot's performance was not up to par. The lifting-body 

pilots included many top test pilots. Consequently, problems in flying the lifting-body 

vehicles were often thought to be the fault of the engineers who had created configurations that were marginally controllable, rarely if ever considered to result from any 

lack of piloting skill. 

Chuck Yeager had his own pilot rating system, the pilot bosses had theirs, and we 

research engineers had our own. As research engineers, we unofficially divided the 

pilots into two categories: those who were research test pilots, who would try hard to 

bring home quality data, and those who were just test pilots, who could expand 

envelopes and bring the aircraft home safely but who were sloppy with regards to data. 

We were fortunate that most of the lifting-body pilots were also true research test pilots 

and that we got the data we wanted. 

The era of the lifting bodies began with a very modest program involving only one 

pilot, Milt Thompson. The program grew over the years to include eight different lifting-body configurations flown by 17 pilots, eight of whom were NASA, the others Air 

Force. Sixteen of the seventeen pilots had fighter aircraft backgrounds and one, Dick 

Scobee, had large airplane experience. 
INTRODUCTION 

I,qfing-body list shotcing nrtmbers ofjlights per lifting body by each of the 17 lifting-body jJiluts (rompiled by Rett) Lore). 

All of the pilots had other test or research responsibilities on other aircraft programs within NASA and the Air Force, the typical lifting-body flights being weeks or 

even months apart. Often, these other programs involved research or developmental 

military aircraft being tested at Edwards at the same time we were flying the lifting 

bodies. We were fortunate in the lifting-body program to be able to tap into this elite 

source of pilots when we needed them. 

Wie were even able to get Chuck Yeager to take time from his busy schedule during the first year of the lifting-body program to fly the M2-F1 and give his assessment 

of this vehicle. Three of the lifting-bod) pilots went on to he astronauts. Fred Haise 

went to the Apollo program and fleh the Shuttle landing approach tests. Joe Engle and 

Dick Scobee became Shuttle commanders for space flights. 

A total of 222 lifting-body flights were made in those twelve busy years. Topping 

the list was the M2-F1 with 77 air tow flights. The HI,-10 Modified and the X-24B hat1 

36 flights each. The X-2QA flew 28 times; the M2-F2 had 16 flights; the M2-F3, 27; 

and the original HL-10 and Hyper I11 had only one flight each. 

Here is a thumbnail introduction to the pilots, given in the order in which they 

first flew \chicles in the lifting-body program: 

Milton 0. Thompson, the first lifting-hod} pilot, flew the M2-F1 on its first flight 

on 16 August 1963. Milt flew the M2-F1 16 more times before the next two pilots, 
WINGLESS FLIGHT 

Milt Thompson--jirst lifting-body pilot-standing beside the M2-FI conjiguration selected forpight (without a centerjin). (NASA photo EC63 206) 

A happy Bruce Peterson---second lifting-body pilot--after he successfully piloted the marginally controL 

lable HL-10 on itsjirstpight. (NASAphoto E66 16199-1) 

xix 
INTRODUCTION 

Bruce Peterson and Chuck Yeager, were invited to fly it. In all, Milt flew the M2-F1 

45 times. He also made the first five flights of the heavy-weight M2-F2 lifting body, a 

grand total of 51 lifting-body flights. All of his flights were glide flights. 

Milt was instrumental in the start-up of the lifting-body program. It would have 

been tfifficult to sell the lifting-body program to project managers without the help of 

Milt's charm. .4fter flying the M2-F2, Milt retired as a flight research pilot, then moved 

into setting up training programs and working with Paul Bikle in evaluating new pilots 

for the later lifting-body projects. 

Bruce A. Peterson, the second lifting-body pilot, made a total of 21 flights on three 

different lifting bodies: the M2-F1 17 times, the M2-F2 3 times, and the HL-10 once. 

On 22 December 1966, he became the first pilot to fly the HL-10. He retired from test 

flying following the crash of the M2-F2 on 10 May 1967. 

Chuck Yeager was the third pilot to fly a lifting body, making five flights of the M2- 

F1, one on 3 December 1963, and two each on 29 and 30 January 1964. Paul Bikle 

wanted his old friend and master test-pilot, Colond (later General) Chuck Yeager, to 

fly the M2-F1 early enough to give an assessment before other Air Force pilots flew 

the vehicle. At the time, Yeager headed up the USAF Aerospace Research Pilot 

School, also known as the Test Pilot School, at Edwards. Bikle thought that Yeager 

gave the most accurate and descriptive flight test report of any pilot that Bikle had 

ever worked with in the Air Force or NASA. Although Yeager never flew any of the 

rocket-powered lifting bodies, he exerted considerable influence, encouraging the Air 

Force in developing the rocket-powered X-24A and X-24B as well as in the conceptualization of the jet-powered X-24J, ~hich was never built. 

Yeager could be very blunt and straightforward when it came to evaluating the 

performances of other test pilots, and perhaps those who received the brunt of his criticism might not hold him in as high a regard as I and others do. Yeager basically divided test pilots into two categories: those who can hack it, and those who cannot. He 

minced no words in his verbal or written criticism of those pilots who made more than 

a limited number of mistakes in the stick-and-n~ddrr department. Nor did he mince 

~vortls in evaluating how well an aircraft handletl or performed. 

The fourth lifting-bod) pilot, Donald L. Mallick made only two lifting-body flights 

with the lightweight M2-Fl on 30 January 1964. James PC: Wood, the fifth Iifting-body 

pilot, made orily car to~s on 6 February 1964. Major Wood was transferred by the Air 

Force to another commantl and did not get a chance to fly the M2-F1 in air tow. He 

had been one of the original X-20 (Dyna-Soar) pilots selected by the Air Force. 

Donald M. Sorlie, the sixth lifting-hotly pilot, made his first air-towed flight in a 

lifting hody on 27 May 1965. The official Air Force "boss" of the lifting-body and 

X-15 A4ir Force test pilots, Lieutenant Colonel Sorlie made five flights in the M2-F1 

and three in thr M2-F2, just enough to evaluate what kind of challrnge would con- 
WINGLESS FLIGHT 

Bill Dana, seventh lifting-body pilot, whofiw 4 lifiing-body con.ratwns including 19flights on the M2- 

F3 for a total of 31 lifting-bodyflights. The HL-10 is shown behind him. (NASA photo E69 20288) 

Then-Capt. Jeraukl Gentry, principal Air Force and eighth lifting-body pilot overall, whofiw 5 lifting-body 

conJiguratwns including 13 on the X-24A for a total of 30 lifting-bodyfights. (NASA photo, EC97 44183-1) 
INTRODUCTION 

xxii 

front his test pilots in these lifting bodies. At the time, he was Chief of the Fighter 

Operations Branch, Flight Test Operations--the primary pool of Air Force test pilots 

at Edw ards AFB. 

'he se~enth pilot to fly a lifting body, Williatn H. Dana, had 31 lifting-body flights 

over a little more than ten years, flying the lifting-bodies over a longer span of time 

than did any other pilot. He had his first lifting-1)ody flight in the M2-F1 on 16 July 

1%5. He also flew the HI,-10 and the M2-F3. His last lifting-hod) flight was in the 

X-24B on 23 September 1975. 

Dana received the NASA Exceptional Senrice Medal for his ten years as a 

research pilot in four of the lifting-body vehicles (M2-F1, HIA-10 modified, M2-F3, 

ant1 X-24B). In honor of his research work on the M2-F3 lifting-body control systems, 

Dana in 1976 received the American Institute of Aeronautics and Astronautics' Haley 

Space Flight Award. 

Jerauld R. Gentry, the eighth lifting-hody pilot, was the chief Air Force liftingbody pilot, making a total of 30 lifting-body flights. Major Gentry made his first airtowed flight on the M2-F1 on 16 July 1965. He also flew the M2-F2, the HI.-10, and 

the X-24A. He made his last lifting-body flight in the M2-F3 on 9 February 1971. 

Major Gentry developed a reputation as an outstanding lifting-body research pilot, flying the X-24A on its first glide flight as well as its first rocket-powered flight, demon- 

~trating a high lekel of skill in gathering the flight data needed I)] engineers in 

espancling the X-24A's flight envelope. 

The ninth and tenth lifting-hotly pilots, Fred Haise and Joe H. Engle, flew thr 

M2-FI on car tons up to altitudes of 25 and 30 feet on 22 April 1966. Neither of them 

flew the M2-F1 from airplane tows, nor did they fly any of the B-52 launched lifting 

l~odies. 

Soon after flying the M2-F1 in 1966, Hai5e was assigned as an astronaut at what 

hecame the Johnson Space Cente1; precluding any atlrlitional involvement with the 

lifting-body project. Later, FIaise wras on the ill-fated Apollo 13 flight. which almost 

ended in disaster following an explosion in space, the topic of the popular movie 

.APollo 13 that premiered in 1995. General Joe Engle also hat1 his assignment to the 

lifting-body project cut short \\hen he was one of 19 astronauts selected in March 

1966 for NASA space n~issions. I would havr liked to have seen how well Joe Engle, 

in particular, woultl have performed oF7er time as a lifting-body pilot. He shared many 

of Chuck Yeager's characteristics: he, too, was full of 'piss and vinegar' as well as one 

of the best stick-and-rudder men around. 

John A. Manke, the eleventh liftitig-bod] pilot, was the second busiest with 42 

lifting-body flights, the busiest being Milt Thompson ~ith 51. Most of Manke's flights 

%-ere r0ckc.t-powered, while all of Thompson's were glide flights, inclurling the remotely piloted Hlper IIT in ~hich Milt "flew" from a grountf cockpit. Xanke's first flight 
WINGLESS FLIGHT 

John Manke, eleventh lijting-body pilot, whoflew 4 different conjigurations including 16 X-24BJights for a 

total of 42 lifiing-bodyflights. (NASA photo EC69 2247) 
INTRODUCTION 

Lt. Col. Michael Love, fourteenth lifting-body pilot, whofiw the X-24B 12 times. (NASA photo E75 29374) 

was a glide flight on the modified HL-10 on 28 May 1968. Manke flew the HL-10 ten 

times, the M2-F3 four times, the X-24A twelve times, and the X-24B sixteen times. 

He made his last flight on 5 August 1975 in the X-24B. 

The twelfth pilot to fly a lifting body, Peter C. Hoag, first flew the modified HL-10 

on 6 June 1969. Major Hoag made his eighth flight on the HL-10 on 17 July 1970. 

This was also the last flight of the HL-10. While flying the HL-10 on 18 February 

1970, Major Hoag set the speed record for all of the lifting bodies-Mach 1.86. 

Cecil William Powell, the thirteenth lifting-body pilot, had his first lifting-body 

flight on 4 February 1971, a glide flight in the X-24A. He flew the X-24A and the M2- 

F3 three times each. His last flight on a lifting-body was a rocket flight on the M2-F3 

on 6 December 1972. 

Fourteenth among the pilots to fly a lifting body, Michael V. Love first flew the X24B on 4 October 1973. A year later, on 25 October 1974, Lieutenant Colonel Love 

set the speed record of Mach 1.75 for the X-24B. On 20 August 1975, he had his 

twelfth and final flight of the X-24B. 

Einar Enevoldson, the fifteenth lifting-body pilot, made his first of two glide flights 

in the X-24B on 9 October 1975. He was one of three guest pilots invited to fly the X24B in glide flights as part of a guest-pilot evaluation test exercise at the end of the 
WINGLESS FLIGHT 

X-24B flight program after the official research flights had been completed. Each of 

the three guest pilots (including Major Francis R. "Dick" Scobee and Thomas C. 

McMurtry) flew the X-24B twice. 

Francis R. "Dick" Scobee, the sixteenth lifting-body pilot, first flew the X-24B on 

21 October 1975. Primarily an Air Force transport test pilot, Major Scobee was the 

only lifting-body pilot with no background as a fighter pilot. He kidded us, saying he 

was selected as a guest pilot to prove that if a transport pilot could fly the X-24B, then 

any pilot could fly future spacecraft versions of the X-24B. 

The X-24B shared very similar speed and performance characteristics with the 

projected Shuttle spacecraft design, so the X-24B was used to collect operational data 

used in the design and development of the Space Shuttle vehicles. Scobee said that 

his experience flying the X-24B inspired him to apply to the NASA Astronaut Corps 

to fly the Shuttle spacecraft. He was selected as an astronaut for NASA in January 

1978. On 28 January 1986, Scobee unfortunately perished in the Challenger explosion. 

Thomas C. McMurtry was the seventeenth and final pilot to fly a lifting body, doing 

so as the third invited guest pilot at the end of the X-24B program. He flew the X-24B 

in glide flight twice, once each on 3 and 26 November 1975.2 

How Wingless Flight Came to be Written 

My life-long love affair with airplanes has kept me from truly retiring. After I 

retired from NASA in 1985, I was recruited to manage the development at Lockheed 

of various Remotely Piloted Vehicles (RPV), working four years at the Lockheed 

Advanced Development Plant known as the "Skunk Works," managing design, vehicle development, and flight-test programs. 

After I left Lockheed in 1989, still unable to pull myself away from an active 

involvement with aircraft, I served as a consultant to various aircraft organizations and 

soon found myself working as a contractor, supporting NASA programs at NASA 

Dryden, Edwards AFB. Once more I was able to work with some of my old NASA 

friends at Dryden, including Milt Thompson. 

Milt had been working on a book entitled At the Edge of Space? which told the 

story of the X-15. After this book was published in 1992 by the Smithsonian 

Institution Press, Milt was asked if he would write a book telling the lifting-body story. 

For several years, I had thought of writing just such a book. However, at the time, I 

2. Thanks to Betty Love for checking and correcting the statistics for th~section. 

3. Milton 0. Thomposon, At the Edge of Space: The X-15 Flight Program flashington, DC: 

Smithsonian Institution Press, 1992). 
INTRODUCTION 

was too busy having fun coming up with new ideas for creating new airplane programs. 

With the new miniature computers and global-positioning satellite systems, I was 

totallq involved with developing autonomously-controlled unpiloted air vehicles of 

all sorts. 

Milt Thompson died suddenly on 6 August 1993. Before his death, Milt had 

begun writing the book that would tell the lifting-body story, but he had not finished 

it at the time of his death, leaving me as the only remaining lifting-body team member who knew the full lifting-body story from beginning to end. If a book telling the 

entire story were to be written, it seemed that I was the only participant left who could 

do it. 

By this time, the professional aernspace writer and historian Richard P. Hallion 

had already published three excelIent histories telling aspects of the story. First Published by the Srnithsonian in 1981, Test Pilots4 tells the complete story of flight-testing, from the earliest tower jumps in 1008 to the around-the-world flight of the Voyager 

in 1986. On the Frontkr,5 published in 1984 as a volume in the NASA History 

Series, is a comprehensive history of flight research at NASA Dryden after World War 

11, 1946-1981. The Hyp~rsortic Revoh~tion,6 published in 1987 1)y the U.S. Air 

Force, is mammoth in scope, covering events from 1924 to 1986from the early rocket experi-ments to the aerospace plane. 

Richard Hallion has already done an excellent job in these hooks in documenting the historic facts as well as the political and managerial aspects of the lifting-body 

story. %hat remains untold is the story that facts alone cannot tell: the human drama 

as it unfolded in the day-by-day activities of the people who lived and breathed the 

lifting-body adventure from 1963 to 1975. 

Wingless Flight tells that story, for I remain convinced that it is about more than 

machines; it is at least as much about the people with the "real stuff," who created 

and maintained the machines, as it is about the individuals with the "right stuff," the 

pilots hho flew the lifting bodies. 

4. Richarti P. Iiallion, Test Pilots: The Frontiersmen of Flight (Washington, DC: Slrlithsonian 

Institution Press, 1992). 

5. Richard P. Hallion, On the Frontier: Flight Research at Dryden, 1946-1981 (Vashington, 

DC: N.4SA SF'-3303, 1984). 

6. Richard P IIallion, The IIypersonic. Re~wlution: Eight Case Studirn in the History of 

lfypersonir Terlrrrology (2 vols.; Wright-Pattt~rson Air Forre Base, Ohio: Special Staff Office, 1987). 

Since these lines were written, another study of Drytien history appeared, 1anr E. Wallace's Fights of 

Discoc~rj.: 50 Iburs at the Dryden Fight Reseclrrh Center (Washington, DC: Y.4SA SP-4309,1996). 

Rasrtl on an earlier version of Wingless Flight and an intrmierv with Dale Reed, this short history rlrvotes 

considerahlr attention to the lifting-lmdy story. 

xxvi 
CHAPTER 1 

THE ADVENTURE BEGINS 

My journey in February 1953 to the NACA High Speed Flight Research Station 

(as the Muroc Flight Test Unit had come to be called in 1949) actually began about a 

decade earlier in two small mountain towns in Idaho, about as far from the center of 

aerospace innovation as one can get. My roots are with farmers and ranchers, my 

grandfather having moved his family meml~ers from Kansas to the sagebrush country 

of southern Idaho to came out their future in agriculture, both of my parents the children of farming families. 

Around age twelve, I was smitten with what would prove to be a lifelong love of 

airplanes. I still remember the summer day when I saw my first sailplane. John 

Robinson had come to Ketchum, Idaho, wilh his one-of-a-kind sailplane called the 

Zanonia to try for some world sailplane records. A beautiful craft, the Zanonia had gull 

wings reminiscent of some of the German sailplanes of the time. Robinson cleared the 

brush from a flat area across the road from my family's home, making a small dirt strip. 

Here, Robinson would use a car to tow the Zanonia aloft, the sailplane rolling on a 

dolly with a set of dual wheels that would drop by parachute after take-off. 

For two weeks that summer, I helped Robinson, untangling the tow-line from the 

brush after the glider had been launched and picking up the parachuted landing gear. 

I loved to lie on the grass, watching the Zanonia riding the air currents around the 

mountain peaks. Robinson set two world altitude records in the Zanonia that summer, 

flying thr waves and thermals above the Sawtooth Mountains. 

I then began building and flying model gliders and free-flight model airplanes. A 

hundred miles stood between me and the next modeler in those days, so I was fairly 

much on my own, except for some occasional help front my mother who was good with 

crafts and taught wood shop at the local grade school. Fairly I learned I had 

to limit the duration of my engine runs, else chance losing my models when the} glided down on the other side of the hills or mountains. 

One September day, one of my models did exactly that. It caught a thermal and 

flew over a nearby mountain. Two weeks later, my father found that model perched 

unharmed on a bush at the bottom of a gully two miles from the ridge it hail flown over. 

I flew that model for another year, during which I equipped it with floats so it could fly 

off of a nearby mountain lake. 

Across the street from my high school in Hailey, about 12 miles south of Ketchurn, 

a grass field where a bush pilot-operator named Bob Silveria kept two airplanes. 

During the summer and fall months, the big radial engine of his old Faco cabin 
THE ADVENTURE BEGINS 

hiplane could be heard lumbering through the Sawtooth Mountains, carrying fishermen and hunters to the primitive wilderness landing strips along the Middle Fork of 

the Salmon River. Silveria also had a 65-horsepower Aeronca Defrnder L-3 airplane 

at the grass field, using it to give flying lessons as well as to transport hunters into the 

flats south of Hailey where they chased coyotes. 

By the time I was sixteen, even my high school physics and chemistry teacher, Mr. 

Kinney, knew that I was interested in airplanes. A private pilot who was good friends 

with Silveria and occasionally rented the little Aeronca airplane across the street from 

the school, Mr. Kinney offered to teach a class in aeronautics if I could round up eight 

interested students. I found six interested boys fairly easily, but 1 had to overcome my 

shyness around the opposite sex long enough to talk two girls into joining us to fill 

the class. 

Mr. Kinney used the little Aeronca as a teaching tool. We learned to hand-prop to 

start the airplane and taxi it around the grass field. We did everything but fly. Seeing 

my enthusiasm, Mr. Kinney encouraged me to apply for a student license and take 

some flying lessons. I did not know that his suggestion was part of a plot hatched 

between him and Silveria to see how soon they could get me to solo. 

On a cool September day in my sixteenth year, I had my first flying lesson. As I 

sat in the front seat of the Aeronca, Silveria told me that my job was to handle the 

throttle, rudder pedals, and brakes, that he would do everything else with the stick 

from the back seat. All I had to do was put my hand lightly on the stick and follow his 

movements. 

Since Mr. Kinney had earlier done a good job in teaching me in the class on how 

to taxi a tail-wheel airplane, I had no problem when Silveria told me to set the trim, 

taxi to position, and start the takeoff run. I knew that my task was simply to steer the 

rudder pedals and touch but not move the control stick. As we rolled across the grass 

field, the tail came up eventually and we rolled along on two wheels. I remember 

thinking what a smooth pilot Silveria was, for I hadn't noticed any movement at all on 

the stick. Soon we were flying, but I still hadn't noticed any movement on the stick. 

We had climbed to an altitude of 500 feet when Silveria, his first words to me since 

the takeoff, said, "Do you know that you made that takeoff by yourself without 

my help?" 

I couldn't believe it, for I was doing practically nothing to fly the airplane. All I 

had done was make very small and gentle inputs to the rudder while we were on the 

ground and once we were in the air. I think I made those small control inputs automatically, perhaps subconsciously, because I had learned from building and flying 

model airplanes that a properly designed airplane can do a pretty good job of flying, 

even without the pilot. 

A few days later, after three and a half hours of flight instruction, I soloed. By age 

sixteen, then, I was totally hooked on aviation. At first, I thought I wanted to be a bush 

pilot in Alaska or somewhere else equally exciting, but my high school principal 

talked me into going to college and studying engineering. Off I went to the University 

of Idaho in Moscow. Unlike other universities at the time, Idaho didn't offer a major 
WINGLESS FLIGHT 

in aeronautical engineering, but all I could afford was Idaho. I majored in mechanical 

engineering, taking as many aeronautical courses as I could. 

Little better than an average student in high school, I found myself getting 

almost straight As in college. I had found my niche in aeronautical engineering, 

thanks to a love of flight and airplanes that hat1 hegun when I was only twelve, a young 

hoy in a small mountain town in Idaho, far away from the center of aviation's 

innovative future. 

As I took college courses, I found myself more and more intrigued by what I was 

reading in magazines about what was happening at Ed~ards AFB in Southern 

California, where a small contingent of NACA people was flight-testing the world's 

first supersonic airplane, the rocket-powered X-1. Little did I know, as I wad these 

articles, that soon I woulct be a part of that small contingent of NACA people, conducting my own aeronautical experiments on the X-1 and becoming personally 

acquainted with the famous test pilot Chuck Yeager. 

Before leaving Idaho in early 1953 to report to work at the High Speed Flight 

Research Station in the Mojave Desert, I did some reading on the history of the NACA 

and the Mojave Desert site. And then I got into my car, drove south fro111 Idaho and 

west across the Nevada desert to the town of Mojave, California, where I made a sharp 

southeastern turn into the middle of nowhere. 

At that time, Edwards Air Force Base was very small and compact, located on the 

edge of Muroc Dry Lake, now known as Rogers Dry 1,ake. The name of the base had 

changed only a few years earlier from Muroc Army Airfield to Edwards Air Force Base 

in honor of Captain Glen IT. Edwards, killed in June 1948 in the crash of a Northrop 

YB-49, an experimental flying wing bomber. 

In late 1946, the NACA had sent thirteen engineers and technicians from the 

NACA Langley Memorial Aeronautical Lal~oratory to Muroc Army Airfield to assist in 

flight-testing the Army's XS-1 rocket-powered airplane. These thirteen individuals 

fairly much made up what was soon to be called the NACA Muroc Flight Test Unit. 

Over the next fifty years, the NACA Muroc Flight Test Unit grew into what is today the 

NASA Dryden Flight Research Center with over 900 NASA employees and contractors supporting NASA's premiere flight-test activities. 

Ground Zero: The Place Where Tomorrow Begins 

The flight-testing of all experimental and first-model military aircraft occurred 

along an ancient dry lake now called Rogers Dry Lake, located on the western edge of 

California's Mojave Desert just south of Highway 58 between the towns of Boron and 

Mojave. Only a few miles northeast is the world's largest open-pit borax mine. Within 

sight of Rogers Dq Take is one of the first immigrant trails through California. 

The original name of the site, the NACA Muroc Flight Test Unit, caomes partly 

from local history. "Muroc" is "Corum" spelled 1)ackwards. The first permanent settlers in the area, the Corum family located near the large dry lake in 1910. Later, they 

tried to get the local post office named Corum. However, there was already one with a 
TFIE ADVENTURE BEGINS 

nearly identical name (Coram) elsewhere in California, so they reversed the letters to 

spell Muroc.' 

What was there about this dry lake that made it ideal as the later site of major aviation flight-test history? About 2,300 feet above sea level, Rogers Dry Lake fills an 

area of about 44 square miles-nearly half again as large as New York's Manhattan 

Island-and its entire surface is flat and hard, making it one of the best natural landing sites on the planet. The arid desert weather also provides excellent flying conditions on almost every day of the year. 

Rogers Dry Lake is the sediment-filled remnant of an ancient lake formed eons 

ago. Several inches of water can accumulate on the lakebed when it rains, and the 

water in combination with the desert winds creates a natural smoothing and leveling 

artion across the surface. When the water evaporates in the desert sun, a smooth and 

level surface appears across the lakebed, one far superior to that made by humans. 

Water on the surface of Rogers Dry Lake also brings to life an abundance of small 

shrimp-several unique species of the prehistoric crustacean-but they disappear 

once ttie desert sun evaporates the water. Annual rainfall here is only about four to 

five inches, considerably less in some years. In extremely wet years, the annual rainfall can rise to six or even nine inches. 

Kinds are quite predictable, usually from the southwest during spring and summer, with a mean velocity of six to nine knots. Sunrises and sunsets can be breathtakingly beautiful, as can the spring wildflowers with enough rain. 

The surrounding area is typical of the California high desert with rolling sand hills 

and rocky rises, ridges, and outcroppings punctuated in the low- spots with dry 

lakebeds. Mountains lie on three sides-at the south, west, ancl north-with the 

mighty Sierra Nevada range to the north rising to over 14,000 feet. Joshua trees cluster among the chaparral and sagebrush. A type of Yucca (a member of the Lily family), the Joshua tree has clusters of very sharp and dark green bayonet-shaped or 

quill-like spines that grow six to ten inches long and that only a botanist would coal1 

"leaves." Like everything else in the surrounding desert, the Joshua tree is well suited for survival in a harsh environment. In summer, temperatures can reach or exceed 

120 degrees Fahrenheit, with 10 to 15 percent humidity. In winter, temperatures can 

fa11 to nearly 0 degrees Fahrenheit. 

In a curious coincidence, two entirely different and likely unrelated men named 

Joe Walker figure prominently in local pioneering history, separated by about 115 

years. In the spring of 184.3, Joseph B. Chiles organized and led one of the first wagon 

trains out from Independence, Missouri, to California. At Fort Laramie in Wyoming, 

he met an old friend, Joe Walker, who joined the California-bound wagon train as a 

guide. Once in California, the wagon train ran low on provisions and split into two 

groups, one on horseback led by Chiles that went north to circumvent the Sierra 

1. Hallion, On the Frontier, pp. xiv-xv. 
WINGLESS FLIGHT 

Nevadas, the other in the wagons led by Joe Walker heading south. The people in the 

Walker party had to abandon their wagons just north of Owens Lake, arriving on foot 

at what is now called Walker Pass at eleven in the morning on 3 December 1843. 

lT7alker Pass, named after the first Joe Walker, is only 56 miles across the southern 

Siei~a Nevadas from Edwards AFB where, 115 years later, another man named Joe 

Walker, the prominent NACA/NASA X-15 research pilot, was engaged in a very different kind of pioneering. 

In the 1930s, early aviators-including the military and private airplane designers such as John Northrop--used Rogers Dry Lake as a place to rendezvous and test 

new designs. During World War IT, the U.S. Army Air Corps conductetf extensive 

training and flight-testing at the site. This is also the general area where a colorful 

social club and riding stable was locatetl, establishetl by the aviatrix Florence 

"Pancho" Barnes and frequented by many of the early and famous test pilots and notables of aviation history. 

In more recent times, the Air Force, NASA, and various contractors have used 

Rogers Dry Lake in conducting flight tests on many exotic and unusual aerospace 

vehicles. In the words of Dr. Hugh L. Dryden-the early NACAiNASA leader, scientist, and engineer-the purpose of full-scale flight research "is to separate the real 

from the imagined. . .to make known the overlooked and the unexpected," words that 

help clarify why a remote location in the western Mojave Desert would become the site 

where innovative NASA engineers and technicians would gather to help create the 

future of aviati~ n .~ 

The official name of the site has changed over the years. It changed its name from 

the NACA High Speed Flight Research Station to the NACA High Speed Flight 

Station in 1954 and then to the NASA Flight Research Center in 1959. It became the 

NASA Hugh L. Dryden Flight Research Center in the spring of 1976, a name it 

regained in 1994 after a hiatus from 1981 to that year as the Ames-Dryden Flight 

Research Facility. However, when I arrived at the site in 1953, it was still called the 

NACA High Speed Flight Research Station, and the people at the facility were conducting all of the NACA's high-speed flight research. They were used to conducting 

high-performance flight research on rocket-powered vehicles that had to lantl unpowered. Unpowered landings with high-performance aircraft became relatively routine, 

but not necessarily risk-free, on the vast expanse of Rogers Dry Lake. 

2. Hugh I.. Dryden, "Introductory Remarkc," National Advisory Coninlittee for Arrondutirs, 

Research-Airplane-Committee Report on Conference on the Progress of th~ X-15 Project, 

(Papers Presented at T,angley 4eronautiral Laboratory, Oct. 25-26, 1956), p. xix. I am indebted to Ed 

Saltrman for locating thls quotation, the words for which are common knouledge at the Center named in 

honor of Hugh Dryden but the source for which is not well known. 
THE ADVENTURE BEGINS 

Flight Research, 1953-1962 

When I an-i~ed at the Station in February 1953, the purely rocket-powered Bell 

X-1 and X-2 as well as the Douglas D-558-11 experimental airrraft were being flighttested, air-launched from B-29s and B-50s (essentially the same as the B-29, but with 

slightly different engines). Before I arrived on the scene, the Air Force had operated 

the B-29s, but the NACA had taken over operating the B-29s by the time I got there, 

includ~n~ theB-29 used for the D-558-11, which hat1 the tiistinction of being the only 

Nay-owned B-29 (Navy designation, P2B). Also being flown then was a second D558-11 ~ith a hybrid turbojet-rocket propulsion system. Other experimental turbojet 

aircraft being flown included the Bell "flying wing" X-4 (technically, a swept wing 

conihined with an absence of horizontal tail surfaces), the Bell variable-sweep-wing 

X-5, and the first high-pelforn~ance delta-wing aircraft, the Convair XF-92. 

At the NACA facility at that time, all new junior engineers were expected to learn 

the flight-research business from the 1)ottom up. Given the limited data systenls of that 

era, plus the lack of high-speed computing capability, a research engineer's job was 

about ninety percent measuring and processing data and only about ten percent analyzing and reporting the flight results. With all the weird and wonderful airplanes at 

that time, stability and control problems were prominent. Most of the senior engineers 

at the hACA facility were busy analyzing and trying to solke these problems. This 

meant there was a lot of pick-and-shovel work for the junior engineers to do. 

My first job assignment involved measuring aerodynamic. loads on the wings and 

tail surfaces of Iarious research aircraft. Hundreds of strain gauges had been installed 

inside the structures of these aircraft as ther were built in the factory. My task bas to 

calil~rate these gauges and other data acquisition devices on the aircraft, including 

control position indicbators, air data sensors, gyros, and accelerometers. 

Today, these tasks are the responsibility of instrumentation engineers. Earlier, due 

to the small staffing at the NACA facility, these tasks fell on the shoulders of the aero 

or research engineers. One advantage back then of doing things this way was that I)y 

the time research engineers finally had enough flight data to analyze, they had good 

knowledge of the accuracies of the instrumentation-so good that if weird glitches 

turned up in the data during flight tests, they were better able to determine whether 

tlie data was real or indicated a prol~lem in the instrumentation. 

My first task in~olved measuring the aerodynamic loads on the X-5 research aircraft, a little airplane that had evolved from a design smuggled out of Germany at the 

end of Wbrld War 11. Bell Aircraft completed the clesign, ltuilding what was to become 

the world's first variable-wing-sweep aircraft. 

My task involbed measuring the bending, shear, and torque loads of the wing and 

tail surfaces on three configurations of the X-5, one each with 20-, 40-, and 60-degree 

wing-sweep angles. This meant that I had to have separate wing strain gauge calibrations for each wing sweep. In those days, calibrations involved manual labor at ahout 

thirty load points on each wing and tail surface. I spent long hours over days and even 
WINGLESS FLIGHT 

weeks on a jack handle, putting incremental loads on the airplane at all of these 

points. 

Each strain gauge output was read off a meter and written down by hand, resulting in stacks of paper with handwritten data, then processetl by hand on the old 

mechanical Frieden calculating machines. Processing involved selecting groups of 

multiple strain gauges and developing equations for bending moments, shear and 

torque. 

A staff of ten women did all the calculations on the Frieden machines. To me, they 

seemed the hardest working people at the facility, each of them spending long hours 

clanking away on a calculating machine. In those days, we worked in old barrackstype buildings with swamp coolers on the windows. The Frieden machines had to he 

carefully coveretl up during desert dust storms, for the dust coming through the coolers could ruin those mechanical wonders. 

Over the years, I I~erame a specialist in this sort of measurement work, doing 

flight research with the X-lE, F-100A, D-558-11, and X-15. During the X-15 program, 

my area of expertise expanded into aerotlynamic heating, and my responsibilities grew 

to include each planned X-15 flight as speeds and altitudes increased far beyond 

those for any existing aircraft. 

As the X-15 pushed closer ant1 closer to its maximum speed of Mach 6.7 (or 6.7 

times the speed of sound) and maximum altitude of 354,200 feet (or 70 miles above 

the earth), the Inconel-X steel and titanium structure of the X-15 could reach teniperatures as high as 3,000 degrees Fahrenheit in areas of concentrated aerodynamic 

heating. The X-15 had been instrumented with hundreds of strain gauges ant1 thermocouples for measuring the stresses and heat in its structure. 

North American Aviation's structural designer of the X-15, A1 Dowdy, ant1 I 

worked as a team examining each planned flight to determine if there was any cause 

for concern about structural failure. For eacsh flight, the flight-planning team and the 

pilot would develop a flight plan on the facility's X-15 flight simulator. With this 

planned flight profile of speed, altitude, angle of attack, and load factor, we could calculate aeroclynamic heating inputs to the external skin on various parts of the aircraft. 

A1 and I selected seven critical areas of structure on the X-15 to monitor in detail 

during each flight program. For example, one wing area included the Inconel-X steel 

skin and the titanium spar caps and webs. From the information gained from monitoring these areas, 1 could then generate time histories of the temperature rise and 

decline in each element of the aircraft's structure. With this data, Al, in turn, could 

determine the stresses within the structure by combining calculated aero loads with 

my calculated temperatures. At flight-planning tech briefings, 1 would then report 

whether I thought the planned flight would be safe from the structural standpoint. 

Throughout the X-15 program, we continued to test our prediction techniques by 

comparing our preflight calrulations with measured temperature data frotri the actual 

flight. For some skin areas, we revamped our calculations to include laminar heating 

when we thought that it would be turl~ulent heating, and vice versa. Turbulent heating 

results in temperatures almost twice as high as those due to laminar heating, but at 
THE ADVENTURE BEGINS 

first we weren't always smart enough to know whether the flow would be laminar or 

turbulent. Later, we became more skilled at predicting external aerodynamic heating. 

We still had to refine our calculations for internal heat flow because the structural 

joints did not transfer the heat as anticipated. We determined the correction factors 

for the heat-transfer equations while the X-15 was still flying at low supersonic speeds 

of up to Mach 3. By the time that structural heating became more critical near Mach 

5 and Mach 6 later in the X-15 program, we could do a much more accurate job in 

predicting structural temperatures. 

The Early 1960s: Concepts of the Lifting Body 

Although I gained a great deal of satisfaction as a researcher in structures on the 

world's first hypersonic airplane, my interests in aeronautics always had heen much 

broader than aircraft structures. Still very much interested in stal~ility and control, 

aerodynamics, and unusual aircraft configurations, I continued to design and build 

model airplanes and to fly Iight planes and sailplanes on my own time. 

I was also fascinated with the space program, following closely the activities of 

Walt Williams, my first boss at the facility, and the people he took with him from the 

NASA Flight Research Center to Johnson Space Center to conduct the Mercury and 

Gemini programs. While reading NASA and Air Force reports on design concepts for 

future spacecraft, I noticed a pattern developing. Although many of these studies 

included concepts of lifting reentry vehicles, when actual space vehicles were 

clesigned, they were always non-lifting or ballistic capsule-type vehicles. 

,4t the time, it was obvious that NASA and Air Force decision-makers had little 

confidence in the concept of lifting reentry and even less for lifting-body types of reentry vehicles. Although it funded man) studies of lifting reentry configurations of all 

types, including lifting bodies, the Air Force soon concluded that lifting bodies were 

too risky-. 

In September 1961, a blue-chip panel of the Scientific Advisory Board chaired by 

Professor C.D. Perkins had recommended to Air Force General Bernard A. Schriever 

that all expenditures on flight hardware be made solely for winged vehicIes, not lifting ttodies. The panel had questioned the control characteristics of a lifting-body 

design, believing they could make conventional landings hazardous. The Air Force 

accepted the panel's recommenclation, decniding to finance only winged reentry vehicle programs: the Boeing Aircraft Company's manned Dyna-Soar X-20 and 

McDonnell Aircraft Con~pany's upiloted ASSET (Aerothermodynarnic/elastic 

Structural Systems Environmental Test). Only a mock-up of the X-20 was ever built, 

Secretary of Defense Robert McNamara canceling the $458-million X-20 program in 

December 1963. In 1964, the $21-million unpiloted ASSET hypersonic glider was 
WINGLESS FLIGHT 

flown successfully four times in hypersonic reentry maneuvers. Never flown subsonically, the four ASSET research vehicles were parachuted into the ocean for recove~y.~

Meanwhile, as NASA decision-makers continued to stay with ballistic shapes for 

the Mercury, Gemini, and ApoIlo programs, some NASA researchers at the field centers continued to study lifting-body reentry configurations. Actually, interest in the 

lifting-body concept among individuals at NASA dates back to the early 1950s when 

researchers-under the direction of two imaginative engineers, H. Julian "Harvey" 

Allen and Alfred Eggers-first developed the concept of lifting reentry from suborbital or orbital space flight at NACA's Ames Aeronautical Laboratory at Moffett 

Field in California. In March 1958, the researchers presented this work at a NACA 

Conference on High-Speed Aerodynamics.4

The initial work of NACA researchers in the early 1950s had been done in connection with studies regarding the reentry survival of ballistic-missile nose cones, the 

results of which were first reported in 1953. Researchers found that, by blunting the 

nose of a missile, reentry energy would more rapidly dissipate through the large shock 

wave, while a sharp-nosed missile would absorb more energy from skin friction in the 

form of heat. They concludetl that the blunt-nosed vehicles were much more likely to 

survive reentry than the pointed-nose vehicles. Maxirne A. Faget and the other 

authors of a paper at the 1958 NACA Conference on High-Speed Aerodynamics concluded that "the state of the art is sufficiently advanced so that it is possible to proceed confidently with a manned satellite project based upon the ballistic reentry type 

of vehicle." Faget's paper also indicated that the maximum deceleration loads would 

be on the order of 8.5g, or 8.5 times the normal pull of gravity on the vehicle.5 

Other authors at the same conference prrsented the results of a study on a blunt 

30-degree half-cone wingless reentry configuration, showing that the high-lifthighdrag configuration would have maximum deceleration loads on the order of only 2g 

and would accommodate aerodynamic controls. This configuration also would allow a 

lateral reentry path deviation of about plus or minus 230 miles and a longitudinal variation of about 700 miles.6 

3. See Richard P. Hallion, "ASSET: Pioneer of lifting Reentry," in Hallion, Ilypersonir Rrt~olution, 

pp. 449-527. 

4. National Atlvisory Committee for ,Aeronautics, NACA Conferenre on High-Speed Aerodynarnirs, 

A Cornpilatwn of the Papers Presented (Moffett Field, CA: Art~es .4eronatltical I.ahoratory, 1958). 

Notahle in this connection was the paper by Four Ames researchers-Thomas J. song, Charles A. 

Helmarh, John 0. Rellrr, Jr., ant1 Bruce E. Tinling-at a session rhaired by Allen. The paper's title was 

"Preliminary Studies of Manned Satellites-Tingless Config~lrations: lifting Body" and appeared on pp. 

35-24 of thr volume just cited. 

5. Maximr .A. Faget, Benjamin? J. Garland, and James J. Buglia, "Preliminary Stutlies of hlanned 

Satellite Tingless Configuration: Nonlifting" in iVAC.4 Conference on High-Speed A~rodynamirs, pp. 

19-33 with the quotation on p. 25. 

6. Wong et al., "Preliminary Studies: lifting Body," pp. 35-44. 
THE ADVENTURE BEGINS 

Following this conference-the la51 held bj the NACA before Congress created 

the NASA later in 195Gthe logical choice for a piloted reentry configuration seemed 

to be the proposed blunt half-cone 2g vehicle with controls and path deviation capabilitj rather than the 8.5g hallistic vehicle with no controls and almost no path tieviation capability. However, this was not to be, due to some practical considerations of 

the time. 

As things turned out, the thrust capahility of the available boosters versus the 

needed pajload weights made it easier to design a small blunt shape to fit on top of 

the Redstone and Atlas rocket boosters. This blunt-nosed ballistic configuration 

became the United States' first piloted spacecraft, the Atlas rocket-boosted Mercury 

capsule, which then evolked into the Apollo program using the Saturn rocket. 

Nevertheless, the concept of wingless lifting reentry (lid not die. The only problem was that we had no experience with this type of vehicle, especially with the anticipated heat loatfs. But the advantages of a ltlunt half-cone or wingless reentry vehicle 

over the space capsules are easy to understand. 

"Lifting" reentry is achieved by flying from space to a conventional horizontal 

landing, using a blunt half-cone body, a wingless body, or a vehicle with a delta planform (like the shape of the current Space Shuttle), taking advantage of any of these 

configurations' ability to generate body lift and, thus, fly. We could not put conventional straight or even swept wings on these vehicles because they would burn off cluring reentry -although a delta planform with a large leading-edge radius might ~ork. 

These kehicles, or lifting bodies as we calletl them, woulcl have significant glide capahilitj down-range (the direction of their orbital tracks) andlor cross-range (the direction across their odjital tracks) due to the aerodynamic lift they could pmduce 

during reentry. 

Space capsules, on the other hand, reenter the Earth's atmosphere on a ballistic 

trajectory and decelerate rapidly due to th~ir high aerodynamic drag. In short, 

although capsules can produce small amounts of lift, they also generate large amounts 

of drag, or resistance. Space capsules are subject to high reentry forces due to rapid 

clecelrration, and ~hej have little or no maneuvering capability. Consequently, rapsules must rely on parachute landings primarily along the orbital flight path. 

In contrast, a lifting body's ability to produce lift and turn right or left from the 

orhit would allow any one of nlany possible landing sites within a large landing zone 

on both sides of the orbit on the return to earth. Furthermore, deceleration forces are 

significantly reduced with a lifting-body vehicle, from ahout 8g to 2g. The lifting-body 

landing "footprint" for a hjpersonic vehicle-that is, one with a speed of Mach 5 or 

greater and a lift-to-drag ratio of 1.5-inclutles the entire western United States as 

well as a major portion of Mexico, a significant improvement over that of a capsule. 

The prospec*t of achieving these advantages of lifting reentry was rather exciting, given 

the limited capahility of ballistic reentry capsules. 
WINGLESS FLIGHT 

Free-Flight Model of the M2-F1 Lifting Body 

Fascinated by the possibility of an airplane that flies without wings, I began talking in 1962 to other engineers and engineering leaders at the NASA Flight Research 

Center and at the NASA Ames and Langley research centers. I found skepticism to be 

abundant, many believing, as various design studies at the time had suggested, that 

some sort of deployable wings would be needed to make a lifting body practical for 

landing. Some of the most conservative clesign studies, not content to stop with deployable wings, even suggested that deployable turbojet engines should he used. 

Obviously, the space and weight allotment in these designs left little, if any, allowance 

for payloads. Even more design reports on lifting botlies gathered dust on library 

shelves as even more decisions were made to use symmetrical reentry capsules for 

spacecraft programs. 

About this time, it occurred to me that for lifting bodies to be considered seriously for future spacecraft designs, some sort of flight demonstration would be needed to 

boost confidence among spacecraft designers regarding lifting bodies. At first, I 

limited myself to launching countless paper lifting-body gliders down the halls, 

while behind my back passersby sometimes rolled their eyes and made circling-finger-at-temple motions. Then, as much to satisfy my own growing curiosity as to 

demonstrate lifting-body flight potentials to my peers, I constructed a free-flight 

model in a half-cone design that was very similar to what would later become the 

M2-F1 configuration. 

I made the frame with balsa stringers and the skin out of thin-sheeted balsa. 

Adjustable outboard elevons and ac1justal)le vertical rudders made up the control system. I began with the center of gravity recommended in Eggers' design studies, then 

changed it with nose ballast. For landing gear, I used spring-wired tricycle wheels. 

I hand-glided the model into tall grass as I worked out the needed control trim 

adjustments. The model showed characleristics of evtreniely high spiral stal~ility. The 

effective dihedral (roll due to a side gust) was very high, and launching the model into 

a bank would cause it to roll immediately to the equikalent of a wings-level position. 

Expanding the flight envelope, I then started hand-launching the model from the 

rooftops of buildings for longer flight times. The outer ele~ons were effecatike I~ut not 

overly sensitive to adjustnierits for longitudinal trim and turning control. 

Experimenting with the vertical rudders, I found the roll response very sensitike to 

~ery small settings of the rudders. In these first flights of the model, I did not experiment with body flaps. The model had a steep gliding angle, but it would remain 

upright as it landed on its landing gear. 

Next, I towed the model aloft by attaching a thread to the upper part of the nose 

gear, then running as one does in lifting a kite into flight. The model was exceptionally stable on tow by hand. Naturally, I then thought of towing the model aloft with a 

gas-powered model plane since I just happened to have a stable free-flight model that 

I had used successfully in the past to tow free-flight gliders. 
THE ADVENTURE BEGINS 

Attaching the tow-line on top of the model's fuselage, just at the trailing edge of 

the wing, created minimum effect on the tow plane from the motions of the glider 

behind it. After sufficient altitude was reached for extended flight, a free-flight vacuum timer released the lifting-body glider from the tow-plane. All flights of the model 

were done at Pete Sterks' ranch east of Lancaster, an area where most of the NASA 

Flight Research Center employees lived at the time. From Sterks's ranch, I had also 

flown other model airplanes as well as my 65-horsepower 1,uscombe light plane. 

I found the inherent stability of the M2-F1 lifting-body model, both in free flight 

and on tow, very exciting-so much so that I knew it was time to make a film to show 

my peers and bosses just how stable it was in flight. To film the flight of the M2-F1 

lifting-body model, I enlisted the help of my wife, Donna, and our 8mm camera. We 

made the film on a nice, calm weekend morning at Sterks' ranch. While I prepared the 

tow-plane and the M2-F1 model for launch, Donna stretched out on the ground on her 

stomach to film the flight from a low angle, making the M2-F1 model look much larger than it actually was. 

Both the flight and Donna's film-making were successful, the film showing the 

M2-F1 stable in high tow, then gliding down in a large circle after the timer released 

it from the tow-plane. The lifting-body model reached the ground much sooner than 

did the tow-plane because the lifting body's much lower lift-to-drag ratio gave it a 

much steeper gliding angle. The M2-F1 made a good landing on Sterks' dirt strip, 

while the tow-plane landed unharmed in the alfalfa field next to the landing strip. 

Since I was just getting started in radio control at the time, I used the free-flight 

approach in these early flights to keep things lightweight and simple. Later, I towed 

the M2-F1 lifting-body model with a radio-controlled tow-plane. 

Starting a Lifting-Body Team 

My mounting enthusiasm began to nib off on my peers at the NASA Flight 

Research Center. The first to join my lifting-body cause was a young research engineer named Dick Eltlredge. (In fact, we were all young at the time.) A graduate of 

Mississippi State's aeronautical engineering department, Dick had been a student of 

an aerodynamicist named August Raspet, who had established a flight-test facility at 

a landing strip near the university where he involved many of his students, inc.lutfing 

Dick, in flight research. As a result, Dick had brought with him to the NASA Flight 

Research Center a great deal of skill and enthusiasm regarding the aerodynamics and 

structures of aircraft design. 

Having built three gliders on his own, Dick had excellent skills in design and fabrication of structures in welded steel, wood, and aluminum sheet-rnetal. At the time, 

the NASA Flight Research Center aTso had a small "Skunk Works" second to none in 

its skillet1 machinists, aircraft welders, sheet-metal workers, and instrument builders. 

Dick knew each of these craftsmen personally, not just at work hut much more through 

contact with them on the weekends, many of these NASA craftsmen also being 

involved with their own airplane-huil(1ing home projects. 
WINGLESS FLIGHT 

Dick Eldredge and Dale Reed resting their arms on the M2-Fl. In the background is a Space Shuttle, which 

benejitedfrom lifting-body research. (NASA photo EC81 16283) 

Dick Eldredge and I made a strange but good team. Since I was tall and he was 

very short, some people thought of us as a "Mutt & Jeff" duo. Together, we would critique and challenge each other's ideas about how to solve design problems until we 

mutually came up with the best solutions. We never wasted time belaboring the problem but, after agreeing on a solution, went on to the next design challenge. I always 

thought of Dick as my "little buddy." 

Dick and I enjoyed bouncing ideas off one another for new aircraft designs. At the 

time, the British Kramer Prize had not yet been awarded for the world's first man-powered airplane. Each year, the prize became more enticing to us as it grew in size to 

$100,000 and opened to persons beyond Britain throughout the world. At lunchtime, 

Dick and I plotted and schemed on how we could win the Kramer Prize. Dick had 

done a lot of research on the various British designs that, while they could fly in a 

straight line, could not make the required figure eight. Most of these designs included hundreds of parts and took hundreds of hours to build. Dick and I agreed that the 

winning design would have to have very low wing loading and be simple to build and 

repair. Unfortunately, we both were young enough to have growing families that 

required a great deal of our time at home, so Dick and I never had the time or means 

for an after-hours project of the sort that might win the Kramer Prize. 
THE ADVENTURE BEGINS 

However, Dick and I had a mutual friend in Paul McCready of Pasadena, who, 

about the time we were forced to abandon our man-powered project, got his family 

involved in a similar project, helped along by a number of volunteers with skills in 

model-building and bicycle-racing. McCready put into action the low wing loading 

and simple structural approach that Dick and I had only been able to talk about. 

At Taft, not too far from Edwards Air Force Base, McCready demonstrated the 

world's first man-powered flight with the Gossamer Condor. His &st flight tests of the 

Gossamer Condor, in fact, had been at Mojave, just down the road from Edwards AFB. 

McCready went on to build a second craft called the Gossamer Albatross, which the 

bicyclist Bryan Allan piloted across the English Channel.? 

Afterwards, I worked with McCready and a backup Gossamer Albatross on a flight 

research program at the NASA Flight Research Center, having gotten approval to 

Proposed Ames M2-Fl, MI-L half-cone, and Langley lenticular bodies. Dale Reed and Dick Eldredge proposed testing the three shapes using a common internal structure for all of them. (NASA photo E62 8933) 

7. See M. Grosser, "Building the Gossamer Albatross," Technology Review 83 (Apr. 1981): 52-63; 

Paul McCready, "Crossing the Channel in the Gossamer Albatross," Society of Experimental Test Pilots, 

Technical Review 14 (1979): 232-43. 
WINGIESS FLIGHT 

make this official NASA project to measure the aerodynamic characteristics of the aircraft with lightweight research instrumentation installed at the Flight Research 

Center. This successful program resulted in a published report on the aerodynamic 

characteristics of the Gossamer Albatross.8 

As a team, once we both were bitten by the lifting-body bug, Dick and I developed a research plan for testing three lifting-body shapes with a common structural 

frame housing the pilot, landing gear, control system, and roll-over structure. The 

three lifting-body shapes were the Ames M2-F1, the MI-L half-cone, and the 1,angley 

lenticular. 

The lenticular lifting-body shape was particularly intriguing because, to many of 

us, it immediately calls to mind the popular flying-saucer portrayed by the media as 

the spacecraft of extraterrestrials. My wife, Donna, however, had her own special 

appreciation of the lenticular shape, dubbing it the "Powder Puff." 

All three of the lifting-body shapes were based on some sort of variable geometry. 

The M2-F1 was a 13-degree half-cone that achieved transonic stability by spreading 

its body flaps much like what's done by a shuttlecock in the game of badminton. The 

MI-L was a 40-degree half-cone that achieved a better landing lift-to-drag ratio by 

blowing up a rubber boat tail after it slowed down. The lenticular lifting-body would 

transition to horizontal flight by extending control surfaces after making reentry much 

like a symmetrical capsule. 

Our concept was to construct the shapes srparately, building three wooden or 

fiberglass shells that could attach to an inner structure common to all three shapes. Tf 

we could build the vehicles to be light enough, they could be towed by ground vehicles across the lakebed before being towed aloft by a propeller-tlriven tow-plane. 

Dick suggested a control system that I liked instantly: a mechanical way of mixing controls that was similar to what is done now in modern high-tech aircraft bq digital electronic control systems. The scheme was to connect a swashplate on the aft end 

of the steel-tube structure to the pilot's control stick and rudder petlals. The swashplate, piloting on one universal joint, took up various positions, depending on the 

combination of roll, pitch, and yaw commands the pilot sent to the front side of the 

swashplate. With push rods hooked up to different locations on the backside of the 

swashplate, and to the horizorltal and-vertical control surfaces on the aft end of the lifting-body shapes, any combination in control-mixing could be achieved. These controls could be altered easily during the flight-test program or changed to fit another 

lifting-body shape. 

8. Henry R. Jrx and David G. Mitchell, "Stalility and Control of the Gossamer Human-Powerecl 

Aircraft by Analysis and Flight Test" (Washington, D.C.: NASA Contract Rrport 3627, 1982). 
THE ADVENTURE BEGINS 

Milt Thompson Joins the Lifting-Body Team 

Fired by enthusiasm, Dick arid I kept charging clown the design road with the lifting-botfy research vehicles so that we could make a pitch to our boss, Paul Bikle, to 

gain his support for a lifting-body program. One day I told Dick, "You know, if we had 

a pilot on our tram, we would have a much better chance of selling the program concept." Then, we talked to Milt Thompson, whom we saw as the NASA test pilot most 

like11 to be interested in our project. 

Milt was a skilled pilot with a distinguished hat.kground as a Naval aviator, 

Boeing flight-test pilot, and NASA research pilot. As one of the twelve NASA, Air 

Force, and Navy pilots who flew the X-15 between 1959 and 1968, Milt had fourteen 

flights in the rocket-powered aircraft to his credit, reaching on separate occasions a 

maximum speed of 3,723 mph and a peak altitude of 214,000 feet. 

Earlier in 1962, before Dick and I talked to Milt about the lifting-body project, 

the Air Force had selected Milt to be the only civilian pilot for thr X-20 Dyna-Soar 

program scheduletl to launch a man into earth orbit and recover with a horizontal 

ground landing, a program later canceled shortly after construction had hegun on the 

X-20 vehicle. Not having an ego problem, Milt loved flying unl~sual or unorthodox aircraft configurations as varied as the rocket-powered X-15 and the ungainly Paresev, a 

vehicle designed and built at the NASA Flight Research Center's "Skunk Works" to 

test the Rogallo Wing concept for spacecraft recovery. 

Milt was easy to talk to and could relate readily to flight research engineers. Very 

methodical in planning flights, he did not take risks beyond the unavoidable ones normal for first-time aircraft configurations, a characteristic that earned him high regard 

from both pilots and project managers. A handsome, wild, and wonderful guy, Milt had 

a winning personality and persuasive cham. All the women seemed to be in love with 

him. Popular, he was a friend to everyone. Dick and I knew that Milt was the guy who 

could help us sell the lifting-bod) program. 

We presented to Milt our idea for testing lifting bodies, asking him if he w-ould join 

us ant3 fly a lifting body-if and when we got one built. Without hesitation, he gave us 

a solid "yes." Now we were a team of three. 

The three of us put our heads together to decide on the next step to take in promoting our program. Milt suggested that if we had one of the originators of the liftingbody reentry concept on our side, we could move our cause along more rapidly. 

I phoned A1 Eggers at the NASA Ames Research Center, located at Moffett Field 

in northern California, and described our idea to him. Very enthusiastic, Eggers asked 

how he could help. At the time, Eggers was a tfivision head at Ames in charge of most 

of the wind tunnels. We were going to need a lot of support in wind-tunnel tests if we 

were to figure out how to fly these crazy aerodynamic shapes. 

Telling Eggers that we were preparing a pitch to sell the idea to Paul Bikle, I 

asked him if he would like to hear the pitch. "Definitely," he replied. We arranged a 

meeting at the Flight Research Center so we could present our idea to both Paul Bikle 

and A1 Eggers. 
WINGLESS FLIGHT 

I presented a simple program plan for building the vehicles in the "Skunk Works" 

shops at the Flight Research Center, instrumenting the vehicles, and then flight-testing them to measure stability, control, and other aerodynamic characteristics in flight. 

After I presented the preliminary design drawings that Dick and I had made, I showed 

the film that my wife had made of my model M2-F1 flights. 

Milt Thompson's endorsement of the plan pushed it over the crest. We received a 

hearty "yes" from both Bikle and Eggers. Eggers offered full use of the wind tunnels 

for getting any data needed to support the program if Bikle would be responsible for 

developing and flight-testing the lifting-body vehicles. It was agreed as well, Ilowever, that we would take it one step at a time, starting with the M2-F1 configuration ant1 

huil(1ing it as a wind-tunnel model to be tested in the 40-by-80-foot wind tunnel at 

Ames. 

Armed with a cause and fired with enthusiasm, we found ourselves gaining more 

and more support from our peers. We even came up with an unofficial motto for our 

lifting-body reentry vehicle project: "Don't be rescued from outer space-fly bark in 

style." With the space program then dependent on the ballistic capsules, the astronauts were being fished out of the ocean, sometimes nearly drowning in the process 

and usually after some degree of sea sickness. Wen Painter-later a prominent engineer in the rocket-powered lifting-body program--drew a cartoon depicting the difference the lifting-body reentry vehicle would make in how astronauts would return to 

earth, his cartoon showing the astronaut landing at an airport in style, greeted hy a 

reception hostess. 

If the great enthusiasm of the builders at the NASA Flight Research Center 

resulted in a wind-tunnel model capable of actual flight, well, as Bikle noted, that 

would be something simply beyond the control of management. Later, we would go 

through the official process of getting approval from NASA Headquarters for flying the 

vehicle. In the meantime, we decided to get to work while everyone was enthusiastic 

and ready to start. With this decision, the lifting-body program was launched. 

CHAPTER 2 

"FLYING BATHTUB" 

Our goal was to design and built1 a very lightweight vehicle that could he towed 

across the lakebed with a ground vehicle and, later, aloft with a light plane, the way 

sailplanes are towed. Based on the tiny model used in the filmed flights, the first lifting-body vehicle was also called the M2-F1-the "Mu signifying a manned behicle 

and the "F" designating flight version, in this case the first flight bersion. 

Months before the M2-F1 was completed, it had already been duhbed the "flying 

hathtul)" by the media. The first time seems to have been on 12 November 1962 in the 

Los Angeles Times article "'Flying Bathtub' May Aid Astronaut Re-entry." The article included a photo of Milt Thompson sitting in a mock-up of the M2-F1 that, 

indeed, looked very much like a bathtub. 

Paul Rikle decided to run the project locally, financing it entirely from discretionary funds. He thought that a volunteer teain at the NASA Flight Research Center, 

supplemented with local help as needed, could build the M2-F1 faster and cheaper 

than NASA Headquarters could through a major aircraft company. As history proves, 

Bikle was right. 

The M2-F1 was built entirely in four months. Engineers at the Flight Research 

Center also kept the cost of designing, fabricating, and supporting the M2-F1 to under 

$30,000, about the cost of a Cessna. At the time the M2-F1 was huilt, someone associated with a major aircraft company was cited anonymously as saying that it would 

have cost an aircraft company $150,000 to build the M2-F1. The extremely low-cost 

M2-F1 program would have invaluable results later, proving to be the key unlocking 

the door to further lifting-body programs.' 

A Matter of Teamwork: Building the IVi2-F1, 1962-1963 

After our meeting with Paul Bikle and A1 Eggers, we were swiftly swept up into 

the enthusiastic atmosphere of the lifting-body program. On his return to the NASA 

Ames Research Center, Eggers asked Clarence Syvertson, his deputy, to coordinate all 

wind-tunnel tests that we needed in support of our design and flight-planning activities. Meanwhile, at the NASA Flight Research Center, Bikle asked me to put together a team to design and fabricate the first lifting-body vehicle. 

Long before I began to put together that team, Dick Eldredge and I had already 

fairly much agreed that the hasic design would include two structural elements, a core 

1. Stephan Erlkinson, "The 1.egacy of the Lifting Body," Air dl: Spnre (April/Maj 1991), p. 51; 

Fldllion, On the Frontier, p. 149. 
"FLYING BATHTUB" 

M2-Fl jin fabrication by Grierson Hamilton, Bob Green, and Ed Browne. (NASA photo E94 42509-13) 

steel-tube structure and a detachable aerodynamic shell. However, the real work lay 

ahead of us in the detailed design of the hundreds of parts needed for the 

actual vehicle. 

To do this work, I selected a design-and-fabrication team made up of four engineers and four fabricators, all of whom were aircraft buffs involved with home-building their own airplanes, most of them members of the Experimental Aircraft 

Association. These individuals had worked together to some extent on previous programs in the Flight Research Center's unofficial "Skunk Works." The group's chief 

designer was Dick Eldredge. To lead the team, we got Vic Horton, a no-nonsense operations engineer who took pride in keeping to schedules. 

Horton picked up a few extra part-time volunteers as the work got underway. 

Hardware designers, besides Eldredge, included Dick Klein and John Orahood. Meryl 

DeGeer calculated stress levels in the structure to verify the adequacy of the design. 

Ed Browne, Howard Curtis, Bob Green, Grierson Hamilton, Charles Linn, George 

Nichols, and Billy Shuler fabricated the internal steel-tube carriage of the M2-F1 as 

well as its aluminum sheet-metal tail fins and controls. 
WINGLESS FLIGHT 

Once we had the initial team, we needed a place to work. We sectioned off a corner of the fabrication shop with a canvas curtain, labeling it the "Wright Bicycle 

Shop." Indeed, we felt very much like the Wright Brothers in those days, working at 

the very edge between the known and unknown in flight innovation. In the "Wright 

Bicycle Shop," we put the drafting boards next to the machine tools for maximum 

communication between designers and faltric.ators. This strategy worked extremely 

well. A fabricator could lean over a designer's drafting board and say, "I could make 

this part faster and easier if you would change it to look like this." 

I think our project was Bikle's favorite at the time. We would see him at least once 

a day, and we got a great deal of extra attention from him. A few chose at the time to 

grumble about Bikle acting as if he were the super project engineer on the M2-F1, but 

I think that we thrived as a team from his presence. For one thing, I have never since 

seen on later projects enthusiasm or morale as high among team members as existed 

on the M2-F1 project. In fact, it really isn't an exaggeration to say that we had trouble keeping the team from working through lunch, during the evenings, or 

on weekends. 

The M2-F1 project also benefited from Bikle's experience and suggestions. While 

we didn't have to use his suggestions, we did need to have good reasons for not using 

them. A time when one of his suggestions helped us a great deal-and there were 

many such times-was when we had everything else thought out and had begun trying to decide how to build the aerodynamic shell. 

The core of the dilemma had to do with the shell's weight, which we hoped to keep 

under 300 pounds, wanting a vehicle of minimum weight so that the M2-F1 would fly 

slowly enough that a ground vehicle could tow it aloft. Dick Elclredge and I were 

thinking about building the shell out of fiberglass, but we weren't sure we could keep 

the weight within necessary limits. 

We knew that our vehicle design lent itself easily to being built in two different 

locations by two different teams, the two main assemblies being joined later. We knew 

that we could build the internal steel-tube carriage, tail surfaiaes, and controls in our 

NASA shop while the outer shell was being built elsewhere by a second team. But 

where and by whom? 

Bikle suggested that we taIk to a sailplane builder named Gus Briegleb, who operated an airport for gliders and sailplanes at El Mirage dry lake, 45 miles southeast of 

Edwards Air Force Base. Bikle also suggested that he might be able to find enough 

money in his discretionary fund to contract Briegleb to build the shell for us out of 

wood. 

One of the nation's Iast artisans building aircraft out of wood, BriegIeb had founded the Briegleb Glider Manufacturing Company during World War I1 to design and 

build wooden two-place trainer gliders for Army pilots being trained to fly troopassault gliders. The two-place trainer gliders were used to train these pilots to fly in 

formation on a tow-line and performing precision dead-stick landings after release 

from Navy R4D tow-planes (same as the Air Force C-47). The troop gliders were used 

extensively during the Allied invasion of France, with the Briegleb Glider 
'TLYING BATHTUB" 

Manufacturing Company being one of only a few companies manufacturing 

the trainers. 

In 1962, when we contacted him, Gus Briegleb was trying to keep alive the art of 

fabricating wooden airplanes by selling kits of a high-performance sailplane that he 

had designed. Between selling these kits and operating the glider-sailplane airport at 

El Mirage, Gus was making a living, but he definitely was not getting rich. 

Briegleb responded enthusiastically when we approached him about building the 

M2-F1 shell out of wood. Although wood eventually gave way to aluminum sheetmetal in the production of aircraft for a good number of excellent reasons, wood is still 

one of the more efficient structural materials for aircraft in terms of fatigue life, vibration damping, and strength-to-weight ratios. Briegleb initially proposed to build the 

shell out of wood for only $5,000. 

Thinking that sum was too low, Bikle asked Briegleb if he had considered overhead, profit, and unforeseen problems that were likely to arise during the building of 

the shell. A builder, not a businessman, Briegleb admitted he had not considered 

these things. Bikle said that he could authorize up to $10,000 for the wooden shell, 

that being at the time the limit for small purchases at the NASA Flight Research 

Center. Briegleb agreed to meet the 300-pound target weight and the strength specifications that Dick Eldredge and I had determined from airload calculations, and he 

agreed to deliver the shell four months from the date the contract was signed. 

Wooden shell of M2-F1 at El Mirage, seen from the rear. (NASAphoto E94 42509-10) 

22 
WINGLESS FLIGHT 

When Briegleb got into the detailed design process, he fount1 that the shell would 

have to he far more complicated than he had originally thought to keep it to the specified weight. He had underestimated the hours needed to build the shell by at least a 

factor of three. The shell had to be made with two internal keels to cany the loads to 

the steel-tube frame. Hundreds of small wooden parts made up these built-up wooden keels. To support the outer skin shape, the keels also had multiple internal crossbracings made of miniature wooden box beams of webs and spar caps, all nailed and 

glued together. 

When we saw the predicament that Rriegleb was in, we sent him some help: Ernie 

Lowder, a NASA craftsman who had worked on building Howard Hughes' mammoth 

wooden flying-boat, the Spruce Goose. Despite having Lowder as a full-time fahricator, Rriegleh says he still ate quite a bit of the $10,000 contract. Nevertheless, 

Rriegleb was very proud of his work, and so were we. He delivered the shell to us on 

time, at cost, and slightly under the 300-pound weight limit. I think we gained a great 

advantage by being able to use the last of America's finest wooden-airplane craftsmen 

to build the shell of the M2-F1. 

As Briegleb's team built the outer shell, NASA craftsmen built the internal steeltube structure. The steel-tube carriage was finished first, in about three months, and 

~hile the wooden shell was still being fabricated at El Mirage, the carriage was being 

rolled around on the landing gear. Eldredge and I had d~signed the M2-F1 so that it 

took only four bolts to attach Briegleb's shell to the internal structure. 

Team Three for Analysis 

Once the two teams wTere in place and building the two main structures of the M2- 

F1, I realized we also needed a third team to do the analysis on aemdynamics, control rigging, and characteristics of stability and control to support flight tests. Using 

the wind-tunnel data on small-scale lifting-body models that I+e were beginning to get 

from the NASA Anles Research Center, I could determine the basic *tic-k-to-surface 

gearing in pitch for the outer elevon surfaces and the upper hotly flap. Rotating the 

lifting body nose-up to moderate angles of attack anlplified to high angles the flow on 

the aft sides of the bulbous M2-F1 shape. 

Tufts of yarn on the small-scale wind-tunnel model had indicated that its outer 

elevon surfaces experienced about twice the change in angle of attack experienced by 

the model's nose. Consequently, I specified gearing for the outer elevons to move three 

times more than the body flap with fore and aft travel of the pilot's control stick. I did 

this so that, when a rlifferential roll side input was made from the pilot's stick, there 

would be no risk of stalling an elevon surface, causing reversal of the roll or loss of 

control of the vehicle during the roll. 

Determining control rigging and gearing for turn control was not as obvious as that 

for pitch control. The M2-F1, and aln~ost all of the later lifting bodies, have extremely high dihedral-that is, with wind from the side (called "sitleslip"), the vehicle 

wants to roll in the opposite direction. Because of this characteristic, rudder deflec- 
"FLYING BATHTUB" 

tions actually resulted in roll rates higher than those produced by differential elevon 

deflections. Since lifting bodies also have extremely low roll damping from having no 

wings to resist roll rates, and since Dutch roll results from the extremely high dihedral inherent in most lifting bodies, we had a potentially dynamic problem in stability and control if we did not do the right thing in designing the control system. 

Obviously, we needed help from the experts in stability and control at the NASA 

Flight Research Center, all of whom were currently working on the X-15 program. In 

its later stages after three years, the X-15 program still had number-one priority at the 

Center. Because the X-15 program was so well organized and ran so smoothly by that 

time, many aspects were getting to be routine, even though there were still some surprises showing up during the speed and altitude buildup as the flight envelope was 

being expanded. Our unofficial lifting-body project was able to recruit the help it 

needed, despite the on-going X-15 program, thanks to Bikle's policy that the NASA 

Flight Research Center had an equal responsibility to aeronautical research directed 

to the future. 

Ken IZiff,$rst member of the lifing-body analytical team, with Dale Reed. (NASA photo E66 15469) 

24 
WINGLESS FLIGHT 

My first volunteer was Ken Iliff, now the Chief Scientist at NASA Dryden, who at 

the time was a bright and enthusiastic twenty-one-year-old engineer just out of college 

and doing a mundane analytical task in reducing X-15 flight data. Iliff poked his head 

in the office where Eldredge and 1 were working and, after inquiring what we were 

doing, asked if there was anything he could do to help us out. "Sure!" I replied quickly, not one to refuse any help T could get. 

After explaining to Iliff that we planned to get a high-speed ground-tow vehicle to 

tow the full-scale M2-Fl model across the dry lakebecl, I asked him to take a stab at 

calculating what the rotation and lift-off speeds w-ould be on ground-tow, information 

we needed in determining the requirements for the tow vehicle. We could have a problem, I explained, if the aerodynamic pitch controls were not strong enough to lift the 

nose, overcoming the nose moments from the wheel drag and the tow-line force. 

Iliff got busy. He calculated rotation speed to be 59 miles per hour and lift-off 

speed to be 85 miles per hour. Later, when we actually ground-towed the M2-F1, we 

measured rotation speed at 60 miles per hour and lift-off speed at 86 miles per hour. 

Needless to say, we were impressed with this young engineer. 

MathematicaI Voodoo 

Although he continued to maintain his obligations to the X-15 program, Iliff 

became more and more involved in our little lifting-body program. He started looking 

at the stability and control characteristics of our strange bird-just in case we did try 

to fly the M2-F1 following the full-scale wind-tunnel tests. Iliff sought help from his 

mentor, Larry Taylor, another engineer then studying pilot-control proble~ns on the 

X-15 who was experienced in applying some of the latest techniques in analyzing 

stability and control problems on new aircraft configurations. Although Taylor 

had applied some of those techniques to the X-15 with success and gained the 

credibility of a number of his aerospace peers, some of the old-time flight-test engineers, including Paul Bikle, considered Taylor a radical practicing a kind of 

engineering witchcraft. 

Taylor claimed he could use mathematics to describe the piloting characteristic 

of a test pilot, then predict the outcome of a planned flight. He called this the "human 

transfer function." Bikle disagreed, saying there was no way to predict how a pilot 

I+-ould perform on any one day, emphasizing that a pilot's performance was impacted 

by events in his personal life, such as haling a spat with his wife or partying the night 

before a flight. 

I felt both viewpoints had valitfity. I agreed with Taylor's viewpoint that there are 

fundamental differences in how individual pilots react to a difficult control task. In a 

stressful situation that leads to problems with pilot-induced oscillation, the gains of 

some pilots rise much faster than those of other pilots. An aircraft can go out of control if it has a tendency to oscillate in a particular direction, especially if the pilot tries 

to stop the oscillation by chasing the aircraft with the controls. Sometimes the airplane 

will halt the oscillations on its own if the pilot will slow down or stop moving the con- 
"FLYING BATHTUB" 

trols. However, this is not the usual or most natural reaction for a pilot during a stressful situation, for as arm and leg muscles tighten up from stress, control movements 

usually increase. 

The master sorcerer of mathematical voodoo, Larry Taylor, was at the time passing his mystical art on to his apprentice, Ken Iliff, especially a strange engineering 

plot called "root locus" that many pilots then thought was pretty far-out stuff. The 

three categorical ingredients of this mathematical potion were the aiq~lane's aerodynamics, inertial data composed of weights from all parts of the ail-plane, and flight conditions such as speed, altitude, and angle of attack. The root-locus plot gave results 

for different types of pilots, ranging from the totally relaxed pilot who does nothing 

wjth the controls to the high-gain pilot who moves the controls rapidly. 

One magical point on the plot called the pole represented the "do-nothing" pilot. 

Another magical point called the zero represented the high-gain pilot or autopilot. A 

line connec*ted these two points, representing all pilots between the two extremes. If 

the line moved into the right side of the plot, the pilotlaircraft combination was 

deemed unstable. predicating loss of control of the aircraft. Despite the fact that in the 

early 1960s even a number of engineers considered the root-locus analysis to be some 

sort of witchcraft, today root locus is a common mathematical tool used by stability 

and control engineers. 

According to Rob Kempel-then with the Air Force and later a stability and control engine~r at the NASA Flight Research Center with considerable influence on the 

design of control systems for experimental piloted and unpiloted NASA aircraft-root 

locus is a tool by which engineers can predic-t potential instability prior to flight so that 

a possibly catastrophic situation can Ite avoided by either pilot training or modification of the flight control system. "The intent of the engineer," says Kernpel, currently 

acti~e in control-system designs, "is to provide the test pilot with a pilotlairplane combination that will remain stable, regardless of pilot gain," workload variations, or 

emergency control situations. 

Ke11 tutored by Taylor in this technique, Iliff set off to predict the M2-Fl's qualities during flight. He rriodeled the lifting body nnathematically for free-flight as well 

as for flight while on to\+. He found that the tow-line force was quite high in opposing 

the high drag of the lifting body, adding a high level of static stability to the system, 

much like towing a high-drag target behind an aircraft. 

Ahout this time, two more volunteers showed up whose help would I)e invaluable 

on the M2-F1. Bertha Ryan and Harriet Smith, two junior engineers who did not have 

strong obligations to the X-15 program, asked me hat they could do to help. In getting Rjan and S~~iith as well as so many other volunteers, I was enjoying a hit of luck. 

The 50 percent of the work force at the NASA Flight Research Center not committed 

to the X-15 program wasn't being taxed fully in support of other official NASA programs. Even in those days, bureaucratic methods of operation caused tremendous lags 

to appear between approval and funcling cycles. Furthermore, peaks and valleys in 

workloads occurred at the field stations whenever NASA Headquarters approved, 
WINGLESS FLIGHT 

turned down, or canceled a program, no matter how well the field managers scheduled work. 

I was one of those Johnny-on-the-spot opportunists who would move in with my 

small program to take advantage when valleys appeared in workloads. Most supervisors liked to keep their people busy, and it didn't hurt the lifting-body project one bit 

to have the local director interested enough in our project to send us new volunteers. 

Bikle had encouraged Ryan to work with us, knowing that since she owned her own 

sailplane, she would have practical as well as analytical skills useful to the project. 

Although engineers today are as often women as they are men, women engineers 

were not common in the early 1960s. After they volunteered on the M2-F1 project, I 

explained to Ryan and Smith that Milt Thompson wanted some sort of simulator for 

practice before flying the M2-F1. Good friends, Ryan and Smith thought the task 

would be fun. They also liked the idea of working as an all-woman simulation teamperhaps one of the first for those times-with Ryan preparing the aerodynamic data 

input and Smith mechanizing the simulation. Neither of them had ever set up a flight 

simulator before, but they felt that while the task would be challenging, they could 

also learn quite a bit by doing it. Actually, all of us were fairly naive about simulators 

in those days, even though a simulator had been set up for the X-15. 

Harriet Smith, a member of the lifting-body simulation team and also of the analytical team. (NASA photo 

E58 3731) 
"FLYING BATHTUB 

Bertha Ryan, another member of the lijting-body simulation team and also of the analytical team. (Private 

photofurnished by Bertha Ryan, NASA photo EC97 44183-2) 

28 
WINGLESS FLIGHT 

When Eldredge and I had designed the M2-F1 control system to be flexible, we 

hati thought we were being clever, never realizing that we created a veritable 

Pandora's box. Instead of having just one version of the M2-F1 to set up on the simulator, we had as many as five, one for each way our variable control system could be 

hooked up in its swashplate design. 

We had six control surfaces on the rear of the vehicle that we could hook up in 

any combination to the stick and rudder pedals for pitch, roll, and yaw control-two vertical rudders, two outboard elevons that we called "elephant ears," and 

two horizontal body flaps at aft top. We also had a removable center fin, but no lower 

body flaps. 

Most of the simulators used at that time were purely analog, requiring 30 or 40 

hand-adjusted electrical potentiometers (called "pots") to he set up for each simulation session. It was very easy to make a mistake while setting up these pots, especially by setting a switch to give a minus instead of a plus sign, or vice versa. The only 

way to guarantee a correct simulation was to require a verification process for each 

simulation session. Despite their inexperience in setting up a simulation, Ryan and 

Smith were very methodical. They kept good notes and records, working hard at doing 

a good job. 

Since pitch control did not seem to be a problem on the simulator, we spent much 

of our time trying to determine the best way to control roll and yaw on the M2-F1. 

Early on, we decided to eliminate the center fin as well as the differential control on 

the body flap. The center fin only made the already high dihedral even higher. 

Besides, we already knew from small-scale wind-tunnel tests that we had plenty of 

directional stability from the two vertical side fins. By making the body flap singlepitch rather than split, it couId be used like an elevator, eliminating the need for the 

center fin as a fence against adverse yaw from a body-flap elevon system. The shop 

team members had already fabricated a two hody-flap system, but by the simple expedient of bolting the right and left flaps together, they made one large flap. 

We had narrowed the lateral-directional control system down to two basic possible schemes. In the first control scheme, right stick deflection would move the outer 

elevons for roll to the right, and the right rudder pedal would move both vertical rudders to the right. In the second control scheme, right stick deflection would move both 

verticaI rudders to the right, and the right rudder pedal would move the outer elevons 

for roll to the right. Working with us as a part of the analytical team by flying the simulator in the ground cockpit, Milt would give us a pilot's rating for each of the configurations we investigated. His rating system was on a scale o_f one to ten, depending on 

the difficulty of changing and holding headings. 

Eldredge and I had fairly much made up our minds in favor of the first control 

scheme, intuition having told us that elevons or ailerons should be controlled by the 

stick while rudders should be controlled by the rudder pedals. Qk were shocked when 

Milt told us that he preferred the second controI system. His reasoning was that roll 

rates resulting from the rudders being deflected were twice as high as those resulting 

from differential elevon deflection. Milt felt that he could control the vehicle by using 
"FLYING BATHTUB" 

M2-F1 simulator cockpit. (NASA photo E63 10278) 

30 
WINGLESS FLIGHT 

proper piloting technique, and he said he would rather have the higher roll rates available to him if he needed them. 

If any research pilot could use proper piloting technique, it was Milt Thompson. 

He was a cool, disciplinetl ~ilot who could think well {luring emergencies or under 

other stressful conditions. He had alreatly proven several times during the X-15 program that he could and would work closely with engineers in solving potential flight 

problems. He also liked to understand fully the idiosyncrasies of an aircraft before he 

flew it. In my opinion, Milt Thompson belongs up there with Chuck Yeager in any estimate of historic greatness for test pilots. Milt Thompson not only had the same stickand-rudder skill and coolness under fire that Chuck Yeager had, but he also had a 

certain elegance in thinking when dealing with engineers. Milt had such an air of 

modest dignity and credihility about him-what today might be called "charismaMthat when he said he preferred the second control system for the M2-F1, we listened 

to him, even though we didn't necessarily like his choice. 

At this point, Iliff did a root-locus plot for both control systems. He determined 

that there was no problem involved with using the first control system, with its use of 

the elevons for roll control. However, he found there could be a large problem with the 

second system which used the rudders for roll control. With the second system-the 

one Milt preferred-the M2-F1 could be driven unstable in Dutch Roll, resulting in 

loss of control of the vehicle, if the pilot's gains were too high. Although Taylor was 

doing a good job in verifying the root-locus technique on the X-15 program, it was still 

too new to be accepted by others as a valid design or planning tool. Despite Iliffs conclusions, Milt still insisted on using the second control system. His plan for the firs1 

car-tow tests was to gently rotate the M2-F1 nose-up until it was flying a few inches 

off the lakebed before he made any rudder or control-stick inputs. Then, he would 

move the controls very slowly to test them out. If things didn't look good, he would set 

the vehicle back down on its wheels, and we could try the other control system. 

While the simulator is a wonderful tool in designing aircraft and planning flights, 

simulator results must he interpreted very carefully. A heavy smoker, Milt would sit 

in the simulator's cockpit totally relaxed, a cigarette in one hand, flying with the other 

hand. Under those conditions, unlike those of actual flight, he had no tendency toward 

driving the Dutch Roll mode unstal)lr, as Iliff had predicted he would in actual flight. 

During the month between the completion of the internal structure and the completion of the wooden shell, Vic Horton decided to test the ground stability and control of the internal structure with landing gear. The wheels and nose gear assembly 

were taken from a Cessna 150 light aircraft. The pilot steered by foot petlals through 

the nose gear. Milt being away on a trip, X-15 research pilot Bill Dana volunteered 

to sit in the pilot's seat while the structure was towed by automobile across the 

dry lakeberl. 

Dana was soon having a great time, sashaying hack and forth like a water skier at 

thirty miles an hour on a 300-foot to^-line behintl the autoniobile. Having good control of the steering, Dana was building a lot of confidence. Then, he pulled far over to 
"FLYING BATHTUB" 

one side and pulled the tow-release to test it out. Unfortunately, he had heen holding 

a large amount of rudder pedal to compensate for the side pull of the tow-line. 

Suddenly, the 1 ehicle veered sharply and started to roll over. Dana countered with 

the rudder pedal. A ~ild oscillation began, the M2-F1 steel-tube skeleton doing a 

wheely to the right, then a wheely to the left. Finally, Dana lost control, and the M2- 

F1 flipped over. Fortunately, the fabricators had huilt a strong rollober structure, and 

both pilot and vehicle came out of the episode without injury. Dana was embarrassed 

by the incident, and we kidded him mercilessly for years, saying we'd call on him 

again if we ever needed to run a manned structural test. 

Final assembly of the M2-F1 began when the wooden shell arrived from El 

Mirage. We lowerect the steel-tube internal structure, minus the landing gear, through 

a large rectangular cutout in the top of the wooden shell. We inserted the landing gear 

legs through holes in the shell and bolted them to the inner steel structure. Four bolts 

on the two wooden keels attached the shell to the inner steel structure. The aluminum 

tail surfaces, built in the NASA Flight Research Center shop, were then bolted onto 

the wooden shell, and controls were hooked up by push-pull rods. Finally, we attached 

to the shell a Plexiglas canopy, made by Ed Mingelle of Palmdale for the M2-F1 after 

Bikle recommended that we go to hiin since he was a specialist in making custom 

canopies for sailplanes. Exactly four months from the day when Bikle had told me to 

begin building, the completed M2-F1 rolled out of the "Wright Bicycle Shop." 

Diagmm sholc~ingcontributions of the various participants in M2-FI corutruction (original drawing by Dnlr 

Red, digitrrl versiorr by DrYderl Graphics Ofice). 

32 
WINGLESS FLIGHT 

M2-F1 steel tube carriage that was tested by BiU Dana in car-tow tests prior to the installation of the M2- 

F1 shell. (NASA photo E63 10756) 

NASA's Muscle Car: Ground-Towing the M2-F1 

Dick Eldredge and I had designed the M2-F1 to weigh 600 pounds. However, like 

most prototype airplanes, it had grown in weight during fabrication, the completed 

vehicle weighing in at 1,000 pounds. From Iliff s calculations of the M2-Fl's tow force 

and lift-off speed, we knew that to do taxi tests with the M2-F1 before the wind-tunnel tests at NASA Ames, we needed a ground-tow vehicle with greater power and 

speed than any of NASA's trucks and vans could provide.2 

First, we needed a ground vehicle that could tow the M2-F1 at a minimum of 100 

miles per hour. Secondly, we also needed a ground vehicle that, at that speed, could 

handle the 400-pound pull needed to keep the 1,000-pound lifting body airborne. In 

meeting these needs, we ended up with what was probably the first and only government-owned hot-rod convertible. 

Once again, a volunteer came along who had the know-how that we needed. 

Working in operations at the NASA Flight Research Center at the time was Walter 

2. Hallion, On the Frontier, p. 150. 

33 
"FLYING BATHTUB" 

Pohtiac tow vehicle next to the M2-F1. Walter "Whitey" Whiteside purchased the Pontiac by special order 

and had it modijied in a hot-rod shop near Long Beach for its special mission. (Private photo furnished by 

Bertha Ryan, NASA digital image ED96 43663-1) 

"Whitey" Whiteside, a retired Air Force maintenance officer who was also a veteran 

dirt-bike rider and expert hot-rodder.3 Whitey volunteered to help us out by finding, 

purchasing, modifying, testing, maintaining, and driving the high-powered ground-tow 

vehicle that we needed. 

At the time, the Pontiac Catalina seemed the best choice, this model having been 

the big winner the year before in Utah at the Bonneville Salt Flats time trials. With 

Boyden "Bud" Bearce's help in the procurement department, Whitey was able to 

make a special order from the factory for a Pontiac Catalina ragtop convertible with 

the largest engine then available, a four-barrel carburetor, and four-speed stick shift. 

NASA engineers at the Flight Research Center equipped the Pontiac with its tow rig 

and airspeed measuring equipment. 

Whitey took the car for modification to Bill Straup's renowned hot-rod shop near 

Long Beach, where the straight-piped Pontiac was modified to run a consistent 140 

miles per hour. There, auto-shop technicians also applied their hot-rod wizardry to the 

Pontiac, producing maximum torque at 100 miles per hour as measured by a 

3. Milton 0. Thompson, At the Edge of Space: The X-15 Flight Program (Washington, D.C.: 

Smithsonian Institution Press, 1992), p. 52. 
WINGLESS FLIGHT 

dynamometer. They added a special gearbox, with transmission gear ratios significantly different from thos~ that hat1 helped the Catalina win at the Salt Flats, enabling 

the Pontiac eventually (once drag slicks were installed) to tow the 1,000-pountl M2- 

F1 to 110 miles per hour in 30 seconds. The Pontiac's souped-up engine got allout 

four miles to the gallon. Whitey got full support from the NASA fabrication shops 

headed by Ralph "Sparky" Sparks. Sparky ant1 his right-hand man, Emmet Hamilton, 

took responsibility for keeping the Pontiac running ant1 making any modific-ations 

required bj Whitey. 

For the safety of the driver and two onboard observers, Whitej had roll bars added 

to the NASA muscle car. He also had radios ant1 intercoms installed. The front passenger bucket seat was reversed and the back seat was removed, replaced hy another 

llucket seat so that a second observer could sit facing sideu-ays. Of course, the Pontiac 

hat1 to have government plates and the NASA logo on both sides. And just so no one 

woultl he encouraged to think the car was someone's personal toy paid for with government funtls, the hood ant1 trunk of the Pontiac were spray-painted high-visibility 

yellow so that the contertihle looketl just like any other flight-line vehicle.4 

When the car was finished at the hot-rot1 shop, Whitey drove it back to the NASA 

Flight Research Center. A niotorcycle fanatic and hot-rodder \+ho lovecl speed, Whitey 

fount1 it difficult to hold back once he got the Pontiac outside Los -4ngeles anti on the 

highway across the desert. Realizing he would get his chance later to open up on the 

dry lakebed, he was being particularly careful to hold the Pontiac's speed to the posted speed limit \$hen he saw in the rearview mirror the red light of a California 

Highway Patrol (CHIP) vehicle closely tailing the Pontiac. Pulling over to the side of 

the highway, Whitey 1%-ondered what he'd done wrong. It turned out that the officuer was 

merely curious, having never before seen a government-owned convertible, especially one ~ilh a souped-up engine. After a careful up-close look and Whitey's explanation of hot$ the car would he used, the officer drove away, shaking his head in 

amazement. 

The Pontiac also caught the eye of other drivers whenever Whitey took it out onto 

little-traveled desert highways northeast of Edwards AFR through Four Corners, often 

into Nevada with its then anything-goes speed limits, to calibrate the car's speedometer, as typically done with research airplanes. Laughing, Whitey recently recalled one 

particular time when he headed out on just such a venture with one of the base's piIots 

4. For other drtails on the Pontiac and its modific~ation, sre Ilallior~, On the Frontier. pp. 15&151; 

Tilkinson, "Ixgacy of the lifting Rotly," p. 54. For some clrtails allout ordering thr Pontiac frorn the factory, ir~tvw., Walter Wllitesidr 1)y Darlrrle Lister, 21-22 June 1996. Both liallion and R'ilkinson identify 

the sourre of the modifications to the Pontiar as hlic,key Thompson's shop. However, in an interview with 

Robrrt C. Hoey and Btatty J. 1.ove on 22 July 1994, R'alter Khiteside was atlamant that the sourre was 

Bill Straup's shop ant1 that Mickey Thompson was ttlr source for only the wllrrls and tirrs. This last interview- is the sourre for several of the tlrtails in the present narrative. 
"FLYING BATHTUB" 

in the car. As the Pontiac runlhled along, engine-exhaust system roaring as the 

speedonieter moved above 100 miles per hour, Whitey glanced at the silent pilot, on11 

to find him ashen-faced ancl trying to clisappear into the seat." 

When we hat1 the M2-F1 completed and ready for wind-tunnel testing at NASA 

Ames, we were still di\ided on which basic roll-control scheme to use. Bertha Ryan, 

Hamet Smith, and Milt Thompson backed their interpretation of simulation results, 

saying the nldders would give the best roll control. Ken Iliff and Larry Taylor countered with what their root-locus plots showed-that using the rudders for roll control 

would lead to pilot-induced oscillation. On the other hand, I thought that the outboard 

elevon surfaces simply lookvd right for roll control, and I believed that rudders were 

meant for yaw-not roll-control. In the end, we agreed to use the scheme Milt 

Thompson preferred, with the pilot's stick hooked to the rudclers for roll control, as 

long as we could reconfigure to the other scheme if that one didn't work. 

Of course, we had no official approval to flight-test the M2-F1, which was supposed to be merely a full-scale wind-tunnel model. Sitting in the cockpit, Milt 

Thompson reasoned that perhaps it wouldn't really be flj ing if we just lifted it off the 

lakebed a couple of inches. Boosting our confidence was the data we had from the earlier small-scale wind-tunnel tests. When approached, Bikle said to go for it, hut to be 

careful. 

We w-ere very careful as we began on 1 March 1963, making several runs in cartow at lower speeds, gradually working up to the nose lift-off speed of 60 miles per 

hour on 5 April 1963. During these runs, Milt became familiar with the cockpit and 

with \isil)ility out the top, through the nose window at his feet, and out the side window level with his feet, these w-indows necessitated by the anticipated high angle of 

attack. He also became adept at nose-gear steering and using the differential brakes 

arid tow-line release. 

After a week of these cautious towings at lower speeds, Milt said he was ready to 

try a lift-off. Following Milt's radioed clirections, Whitey took the Pontiac and the 

M2-F1 on tow up to 86 miles per hour, the 1,000-foot tow-line giving Milt plenty of 

maneuvering room. 

Slowly Milt I-trought the nose of the little lifting hody up until the M2-F1 got light 

on its wheels. Then, something totally unexpected happened. The M2-F1 began 

bouncing back and forth from right to left. Milt stopped the bounce by lowering the 

nose, putting weight back on the wheels. Several times he again 1)rought the nose up 

until the M2-Fl was light on its wheels, and each time the vehicle reacted the same 

way, Milt ending the bounce by lowering the nose as he had the first time. 

I,ater, in our little de1)riefing room, Milt said that he felt that if he had lifted the 

M2-F1 off its wheels, it would have flipped upside down in a roll. IT$ started theorizing ahout the cause of the pro1)lem. Milt felt it hat1 something to (lo with the landing 

5. Whiteside inteniew by Lister for incident ~ith the pilot. 
WINGLESS FLIGHT 

gear, wondering if there wasn't enough damping in the oleo-type shock system. Ken 

Iliff suggested that maybe Milt was feeding the roll motions with the stick or rudder 

pedals. Absolutely not, replied Milt, adding that he had made sure during lift-off that 

he wasn't making roll or yaw control inputs. 

We planned to get a little data for analyzing the pr01~len1 by installing an instrumentation system in the M2-F1 after we returned from wind-tunnel testing at NASA 

Ames. Refore that, however, using a ground-chase vehicle, we made some 16mm 

movies taken from the rear of the M2-F1, having painted references stripes on the rudders so we could determine their positions. The movies showed that the rudders were 

moving back and forth during lift-off. When Milt saw the movies, he concluded that 

slop and inertial weights in the rudder system-and not the pilot-were causing the 

rudders to move. 

Larry Taylor suggested that we construct data from the movie frames. Using a 

stop-frame projector, we could determine right and left rudder positions ant1 body roll 

angle on the M2-F1 by its position against the horizon in the background. We projected the filmed images of the M2-F1 onto a large sheet of paper we had hung on the 

wall. Using a protractor, we measured the roll angle and positions of both rudders in 

each movie frame. Using the frame rate of the projector, we then produced plots or 

time histories of the rudder movement and roll angle. Prociuiuing flight data in this 

way was hard, niundane work. Ken Iliff, Larry Taylor, and I took turns working with 

the data until we hail in hand the results that Iliff and Taylor needed to analyze 

the problem. 

In the hangar, we examined the rudder control system, finding it exceptionally 

stiff. No way could the rudders be moved without moving the pilot's stick. We exarnined the weight distribution of the rudder system, looking for how inertia could caause 

the rudtlers to move during vehicle roll. We still could not find the cause of the 

rudder motions. 

Ken Iliff compared the phase relationships het>+een rudder position and roll 

angle, giving Lany Taylor his findings. The control motions were typical of what a pilot 

would put in to combat roll oscillations. Finally, Larry Taylor and Ken Iliff put together a strong statement, saying they had no doubt that, knowingly or unknowingly, the 

pilot was working to combat the roll and that continuing to try to fly the M2-F1 with 

the control system driving the rudders from the pilot's stick would, during roll control, 

lead eventually to loss of control of the vehicle. They insisted that the current control 

system be abandoned and the other control systern driving the elevons from the pilot's 

stick Ite hooked up for the next series of car-tow tests. 

We couldn't share their conclusion and recommendation with Milt Thompson at 

the time, Milt being away on a trip. We had only one week left after Milt's return for 

car-tow tests before we were scheduled to go into full-scale wind-tunnel tests at NASA 

Ames. Given the strength of Taylor and Iliff's conviction about the control systems, I 

didn't want to waste time doing more car-tow tests with the original control system, so 

I asked Vic Horton to change the control system as Taylor and Iliff had recommended so that, when Milt returned, the M2-F1 would be ready for more car-tow tests. 
"FLYING BATHTUB" 

After I matle this decision, I noticed that the group had lost some of its hannony 

and camaraderie. Tension l)egan to build lletween group members as they began to 

realize that a pilot's life coultl he at stake in this disagreement within the group over 

Rhich roll-control system ne used in the M2-F1. Milt Thompson was such a personable guy and worked so closely with us almost daily that emotions started emerging 

whenever critical decisions had to be made. T began to think that maybe it was better 

to have the research pilot more distant frorn the project people. 

By hacking Iliff and Taylor's recommendation, I had alienated Bertha Ryan and 

ITarriet Smith to some extent. Ryan read me the riot act for not including Milt in thr 

decision to change the control system, saying that, after all, it was his life at .;take. I 

replied that Milt Thompson still had ceto power as the pilot and that, if he insisted we 

do so, we would change hack to the original control system. Ryan seemed satisfietl by 

what I had said, hut harmony on the project remained strained frorn that point. Even 

bigger conflicts would come later in the lifting-body program as the project grew. 

,is soon as Milt Thompson was back, I told him about the change made in the rollcontn)l system. He was disappointed, Ranting to do some more testing while using thr 

previous control system, but he accepted the change, saying he still thought the problem was caused 1lp the landing gear ant1 that, when the new control hookup didn't 

solve the problem, we could go back to the original hookup. 

With Milt Thonipson onboard, we again hooked up the M2-F1 to the Pontiac and, 

with Whitey at the wheel of the Pontiac, off they charged across the lakehed. 

Cautiously, Thompson rotated the nose of the M2-F1 until there was veq little weight 

left on the wheels. He continued to rotate the nose until the wheels were about three 

inches above the lakehetl. The h12-F1 remained steady as a rock. We made another 

run, this time to an altitude of three feet. Thompson was gentlj maneuvering the 

M2-F1 right and left behind the Pontiac, but the lifting body showed no tendency 

to oscillate. 

BJ now, Rllitey had gone to Mickej Thompson's hot rod shop in 1,ong Beach to 

replace the Pontiac's rear tires with drag slicks, a change that increased the car's towing speed to 110 miles per hour. Normally, drag racers use the wide, high-traction, 

threadless tires generally known as "slicks" because torque from the drive train to the 

lower gears is greatest at the start of the very short race known as a "drag," when tire 

slippage is most likely to occur. Our experience was exactly the opposite, with the 

height of drag found at the high-speed end of a to^. At about 90 miles per hour minus 

the slicks, the tires on the Pontiac would start slipping. Adding the drag slicks on the 

rear wheels of the Pontiac increased the towing speed enough to allow Milt Thompson 

to climl) to twenty feet in the M2-F1, release the tow-line, ant1 get about ten seconds 

of free flight before the flare landing. 

Using the new control system, the M2-F1 handled well, both on and off tow in 

flight. Milt Thompson seemed to be happy with the control system. Neither Ryan nor 

Smith ever suggested later that we go hack to the original control system. Not being 

an "I-told-you-so" sort of guy, I never again brought up the topic. And never again did 
WINGLESS FLIGHT 

we discuss control-rigging within the group, other than how to reduce stick forces with 

aft stick positions. 

The Pontiac towed the M2-F1 for the first time on 1 March 1963, and before .April 

was over, it had towed it a total of 48 times. While the Pontiac was prominently a part 

of the M2-F1 adventure, it was no secret that the rar didn't exactly resemble the usual 

flight-line vehicle. According to Whitey, whenever someone from NASA Headquarters 

was visiting the Flight Research Center, Paul Rikle would slip away momentarily to 

phone him, telling him to hide the car. Whitey would pull the Pontiac behind a shed 

and throw a rover over it, the Pontiac "grounded" until the visitor left." 

What happened to the NASA muscle car once the M2-F1 program ended? Near 

the end of 1963, the Pontiac was shipped to NASA Langley Research Center in 

Virginia and used in tests at Wallops Island. There was some regr~t expressed at the 

NASA Flight Research Center when the Pontiac left, fairly much captured in a romment printed at the time in the X-Press, the NASA newspaper at Edwards Air Force 

Base: "No longer ran we drive along the lakebed and pass the airplanes in flight."7 

6. Whiteside interview by Lister for the grounding of thr Pontiac. 

7. As quoted in Hallion, On the Frontier, p. 150n. 

CHAPTER 3 

COMMITMENT TO RISK 

For the 350-miIe trip from Edwards Air Force Base to the NASA Ames Research 

Center at Moffett Naval Air Station in Sunnyvale on the southern end of the San 

Francisco Bay, we removed the "elephant-ear" elevons from the M2-F1 and loaded 

the vehicle on a flat-bed truck. The ten-foot width of the lifting body on the truck's bed 

causetl it to 1,e classified as a wide load, requiring two escort vehicles, one in front and 

one in back of the truck. The M2-F1 created some sensation along the route. The drivers had a lot of fun talking about it to the people who crowded around them on stops 

along the way, wanting to see it up close. 

The NASA Ames Research Center is locatetf in the heart of Silicon Valley, a few 

miIes down the road from Stanford University. Moffett Naval Air Station had been the 

western operational base for Navy dirigibles in their heyday. The Navy dirigible 

Macon was a flying aircraft carrier, launching and recovering prop-driven fighter airplanes from its belly. The Navy was very proud of its dirigible fleet until two disasters 

happened: the Shenandoah crashed in an East-coast wind storm, and the Macon 

went down in the ocean off Monterey, California. Two hangars that housed these dirigibles still exist at Moffett. These hangars and the NASA Ames wind tunnel-its 

return section as tall as a ten-story building-are such prominent structures that they 

can be seen for miles 1)y ground or air. 

A bank of very large fans driven by eIectric motors generates the "wind" in the 

test section of the tunn~l. Routed to the farility are power lines and a special substation. Operating the wind tunnel in those days required special coordination with the 

Edison Electric Company because of the need to have operators on standby to turn on 

extra generators when the tunnel was in use. To avoid conflict with peak daytime 

industrial electrical needs, wind-tunnel tests were often scheduled during night hours. 

While it could take months or even years to get tests scheduletl for this tunnel, A1 

Eggers had assigned a priority to the M2-F1 wind-tunnel tests. We hat1 two weeks to 

condurt them. We had put together a test team consisting of hoth Vie Horton's hardware people and some of the analysis tram. Horton participated in some of the data 

analysis, co-authoring with Dick Eldredge and Dick Klein the M2-F1 flight and windtunnel liftldrag results.] 

1. Victor VC! Horton , Richard C. EItlretfge, anti Richard E. Kleii~, Flight-Determiner1 Lotcr-Sf)eec1 

Lift rrnrl Drrzg Charart~ristics of the Lightuvight 1M2-FI Lifting Rody (V(isliingi~~n, D.C.: NASA 

T? D3021,1965). 
COMMITMENT TO RISK 

M2-Fl mounted in the Ames Research Centerfs 40x80-foot Wind Tunnel for testing. (NASA photo A-30506- 

15, also available as NASA photo EC97 44183-3) 

42 
WINGIESS FTJGHT 

While the NASA Ames crew operated the tunnel, our crew from the NASA Flight 

Research Center worked with the M2-Fl--quite a different sort of atlventure for a 

1)unch of tlesert rats used to airplanes that fly in open sky over miles of sand and rock. 

I found a traiIer park nearby where I could park my small travel trailer for the two 

weeks, having brought my wife and our two daughters along as well. 

The inside of the ~ind tunnel was an awesome sight, especially at night. 

One night, as the M2-F1 team was preparing for a test, I took my fatnily on a tour of 

the tunnel. We boarded an open-cage elevator on the gound floor, then rose through 

a darkness of steel beams and unlit open spaces to the floor of the dimly lit test section. The tunnel was a huge closed-circuit system in the shape of a race track, its 

entire length being about half a rnile. Soot from engines stained the walls, making 

the interior of the tunnel dark and dingy, adding an eeriness to the atmosphere. 

My wife, Donna, said the tunnel would be a wonderful place to make an 

Alfred Hitchcock movie. 

When we were ready to begin wind-tunnel testing, we hat1 the M2-F1 hoisted high 

overhead by a crane, then lowered through a large hatch in the top of the test section. 

The vehicle sat 20 to 25 feet off the floor on top of three tapered poles resembling stilts 

that were mounted on a turntable balanced on the tunnel's floor, the M2-F1 attached 

near its landing gear to the poles. 

%%at we ditl in testing the M2-F1 was unique, soniething that proba1)ly coul(1n't 

he done now due to NASA's emphasis upon safety. We didn't have remote controls on 

the M2-F1, even though most wind-tunnel nioclels of vehicles have them. To move the 

testing along more rapitlly, we talked the NASA Ames wind-tunnel crew into letting 

us take turns sitting in the cockpit, setting the pilot's controls at different settings by 

using plywootl form hoards. By keeping someone in the cockplt during the testing, the 

wind tunnel could be kept running, with necessary control changes made hy the person in the cockpit. Othenvise, it would have taken a long time to get the tunnel's wind 

speed sta1)ilized each time we started up again after shutting down the tunnel to make 

a change in control setting, angle of attack, or sitfeslip. 

Ed Bro~me, Dick Eldredge, Milt Thompqon, and I tried out the cockpit for size. I 

fount1 it scary sitting up there over 20 feet off the ground inside a pl~wood barrel-like 

vehicle perched atop three spindly poles inside a dark cavern, shaking around as a 

windstorm screamed past at 135 miles per hour. I then decided that the lwst use of mq 

time woul(l1)e directing the tests in the safe confines of the wind tu~lnel control room. 

With the wind-tunnel operators and I peering at the wind tunnel pilots through thick 

wintlows in the tunnel walls, they felt like some kind of biological 1al)oratory specimens under scrutiny. 

We had an intercom system set up for communicating between the cockpit and the 

control room-a much better waq to communicate, we felt, than holding up messages 

scribbletl on paper to be read through the ~ehicle's canopy, especially when asking for 

help cluring sudden attacks of claustrophobia or because of a final call of one's bladder for relief. Whenever the wintl tunnel pilots moved the controls or the wind keloc- 
COMMITMENT TO RISK 

ity increased, they could feel the vehicle move as the poles supporting it flexed, an 

experience they all found disconcerting until they got used to it. 

Milt Thompson, however, even wanted to conduct another wind tunnel test. As he 

said years later, "I tried to get them to attach a rope to it and let me actually try to fly 

it in the tunnel, but they wouldn't go along with that."2 What Milt had wanted to do 

was sit in the cockpit of the M2-F1 on the floor of the tunnel, the tow-line tied 

upstream of the vehicle. However, the tunnel's crew was not very enthusiastic about 

Milt's suggestion, saying they could see the tow-line breaking and Milt and the M2- 

F1 ending up plastered against the turning vanes at the end of the tunnel. Even offering to attach slack safety lines during his "flight" did not keep the tunnel's crew from 

turning thumbs-down on Milt's request. 

Before we started the formal data-gathering part of the tunnel tests, Milt found 

excessively large stick forces at aft stick positions while sitting in the cockpit and 

moving the controls around at different air speeds and body angles in the airstream. 

To minimize hinge moments, we had designed the outer elevons' pivot points to be 

slightly forward of the elevons' center of pressure. However, the trailing-edge body 

flap had been hinged at its leading edge, producing large hinge moments and stick 

forces. Using the wind-tunnel's fahrication shops, Vic Horton and his crew attached 

stand-off aluminum tabs on the body flap to help hold up the trailing edge, deviating 

force on the stick. While the tabs didn't entirely eliminate the stick force, Milt considered it enough lessened to be tolerable. 

There was another problem involving a phenomenon calletl a "KArmAn vortex" 

that can also occur behind large trucks on the highway. 4 driver in a car at certain 

distances behind a truck in calm w-ind conditions sometimes can feel a "KArmBn vortex" as the airstream whips back and forth. With the M2-F1, at certain airspeeds in 

the tunnel, a low frequency beat was being fed back to the vehicle's control stick. 

After taping tufts of yarn around the aft body and control surfaces of the M2-F1, we 

discovered that a large, oscillating KArmAn vortex was coming off the body's base and 

heating against the body flap.3 

The NASA Arnes resiclent aerodynamicist, experienced in vortex flo~s, suggested 

that if we could change or disturb the base pressure slightly, we might be able to break 

up the single large vortex into a 1)unch of rriuch smaller ones that woultf not beat so 

badly on the flap control surface. Once again, Vie Horton's crew went back into the 

shop, this time making two aluminum scoops and mounting them at the base on each 

side of the vehicle's body. The idea was to scoop air from the sides of the body into 

the cavity behind the base, thus increasing the base pressure and, we hoped, destroying the KBrmlin vortex. Milt climbed hack into the cockpit, ant1 we tested the M2-F1 

2. %ilkinson, "Ingac> of the 1,ifting Bud>," p. 54. 

3. On the KArmfln vortrh, srr Michael H. Corn, The Unit'ersal Man: Theodore tion Krimrin's I,i$e 

in .ileronnutics flashington, D.C.: Smithsonian Institution Press, 1992), pp. 23-24. 
WINGLESS FLIGHT 

with the scoops. It worked. Having made two aerodynamic fixes to the vehicle, we 

were ready for the formal data-gathering portion of the wind-tunnel tests. 

Dick Eldredge took the first shift, sitting in the cockpit and setting the controls 

with the plywood form boards. We were on a roll that day, cranking out data faster than 

we had before. Earlier, we had lost three days of our scheduled time in the wind tunnel while waiting anxiously as the tunnel's crew repaired its balance-data measuring 

system. After Eldredge had spent two hours in the cockpit, we asked him over the 

intercom if he woultl like someone else to take over. He declined. We asked him again 

every two hours until we had tested for eight hours straight with Eldredge in the cockpit, knowing he had only some water with him. Finally, after eight hours, Eltlredge 

admitted that he was getting hungry and needed to go to the bathroom. 

Data from the tunnel's measuring system came to us on tabulated sheets showing 

side, vertical, and aft force measurements as well as moments of roll, pitch, and yaw. 

The sheets also provided air speed, angle of attack, and sideslip The M2-F1 "pilot" 

-whoever happened to be sitting in the cockpit during the test-alho made notes 

regarding the control settings. We then correlated the data from the notes with that 

from the tunnel's measuring system. 

The analytical team members hand-plotted on graph paper every single data 

point, using a room downstairs that had been set up for us. Hundreds of hours were 

involved in this work, each of us on the analytical team-Ken Iliff, Bertha Ryan, 

Harriet Smith, and myself--doing our share of the work. I think even Milt Thompson 

plotted a few points. 

Whenever I saw the hardware crew had completed a task, I put its members to 

work plotting data as well. Once, when 1 did this, I didn't make myself too popular. 

They had been entertaining themselves with a game during a work lull, while the tunnel's crew was doing calibration checks on the measuring system. One by one, they 

were running across the tunnel floor, up the side of the curved floor, and putting a 

chalk mark as high on the wall as they could reach, the o1)ject of the game being to 

see who could make his mark the highest. After watching them for awhile, 1 had said, 

"If you guys aren't doing anything, come on down and help us plot data." Ob~iously, 

plotting data wasn't nearly as much fun as the game the) had been playing, but they 

helped us anyway. A few years later, those marks were still on the tunnel's walls. Now, 

over thirty years later, I have often wonderecl if those marks are still there. If they are, 

they are probably covered up with additional layers of soot 1)y now. 

Some aspects of the good old days weren't so good, and one of them was having to 

spend those hundreds of hours hand-plotting data. Totlay, most wind tunnels have 

fully automated data systems with final plots rolling out of the machine soon after a 

tunnel test is finished. Today's engineer can analyze the data as it comes from the tunnel tests, modifying the test program in real time if an aerodynamic quirk shows up. 

When our two-week stint at the NASA Ames wind tunnel ended, we packed up 

our data and trucked our little lifting-body vehicle back to its hangar at the NASA 

Flight Research Center. When we replaced the data in our simulator, based on the 

small-scale wind-tunnel tests, with the new data from the full-scale tests, we saw a dif- 
COMMITMENT TO RISK 

ference. We knew that the only way to confirm the flight potential of the M2-F1 was to 

move on at once into actually flying it. 

Gearing Up for Flight-Testing the M2-F1 

Immediately after returning to the NASA Flight Research Center, we began planning how to move directly into air-towing the M2-F1 into flight. The tow-plane we 

decided to use was NASA's R4D utility aircraft, a Navy version of the Air Force's 

C-47, both being military versions of the legendary DC-3. Fondly dubbed the "Gooney 

Bird," the Douglas C-47 aircraft played a significant role (luring World VC'ar I1 as a 

glider tug during campaigns in Sicily, Normandy, and elsewhere. Now, the Gooney 

Bird was about to enter abiation history again as the tow-plane for the first liftingbody vehicle. 

NASA's Cooney Bird was being used in several other ways, niostly as a transport 

aircraft. It had long been used at the Flight Research Center to shuttle people to and 

from ,4mes in support of joint activities. It was also being used in the on-going X-15 

program to ferry people and equipment between Nevada Iakebed emergency-landing 

sites and remote radar-tracking stations. 

For a while we couldn't find a glider tow-hook for the Gooney Bird. Of World-War 

TI vintage, this device was no longer in the military inventory. Finally, Vice Horton 

scrounged up one from a surplus yard in Los Angeles. We had no more than attached 

it to the tail of our Gooney Bird and run the release-line control up to the cockpit of 

the M2-F1, however, than we began to see dark clouds gathering over the lifting-body 

project as other people at the Flight Research Center began to believe that we were 

actually serious about flying the M2-F1. 

First, Joe Vensel, local NASA Chief of Flight Operations, said that we coul(1n't fly 

the M2-F1 without installing an ejection seat. Eldredge and T told Vensel that we 

wished he had come up with this requirement when we were designing the vehicle. 

Fortunately, since the pilot sat at the renter of gratity in the M2-F1, we found that we 

could add the ejection seat without unbalancing the lifting bodj. However, when we 

added the ejection seat and instrumentation, the M2-Fl's weight rose to 1,250 

pounds. To fly, the heavier vehicle required higher airspeeds than we had anticipated. 

Because of this change, Dick Eldredge, Meryl DeGeer, and I went back over the 

structural load capacity of the M2-F1. We found that the most critical part of the structural design was the bending moment at the base of the vertical tails. The most severe 

flight condition, consequen~ly, would be a high-speed dive in which the vehicle was 

forced into a high sidesIip angle with the roll control (elevons) put in the wrong direction, adding to that bending moment. Using the simulator, we found that the only way 

a pilot could encounter that dangerous condition would be by attempting an aerobatic roll. A placard we added to the instrument panel in the cockpit clearly defined this 

limitation in four words: "No Aerobatic Roll Maneuvers." 

At that time, the Weber Company was in the process of developing what we needed, a zero-zero ejection seat-that is, an ejection seat that operates even with the air- 
WINGLESS FLIGHT 

craft on the ground stancling still (at zero altitude and zero veloc.ity). The company 

was modifying a lightweight seat designed for the T-37 jet trainer to use a rocket rather 

than a ballistic charge for ejection. Joe Vensel came up with funds from his operations 

budget to pay Weher for this ejection seat to install in the M2-F1. 

Very likely, the M2-F1 used one of the first zero-zero ejection seats ever made. 

Since Weber hat1 not yet fully demonstrated the seat at the time, we arranged for a 

series of tests at the south lakebed \%here ejection seats were generally tested. Meryl 

DeCeer and Dick Klein worked with Weber in demonstrating and testing the seat. 

nick Klein constructed a plywood mockup of the M2-Fl's top deck and canopy 

through which to fire a dummy sitting in the ejection seat. This clulnmy was fired up 

six times in the ejection seat. On each of the first five times, something went wrong 

and we had to make an adjustment. 

Meryl DeCeer remembers Milt Thompson watching one of these tests. After the 

dummy and the seat smashed through the M2-F1 canopy mockup with rocket burning 

bright, the dummy separated from the seat at the top of the trajectory. The seat safely 

descended to the ground on a special parachute that Weber had ad(led to save the seat 

for use in future tests. Rut the dummy, with its parachute still unopened, went sailing 

through the air head-first like Superman, its arms flapping. 

As the dummy arched toward the ground, DeCeer glanced around at Milt 

Thon~pson. His face contorted, Milt was shouting at the dummy, "Flare! Flare! Damn 

you, flare!" The dummy ignored him and kept on flapping its arms as if trying to fly. 

The durnmy crashed headlong into the bushes. Onlj then did its parachute flare open. 

Everything worked well on the sixth test of the ejection seat, and the seat was 

installed in the M2-F1 without repeat testing to prove reliability. A year later, in 1964, 

an updated version of this seat was iristalled in the NASA Lunar Landing Research 

Ghicle (LT,RV), the same seat that saved the lives of astronaut Neil Armstrong and 

pilot Joe Algranti when control systems failed in the Lunar Landing Training Vehicle 

at Johnson Space Center during training missions for landing on the moon. 

Next, Thomas Toll, Chief of the Research Di\ision, began to have serious tfoubts 

about flying the M2-F1. A respected hut conservative researcher who had transferred 

to the NASA Flight Research Center from NASA Langley in Virginia, Toll had been 

one of the men responsible for the concept of the X-15. He felt that as long as we 

weren't flying the M2-F1 more than a few feet off the ground on car-tow, the data 

return was likely worth the effort, cost, ant1 risk. 'Merely flying the M2-F1 on car-tow, 

he believed, would be a good learning tool for sharpening engineering skills in aerodynamics and stability and control, and it was also possible that the car-tow flights 

might even produce some useful data on lifting bodies.$ 

However, we were now thinking aLout flying the M2-F1 to high altitudes behind 

a tow-plane and that, he felt, was quite another matter. His serious misgivings seemed 

mostly to have to do with the fact that Milt Thompson had encountered a dangerous 

21.. For Toll's position, Hallion, On the Frontier, p. 151. 

47 
COMMITMENT TO RISK 

lateral oscillation the firs1 lime he flew the M2-F1 on car-tow. Toll did not believe that 

any potential return in air-tow flight data was worth the risk to the pilot. 

Toll had two other main reasons for opposing air-towing the M2-Fl into flight. 

First, he felt that the very low wing- or body-loading at which we were flying was not 

representative of a potential full-scale spacecraft, for an actual spacecraft the size of 

the M2-F1 would most likely weigh 10,000 to 15,000 pounds, ten times the weight of 

our M2-F1. Secondly, we weren't using any of the automatic control features, such as 

rate dan~ping or automatic, stabilization, that probably would be used in a spacecraft. 

Paul Bikle tried to reason with Toll, assuring him that he felt it was worth the risk 

and that he would like to have Toll's endorsement. Rut Toll refused, going on record 

as refusing to endorse the planned M2-F1 air-tow operation. When Bikle went ahead 

and gave us the green light to proceed without the concurrence of NASA Heatlquarters 

or his own Chief of Research Engineering, he essentially was making a decision that 

could put his career with NASA on the line. 

What Bikle did was an act of the kind of courage that 1 had never before seen in 

a manager. Essentially, he risked his career to support something that he believetl in. 

There are basically two kinds of courage in the aerospace industry: the courage of test 

pilots who risk their lives, and the courage of managers who risk their careers to support decisions they believe are right, even when others disagree strongly. In his book 

The Right Stuff, Tom Wolfe was correct to immortalize pilots as heroes.5 On the 

other hand, program managers are responsible not only for the pilots who have "the 

right stuff" hut also for the people involved in the program who have "the real stuff,'' 

as I have called it. When test pilots pay the ultimate price while risking their lives to 

test new aircraft, history rement1)ers them as heroes who gave their all to aeronautical research. However, when program managers make a challenging decision simply 

because they believe it is the right thing to do, they risk being laheled failures or going 

down in history as bumbling idiots. 

Today's program managers rarely encounter such risk, many of them using the 

bureaucratic process to build up walls that protect their careers. Today's manager can 

avoid risk by having decisions made by committees or by dividing programs into 

enough parts that it's not clear who is responsible for what. Another strategy that some 

program managers use to avoid risk is to be involved only with low-risk portions of a 

program, handing off high-risk portions to other managers who, if the program fails, 

can always defend themselves from blarne by saying they were ordered to do the job. 

If the program succeeds, then the original progranl managrr can step hack into the 

picture and take credit for the successful venture by clainiing it was his or her idea 

all along. 

Paul Bikle would not have done well in today's managerial environment. He 

lacked the political imperative needed to work the system in his favor. He was so open 

and honest that everyone knew exactly what he was thinking-except when he was 

5. TORI VEi~lfe, The Right Stuff (New I&-k: Ferrar, Strauss, Giroux, 1979). 

48 
WINGLESS FIJGHT 

playing cards with the crew during lunch. That he was so open and "readable" was a 

trait that worked well for those working under him, for they knew where he stood. But 

it wasn't a trait that helped him in dealing with the hierarchy that rleveloped grailually over him at NASA Headquarters. 

Long after the lifting-body program was over, when Milt Thompson had retired as 

a research pilot and entered management at the Flight Research Center as its Chief 

Engineer, we talked about the episode wit11 the Chief of Research Engineering back 

in 1963 and how people in different positions can view the same situation very differently, depending on their positions. As a research pilot, MiIt Thompson hat1 the 

reputation of being a wild and crazy guy who would take every calculated risk that his 

bosses would allow. But when he became a manager, he became very ronservative, not 

allowing other pilots to take the same kinds of risks that he had taken as a pilot. In 

this sense, a manager is rather like the father who won't let his son ride motorcycles 

even though he had done so when he was a young man. ,4s a manager, Milt Thompson 

said he could fully appreciate the position taken by the Chief of Research Engineering 

in vetoing the M2-F1 flight tests. He conjectured that if he had been in the Chiefs 

position, he might also have questioned the rationale for the M2-F1 flights. 

Gooney Bird Meets Flying Bathtub: First Air-Tow, 

16 August 1963 

After the ejection seat had been installed in the "Flying Bathtub," Milt Thompson 

made a fe~ more tests on car-tow, adjusting to the heavier weight and checking out 

the flight instrumentation system. Re did as thorough a flight readiness review as we 

could before moving into air-towing the lifting body, wanting to make sure there was 

not something we were overlooking. 

One day while we were still getting ready to begin air-tolzs, Milt said to me privately that he had complete confidence in me to make the right decisions and that he 

was putting his life in my hands. That was the best and most sincere compliment 1 

have ever received during my career. 

By now, George Nichols and Glynn Smith, instrumentation technicians who had 

joined the lifting-1)ody group of volunteers, had installed the instrumentation needed 

to radio data to the ground. Since the M2-F1 was an extremely simple glider with no 

onboard electronic systems, data from only 15 sensors would be sent to the ground. 

(By contrast, data from 400 to 500 sensors-later about 1100-was transmitted by 

radio during a typical X-15 mission.) In the M2-Fl, the sensors would tran4mit air 

data, including airspeed, altitude, angle of attack, and angle of sideslip; verticaal, side, 

and longitudinal accelerations; gyro data, including roll, pitch, and yaw rates; and 

control position data from the single elevator, two rudders, and two elevons. 

Stability and control flight data would he transmitted by radio back to the antennae on the roof of the main NASA building that housed the control room, 10 miles 

from the lakebed take-off site. Here, Ken Iliff, Bertha Ryan, and Harriet Snlith would 
COMMITMENT TO RISK 

watch plotting recorders equipped with ink pens generating traces of the data received 

from the measuring sensors aboard the M2-F1. The data would also be recorded on 

tape for analysis after the flight. Also in the coritrol room during the flight ~pould be 

the mission controller, research pilot Bill Dana, who, exactly two years later, would 

pilot the M2-F1 for the first time and then spend a total of ten years as a lifting-body 

pilot. But for the first air-tow flight of the M2-F1 on 16 August 1963, he would be on 

the ground, serving as that all-important link between the pilot in the cockpit and the 

engineers in the control room. 

De\ eloped for the X-15 program, the control room at the NASA Flight Research 

Center also contained two large plotting 1)oanL that drew the track of the aircraft on 

maps of the surrounclirig terrain, l~ased on data received by the radar-tracking dish 

antenna atop the building. The control rooms later l~uilt at the NASA Johnson Space 

Center in Houston, Texas, for the first hunlan space programs (Mercury, Gemini, and 

Apollo) were patterned after this control room at the NASA Flight Research Center. 

For the first air-tow of the M2-F1 I~ehind the Gooney Bird, we set up for take-off 

at the extreme south end of Runway 17, the longest lakrhed runway on Rogers Dq 

Lake at Etlwards AFB. We really didn't know how well the M2-F1 could make turns 

11ehind the Gooney Bird. An adtlitional advantage of using the longest runway was 

that, if the tow-line broke or released, Milt could glide straight ahead, making a landing on the lakebed, Runway 17, using only half the length of the almost 15-mile-long 

lake1)ed. Piloting the Gooney Bird woultl he NASA X-15 pilot Jack McKay. 

The plan was that when the Gooney Bird reached the north end of Rogers Dq 

I,ake, McKay would make a large circle counterclock-wise over the lakehed while rising to an altitude of 12,000 feet. Once there, the M2-F1 would be released off the towline. Vic. Horton would ol-,sewe the M2-F1 flight from the small r)lexiglas dome atop 

the Gooney Bird, watching the M2-F1 in tow behind the Gooney Bird and keeping 

McKay advised on what was happening with it. I woultl be monitoring the flight from 

a radio van at the take-off site. 

4t seven o'c-lock or1 the morning of 16 August 1963, the winds were dead calm on 

the ground and only about five knots at 12,000 feet. A ladder was needed for boarding the M2-F1. Milt was assisted by the crew chief, Orion B. Billeter, since considerably care was needed to avoid stepping on the thin wooden skin of the vehicle'4 upper 

body decak. Once Milt was strapped into the ejection seat, his helmet radio was 

checked out. Then, the canopy was lowered and secured in place, ant1 the ladder was 

pulled away. After the tow-line was hooked to the M2-F1, Rilleter pullecl on it while 

Milt c-hecked the release hook. The procedure was repeated with the tow-line and 

release on the Gooney Bird. 

NASA Don Mallick (who aoul(1 flj the M2-Fl four months later) ant1 Jack 

McKay started and checked out the Gooner Bird's engines. Refore take-off, McKay 

tried to avoicl blasting Milt with too much dust from the lakehed. Ready to go, Milt 

gave a thuml~s-up. After checking with the Edwarcls rZFB control tower, the hase's 

ambulance and fire truck, and McKay in the Gooney Bird, mission controller Bill 

Dana gave the go ahead for take-off. 
WINGLESS FLIGHT 

M2-F1 in tow behind R4D "Gooney Bird," with the nose positioned high so the tow plane is visible through 

the nose window. (NASA photo E63 10962) 

Gently easing the throttles forward on the Gooney Bird, McKay began to roll slowly down the lakebed. The Gooney Bird accelerated until its tail lifted off the ground. 

Very gently Milt lifted the M2-F1 off the ground exactly as he had done during the cartows, slowly climbing on the end of the 1,000-foot tow-line until the M2-F1 was about 

20 feet higher than the Gooney Bird and he could see the tow-plane through the nose 

window between his feet. He had to be fairly precise in maintaining position to keep 

the tow-plane in sight through the small nose window. The Gooney Bird gently lifted 

off the ground, Milt flying the M2-F1 in perfect formation behind and above the towplane. 

After a few minutes of climbing, Milt radioed that the M2-F1 was very solid and 

that it was easy to hold high-tow position behind the Gooney Bird. Because we hadn't 

installed a pilot-adjustable pitch trim system, however, he had to hold back pressure 

on the stick. We had omitted doing that, just to keep it simple. The trim tabs we'd 

installed on the body flap during the wind-tunnel tests would trim out most of the stick 

forces in free flight but not on tow. 

McKay held to a speed of 100 miles per hour as the Gooney Bird climbed to 

12,000 feet. Over the radio, Milt said that he was beginning to relax and enjoy the 

flight. Nevertheless, he still had to give constant attention to keeping the Gooney Bird 

in sight through the nose window of the M2-F1. The Gooney Bird made three large circles over the northern lakebed during the twenty minutes taken to climb to 12,000 
COMMITMENT TO RISK 

M2-F1 being air towed. Notice the side windows above the nosegearfor increased visibility near touchdown. 

(NASA photo EC63 229) 

feet. By this point, NASA pilot Fred Haise was flying alongside Milt in a T-37 jet 

trainer as a chase-observer. 

The plan was for Milt to release the M2-F1 from the tow-line at this elevation 

while heading south over the northern portion of the lakebed. He was to make a 180- 

degree turn to the left, make a practice landing flare at about 9,000 feet altitude, and 

then push over and continue another 180-degrees to the left in order to line up on 

Runway 18, heading south. The average rate of descent was about 3,600 feet per 

minute, giving Milt about six minutes to learn to fly the M2-F1 before having to make 

the crucial one-shot landing maneuver. 

Unlike the normal landing of an airplane, landing the M2-F1 was more like 

pulling out of a dive. A pushover maneuver had to be done at about 1,000 feet to build 

airspeed up to about 150 miles per hour, followed by a flare at about 200 feet altitude 

from a 20-degree dive. The flare maneuver would take about 10 seconds, leaving three 

to five seconds for the pilot to adjust to make the final touchdown. Milt had the option 

of hitting a switch to fire a rocket motor, giving him five to six more seconds to adjust 

sink rate before touchdown. 

Watching from the ground, it seemed that the M2-F1 literally fell out of the sky. 

Since the vehicle had come level while Milt was making his practice landing at altitude, he radioed that he was going for the real one. Bill Dana, whose call sign was 

"NASA 1," confirmed that the practice landing had also looked good on the charts in 

the control room. Having made strip chart overlays earlier while Milt was practicing 
WINGLESS FIdGHT 

landings on the simulator, Ken Iliff, Bertha Ryan, and Harriett Smith had been able 

to do real-time comparisons while Milt was doing his practice landing maneuver. 

However, if Milt hadn't been aide to achieve level flight during the practice landing, our ground rules were that he was to eject, letting the M2-F1 crash. We considered the M2-F1 cheap enough to be expendable. Such a ground rule wouldn't sell in 

totfay's flight-testing of expensive airplanes, former NASA pilot and astronaut Fred 

Haise recently told me. 

Our ground vehicles were parked well to the side of Runway 18, opposite Milt's 

planned landing point. It was scary watching him dive for the ground, and I held my 

breath. Milt leveled out, making a picture-perfect landing at the planned touchdown 

spot without using the rocket. I finally remembered to breathe as he rolled straight 

ahead and turned off the runway, coasting to a stop. All of us, including Paul Bikle, 

surrounded the M2-F1 while Orion Billeter helped Milt out of the lifting body. We 

were one bunch of happy people as we stood there, shaking Milt's hand. Later, the 

debriefing room was wall-to-wall smiles as Milt described a flight that went exactly as 

planned. 

We had a party that night at my house, but it bore no resemblance to the typical 

wild X-15 parties of heavy drinking that Milt Thompson described in his book, At the 

Edge of Space."ince the X-15 program involved most of the p~rsonnel of the Flight 

Research Center in some way, X-15 parties were always held at Juanita's, then the 

biggest bar in Rosamond, just outside the western bounda~y of Edwards AFB. Almost 

exclusively stag, the X-15 parties were mostly attended by NASA's ex-military pilots, 

aircraft crews, and flight planners. As Milt relates, most of the X-15 parties continued 

at Juanita's for four or five hours, then moved to one or more of the bars in Lancaster. 

Unlike the X-15 program, the lifting-body program had research engineers steering its path from the very beginning. After success with the M2-F1, additional liftingbody vehicles would continue to be designed and built throughout the twelve years of 

the lifting-body program, involving the cooperation and teamwork of research and 

design engineers at three NASA centers (including Ames and Iangley) as well as the 

research engineers at contractors Northrop and Martin. 

The lifting-body program was also the first program at the NASA Flight Research 

Center significantly influenced by women engineers. Bertha Ryan and Harriet Smith 

not only played major roles in the development of the M2-F1 but continued to do so 

with other lifting-body vehicles, by which time other women at the NASA Flight 

Research Center were also involved in the program. Afterwards, Harriet Smith moved 

on to project management at the NASA Flight Research Center, while Bertha Ryan 

opted to remain in research engineering, later designing missiles for the Navy at the 

China Lake Naval Weapons Center, about 50 miles north of Edwards AFB. Since the 

days of the lifting-hody program that ended in 1975, women have increasingly entered 

the world of aerospace technology, so that now it is common to see women in engineering, as part of flight crews, and as pilots and astronauts. 

6. Thompson, At the Edge of Space, pp 71-73. 
COMMITMENT TO RISK 

The successful flight of the M2-F1 w-as a special triumph for us, a little team of 

"amateurs" pulling off a 1)ig one. Despite having Paul Bikle's full hacking, many of 

the "professionals" on the X-15 program hacl continuetl to consider the M2-F1 a highrisk project due to our lack of experience. Of course, it's a little hard to have much 

experience when doing something that has never been done before. We matured at 

once after that first flight, rapicllp moving up in credibility and status. 

A few weeks after the successful flight of the M2-F1, on 3 September 1963, aviation news reporters first viewed the craft at the NASA Flight Research Center. The 

M2-Fl quickly became a hot item in aviation periodicals. 

While a few people at NASA Headquarters were aware of the lifting-hodj project 

until about a week after the historic first flight of the M2-F1 in mid-August, they did 

pay much attention to it, mainlj because we hadn't requested any money for the program. Ho~ever, the NASA administrator in Washington, D.C., James E. Wel)l), 

remained unaware of the successful first flight of a lifting body until, while testifying 

hefore a congressional committee, he was asked about it 1)). a congressman who, having reatl allout it in the press, wanted to know if NASA was starting a new multi-l~illion-dollar space program that Congress neither knew about nor had approved. Bikle's 

phone began ringing immediately after this incident, which ob~iouslj had heen 

embarrassing for the administrdtor. Then Webb fount1 out that we had spent only 

about $30,000 on the program and that there was no billion-clollar plan in the making, things cooled down ant1 we were allowetl to continue with our M2-F1 flight tests. 

December 1963: Peterson, Yeager, and MaIlick Fly the M2-F1 

After Milt's first flight, the M2-Fl became very operational. A+ a simple glider, it 

had no systems to maintain, except the research instrumentation system. A part-time 

crew chief could easily keep the M2-F1 on flight status. The Goone) Bird was available most of the time to us as a tow-plane because it was being flown almost eveq day 

on support missions for other programs ant1 had a full-time crew chief. 

Milt Thompson flew the M2-F1 on its first seventeen flights in 1963-five in 

August, two in Srptember, six in October, three in November, ant1 one in December. 

These flights were made specific-ally to tfefine the craft's aerodynamics and stal~ility 

and control characteristics. Flight research is most kaluaLle when the data is used, as 

it was in these first flights, in comparison with wind-tunnel test results in correcting 

or completing aspects of design and prediction based on those results. 

After these flights, Paul Bikle ant1 Milt Thompson decided it was time to start 

checking out other pilots in the M2-F1, beginning with Bruce Peterson and Colonel 

Chuck Yeager. A NASA test pilot and a fonner Marine Corps pilot, Bruce Peterson 

liacl sened along with Milt Thompson in 1962 as one of two project pilots on the 

paragliclrr research vehicle, or Paresev, program that was designed to evaluate the use 

of an inflatable flexible wing in the space program as a way by which astronauts could 

leave a spacecraft anti return to Earth in a vehicle capable of making an airplane-like 

landing. The similarity with the M2-F1 is that both vehicles were gliders towed into 
WINGLESS FLIGHT 

M2-Fl pilots (Chuck Yeager in cockpit, Bruce Peterson to his left, and Don Mallick) being checked out by 

Milt Thompson (on stool). (NASA photo E63 10628) 

flight by winged aircraft, and both programs were excellent examples of Paul Bikle's 

low-cost and do-it-quick approach. Paul Bikle wanted his old friend, Chuck Yeager, 

then head of the USAF Test Pilots School at Edwards AFB, to fly the M2-F1 and give 

his assessment of the vehicle before other Air Force pilots were allowed to fly it.7 

During the last week in November, Peterson and Yeager were initially checked out 

on the M2-F1 during extensive car-tows up to an altitude of 20 feet. Thompson scheduled both for flights in air-tow by the Gooney Bird on 3 December, using a five-milelong lakebed runway so that there would be nothing critical about where touchdown 

occurred on the runway so long as a good flare was made to keep from breaking the 

M2-F1 in hard landing. With Bill Dana and Don Mallick piloting the tow-plane, 

Peterson and the M2-F1 were towed aloft to 12,000 feet in the first flight of the day. 

Peterson released the tow-line, making a very good landing on the lakebed. However, 

the M2-F1 had landed some distance from the van containing Milt Thompson and 

Chuck Yeager, which was sitting beside the runway. 

7. For further information on the Paresev program, see Hallion, On the Frontier, pp. 137-140; Lane 

E. Wallace, Flights of Discovery: 50 Years at the NASA Dryden Flight Research Center 

(Washington, D.C.: NASA SP-4309, 1996), pp. 131-33. 
COMMITMENT TO RISK 

Next, it was Yeager's turn to have his first lifting-body flight. Naturally competitive, Yeager suggested going for a spot landing on the runway just opposite the van 

parked beside the runway. Dana and Mallick towed Yeager aloft, as they had Peterson. 

Yeager opened up the flight envelope on the M2-F1, flying 1)oth faster and slower in 

his practice landing maneuver at altitude than had Milt. Then, he dove the M2-F1 at 

the lakebecl in a steeper angle than Milt had used, leveled out, and made a greasedon landing in front of the van. Climbing out of the M2-F1, Yeager exclaimed, "She 

handles great!I18 

It was a beautiful, but cold, December morning. The winds were still calm, and 

the Gooney Bird hat1 heen climbing very well in the cold weather. Milt suggested that 

Peterson and Yeager each get two more flights in for the day. Responding to Yeager's 

challenge, Peterson set up in his second flight to touch dorun just in front of the van. 

What Peterson and tlie rest of us didn't realize was that we engineers had n~ade a

little mistake. Since Milt had started flying the M2-F1 in August ant1 the weather had 

been quite warn1 whenever he flew the vehicle that fall, we had serviced the shock 

struts in the main landing gear with a standard viscosity oil. That was fine for Milt's 

earlier flights. However, on this early December morning, after two flights to altitude 

in temperatures below freezing, the oil had hardened to the consistency of nlolasses. 

When Peterson landed the M2-F1, the landing gear was rigid, the struts immobized by the thickened oil. At touchdo~vn, the main wheels separated from the vehicle and bounced across the lakebed, as shown in the film of the landing made by the 

forward-looking camera mounted behind the pilot's head. The four bolts connecting 

the wooden shell to the inner steel tubing also tore out, dropping the wooden shell 

about six inches until it settled around Peterson in the cockpit. 

Not injured, Peterson was the brunt of jokes about this landing for years afterwards. Structural repairs were easily made to the M2-F1. The original Cessna 150 

landing gear was replaced with the more rugged gear of a Cessna 180. Different struts 

were added with multiviscosity oil. Before continuing flights nearly two months later 

in late January 1964, we expanded the research data system to measure more parameters for extraction of aerodj namic derivatives. 

The first flights of the new year were made on the morning of 29 January, with 

Bruce Peterson, Wilt Thompson, and Chuck Yeager each making two flights. Yeager 

said he was having a ball flying the vehicle. The next morning, NASA pilot Don 

Mallick checked out in his first two and only lifting-body flights after Yeager made his 

fourth and fifth (last) flights in the M2-F1.9 

During the briefing session before the day's flights, I had denied Yeager's request 

to be allowecl to roll the M2-F1. He believed that he coulcl make a perfect barrel roll 

in the little Iifting body. I explained that Dick Eldredge and I had designed the 

M2-Fl to weigh 800 pounds and fly at a slower speed, not knowing the vehicle would 

8. Quoted in Hallinn, On the Frontier, p. 152. 

9. The fire flights incl~ldr only the air tows, not those in the M2-F1 towed 1)y the Pontiac. 
WINGLESS FLIGHT 

have to grow in weight to 1,250 pounds by adding an ejection seat, heavier instrumentation, and a landing rocket. I also explained that we weren't that confident in analyzing loads in a roll maneuver, for not only were there bending moments from side 

loads in sideslips, but loads also were transmitted to the vertical tails from the asymmetrical "elephant ears" attached to them. In short, we couldn't he sure the tail would 

remain intact during a roll, given the vehicle's heavier weight. 

Yeager didn't try to roll the M2-F1 on his last flight that morning. As experience 

later showed, however, Yeager likely could have barrel-rolled the vehicle successfully that morning, for over a year later the M2-F1 was rolled unintentionally in two 

flights and the tail remained intact. Although Yeager never flew a lifting body after his 

fifth flight in the M2-F1, he remained very enthusiastic about the concept, exerting a 

good deal of influence in encouraging the Air Force to develop the rocket-powered lifting bodies, the X-24A and X-24R, and the jet-powered X-24J. 

Serious Research Flying, 1964-1965 

After January 1964, we settled down into a year of serious research flying. Milt 

Thompson and Bruce Peterson often alternated as pilot, the M2-F1 flown a little over 

twice a month on average, as quickly as the research analysis team could digest 

data from one flight and plan the next. We made a total of 29 flights, 11 of them 

by Peterson. 

Working together, Ken Iliff, Bertha Ryan, and Harriet Smith had put together a 

planned program for extracting data from three basic types of flight maneuvers-the 

steady state, quasi-steady state, and dynamic. In a typical steady-state maneuver, for 

example, the M2-F1 would be flown straight ahead and sta1)ilized at different airspeeds in the glide, resulting in data for Jon Pyle and Etl Saltzman on lift, drag, and 

elevator trim. In a typical quasi-steady-state maneuver, the pilot would put the M2-F1 

into a gliding wind-up turn and gradually tighten the turn, increasing the "GI' load 

(gravitational pull) by increasing back stick pressure, allowing lift, drag, and trim data 

to be measured at higher airspeeds and with structural deflections, if any. 

In a typical dynamic maneuver, the pilot would stabilize the M2-F1 in a steady 

glide and then pulse one control at a time, with the pulse usually in a doublet. For 

example, if the goal was to get data on aileron characteristics, the stick would be 

moved to the right and held, moved to the left and held, then returned to neutral and 

held fixed by the pilot. Then, the vehicle would be allowed to oscillate with controls 

frozen by the pilot. This maneuver would be repeated for several airspeeds or angles 

of attack, researchers extracting aileron characteristics from the doublet portion of the 

maneuver and airframe characteristics from the final portion of the maneuver involving oscillation with controls frozen. This maneuver was also done for defining yaw control by rudder and pitch control by stick fore and aft. 

For the aerodynamic characteristics of the M2-F1 to be defined completely, 

Thompson and Peterson had to perform almost 100 maneuvers. With only about six 
COMMITMENT TO RISK 

minutes available as the M2-F1 glided down from 12,000 feet, the pilots used flight 

cards to squeeze in as many maneuvers as possible before having to set up for landing. Each flight averaged four maneuvers during those six minutes. 

Aerodyr~arnicists define the characteristics of a given airplane shape by the use of 

aerodynamic derivatibes coming from three types of air forces: those caused bj wind 

flow direction, angle of attack, and angle of sideslip; control deflections; and rotary 

motions. While there was plenty of uintl-tunnel data on the M2-F1 to compare with 

flight data on the first two types of air forces, there was no wind-tunnel data for the 

third, those air forces caused by rotary motions of the vehicle. The first two types could 

be evaluated easily in the wind tunnel with the model held stationer). on strings or 

pedestals. However, the third tjpe ran l)e evaluatetl only hy using ela1)orate mechanisms to rotate the nod el rapidly in all axes (roll, yaw, ancl pitch). No attempt was 

made at NASA Ames to obtain this type of dynamic or damping data during the windtunnel testing of tlie M2-F1, not only because of the huge expense involced in &\eloping the mechanisms, hut especially because of the lack of cotifidence in this type of 

wind-tunnel data, the elaborate mechanisms interfering with the airflou around 

the model. 

We "guesstimated" the rotary data that u-e put into the simulator along with the 

other data resulting from wind-tunnel measurements. Often, these "guesstimates" 

turned out to 1)e off by a factor of three or four since, at the tirne, we tlitln't have goocl 

techniques for estimating aerodynamic rotary damping tferibatives. Ken Iliff and Larry 

Taylor put their heatls togethvr, trying to come up with a solution. 

They decidecl to convert Taylor's garage at his home in 1,ancbaster into a wi~itl tunnel for measuring rotary derivatives, using the original small-scale model of the 

M2-F1 that I had built. TayIor built a long box with a five-horsepower electric fan in 

one end, plus straightening vanes and a special test he(-tion in the middle. They sealed 

the garage door so the entire garage could 1)e used to return the air to be recirculatetl 

through the box inlet, thus making it a more efficient closed-loop tunnel. Taylor also 

designed and rigged a balance system composetl of strings, pulleys, and a very sensitive string tension measuring device so the M2-F1 model could be rolled, yawed, or 

pitchecl at different rates. Of course, liglitueight household o1)jec.t~ hanging in the 

garage had to be anchored to keep tlwm from 1)lowing around in the garage. These athome wind-tunnel tests provider1 the data for tlie simulator estimates and for comparison uith actual flight data. 

Iliff and Taylor also applied a trial-and-error technique, originated by Dick Day 

on the X-2 project, that used the analog flight simulator for extracting derivatiies in 

flight. They changed settings on the simulation one at a time until hey got time histories of (Iy riamic maneuvers from the simulator to match up with those recordetl from 

flight. Although this was a long ant1 tedious process uith limited accurac), it was the 

on14 way we knew at the time for doing this task with analog systems. Hamet Smith 

was primarily responsible for extracting cleritatives from the M2-F1 fligh~ data, using 

this technique with the analog simulator. In 1965, Smith published a report entitled 

"Evaluation of the Lateral-Directional Staltility and Control Characteristics of the 
WINGLESS FT,TGHT 

lightweight M2-F1 lifting Body at Low Speeds," showing the flight results with windtunnel comparisons.10 

Iliff and Taylor also had new tools coming into use by which to sharpen their 

trade, for the digital computer revolution was in full swing by this time. Within a few 

years, they developed a new computer technique called "the maximum likelihood 

estimator," hy which dynamic-maneuver flight data could be input into a digital computer to produce aerodynamic derivatives-a technique producing very accurate 

results so long as the flight data used is high in quality and accuracy. In fact, "the 

maxin~uni likelihood estimator" that IIiff and Taylor originated (luring the lifting-body 

era at the NASA Flight Research Center is currently being used by flight-test organizations in the United States and in various countries around the world." 

Aerobatics in the Flying Bathtub 

Over the next two pears, 1965 antl 1966, the M2-F1 was used primarily to check 

out and familiarize more pilots with the lifting body, including NASA pilots Bill Dana 

antl Fred Haise and Air Force pilots Joe Engle, Jerry Gentry, and Don Sorlie. By this 

time, flying the M2-F1 was also a kind of preparatory task undertaken 1)y pilots who 

hoped later to fly the M2-Fl's heavyweight successor, the M2-F2. The M2-F1 made 

28 air-tou flights during 1965 and 1966, and by the time the first lifting body was 

retired from flight in August 1966, it had heen flown by ten pilots ahout 400 tirnes by 

car-tow and 77 ti~ries by air-tow. Fred Haise and Joe Engle flew the M2-F1 only on 

car-tows to 25 arid 30 feet in altitude on 22 April 1966, their experience with the lifting body cut short due to their being selected as astronauts for NASA space missions. 

Milt Thompson ant1 Vic Hol-ton developeil a formal lifting-t~ody pilot checkout 

procedure that required each pilot to make 24 car-tows I~efore his first air-tow flight. 

The first three car-tows involved nose-gear steering with to^-line releases at up to 45 

10. Harriett J. Smith, Evah~ation of th~ Lat~ral-Direc.~ionnI Stability and Control 

Churcicieristirs of the Lighi~ceight M2-Fl Lifting Body at Lozc Speeds (Tashingtot~, D.C.: NAS.4 

Technical Note D-3022, 1965). 

11. Another name for "maximum likelihood estimator" is paratneter estimation, which can also be 

tlescrihed as a series of matheniatic>al procedures developed ljy Drytler~ researchers to extracat prrriously unohtainal~le aerodynamic values front actual aircraft responses in flight. This contribution allowed 

Higlit researchers for the first titile to compare c:ertain flight results with predictions. iZ disrussion of this 

technique appears in 1,aw~ence a'. Taylor ant1 Kenneth W. Iliff, ".4 blodifird Newton-Rapllson Method 

for Detemiining Staljility Derivatives frorn Flight Dat;~," paper presented at the Second Intt~rnational 

Confer~nce on Computing Methods in Optimization ~roblenls, San Remo, Italy, Sept. 9-13,1968. On this 

matter, see also Kenneth W. Iliff, "Parameter Estimation for Flight Vehic.les," Journal of Guidance, 

Control, cind Dynamics , vol. 12 (Sept.-Oct. 1989): 605-22. 
COMMITMENT TO RISK 

miles per hour. The next six car-tows involved nose-wheel rotations up to 60 miles per 

hour. The final fifteen car-tows involved doing lift-offs at up to 95 miles per hour to 

familiarize the pilot with roll control with elevons and yaw control with rudders. 

Although the number of car-tows required seemed excessive to the pilots, Milt 

Thompson felt the requirement was necessary to minimize the risk of injury to a pilot 

or damage to the vehicle during car- and air-tows. 

Before moving on to air-tows, the pilots were also familiarized with the flare portion of lifting-body flight by means of a three-drgrees-of-freedom sinlulator and a 

shadowgraph presentation. This pe-flight procedure included familiarizing the pilots 

with the capabilities of the landing-assist rocket. 

On 16 July 1965, it was Captain Jerry Gentry's turn to get checked out in the M2- 

F1. An Air Force test and fighter pilot who later made the first flight of the Air Force's 

X-24A and then flew missions in Vietnam, Gentry found flying the M2-F1 on air-tow 

to be challenging. 

The lifting body was hooked by tow-line onto the Gooney Bird, and the takeoff 

began. Gentrq lifted the M2-F1 into formation above and behind the Gooney Bird on 

the end of the 1,000-foot tow-line. Then, the Gooney Bird, piloted by Fred Haise, lifted off. At about 200-foot altitude, while Gentry was climbing, something began to go 

wrong. Gentry began making small roll inputs to correct the right and left positions of 

the lifting body relatihe to the Goonel Bird, his corrections growing larger and larger. 

All at once, we had another pilot-induced oscillation in the making. 

As the amplitude of the oscillation increased, so did the urgency of radio contacts 

with Gentry: 

"Level your wing ..." 

"Level your wings!" 

"Release ..." 

"Release!" 

"Eject!" 

"Eject!" 

A45 the Gooney Bird slowly climbed to 300 feet al~ove the lakebed, Vic Horton was 

watching the M2-F1 through the tow- lane's observation dome, the rocking motion of 

the M2-F1 growing larger and larger. He watched in horror as the M2-F1 rollrd 1)ellyup and disappeared from sight below the tail of the Gooney Bird. Both Gentry and the 

safet) monitor aboard the Gooney Bird released the tow-line, realizing the situation 

was conipletely out of control. iTic Horton wTas convinced that he'd next see pieces of 

the M2-F1 scattered across the lakel)ecl, which, had it happened, coultl have been the 

end of the lifting-body program. 

When it was released from the ton-line, the M2-F1 was inverted with its nose high 

and tra~eling at approximately 100 knots airspeed, or about 115 miles per hour. The 

prd)al)ilitY of recovery from that corldition %-as virtually zero. During a normal landing, with the vehicle straight and level, the flare would be initiated at that 300-foot 

altitude at a sta1)ilized speed of 120 knots, or 138 miles per hour. Theoretically, at 

least, it was impossible to get the nose down in time to pick up the speed needed to 
WINGLESS FLIGHT 

M2-Fl dummy ejection seat test setup at South Edwards. (Air Force photo JN-043-1, available as NASA 

photo EC97 44183-4) 

accomplish flare. Fortunately, Gentry ignored theory and, after release from the towline, completed the barrel roll, touching down on the lakebed at the bottom of the 

roll ... all in nine seconds. It was a hard roll that broke the landing gear but it produced 

no other damage or injuries, except to Gentry's pride. 

Gentry was so upset that he insisted on trying another flight immediately. Other 

members of the operation, including the instructor pilot, were in such a state of shock 

at the time that they agreed to try again, even though the M2-F1 was obviously listing 

heavily to one side due to its broken landing gear. Luckily, cooler heads had observed 

the entire incident from the office of the Director of Flight Operations. A stern call 

came over the radio to knock it off and get back in here. 

During the next thirteen months, while Gentry practice more car-tows, the 

repaired M2-F1 was flown nine times by Milt Thompson. On 16 August 1966, Gentry 

got his second chance at a checkout flight on the M2-F1. None of us expected history 

to repeat itself, but it did. We watched in shock as the same sequence of events rapidly developed, a low-amplitude lateral oscillation beginning immediately after liftoff, 

rapidly building to greater than plus or minus 180 degrees. Once again the tow-line 

was released with the M2-F1 upside down at 300 feet above the lakebed. Gentry must 

have found something familiar about the episode, for this time he released the tow, 

completed the barrel roll, came wings level, ignited the landing rocket, and made a 

perfect landing. 
COMMITMENT TO RISK 

The second time around there was no damage to the vehicle, but Bikle apparently had had enough. "That's it!" he said. Bikle saw towing as a special problem with 

the M2-F1, believing that in future we should look into launching lifting bodies from 

bombers. Bikle stuck by his decision, grounding the M2-F1 permanently. With that, 

the first lifting-body vehicle was retired from flight. 

Gentry later was able to prove to Bikle, Thompson, and Lieutenant Colonel Don 

Sorlie, the official boss of the Air Force's lifting-body pilots, that his problems in the 

M2-F1 were caused simply by a lack of visibility. Being much shorter than the other 

pilots affected his eye position in the cockpit of the M2-F1 consideral~ly, so much so 

that after the lifting body and the Gooney Bird left the ground on tow, he could see 

neither the Gooney Bird nor the horizon through the nose window, making it humanly impossible to control the vehicle's attitude. 

Recalling the event years later, Gentry said with a laugh, "Oh, hell, I was upside 

down twice on tow. As soon as I could figure out which way the roll was going, I put 

stick in with the roll and went on around. When I got momentarily to wings-level, I 

off. Barely had time to release the tow, flare, and whump. The second time it 

happened, I said, 'Well, I've been here before.' I'd gotten good enough at it that I even 

glided for a few seconds."l2 

Whether Gentry would he allowed to continue flying lifting bodies in future phases of the program rested entirely on the ruling of Bikle and Thompson after conferring 

with Sorlie. They decided to allow Gentry to continue with the rocket-powered lifting 

bodies. In 1992, in his acceptance speech at a Test Pilots' Walk of Honor awards ceremony in Lancaster, Gentry expressed appreciation for Bikle and Thompson's decision. While he was flying the lifting bodies, Gentry was the project pilot on the F-4E 

and later did flight tests on other aircraft including the F-4C/D, F-104, F-Ill, 

and F-5. 

Significance of the M2-F1 Program 

The M2-F1 program proved to be the key unlocking the door to further liftingbody programs, including the current Shuttle spacecraft and several other vehicles 

currently in-progress, such as the X-33. Flight tests of the M2-F1 supplied the boost 

in technical and political confidence needed to develop low lift-to-drag-ratio, unpowered, horizontal-landing spacecraft. 

Technical reports written by the engineers who were part of the M2-F1 program 

also were important, establishing the lifting-body as a concept. For example, "FlightDetermined Low-Speed Lift and Drag Characteristics of the Lightweight M2-F1 

Lifting Body" by Victor W. Hortnn, Richard C. Eldredge, and Richard E. Klein compared wind-tunnel and flight data to establish the fact that a lifting body with a maximum lift-to-drag ratio of 2.8 measured in-flight could be landed successfully and 

12. Kilkinson, "Legacy of the lifting Rotly," pp. 54-55. 
WINGLESS FLIGHT 

repeatecllj by an unassisted pilot.17Furthermore, the findings of the M2-F1 stal~ilitjand-control engineering team-Ken Iliff, Bertha Ryan, Harriet Smith, and Larry 

Taylor-demonstrated that a radically-shaped flying machine such as the M2-F1 did 

not need automatic. control augmentation to have acceptable and even good handling 

qualities, a conclusion confirmed in Harriet J. Smith's "Evaluation of the 1,ateralDirectional Stability and Control Characteristic-s of the Lightweight M2-F1 Lifting 

Body at Low Speeds."'% 

In the 19605, the lifting-body concept u-as so tentative in the minds of spate planners that the M2-F1 program seemed destined to have pronounced effect on the direction taken afterwards in space vehicles, the potential for cleveloprnent of 

horizontal-landing spacecraft fairly much dependent upon our success. Any one of 

three different effects could have followed from the three major outcomes poqsible for 

the M2-FZ program: 

First, the M2-F1 program could have halted after the car-tows at very low altitudes, as would ha\e happened had Paul Bikle agreed uith the then Chief of the 

Research Division at the NASA Flight Research Center. Had this happened, the 

expressed lack of confidence in the flight concept could have prevented the later 

acceptance of any proposed follo~v-on lifting-body programs, which, in turn, could 

have slowed or prevented the later development of a horizontal-landing spacecraft 

such as the current Shuttle. 

Second, if we hat1 had a serious accident ~ith the M2-FI in which a pilot was 

injured severel) or killed, it isn't likely that any additional lifting-body flight-test programs would have taken place, making even less likely the later dekelopment of 

today's Shuttle and other horizontal-landing spacecraft. 

Third, the M2-F1 program could he an adventure in success and open the door 

for future lifting-body programs. Fortunately, this is exactly what happened. And the 

door remains open for generations yet to come of the progeny of the original lifting 

l)ody, the lightweight M2-F1. 

13. Victor a'. Horton , Richard C. Eldredge, mid Richard E. Klein, Flight-Determiner1 Lou,-Speed 

Lift ctnd Drug Characteristics of the Lightweight 1712-Fl Lifting nody (Washington, D.C.: NASA 

TN D3021,1965). 

14. Harriet! J. Smith, Eval~intion of the Lateral-Directional Stability and Control 

Characteristics of the Lightweight M2-Fl Lfin Body at Low Speeds (Washington, D.C.: NASA 

Technical Note D-3022, 1965). 

CHAPTER 4 

ON TO THE HEAVYWEIGHTS 

When Paul Bikle grounded the M2-F1 pernianently in mid-August 1966, a 

ground swell of interest in lifting-body re-entry vehicles had been growing for over two 

years within NASA. The initial flights of the M2-F1 had shown that the lifting-body 

shape could fly. As early as two weeks after the first car-tows of the M2-F1 in April 

1963, Bikle had shared his confidence in lifting bodies with NASA Headquarters, 

writing Director of Space Vehicles Milton Atnes that the more the Flight Research 

Center got into the lifting body concept, the better the concept looked. 

Bikle also mentioned that he was noticing "a rising level of interest" in the lifting-hotly concept at the Ames and Langley centers. By 1964, NASA Headquarters 

and these two Centers had considerably increased their participation in the liftingbody concept through the Office of Advancecl Research and Technology (OART) 

under the direction of NASA Associate Administrator Raymond Bisplinghoff. 

By this time there were also many lifting-body advocates within the aerospace 

industry and the Air Force. The successful flights of the M2-F1 had accelerated the 

aerospace community's interest in the possibility of applying the concept of lifting reentry to the next generation of spacecraft. After our M2-F1 success, the lifting body 

quickly rose toward the top of the Air Force's priorities in re-entry designs. Although 

there were still many in the Air Force holding out for variable geometry wings and jet 

engines to assist in landing recovery, wingless and unpowerecl vehicles hat1 become 

more prominent in both NASA and Air Force studies.] 

Change in Plans: On to Rocket Flight 

1 had originally planned to fly three lightweight lifting-body shapes. Once the M2- 

F1 had been built, I was ready to move on to the other two shapes, the MI-I, and the 

lenticular. By this time, however, interest in huilding the other two shapes into vehicles had waned, replaced by the urge to fly a rocket-powered lifting body at transonic speeds. 

After the M2-F1 was built in 1962,T went to NASA Ames and NASA 1,angley to 

confer with other engineers about tleveloping lifting re-entry configurations. At NASA 

I,angley, T discovered that the leading lifting-body advocates among the engineers 

were rapidly making progress. Eugene Love was leading the lifting-body interest at 

NASA Langley, with Jack Paulson, Robert Rainey, and Bernard Spencer conducting 

1. Entire thrw paragraph, ahow, including quulaliori, based upon Hallion, On the Fronri~r, 

pp. 151-53. 
studies and wind-tunnel tests on candidate designs. Although they were still considering deployable wings and jet engines, a powered and ~vingless lifting-hody c-onfiguration-the HL-10 (for Horizontal Lander)-emerged as a strong contender after our 

success in flying the M2-F1. 

NASA Headquarters assigned Fred DeMerritte as program manager for coordinating lifting-body actibities at various sites, including the Flight Research Center, 

An~es, ant1 Langley. We felt fortunate to have DeMerritte as program manager, for he 

was a team worker who listened to us. His skill in cutting through red tape 

helped us move the lifting-body program along. We set up a planning team composed 

of three members, one for each of the three NASA sites. Khile I represented the Flight 

Research Center, George Kenyon and Bob Rainey represented Ames and 1,angleq; 

respectively. Since Johnson Space Center in Houston, Texas, had become the leading 

Center for manned space exploration, the planning team niet at Johnson with its representat ires. 

After Kenyon, Rainey, and T presented the views of our colleagues, we quickly 

narrowrd in on two important objectives. First, future flight tests on lifting bodies 

should Ie at wing loatlings or weights five to ten times more than those of the M2-Fl. 

Secondlj, flight-test hehicles should be capable of the higher speeds in the transonic 

and lower supersonic speed ranges where large changes in lifting-body aerodynamics 

occur. 

After my return to the NASA Flight Research Center, I put together a plan for a 

heavyweight M2-F1 with the same dimensions as the original vehicle, proposing to 

launch the heaqw-eight version froni the Center's B-52 in a way similar to how the X15 was launched. The X-15 program was no longer using the LR-11 rocket engines, 

and we could use them now in our lifting-hod! program. The LR-11 engine consists 

of four separate barrels or chambers, each barrel (leveloping some 2,000 pounds of 

th111st for a total thrust of about 8,000 pounds. The pilot had four increments of throttling capability since each barrel could be operated separately. Two LR-11 engines in 

the X-15 had achieved 16,000 pounds of thrust, the rnginrs burning a combination of 

water and alcohol, with liquid oxygen employed as the oxidizer. The 33,000-pound X15, including the 18,000 pounds of fuel and oxidizer that it c-anied aloft, had 

achieved Mach 3.50 with the two LR-I 1 engines. We figured that we could achieve 

our transonic speed objective hy using one TAR-1 to get (.lose to Mach 2 flight in an 

aluminum version of the M2-F1.2 

To get a simple weight estimation for the aluminum lifting I~ody, I compared the 

wingless weights of two aircraft that had used the LR-11s earlier, the X-1 and the D2. Paragraph has~d in part on Thompson, ;it the Ecf,g~ ofSyac~, pp. 46-47,85, but that source gives 

information on the LR-1 I engines tl~a~ %-ere not upratetl. The powered lifting bodies use(] uprated engines 

with upwards of 8,000 Ihs. of thrust venu* the 6,000 11)s. of the original 1.R-11. Srr Frank W-ir~ler, 

"'Black Betsy': The 6000C-4 Rocket Engine, 1945-1989. Part 11," .-lctn .4stronnrrticn 32, No. 4 (1994): 

313-1 7, and nu\ it1 Raker, SpnceJiBht rir~dRock~rry: ./I Chronology (Xew York: Facts on File, 1996), 

p. 167. 
nTINGLESS FLIGHT 

558, coming up with a target weight of about 10,000 pounds. I estimated the vehicle 

weight of the aluminum M2-F1 would be 5,000 pounds, including one LR-11 engine. 

Given the large volume inherent in the lifting-body shape, I foresaw little difficulty in 

installing tanks to carry another 5,000 pounds of fuel and oxidizer, bringing the 

launch weight up to about 10,000 pounds. 

One problem arose right away in designing the vehicle. In the unpowered M2-F1, 

the pilot and ejection seat had been positioned on the aircraft's center of gravitj, where 

the fuel tanks would need to be in the rocket-pow-ered version. Fortunately, there was 

enough depth in the basic M2-F1 shap~ to move the pilot and canopy forward of the 

center of gravity. Earlier I had hoped that we could preserve the M2-F'l's original 

shape in the aluminum version so that the wind-tunnel and flight data measured on 

the original version would remain valid for the aluminum follow-on. Moving the 

canopy forward, however, meant aerodynamic changes that made newT wjntl-tunnel 

tests mandatory. 

I c.alculated the aircraft's performance, assuming an air launch of a 10,000-pound 

M2-F1 from a B-52 at 45,000 feet, with an 8,000-pound-thrust LR-I1 engine burning 

down to a burnout weight of 5,000 pounds. The result showed that a speed close to 

Mach 2 couId be achieved. 

Birth of the M2-F2 

The cost of a rocket-powered lifting-body program could be cut substantially, I 

found, by using the present facilities and personnel for maintaining and operating the 

LR-11 engines and 1)y using NASA's B-52 as a mothership for launching the lifting 

body. We could design and fabricate an adapter to be used in launching the lifting 

body that would attach to the B-52's wing pylon used in air-launching the X-15. When 

I presented my idea for the rocket-powered lifting-1)ody program to Paul Bikle, he said 

it sounded good and suggested I try the idea out on others at the NASA An~es 

Research Center. 

I presented the idea to members of the NASA Ames wind-tunnel team, including 

Clarence Syvertson, George Kenyon, and Jack Bronson. While they liked the idea, 

they said the "elephant ears" on the M2-F1 would have to go because they would burn 

off during re-entry from space. They were concerned that these outer horizontal 

elevons woulcl create a serious heating problem from shock-wave and boundary-layer 

interaction as well as shock-wave impingement. I tried to talk them into leaving them 

on, knowing the elevons worked very well for roll control on the M2-F1 and provided 

a lot of roll damping to help retard any potential problems in roll oscillation. But they 

insisted that they had to go, saying there were no materials that could take the potential heat that would be generated on the elevons' leading edge ant1 the slot between 

the elevon and vertical tail. After the NASA Ames team presented the M2-F2 configuration that it recommended for space re-entry, the team said we should use the M2- 

F2 in place of the M2-F1 shape in a rocket-powered transonic research program. 
The roll control on the M2-F2 consisted of split upper flaps of the sort we had originally built on the M2-F1 but abandoned before we had started flight-testing. The 

NASA Ames team also added an extra body flap on the lower surface so that the upper 

split flaps and the lower body flap could be opened like feathers on a shuttlecock to 

give the longitudinal stability needed at transonic speeds. 

Even though the extra body flap caused increased drag, the NASA Ames team 

members defended their decision made on the basis of wind-tunnel test results. Ken 

Iliff and I expressed concern about adverse yaw from the split-flap roll control. They 

said we could cancel it out by designing an aileron-rudder interconnect into the control system. This sounded reasonable in theory, but those flaps would complicate our 

lives greatly when we actually flew the M2-F2. The simplest and most straight-forward 

design solutions had always appealed to me, and keeping the "elephant ears" still 

seemed to me the simplest and most direct option. 

Not giving up easily, I asked the NASA Ames engineers about the pressure on the 

upper-body flaps caused by the aerodynamic interaction of the rudders. They said I 

shouldn't worry about that, for they had prevented that problem by making the rudders operate like split flaps with outward movement only. The stationary inner surface 

of the vertical fin adjacent to the rudder would shield the split elevon upper flaps from 

rudder pressure, they claimed. They defended the feature, saying the transonic shuttlecock effect was needed in both yaw and longitudinal axes. Moving both rudders outboard, they added, provided directional stability in the transonic speed region-and 

added more drag, of course. 

Meanwhile, Iliff and the Dryden analytical team had done a great deal of work on 

data bases for not only the M2-F2 but for a generic M2 vehicle, the HL-10, and an 

earlier version of the X-24 called the SV-5. Harriet Smith and Bertha Ryan worked 

with simulation programmers to develop analog engineering simulators for study of the 

unusual aircraft dynamics of the IIL-10 and the various M2 configurations. Based on 

dynamic itudies, the team believed that a center fin was the best solution to problems 

of instability that they hat1 identified. However, the Ames team argued that the 

increase in dihedral effect from a center fin would make the M2-F2 much more sensitive to side gusts. Milt Thompson agreed with the Ames team that it was not a good 

idea to make the vehicle more sensitive to gusts. 

By now, the lifting-body program was snowballing. We were getting even more 

input continually from NASA engineers at other sites who were experienced in aircraft 

and spacecraft design. I began to feel it might he time for me to hack off from my simple approach and let more of these experts contribute to the program. Designing control systems for lifting bodies was going to 1)e a major effort requiring a lot of expert 

help, I felt. As a result, we froze the M2-F2 configuration with the fonvard canopy 

location and the greatly modified aerodynamic controls on the aft end of the I)otfy. 

Paul Bikle, Milt Thompson, and I put together a program proposal for NASA 

Headquarters. Because of the growing importance of our a(-tivity to the future of lifting re-entry, we suggested that two M2-F2s be built at the same time to provide us with 

a backup in case one vehicle was damaged and to allow us to do separate experiments 
WINGLESS FLIGHT 

simultaneously. We presented our proposal to Fred DeMerritte and his bosses at 

NASA Headquarters. After listening to us, DeMerritte said they'd rather we substituted the NASA Langley HL-10 for the second M2-F2. 

Gene Love and the contingent from NASA I,angIey had made presentations to 

NASA Headquarters the week before we presented our proposal. Given the close 

proximity of the Langley Research Center in Hampton, Virginia, to NASA 

Headquarters in Washington, D.C., it was common for Langley representatives to be 

at the Washington headquarters almost daily. Unofficially, NASA 1,angley had always 

been considered the "mother" research center, and NASA Headquarters seemed to be 

more influenced by Langley than by any other NASA research center. 

Birth of the HL- 10 

In 1957, while A1 Eggers and his NASA Ames team were studying half-cone rrently configurations, NASA Langley researchers were conducting hroader re-entry 

studies, including winged and lifting-body vehicles. Hypersonic studies conducted at 

Langley7s aerophysics division were evaluating various aerodynamic shapes. Preliminary goals at Langley in design features for a re-entry vehicle included minimization 

of refurbishment in time and money, fixed geometry, ION deceleration loads from 

orbital speeds, low heating rates, ability for roll and pitch modulation, and horizontal 

powered landing. 

According to these studies at I.angley, a re-entry lifting-body vehicle with negative camber (that is, with the curved portions of wing surfaces turned upside-down) 

and a flat bottom might have higher trimmed lift-to-drag ratios over the angle-of-attack 

range than those of a blunt half-cone dvsign. The negative-camber concept was used 

in 1957 in developing a vehicle-initially referred to as a Manned Lifting Re-entry 

Vehicle (MLRV), but now referred to simply as a lifting body-that was stable about 

its three axes and retained a flat lower surface for better hypersonic lifting capability. 

These studies at Langley found that a vehicle with an aerodynamic flap, a flat bottom, 

and a nose tilted up at 20 degrees would be stable about the pitch, roll, and yaw axes 

and trim at angles of attack up to approximately 52 degrees at a lift-to-drag ratio in 

excess of 0.6. 

In a paper presented at the 1958 NACA Conference on High-speed 

Aerodynamics, NASA Langley's John Becker described a small winged re-entry vehicle embodying all of the features that had earlier been identified as design goals at 

Langley, including low lift-to-drag ratio for range control, hypersonic maneuverability, and conventional glide-landing capat)ility.3 The vehicle in Becker's paper also 

3. John V. Beck~r, "Preliminarq. Studirs of Manned Satellite5-Wing~d Configurations," h"4CA 

Conference on High-Speed ,4erodynamics: A Compilation of Papers Presented (Moffett Firld, CA: Amps 

Aeronautical Laboratory, 1958), pp. 45-57. 
ON TO HEAVYWEIGHTS 

included a flat-bottomed wing with large leading-edge radius and a fuselage crossing 

the protected lee area atop the wing. This configuration, however, wasn't selected to 

carry the first American astronaut into space. Officials at Johnson Space Center opted 

instead for a ballistic capsule, the Mercury "man in a can.'' Their decision, however, 

did not deter researchers at NASA Langley from continuing to tlevelop concepts and 

design goals for a lifting re-entry vehicle. 

In the earl) 1960s in its space mission studies, 1,angley's astrophysics dikision 

began moving away from winged to lifting-body configurations. The first seven refined 

mission vehicle goals of 1962 echoed the desirable characteristics of re-entry tehicles 

described in these studies. One goal was a hypersonic lift-to-drag ratio near 1 without 

elevon deflection, thus avoiding heating problems near the elevons in the maximum 

heating portion of the trajectory. Another goal was high trimmed lift at hypersonic 

speeds, providing high-altitude lift modulation. A subsonic lift-to-drag ratio of 

approuimatelj 4 was desirable for horizontal runway landings without power during 

emergencies. Furthermore, the vehicle's hody should provide high volumetric efficiency (the ratio of the useful internal bolume to the total exterior volume encompassed by the external skin) with a 12-person capability, and it should have 

acceptable heating rates and loads at all speeds, possibly including super-orbital 

ones. Also essential were launch-vehicle compatibility ant1 stability and control over 

the speed range. 

Evolving configurations at Langley were refined to meet these mission goals. 

Trade-off studies interrelated sweep, thickness ratio, leading-edge radius, and loration of maximum thickness. The negatively cambered HI,-10 lifting-body design 

emerged in 1962. It then entered an intermediate stage of evolution, involving nearly 

every research division at Langley in intensive efforts to identify and find solutions for 

problems associatecl with this type of configuration. Interestingly enough, much 

debate still raged over negative camher versus no camber (or symmetrical shape), 

fueling even more derailed studies. In the end, negatively cambered and symmetrical 

(no camber) configurations were evaluated in terms of the mission goals. Three more 

mission goals were also added, becoming serious issues in selecting camber: low-er 

heating rates and loads comparison, lower angle of attack for a gilen subsonic Iift-todrag ratio, and reducbed subsonic. flow separation. The negativeIy cambered HL-10 

met nine of the ten mission goals, the symmetrical design meeting only five. The only 

goal not met Ily the HL-10 was the lower angle of attack for a given subsonic lift-todrag ratio. 

The HL-10 evolved as a flat-bottomed, fixed-geometry hody with rounded edges 

and a split trailing-edge elevon capable of symlnetric upward deflection, providing the 

pitch trim and stability required for hypersonic re-entry and subsonic flight. The trailing-edge elevon would also deflect differentially for roll control. For even more directional stability, tip fins were added. The lower su~face was negatively cambered, 

assuming a rocking-horse shape to provide longitudinal trim. The aft end of the upper 

surface was gradually tapered, or boat-tailed, reducing subsonic base drag and 

decreasing problems in transonic aerodynamics. There was enough forward volumet- 
WINGLESS FLIGHT 

ric distribution within the HL-10 to meet center-of-gravity requirements for subsystems and crew in balancing the vehicle for flight. 

As research and development on the final vehicle design hegan at Langle); 

research centered on such issues as trajectory analysis and entry environment, heat 

transfer, structures and thermal protection, aerodynamics, dynamic. stability and control, handling qualities, landing methods, emergency landings on land and water, 

equipment and personnel layout, and viscous effects including Mach number, 

Reynolds number aerodynamic scaling factor, and vehicle length. 

Because the shape resembled that of a hydroplane racing boat, Langley also conducted tests with HL-10 nlodels for horizontal landings on water, using its water test 

basin facility. However, even more water-landing tests would have been needed to 

optimize the HL-lo's shape for water landings. 

A disadvantage then and now of lifting bodies is that they suffer an aerodynamic 

heating penalty due to the fact that they spend more time within the entry trajectory 

than do ballistic missiles. Consequently, methods of thermal prot-ection were extensively researched. Using small and thin-skinned inconel models, engineers also made 

detailed wind-tunnel tests, measuring heat-transfer distributions at Mach 8 and 20. In 

great detail, experimental heating was measured on the models' shapes. 

The volumetric efficiency for the proposed HL-10 was relatively high in several 

designs. One 12-person configuration had an estimated length of 25-30 feet, a span of 

21 feet, and a pressurized volume of 701 cubic feet. It also had an attached rocket 

adapter module and a full-length raised canop?. Some vehicle designs were 100 or 

more feet long. 

The camber issue settled, by 1964 the HL-10 had assumed a swayhacked shape, 

like that of a child's rocking horse. To determine the best fin configuration, LangIey 

conducted studies using ten wind-tunnel models-ranging from a 4.5-inch hypersonic one with twin vertical fins to a 28-foot low-speed version with a single central dorsal fin. Researchers investigated single-, twin-, and triple-fin arrangements, 110th 

lower-outboard and dorsal, along with various modifications to the aft end of the vehicle's body. Finding an acceptable fin arrangement involved a compromise between 

suhsonic trimmed performance and hypersonic trim and stability. Langley proposed 

that be build the configuration that offered the best compromise, a triple-fin HL-10. 

NASA-Northrop Program: Building the M2-F2 and HL- 10 

I formed a team at the NASA Flight Research Center that then wrote a Statement 

of Work for designing and fabricating the M2-F2 and HL-10. Besides furnishing the 

I,R-11 rocket engines, NASA would provide all wind-tunnel data as well as aerodynamic load and B-52 captive-load specifications. NASA would also do all control-system analysis and simulation needed for specifying control laws and gains in the 

automatic functions of controls. The contractor's main responsihility would be to 

design and build the hardware in concert with the NASA analytical team. 
Fortunately, operations engineers and technicians on the X-15 program helped us 

write the specifications on pilot life-support, electrical power supply, hydraulic control, landing gear, rocket, and rocket fuel subsystems. One of my long-time friends, 

John McTigue, then operations engineer on the third X-15, helped me specify the 

work for operational systems. Milt Thompson and Bruce Peterson helped me write the 

portions relating to the pilot's controls and cockpit displays. 

In February 1964, having authorization from the NASA Associate Administrator, 

Raymond Bisplinghoff, we went "on the street" with a Request for Proposal (RFP), 

soliciting bids from 26 aerospace firms for designing and fabricating the two rocketpowered lifting bodies. Fortunately, several companies were interested in our program, believing that the next generation of spacecraft would habe horizontal landing 

capability and that any aerospace contractor participating in our experimental lifting1)ody program would have an edge over other firms in later space programs. Five companies su1)mitted bids, and our choice eventuaIly was narrowed to two of them: North 

American Aviation (later to become Rockwell International, Rockwell's aeronautics 

and space divisions now part of Boeing) and Northrop Corporation. 

Many supposed that North American (later selected as the prime contractor on the 

Apollo program) would be a shoo-in for the job, since North American had built the 

X-15. However, the Norair Division of Northrop clearly had the superior bid, the 

NASA Flight Research Center awarding the contract to Northrop on 2 June 1964. The 

RFP's timing worked in both Northrop's and NASA's favor. Northrop had intact the 

team that had just finished developing the prototype T-38 aircraft. A 19-month interval between the T-38 and another major program allowed Northrop to assign this team 

of their best people to our lifting-body program. Consequently, Northrop could keep 

this team together while NASA got the best bargain in skilled people for its program. 

Northrop's proposal listed all key persons from this team that wouItI be working on our 

program, providing us as well with their resumes. Ralph C. Hakes of Nol-throp was 

assigned as Project Director with Fred R. Erb serving as Northrop's chief systems and 

mechanical designer. 

Northrop's proposal presented a detailed preliminary design with drawings showing the use of many off-the-shelf components, including modified T-37 ejection seat, 

Northrop's T-38 canopy operatindocking mechanism and ejection system, T-38 stick 

grip, modified T-39 dual-wheel nose gear, Northrop's F-5 main gears with T-38 wheels 

and brakes, Northrop's X-21 hydraulic control actuators, and silver-zinc batteries for 

hydraulic and electrical power. Northrop signed a fixed-price contract requiring deliveq- of the two vehicles in 19 months for $1.2 million each, a bargain-basement price 

for NASA, even in the 1960s. According to one aerospace spokesman, at that time the 

M2-F2 and HL-10 could have cost $15 million each. In the mid-1960s, Northrop was 

non-union, giving the corporation flexibility in adapting the most economical and efficient methods for producing the two lifting bodies. Northrop not only delivered the 

vehicIes on time but also did so with no cost overruns, two out-of-the-norm 

accomplishments for aerospace programs to that time and since. 
WINGLESS FLIGHT 

Northrop purposely kept its project organization lean and flexible, with an average of 30 engineers and 60 shop personnel, each averaging 20 years of aerospace 

experience. As Ralph Hakes later recalled, the engineers involved were "all twentyyear men who had worked to government specifications all their lives and knew which 

ones to design to and which to skip." He added that NASA's "people and ours would 

talk things over and decide jointly what was reasonabIe compliance with the specifications. Decisions were made on the spot. It didn't require proposals and counter-proposals." 4 

NASA and Northrop's program managers devised a Joint Action Management 

Plan accenting five guidelines for efficiency: keep paperwork to a minimum, keep the 

number of employees working on the project to a minimum, have individuals-not 

committees-making decisions, locate the project in one area where all needed 

resources could be easily and quickly gathered, and fabricate the vehicles using a 

conservative design approach. Consequently, engineering and factory areas were 

located in the same building, and veteran shop technicians fabricated and assembled 

components from a minimum of formal drawings and-in some cases-solely from 

oral instructions. A special photographic process transposed drawings onto raw metal 

stock, avoiding costly jigs and fixtures. Northrop's project personnel maintained a very 

close operational relationship with NASA's personnel, maximizing the joint team's 

ability to react swiftly in solving problems and making changes. 

The overall tone of cooperation in this joint NASA-Northrop program had been 

established from the beginning by Paul BikIe and Northrop's Richard Homer. The two 

men had much respect for each other and a good person-to-person understanding of 

how the program was to be conducted. Horner and Bikle had worked together often in 

the past. Horner had worked for the Air Force from 1945 until June 1959, when he 

became NASA associate administrator until July 1960. Afterwards, he became executive vice president of Northrop. Together, Bikle and Horner agreed to do away with 

red tape and unnecessary paperwork, a simplification that had a dramatic. effect on 

keeping costs low and efficiency high. Both men had impeccable reputations and 

credibility, keeping their word on agreements. Even though this was a fixed-price contract, Bikle and Horner agreed that it would be to both NASA's and Northrop's best 

interests to build these lifting bodies in the most cost-effective and timely manner. 

The Program That Almost Was: Little Joes and the M2 

About this time, another opportunity arose to conduct a low-cost program using 

surplus equipment. Four Little Joe solid rockets, used to test the Apollo capsule's 

escape system, were available at the NASA White Sands rocket testing facility in New 

4. Quoted in Hallion, Orr the Frontier, p. IT%. 
ON TO HEAVYWEIGHTS 

Mexico. I began to explore the possibility of mounting an M2-F2 configuration on top 

of a Little Joe booster for a vertical launch and possible flight to Mach 6. 

Earlier, before it was assembled with the steel-tube carriage structure, I had had 

a fiberglass mold made from the M2-F1 wooden shell, just in case it was damaged in 

flight tests or we wanted to build another, heavier, M2 out of fiberglass instead of wood. 

Using this mold, I could make a vehicle with a thick fiberglass skin capable of 

withstanding speeds up to Mach 6. The vehicle would be made much like a hoat, its 

thick skin acting like an ablative coating to cool the structure from aerodynamic heating at high speeds. It would be unpiloted with a rocket climb and push-over trajectory followed by a pre-programmed turn. 

Also available for recovering the M2 after it had slowed down to about Mach 2 

were some surplus parachute systems from the Gemini program. John Kiker of the 

Johnson Space Center, in charge of developing the parachute spacecraft recovery systems for NASA's Gemini and Apollo programs, offered his services in adapting the 

parachute systems for recovery of the M2. Once we found out we had mutual interests 

it1 flying experimental radio-controlled model airplanes, Kiker and I became and have 

remained friends. In the early days of Shuttle development, Kiker had constructed flying scale models of the Boeing four-engine 747 and the Enterprise, then demonstrated a successful launch of the model Enterprise from the Lack of the model 747 

at Johnson Spare Center. This test, using Kiker's models, was done before the 

approach-and-landing tests of the full-scale Ertterprise at Edwards AFB in 

October 1977. 

After I talked with Kiker, I telephoned Dick Thompson, the manager of the NASA 

White Sands facility, about using the Little Joe 1)oosters to launch an M2. Thompson 

liked the idea and said he could furnish the personnel for servicing the rockets, 

preparing them for launch, and conducting the launch operation, if the Flight 

Research Center would be responsible for the M2 payload. I found myself trying hard 

to restrain my excitement, for I had already located a surplus hydraulic control system and a prograrnma1)le missile guidance system. It was all going too smoothly, too 

quickly, too easily to be l~elievahle. About then, a big dose of reality intruded, ending 

this tiny program before it had even hegun. 

Dick Thompson contacted me, saying the Little Joe rockets were out-of-date anti 

would require an inspection Lefore they could he used. Being naive about how much 

such things cost, it didn't occur to me that it ~~ould cost very much to inspect something as simple as a solid rocket. So it blew my mind when Thompson told me that an 

inspection would cost about $1,OCK),000 per rocket-about half the cost of the 

Northrop contract for the t~o lifting bodies. Apparently, the inspection involved much 

more than simply x-raying the solid propellant for cracks. 

I reasoned with Thompson, trying to find a way to use an abbreviated inspection 

since the test flight would be unpiloted. Thompson was adamant, however, opposed to 

allowing even the potential for an explosion on the launch pad, NASA space policy 

having hecome very conservative after the early days of numerous rocket explosions 

on the pad. 
WINGLESS FLIGHT 

Thus ended the program that almost was. It had been a good idea, just not a practical one. In the future, others' ideas would have better chances for success. 

NASA-Air Force Lifting-Body Program 

Since 1960, the Air Force had also been conducting studies of piloted, maneuverable lifting-body spacecraft as alternatikes to the ballistic orbital re-entq concepts 

then in favor. Given the long history of cooperation and joint ventures between the Air 

Force and the NASA Flight Research Center at Edwards AFB, it was only natural for 

them eventually to pool their resources in the flight-test portion of the lifting-1)ody program, much the way they had in the X-15 and earlier X-plane programs. 

Murh as Walt Williams had done before him, Paul Bikle had always worked closely and effectively with others at the Air Force Flight Test Center. This spirit of cooperation extentfed to all personnel levels. Since the early days of the NACA station at 

Muroc in the late 1940s, there had been few, if any, disagreements at the \$ark-level 

between NASA and Air Force personnel, and any that existed had been imposed from 

ahove. 

In the early spring of 1965, as Northrop entered its final months of fabricating the 

first of the two heavyweights, Paul Bikle recognized that the lifting-body prog-am was, 

like the X-15 program before it, becoming too large for the Flight Research Center 

(FRC) to manage and operate alone and that NASA and the Air Force had similar 

interests in the lifting bodies. Bikle met with his Air Force counterpart, Major General 

Irving Branch, commander of the Air Force Flight Test Center (AFFTC), throughout 

the early spring. 

Fro111 those meetings emerged a me~norandum of understanding between the two 

centers on 19 April 1965, nearly two months before the M2-F2 was completed at 

Northrop's plant in Hawthorne, California. Drawing on the two centers' shared experience with the X-15 program and allutling not only to the excellent working relationship hetween NASA and the Air Force but also to similarities between the X-15 and 

lifting-body programs, the memorandu~n of understanding created the Joint 

FRCIAFFTC Lifting-Bocly Flight Test Committee. Ten members made up the committee headed up by Bikle as chairman and Branch as vice-chairman. Six of the remaining eight members included one representative each from the NAS,4 and Air Force 

pilots, engineers, and project officers. A NASA instrumentation representative and an 

Air Force medical officer completed the committee. 

The joint flight-test committee hat1 responsibility not only for the test program but 

also for all outside relations ant1 contacts. Maintenance, instrumentation, and ground 

support for the vehicles remained the responsibility of the Flight Research Center. 

The Air Force Flight Test Center assunled responsibility for the launch and support 

aircraft, the rocket power plant, the personal equipment of the pilots, ant1 medical 

support. The two centers assumed joint responsibility for research flight planning, 

flight tlata analysis, test piloting, range support, and overalI flight operations. 
ON TO HEAVYWEIGHTS 

John McTigue, NASA lqting body project manager. (NASA photo EC76 5352) 

76 
WINGLESS FLIGHT 

Career Decision: Manager or Engineer? 

As the lifting-body program grew larger, it needed a full-time manager to coordinate activities among the NASA Flight Research Center, the Air Force Flight Test 

Center, and the contractor, Northrop. Called into Paul Bikle's office one day, I was 

confronted with a career decision. Bikle gave me a choice. I could move into management of the program, which wouId pull me away from involvement in day-to-day 

technical and engineering activities, or I could stay with engineering. 

Bikle told me that he thought I would be happier and NASA woultl benefit more 

if I remained in engineering, free to continue generating new technical ideas. He said 

that if I continued working within the program's technical engineering team, I could 

serve as NASA's project engineer, coordinating all technical activities for the NASA 

and Northrop engineering teams. He gave me a few days to make my decision, saying 

that if I opted to remain in engineering, he would appoint John McTigue as liftingl~ody project manager. I decided to stay with engineering. 

As an operations engineer on the X-15, McTigue had gained experience in scheduling crews and technicians to meet flight schedules. Bikle believed McTigue u-ould 

make good use of this experience in building up and servicing all systems needed to 

operate the lifting bodies. McTigue was also very familiar with the rocket, hydraulic, 

and life-support systems of the X-15s, which were, in most cases, identical to those of 

the lifting bodies. Furthermore, Rikle earlier had created a competitive spirit among 

the three X-15 operations engineers in meeting or beating flight schedules by betting 

against these engineers. On several occasions, Bikle had lost his bet and McTigue had 

won. Obviously, Bikle was impressed with McTigue as a manager who would keep the 

program on schedule. 

NASA and Northrop Single-Team Engineering 

Having a flight-test facility at Edwards AFB for testing F-5s, T-38s, and X-21s, 

Northrop ran a little commuter-plane operation daily between its plant in Hawthorne 

in the Los Angeles basin and Eclwards AFB, using a couple of Piaggio twin-engined 

airplanes. During the 19 months of the lifting-body contract, I and the rest of the 

NASA engineering team commuted almost daily by Northrop's planes to the 

Hawthorne plant, where I spent nearly half of my time during this period. 

In the lifting-body program, NASA engineers did not have the "do-as-1-say" 

relationship with Northrop engineers that was typical between customer and contractor in the aerospace industry. Instead, we worked together as a single team to make 

the best possible product. The keys to our success were mutual respect, trust, and 

cooperation. The Northrop engineers respected and trusted not only the expertise of 

the NASA engineers in aerodynamics and in stability and control analysis hut also our 

operational experience with rocket-powered aircraft. Equally, the NASA engineers 

trusted and respected the outstanding ability of the Northrop engineers in fabrirating 
ON TO HEAVYWEIGHTS 

airframes. Working one-on-one in small groups, we made on-the-spot decisions, 

avoiding the usual time-consuming process of written proposals and counterproposals 

in solving and rnaking changes. 

One day, we were called together by a Northrop engineer named Stevenson who 

was responsible for the M2-F2's weight and balance. He showed us through his latest 

calculations that maintaining weight balance on the M2-F2 was becoming a large 

prohleni, given the twin challenges of a narrow nose area, limiting space for systems, 

and the requirement for locating multiple actuator systems in the aft end with all control sul-faces. We needed to do something drastic to restore llalance by putting ballast, 

or weight, in the nose. Otherwise, the vehicle would be tail-heavy. 

An aircraft designer usually considers having to add ballast to a new vehicle as a 

negative reflection on his or her ahility to provide an efficient design. Ballast adds 

nothing desiral~le. It puts higher loads on the structure and decreases the aircraft's 

performance. 

We faced a large dilemma. The usual solution would have been to put depleted 

uranium around the pilot's feet in the aircraft's nose. Having a much higher density 

than lead, depleted uranium is commonly used for balance in aerospace vehicles 

when there is limited room for ballast. However, NASA pilots Milt Thompson and 

Bruce Peterson, as well as the chief Air Force lifting-body pilot, Jerry Gentry, didn't 

like the idea of cooking their feet in radiation, so we had to come up with another solution. 

Stevenson did a cost trade-off study for using gold as ballast in the nose. He also 

demonstrated how the high-density gold bricks could be cut and fitted into the structure around the pilot's feet without blocking the pilot's vision through the nose window. The $35-per-ounce price for gold at the time was still cheaper than the lal~or 

costs would he for ljalancing the vehicle by redesigning the structure in the aft portion of the M2-F2 and moving equipment forward. 

The little group of NASA and Northrop engineers sat around a table, equally desperate to solve this problem. By the time this problem arose, the two teams of engineers had coalesced into one. Everyone focused on solving the problem, not pointing 

fingers at others' mistakes. Thinking aloud, I suggested that if we could actually put 

something useful in the nose, rather than siml)ly adtling I)allast, we might salvage our 

pride as designers. Immediately, another engineer suggested we put some extra structure around the pilot to give him added protection in case of a crash. As a group, we 

jumped on that idea, with no debate or dissent, and within thirty minutes we hat1 

sol\rtf the problem by changing the design, replacing the 50G cockpit with a nearly 

300G cockpit that had a very heavy steel frame around the pilot. As it turns out, the 

decision to add the protective cage-like strucbture around the pilot helped to save pilot 

Bruce Peterson's life when the M2-F2 crashed two years later. Only the cockpit 

remained intact in that horrendous accident that left the rest of the aircraft looking 

like a crumpled beer can at a Hell's Angels' party. 

In similar ways, we approached and solved other engineering problems as ther 

arose. Time used for casting blame and engaging in agonizing clehates over proposed 
WINGLESS FLIGHT 

solutions simply leaves that much less time for designing and building. Furthermore, 

the NASA engineers mainly considered themselves to be support ant1 backup for the 

Northrop team working at the Hawthorne plant. For example, rather than asking the 

Northrop team to come to Edwards AFB for meetings or for looking at hardware, we 

would hold the meetings or take the hardware to Hawthorne, minimizing loss in time. 

Things were going so smoothly, unlike typical aerospace projects, that something 

just had to happen-and it did. 

NASA Langley Modifies the HL-10 

After the contract had been signed by Northrop and the Flight Research Center, 

NASA Langley continued wind-tunnel tests on the HL-I0 and discovered that the 

trimmed suhsonic lift-to-drag ratio was only slightly more than 3, considerably below 

Langley's established goal of 4. Furthermore, negative directional stability showed up 

at low supersonic speeds and at some angles of attack. 

To fix these problems, 1,angley initially considered atltling an ejectable tip-fin 

scheme, only to discard the idea, finding it unacceptable to be ejecting tip fins during 

the final phase of a mission. Then, working from wind-tunnel test results, Langlej 

engineers changed the tip-fin shape, developing a configuration that increased area, 

toe-in angle, and roll-out angle. They also added simple two-position flaps to the trailing edge of the tip fins and upper elevon to vary the base area. Closing these flaps 

would also minimize the subsonic base drag. This modification brought the maximum 

lift-to-drag ratio to nearly 3.4, still short of the target 4.0. However, it improved the 

directional stability. 

On 3 February 1965, nearly 10 months into the 19-month contract with Northrop, 

Langley presented its proposed HL.-10 morlification at a meeting held at the Flight 

Research Center. Attending the meeting were several of the top Langley engineersinclucling Eugene Love, Robert Rainey, and Jack Paulson-as well as NASA 

Headquarters' Fred DeMerritte, chief of the lifting-body program for the Office of 

Advanced Research and Technology, through whom we received our funcling for the 

follow-on lifting-body program. The proposal was to add six more control surfaces to 

the HL-10. These would be two-position surfaces consisting of elevator flaps, locatecl 

on the upper surface of the elevon, ant1 outboard tip-fin flaps. 

The result was a required design change and modification to the contractual 

agreement with Northrop. The modification was done as required, but it was done 

minus the wholehearted support of NASA and Northrop program managers and engineers. However, later in the HI,-I0 program, the required change came to be seen as 

an excellent decision. The modification simplified the flight-control design. It also 

allowed the pilot to move during flight from suhsonic to supersonic speeds simply by 

throwing a switch, requiring less trim change in the pilot's control-stick position. 

The pilot coul(1 now easily convert the HL-10 from a "shuttlecock" to a low-drag 

subsonic configuration. 
ON TO HEAVYWEIGHTS 

Included in the modification was an enlargement of the center ant1 tip fins that 

improved trim and stability at transonic and supersonic speeds and increased the liftto-drag ratio in the approach to landing. At subsonic speeds and during landing, the 

two-position flaps on the upper elevon surface, split rudder, and tip fins retracted for 

maximum boat-tailing (minimum base area) on the aft portion of the vehicle. At high 

subsonic, transonic, and supersonic speeds, the movable flaps deflected outwardly, 

minimizing flow separation at control surface areas. 

M2-F2 Roll-Out 

The modification to the HL-10 meant that the M2-F2 was the first to be finished, 

rolling out of Northmp's Hawthorne plant on 15 June 1965. The next day, it was 

trucked over the mountains north of Los Angeles to Edwards AFB. At its unveiling, 

the M2-F2 lacked the LR-I1 rocket engine, but we planned to fly it first as a glider, 

then modify it for powered flight. 

Made of aluminum, the M2-F2 weighed 4,630 pounds, was 22 feet long, and had 

a span of 9.4 feet. Its retractable landing gear used high-pressure nitrogen to extend 

the landing gear just before touchdown. The boosted hydraulic cvontrol system was 

pressurized by electric pumps running off a bank of nickel-silver batteries. A Stability 

Augmentation Sjstem (SAS) in all three axes helped the control system in damping 

out untiesirable vehicle motions. For instant lift to overcome drag momentarily during 

the prelanding flare, the pilot could use the vehicle's four throttleable hydrogen-peroxide rockets, rated at 400 pounds each. The M2-F2 also had a zero-zero seat, a modification by Weber of the one used in the F-106 Delta Dart. 

We put the M2-F2 next to the M2-F1 for a family photograph. Except for being 

identical in size, there were few similarities. The M2-F2 lacked the M2-Fl's "elephant 

ears," had an extended boat-tail and forward canopy, and would ekentually weigh 10 

times as much as the M2-F1. 

M2-F2 Wind-TunneI Tests 

Soon after the first heavyweight lifting body arrived at the NASA Flight Research 

Center, more team members were assigned to the M2-F2, including operations engineer Meryl DeGeer, crew chief Bill I,ePage, and assistant crew chief Jay I,. King. In 

helping to ready the M2-F2 for flight testing and research, Bill Clifton did the 

instrumentation engineering and John M. Bruno, '41 Grieshaber, and Bob Veith 

installed the flight research instrumentation. 

Since full-scale testing of the M2-F1 had worked out well, the NASA Ames windtunnel team suggested that we measure the M2-F2's aerodynamic characteristics at 

landing speeds in the 40-by-80 wind tunnel. DeGeer and LePage agreed, wanting to 

test under w-ind-tunnel conditions the vehicle's control system, landing-gear deployment, and emergency ram-air turbine that would provide hydraulic power for operat- 
WINGLESS FLIGHT 

ing the controls if the battery driving the pumps failed in flight. By August 1965, 

100 hours of wind-tunnel tests would be completed on the M2-F2 within a period of 

two weeks. 

In late July, the M2-F2 was loaded on a truck for its trip north to the NASA Ames 

Research Center, stining up memories for many of us of the similar trek two years earlier with the M2-F1. This time, however, the wind-tunnel testing would be more complex than that done on the "flying bathtub." Several changes replaced nearly 

everything done by the person who had sat in the cockpit throughout the M2-Fl's 

tests-as well as much of the hand-plotting of Lest data-allowing the wind-tunnel 

tests on the M2-F2 to move along more rapidly. 

Hoses ran from an aircraft hydraulic power cart to the vehicle atop the pedestal, 

powering its control system. Pilot linkages from the cockpit to the hydraulic servos 

were replaced with miniature electric screw jack actuators. Toggle switches in the 

wind-tunnel's control room activated these actuators that, in turn, controlled the 

hydraulic-. actuators moving the control surfaces to various settings. 

We also made use of the flight instrumentation onboard the M2-F2, parking one 

of our mobile ground-receiving stations outside the wind tunnel and hard-wiring it to 

the vehicle's instrumentation. In this way, sensors inside the aircraft allowed air 

speed, angle of attack and sideslip, and contrc~l positions to be recorded along with 

data from the wind tunnel's measuring system. With all this help replacing what hat1 

earlier been done only by human hand during the M2-Fl's tests, Bertha Ryan could 

assume sole responsibility for assimilating all wind-tunnel data on the M2-F2. 

Nevertheless, there still remained a lot of data-plotting that had to be done by hand. 

We began with testing the operational systems, which required a person in the 

cockpit to operate the landing-gear deployment handle and the ram-air turbine unit. 

DeGeer volunteered and clirnhed into the cockpit. However, the vehicle's canopy had 

been covered with paper to protect it from scratches during the tests, and DeGeer 

began to get claustrophobic right away. LePage opened a peephole in the paper so 

DeGeer could see outside. 

After the wind tunnel was brought up to speed, it began to get hot in the cockpit, 

seemingly due to all the bright lights used to illuminate the vehicle. Trying to cool the 

interior of the cockpit, DeGeer opened the ram-air doors. Of course, the air coming 

into the cockpit was even hotter, the tunnel actually heating the air. Despite his discomfort, DeGeer deployed the landing gear and the ram-air turbine. Both systems 

worked well, and we could move along to the aerodynamic testing that didn't require 

literally having a warm body in the cockpit. Afterwards, DeGeer said he had gained 

great appreciation from his own experience for what Dick Eldreclge must have 

endured two years earlier, sitting in the cockpit of the M2-F1 in the wind tunnel for 

eight hours. 
ON TO HEAVYWEIGHTS 

Wind-Tunnel Tests of M2-F2, HL-10, and B-52 Models 

Because of the potential for either heavyweight lifting body to collide with the B52 motherplane immediately following launch, we conducterl another set of wind-tunnel tests in 1965, this time at NASA I.angley, using models of the B-52 bomber and 

the M2-F2 and HL-10 lifting bodies. During these tests, the airflow around the lifting 

body hanging in launch position was tfeflrcted upstream by the B-52's nose as well as 

(near and just above the lifting body) by the B-52's wing. This indicated that angular 

flow could cause the lifting 1)otIy to roll and pitch immediately following hook release 

from the R-52. Since this could occur in a mere fraction of a second, the pilot would 

not be able to react fast enough to avoid a roll-off and possible vertical-fin contact with 

the B-52's launch pylon. In some rases, the automatic and gyro-driven rate damper 

might be able to react that quickly, the controls preset before launch to counter any 

unwanted motions after launch, but it was just as likely to be too slow to keep the lifting hotly from making contact with the B-52. 

Launch studies by Wen Painter and Bewin Kock found that the M2-F2's vertical 

fins would make contact with the B-526 pylon used in launching the X-15. 

Consequently, the adapter used for launching the M2-F2 from the pylon was modified 

to lower the lifting botly. In the wind tunnel, the lifting-body model was positioned 

at different points below the B-52 as well as in launch position, nit11 forces and 

moments measured on the M2-F2 then used to calculate the vehicle's flight path and 

attitude as it fell away from the B-52. Similar wind-tunnel tests much earlier on a 

model of the X-15 had also succeeded in predicting the motions of the X-15 after 

launch from the R-52. Our tests used the same B-52 model that hat1 been used in the 

X-15 wind-tunnel tests. 

years later, Jerry Gentry, one of only four pilots to fly the M2-F2, recalled how he 

and others dowmplayed the fear that still existed after the wind-tunnel tests that the 

lifting body might fly back up into the B-52 after it separated from the pylon. "There 

was no question which way you were going when the B-52 dropped you," he said. 

"One guy used to say that if they dropped a brick out of the B-52 at the same time [he] 

released, [heI'd beat the brick to the ground."5 

Moving Toward Flight 

After we trucked the M2-F2 back to Edwards AFB, we began preparing for its first 

glide tests. Our staff expanded to meet these needs. Added to assist DeGeer were 

Norm DeMar, who acted as lead systems engineer, and Northrop's Jim Croshy, systems 

electrical engineer for the yet-to-he-installed rocket engine. The crew under the direc5. Filkinson, "Txgacy of the rifting Body," p. 55. 

82 
WINGLESS FLIGHT 

Cornell T33A, equipped with a computer control system to simulate predictedflying qualities of the M2-F2. 

This aircraft was later outfitted with drag devices to simulate the steep glide slope of the M2-F2. (NASA 

photo EC87 126-7) 

tion of crew chief LePage and assistant crew chief King grew to include mechanics 

Chet Bergner and Orion Billeter, electrician and electronic technician Millard I. 

Lockwood, and inspectors Bill Link and John E. Reeves. For seven months, Jack 

Gates, Mil Lockwood, and Wen Painter worked on the problems remaining in the 

Stability Augmentation System, resolving them by May 1966. 

As with the M2-F1, Milt Thompson was selected by Bikle and Chief of Flight 

Operations Joe Vensel to pilot the M2-F2 in its first glide test. A list of five more future 

pilots for the M2-F2 was also drawn up, including NASA pilots Bruce Peterson, Bill 

Dana, and Fred Haise as well as Air Force pilots Donald Sorlie and Jerry Gentry. As 

the "angry" qualities of the M2-F2 revealed themselves later in actual flight, only 

three of these pilots-Peterson, Sorlie, and Gentry-would, in addition to Thompson, 

actually get to fly the M2-F2. 

As part of the pilot preparation for the first flights of the M2-F2, Ken Iliff and 

Larry Taylor designed a flight experiment, using a highly modified and variable-stability Lockheed T-33A jet trainer from the Cornell Aeronautical Laboratory of Buffalo, 

New York, to simulate the flight characteristics of the M2-F2. When the petal-shaped 

surfaces called "drag petals" that had been installed on the T-33A's wing-tip tanks 

were extended in flight, the aircraft's lift-to-drag ratio varied from its usual 12-14 to 

as low as 2, approximating the lift-to-drag ratio of the M2-F2. The T-33A was part of 

a cooperative pilot training and aircraft simulation program that the NASA Flight 

Research Center had launched earlier with Cornell, the T-33A used initially to simu- 
ON TO HEAVYWEIGHTS 

Rudderlaileron 

interconnect 

ratio 

20 24 26 32 

Angle of attack, deg 970832 

Graph showingpredicted M2-F2 lateral control boundaries. The pilot had to reset the rudderlaileron-interconnect control wheel in the cockpit as the angle of attack changed in order to avoid loss of lateral control. 

late the low lift-to-drag ratio characteristic of the X-15 during re-entry. The T-33A was 

used at the Flight Research Center for in-flight simulation of the M2-F2 in the winter 

and spring of 1965, with Cornell's test pilot Robert Harper and then Thompson, 

Peterson, and Haise executing typical lifting-body approaches in the T-33A. 

The analytical team consisting of Iliff, Bertha Ryan, Harriet Smith, and others was 

concerned with the results of this flight experiment as pinpointing a potential lateral 

control problem in the M2-F2, although the pilots felt they could live with the problem after flying the T-33. In any event, they were well aware, before the actual M2-F2 

flights began in July 1966, that lateral control of the craft would require considerable 

attention and technique on their parts. Iliff suggested delaying the flight tests until a 

center fin or a control scheme with a lead-lag compensator could provide a suitable fix 

to the lateral control problem. However, Milt Thompson, with backing from the Ames 

wind tunnel team, believed the problem could be solved with proper control rigging 

and pilot technique. 

I then went along with Thompson and the Ames team, but it bothered me that Iliff 

in particular was not happy with the approach. We had Northrop install a small wheel 

in the left side of the cockpit so the pilot could adjust the rudder aileron interconnect 

in flight. Thompson continued to express confidence that the pilots could rely on their 

skills to adjust the rudder aileron interconnect ratio manually in flight. 

The interconnect ratio had to be high to roll the M2-F2, due to its extremely high 

dihedral at high angles of attack as well as adverse yaw of the differential upper flaps 

(elevons). At low angles of attack and high speed, however, using too much rudder for 

roll control would result in a pilot-induced oscillation. If the pilot did not set the interconnect wheel properly to match flight conditions, he could have serious problems 

controlling the vehicle in roll. Indeed, we were asking a lot from the M2-F2 pilots. 
WINGLESS FLIGHT 

Little did we know then that in the M2-F2 we had created a monster ready to bite the 

first time a test pilot became distracted. 

We weren't in a rush to make the first glide flight, preferring to be absolutely sure 

that everything was in order. We did seven captive flights with Milt Thompson sitting 

in the M2-F2 attached to the B-52's X-15 pylon. Operational anomalies turned up on 

each of the captive flights that had to be corrected on the flight that followed. The captive flights turned out to be excellent rehearsals for everyone involved in the control 

room, on the ramp, in the B-52, and, of course, in the cockpit of the M2-F2. 

CHAPTER 5 

ANGRY MACHINES 

By 1966, the Air Force was considering developing its own lifting-body configuration to add to the program. To gain experience in engineering and flight planning 

useful later in developing and testing its own lifting hody, the Air Force participated 

in the M2-F2 project. Heading up the Air Force's lifting-hod) effort was program manager Robert G. "Bob" Hoey, who had extensive experience with the X-15 and experimental flight testing. Air Force Captain John Durrett assisted with general 

engineering. In January 1970, after the X-15 program ended, program engineer 

Johnny Armstrong joinecl the Air Force's lifting-1)otly team. Although the team was 

relatively young, it had considerable experience in experimental flight testing. 

Hoey and Armstrong had worked together as Air Force flight-test engineers in the 

highly successful X-15 program. Before he became NASA director at the Flight 

Research Center in 1959, Paul Bikle had served as technical director for the Air 

Force Flight Test Center at Edwards AFB. Hoey, who had been at Edwards approximately twelve years, had a good relationship with NASA management, including 

Bikle. The success of the X-15 program made it easy for us at NASA to consider the 

Air Force's lifting-body team as "the experts." Bertha Ryan worked closely ~ith Hoey 

and the rest of his team as the NASA stability and control engineer ant1 aerodynamicist for the M2-F2. ExcelIent communication existed between the lifting-body teams, 

with the Air Force offices only about a mile down the road from those of NASA. 

Hoey and his team modified an X-15 simulator to use for training pilots and planning the first 15 flights of the M2-F2, while we at NASA were upgrading our own M2- 

F2 simulator ant1 changing computers. Hoey's team loaded its simulator with the 

M2-F2 data from the wind-tunnel tests. Before the first flight of the M2-F2, Milt 

Thompson spent many hours on the simulator, becoming well acquainterl with the 

vehicle's stability limits, including the boundaries for pilot-induced oscillation (PIO) 

and roll-control reversal. 

First Flight of the M2-F2 

For its first glide flight on 12 July 1966, the M2-F2 Mas mated with the B-52 

mothership, carried aloft, then launclie~l on a north heading at 45,000 feet. The launch 

was very mild, Milt Thompson reported, with at most 28 degrees of right roll following launch. The flight plan called for two 90-degree turns to the left with a landing to 

the south on the 1akel)ed's Runwaj 18. He made a sirnulatetl landing starting at 

22,000 feet, coming level at 19,000 feet between the two 90-degree turns, firing the 

peroxide rocket during the landing simulation with no noticeable changes in attitude 

(orientation) with thrust. 
ANGRY MACHINES 

M2-F2 mated with B-52 to be carried aloft for launch. (NASA photo E65 13865) 

Using the manual control to lower the interconnect ratic between the ailerons and 

rudder to 0.4 on the pushover at altitude, Milt felt that the vehicle's roll response was 

not great enough as he tried to begin the second 90-degree turn as planned at 16,000 

feet and 190 knots. He increased the interconnect ratio to 0.6, in effect adding rudder as he began the final turn. During the turn's pushover, the M2-F2 developed an 

uncomfortable lateral-directional oscillation. 

Milt tried to turn the interconnect ratio down, but, as he later said, he turned it 

the wrong way just as he was turning final. Rather than decreasing it, he had accidentally increased it to 1.25. The oscillations increased to 90 degrees, the flight films 

showing the vehicle swinging madly from side to side. The view through the windshield inside the M2-F2, as captured on film by the camera behind Milt in the cockpit, showed a horizon rolling rapidly from vertical to vertical. Quickly realizing the 

error, Milt reduced the interconnect ratio back to 0.4, which decreased rudder. He 

took his hand off the control stick, and the oscillations damped out rapidly. 

He reached a pre-flare speed of 280 knots at 1,200 feet altitude. At flare completion, speed was 240 knots. Landing gear was deployed at 218 knots, accompanied by 

mild pitch transient, or change in attitude. Milt landed the M2-F2, the vehicle touching down at the exact spot planned at 164 knots, then coasting 1.5 miles across the 

lakebed. Lasting not quite four minutes, the first flight of the M2-F2 appeared to be 

an unqualified success. 
WINGLESS FLIGHT 

Jay L. King, Joseph D. Huxman, and Orion B. BilZeter assist Milt Thompson in boarding the M2-F2 

attached to the B-52. (NASA photo EC66 1154) 

During the debriefing afterwards, Milt apologized for nearly losing control of the 

vehicle by moving the interconnect wheel the wrong way. Later, we found two errors 

had been made in the simulator. First, by employing the Air Force's X-15 simulator 

cockpit, we had used the existing X-15's speed brake handle instead of the M2-F2 

pilot's interconnect wheel. Second, the interconnect control direction was the reverse 

of the wheel in the actual aircraft. In short, Milt had been practicing with a simulator 

that did not represent the M2-F2, a serious foul-up that both we and Bob Hoey's Air 

Force simulator team found embarrassing. What might have been a disaster in the air 

was averted by Milt's quick adaptability and knowledge of the lifting body's characteristics. Realizing that the interconnect settings were incorrect, he took appropriate 

if intuitive corrective action. 

One more error-this time, a minor one---was made during the M2-F2's first 

flight. Vic Horton had been onboard the B-52, his only task to turn on the 16mm camera 10 seconds before launch to film the top of the M2-F2 as it fell away from the B52. He forgot to turn on the camera. After the crew briefing for the second M2-F2 

flight, Wen Painter and Berwin Kock presented Horton with a "Launch Panel Camera 

Switch Simulator." It was made out of a cardboard box and had a large lever marked 

CAMERA ONIOFF. As the crew laughed, Horton turned the lever to CAMERA ON. 

A banana rolled out. The crew howled with laughter. Horton grabbed the banana and 

threw it at Painter and Kock. 
ANGRY MACHINES 

Milt's Last Lifting-Body Flight 

On 2 September 1966, Milt Thompson matie his fifth flight on the M2-F2, his last 

lifting-botfy flight. EIe had decided to make a career change, moving into management 

with the Flight Research Center. NASA lost a superb research pilot %hen Milt 

Thompson retired from the cockpit, but we later reaped great benefit from his experience %hen he hecame chief of the research projects offic-e at the Center in January 

1967, responsible for all flight projects, including those of the X-15 and the lifting 

ljodies. Milt never spoke puhlicl) in those days about why he made the career change. 

Some surmised that he might have felt he had used up his "nine likes" in the close 

calls he had had as a pilot. 

One of those close calls happened on 20 Decernber 1962, about eight months 

before he flew the M2-F1. He was flying an F-104 chase aircraft. As he prepared for 

landing, he was lowering the flaps when the mechanical cross link between the right 

and left flaps broke. The flaps were stuck, one up and one down, and the F-104 started rolling. Somehow Milt managed to maintain altitude while the aircraft made a 

series of 360-degree rolls across the sky. He tried recycling the flaps and resetting the 

circuit hreakers during the rolls, but to no avail. 

As the F-104 continued to roll, Milt managed to steer it over the bombing range 

at Edwards AFB. Since the aircraft was only about 5,000 feet above the ground, Milt 

made a carefull) timed ejection when the cockpit was pointed upward. He floated 

down in his parachute, landing safely on the bombing range. 

The F-104 went down about t\vo miles from where Milt had lantled, the aircraft 

digging a huge black hole in the ground upon impact. Milt gathered up his parachute 

and ~alked half a mile along the edge of the bombing range to a road leading to the 

rocket test site on Leuhman Kidge. He stuck out his thunil) and hitched a ride in a 

pickup truck that brought him back to the NASA building. 

When he walked into the office, a full-scale search was already underway. 

Helicopters were landing at the crash site. No one had seen Milt eject or spotted his 

parachute descending. The assumption was that his bod) would be found in the 

wreckage of the F-104. The mood changed from heavy sadness to surprised relief 

when Milt walked into the office. 

After he retired as a NASA pilot in 1966, &lilt later made (to my knowledge) only 

one public statement about his career change, and he made it in his book, At the 

Edge of Sl1nc~, publishecl in 1992. There, he explains it was boredom, not fear, that 

led to his career change, saying that he had made up his mind and e\ en clisc~ussed the 

career change with Bikle nearly two months earlier, Lefore he 1)egan fljing the M2-F2 

in July. 

"I felt that the exciting programs were winding down," he mote, "and I could 

not see any new challenging programs coming up in the near future. I really enjoyed 

the challenge of an X-15 flight or a lifting-body flight, hut I was getting bored with 

- 
WINGLESS FLIGHT 

M2-F2 in landingfire, gear up, closely followed by an F-104 chase airplane. (NASA photo EC66 1567) 

p. 67 

the routine proficiency flying that was required between research flights. When a 

pilot gets bored with flying, it is time to quit."l 

Gentry Fast Forwards 

By 12 October 1966, the M2-F2 had been flown ten times-five by Milt 

Thompson, two by NASA research pilot Bruce Peterson, and three by Air Force test 

pilot Don Sorlie. Sorlie also got into a PI0 problem on his first flight in the M2-F2, but 

he had planned ahead of time what he would do if it happened, and he had sufficient 

altitude to execute a full recovery. After two more flights with no additional problems, 

Sorlie gave the okay for Air Force research pilot Jerry Gentry to fly the M2-F2. 

Gentry's first flight in the M2-F2 on 12 October went smoothly according to flight 

plan from B-52 launch to just before touchdown. Then, the unexpected happened. At 

about 100 feet above the ground, mere seconds before touchdown, Gentry reached for 

the landing gear handle-and couldn't reach it. What happened next was the result of 

quick thinking. Within no more than five or six seconds, he loosened the shoulder harness, leaned forward, pulled the handle, tightened the shoulder harness, and continued with the landing. 

1. Thompson, At the Edge ofspace, p. 276. 

91 
ANGRY MACHINES 

For a second time, the M2-F2 was saved from disaster by the quick thinking and 

skill of the pilot. Northrop had designed the cockpit tlimensions to accommodate Milt 

Thompson and Bruce Peterson. No consideration had been given to the needs of 

smaller or shorter pilots, including arm span. A second error was a faulty preflight 

checkout procedure, for Gentry's inability to reach and pull the landing gear handle 

while secured in the shoulder harness should have been discovered then, not seconds 

before touchdown. 

Gentry became the Air Force's chief lifting-body pilot on the M2-F2 and, later, the 

HL-10. With the retirement of Milt Thompson from research flying, there were now 

only two official lifting-body pilots, Gentry for the Air Force and Bruce Peterson for 

NASA. Before the first flight of the HL-10 in late December 1966, Peterson made two 

unpowered flights in the M2-F2. Between July and late December, four piIots-Milt 

Thompson, Bruce Peterson, Don Sorlie, and Jerry Gentry-had made a total of fourteen flights in the M2-F2. 

Air ForceiNASA Simulators 

When the HL-10 arrived from Northrop, it was trucked to NASA Ames for windtunnel testing, as had been done with the M2-F2. The only difference was that data 

handling was even more automated with the HL-10 than it had been with the M2-F2, 

thanks to our and the wind-tunnel crew's greater experience and practice in testing 

the earlier lifting bodies. The HL-10 project was also better staffed with NASA personnel than the M2-F2 had been, the average flight-test experience being three to six 

years. However, while the M2-F2 team was made up of both NASA and Air Force 

research or analytical engineers, the HL-10 project was essentially a solo in engineering bj NASA. 

Bob Hoey wanted to maintain hands-on experience with the aerodynamics of the 

M2-F2, even after we had developed our own M2-F2 simulator, so he tlecided to keep 

the original hf2-F2 simulation at the Air Force Flight Test Center. Later, the NASA 

team at the Flight Test Center concentrated mainly on the simulation of the HL-10. 

For a period of time, there were two M2-F2 simulators, one at the Air Force and 

one at NASA. Even though both simulators used the same wind-tunnel data, the way 

in which the data was processed and interpreted by the computers within the simulators was different. Once a week, I (mompared the technical results from both simulators. Generally, the simulators gave the same results. However, now and then, slight 

differences ~~ould appear in the results, followed by lively discussions of which were 

correct. I felt this was a healthy activity, especially when both simulations concluded 

that the 1112-F2 was safe to fly and when neither set of results required alteration in 

the vehicle's control settings, stability augmentation system gains, or flight procedures. Joe Pieill my boss and head of NASA's research division, felt uneasy about the 

lively discussions, seeing them as discord. He basically felt that if there was only one 
WINGLESS FLIGHT 

Robert G. (Bob) Hoey, Air Force Zifing-body program manager. (Air Force photo, available as NASA photo 

EC97 44183-5) 

M2-F2 simulator, the Air Force and NASA lifting-body teams would work together 

even more harmoniously. 

New Lifting-Body Project Engineer 

By 1966, I was finding my job as lifting-body project engineer more a job of managing people and solving their problems than of directing a technical effort. Once 

again, as I had in 1965, I found myself facing a career decision. 

Over the years, I had worked with Garrison "Gary" Layton on several NASA programs. On our own time, we also had helped one another in our common hobby, flying 
ANGRY MACHINES 

experimental radio-controlled model airplanes. As I grew more concerned at how far 

I was getting away from technical engineering and into management, Gary Layton 

mentioned that he would like the opportunity to take over as the lifting-body project 

engineer so that I could have the opportunity to get back to the type of work I loved, 

especially developing some ideas I was having for remotely controlled vehicles. 

Layton and I went to our bosses, Paul Bikle and Joe Weil, to get their approval for 

Layton to take over as lifting-body project engineer. Once the change was approved in 

1967, I became at once involved in a continuing series of about 20 unpiloted vehicle 

programs at the Flight Research Center until my retirement from NASA in 1985. 

The unpiloted, or remotely piloted, vehicle programs appealed especially to me 

Bob Kempel, HL-10 stability and controls engineer. (NASA photo EC86 33445-1) 

94 
WING1,ESS FLIGHT 

because they were easy to keep small ant1 innovative and they involved conducting 

experiments of higher risk, 

I have always felt that my talent with people is as a catalyst, a person who can 

help get individual team members launched creatively in different directions of exploration, especially when the venture is into new and uncharted territory. My talents at 

NASA seemed best used in small programs of no more than 10-15 people, the larger 

programs soon becoming complex matters of management and bureaucracy best left 

to those with talents in those areas. 

NASA's HL-10 Team 

Operations engineer Herb Anderson headetl the 13-member HI,-10 hardware 

team that included crew chief Charles W. Russell; mechanics Art Anderson, John W. 

"Bill" Lovett, and William "Bill" Mersereau; aircraft electricians Dave Garcia and 

Albert B. "Al" Harris; instrumentation engineer Plrilliam D. Clifton; instrumentation 

technician Richard I,. Blair; operations systems engineers Andrew "Jack" Cates and 

George Sitterle; and inspectors Bill Link and John Reeves. The HL-10 11-member 

analytical team consisted of aerodynamicist Georgene 1,aub; systems engineers John 

Edwards, Benvin Kock, and Wen Painter; stability and control engineers Robert W. 

"Boh" Kempel and Larry Strutz; simulation engineers Don Bacon, Larry Caw, and 

Lowell Greenfield; and two members of the United States Army, Lieutenants Pat 

Haney and Jerry Shimp. 

Bob Kempel assumed the leading role in the analysis of the stability and control 

characteristics of the HL-10, taking over the analytical role previously performed by 

Ken Iliff and Larry Taylor. In developing the control laws, Kempel worked hand-inhand with the NASA Langley wind-tunnel team and the Northrop aircraft designers. 

Kernpel had watched the evolution of the M2-F2 configuration, anti he was aware of 

the vehicle's marginal lateral-directional control characteristics. He swore that he 

woultl do everything he could to make the HL-10 the best flying lifting-body. 

"We were the neophytes," Kernpel recalled later of the tension surrounding the 

first flight of the HL-10. The team preparing the HId-10 simulation had only three to 

six years of experience. Still "untried and unproven," to use Kempels words, the HI,- 

10 team wasn't really a full-fledged team yet. "We were a group of individuals working as individuals toward a common goal," Kempel said. "Our approach to completing 

our tasks was not necrssarily lacking in quality hut, rather, lacking in experience."Z

Pilots who "flew" the HL-10 real-time simulator found the vehicle's handling and 

lift-to-drag ratio suspiciously gootl, compared to those of the M2-F2. Others-including Paul Bikle, the Air Force's M2-F2 team, and NASA project manager John 

2. Robert E: Kempel, Wkneth D. Painter, and Milton 0. Thompsnn, DPL- loping nnd Fhght Trsting 

the JIL-I0 Liffing Body: .4 Prerursor to the ,Sjonr~ Shuttle (Tdshington, DC: NAS.2 Reference 

Publication 1332, l994), pp. 21-22. Since Kempel was the principal author IJF this paper, to avoid con- 

~oluted phraseology the narrati~e treats the words in it as his. 
ANGRY MACHINES 

McTigue-were equally skeptical of the HL-10's simulation results. However, the 

simulator showed the HL-10 to be much more stable and generally much easier to 

handIe than the M2-F2, besides having a better lift-to-drag ratio. 

''R+ always had a difficult time convincing the pilots that we really did know what 

we were doing," Kempel said. "Before flight they remained skeptical. Our desire, of 

course, was to have simulations somewhat pessimistic rather than the other way 

around. We did not want to foster overconfidence." 

It wasn't easy instilling even minimal confidence as "the new kids on the block," 

recalled Kempel. "Managers would pass us in the corridors and shake their heads." 

The comment most often heard was, "It can't be that good!"3 The team's work continued, nevertheless, kept on track by Gary Layton. Despite the team's lack of assurance, all objectives were met in preparation for the first flight of the HL-10. 

HL- lo's Maiden Flight 

Shortly before Christmas, the HL-10 team convinced Paul Bikle and the rest of 

NASA and Air Force management that it was ready for the first glide flight. TMT~ captive flights of the HL-I0 on the B-52 followed, allowing the team to practice going 

through check lists and control-room procedure, as well as correct anomalies that 

appeared in hardware or procedure. 

On 21 December, the HL-10 was positioned beneath the B-52's right wing, lifted 

into position, and attached. Preflight checks were completed. However, the flight was 

aborted later that day due to an elevtrical tip-fin flap failure. Since only the subsonic 

configuration would he flown initially and the flaps would not be moved outboard for 

the first flight, the wiring was disconnected and stowed. 

All preparations for the first free-flight of the HL-10 were completed early the 

next day, 22 December. Strapped into the cockpit, project pilot Bruce Peterson completed the preflight checks. The canopy was lowered once all ground preparations had 

been completed. The B-52 taxied to Edwards' main runway, Runway 4. The take-off 

was smooth. The flight plan called for a launch point about three miles east of the eastern shore of Rogers Dry Lake, abeam of lakebed Runway 18, almost directly over the 

Air Force's Rocket Propulsion Test Site (now known as the Phillips 1,aboratory). 

Launch heading was to be to the north with two left turns. The ground track looked 

much like a typical left-hand pattern with the launch on the downwind leg, then a base 

leg, a turn to final, and a final approach to landing on Runway 18. 

At 10:30:50 a.m. PST, the HL-10 was launched from the B-52 at 45,000 feet and 

at an airspeed of 195 miles per hour. Actual launch proved to be very similar to simulator predictions. Although airplane trim was much as expected, Peterson sensed 

what he described as a high-frequency buffet in pitch and somewhat in roll, later
WINGLESS FLIGHT 

specifically identified as a "limit cyclem-that is, a rapidly increasing oscillation of a 

control surface that occurs when the sensitivity (or "gain") of the automatic stabilization system is too high. As speed increased, the limit cycles got noticeably worse. 

During the first left turn, Peterson noticed that the sensitivity of the pitch stick was 

excessively high. As the flight progressed, the limit cycles increased in amplitude, 

and it became obvious that the longitudinal stick was excessively sensitive. 

Throughout the flight, Peterson and systems engineer Wen Painter were in constant communication through flight controller John Manke, making gain changes in 

the vehicle's stability augmentation system (SAS). During the somewhat premature 

landing, the SAS gains were set at the lowest rate possible without being shut off. 

Pitch problems masked the difficulties in the roll axis. Peterson initiated the landing 

flare at approximately 370 miles per hour (mph) with touchdown at about 322 mph, or 

about 35 mph faster than anticipated. The first flight of the HL-10 had lasted 189 seconds-that is, three minutes and nine seconds from launch to touchdown-with an 

HL-10 turning to line up with lakebed Runway 18. The main part of Edwards Air Force Base is at the top 

of the photo and North Base is shown on the right. (NASA photo E69 21089) 

97 
ANGRY MACHINES 

average descent rate of nearly 14,000 feet per minute. Following Painter's requests for 

adjustments in SAS gains, Peterson had done an excellent job of flying and landing 

the marginally controllable HI,-10. 

Peterson remained greatly concerned about the pitch sensitivity and limit cycles. 

To be precise, a limit cycle is a condition in a feedback control system that produces 

the uncontrollable oscillation of a control surface due to closed-loop phase lag that, in 

turn, results from excessive lag in the system (called "hysteresis"), accumulated free 

play of mechanical linkages, and power actuator non-linearity. The amplitude of the 

cycle increases with each augmentation to airspeed and system gain setting. 

The particular limit cjcle that occurred during the first flight of the HL-I0 was a 

2.75 Hz oscillation (0.4g peak-to-peak) feeding through the gyro-driven SAS. 

Primarily the problem was in the pitch axis, although it also affected the roll axis. The 

problem was more severe during the final third of the flight, despite the fact that the 

SAS gain had been reduced from 0.6 to 0.2 deg/deg/sec. Afterwards, for the entire first 

HI,-10 flight, Peterson gave the pitch axis a Cooper-Harper pilot rating of 4, a rating 

indicating that deficiencies u-arrant improvement and are not satisfactory without 

improvement. 

The flight proved to be a large disappointment for the HL-10 team. It seemed to 

confirm the opinion of others who had said that the team didn't know what it was 

doing. The team's morale was at low ebb, the flight results quite poor in comparison 

with the expected results of preflight simulation and analysis. 

After the holidays, as 1967 began, team members concluded that if they fixed the 

stick sensitivity and lowered the SAS gains, they could probably try another flight. 

There was, hou-ever, one lone dissenter in the group. Systems engineer Wen Painter 

was not convinced that the team completely understood all of the prohlems. 

Continuing to anaIyze the results of the first flight, Painter argued against another attempted flight, despite the fact that Bruce Peterson had convinced Bikle that the 

team should try again. Their confidence shaken by the firs1 flight's results, the team 

gave in to Painter. Rikle hacked Painter fully, saying that if Painter didn't sign the 

ship's book-that is, okay the flight-there would be no flight. Following Painter's 

suggestion, the team initiated an in-depth unified analysis of the data from the first 

flight. Very subtly this effort would niold them over time into a real team of proven 

experience. 

Post-Flight Analysis 

Two serious problems identified even before touchdown were substantiated in 

pst-flight analysis: large amplitude limit cycles in the pitch SAS and extreme sensitivity in the longitudinal stick. 

Thr problem with limit cycles apparently was caused by higher-than-predicted 

elevon control effectiveness and feedback of a 2.75 Hz limit-cycle oscillation through 
WINGLESS FLIGHT 

the SAS. The solution involvecl using lower SAS gains ant1 modifying the structural 

resonance 22 Hz mode lead-lag filter that had been installed before the first flight. The 

modification consisted of a lead-lag network in the SAS electronics and a notch filter, 

a device that removes a nuisance frequency while having relatic,ely little effect on 

lower and higher frequencies. 

The problem with longitudinal stick sensitivity was relatively simple to solve with 

a basic gearing modification. On the first flight, the stick gearing of 6.9 deg/inch of 

elevon proved to be much too sensitive. The nonlinear gearing used in flights 10-37 

was approximately 3.5 dedinch in the elevon range for landing--or about half of what 

it had been during the first flight. This type of is easy to miss when all preparations for flight are made on a fixed-base engineering simulator, a "safe" environment 

that is relatively relaxed for the pilots who know that if anything goes wrong, they can 

simply reset the computers. Furthermore, the trim characteristics of a new7 aircraft are 

not known precisely. Stick sensitivity, whether longitudinal or lateral, has always been 

difficult to determine in fixed-base simulations. Pilots always want a very responsive 

aircraft. 

A third problem proved more elusive, not apparent to the pilot or test team during the initial post-flight analysis: lack of longitudinal or lateral-directional control at 

some portions of the flight. Peterson had realized during the first flight that something 

wasn't right at high gains and consequently had flown a faster landing approach. 

Understanding and resolving this problem would require more thorough flight investigation antl the assistance of NASA Langley, grounding the HL-I0 for fifteen months. 

In-Depth Flight Investigation 

Wen Painter had insisted that even more analysis needed to be done to find out 

why IateraI caontrol was good sometimes and almost totally lacking at other times, so 

Bob Kempel launched an in-depth investigation. The assumption before the first flight 

of the HL-10, according to KempeI, hat1 been that the simulation generated from 

wind-tunnel test results, an analog computerized mathematical model of the HL-10, 

was relatively accurate in representing the actual flight vehicle. The expectation, then, 

was that if flight-recortfed control inputs were fed into the computerized model, the 

dynamics (or motions) of the simulator should be similar to those of the actual vehicle-a technique used for years to validate aerodynamic data by actual flight data. 

Ideally, the simulation matches the flight exactly; however, such perfection is rarely 

realized. When the simulation antl flight data don't match, aerodynamic parameters 

are a(justet1 to duplicate as closely as possihle the flight motions. In this way, engineers can then determine how wind-tunnel aerodynamics differ from flight and, perhaps, even why they differ. 

The first engineering task in the in-depth flight investigation involved selecting 

twelve specific. maneuvers from five to fifteen seconds in duration from the flight 
ANGRY MACHINES 

Wen Painter, HL-10 systems engineer who promoted the engineering investigation resulting in the grounding (and aerodynamic jix) of the HL-10 for a 15-month period after its first &ht. (NASA photo EC79 

11441) p. 71 

results. Next, the engineers tried to match these maneuvers with those generated by 

computer, a good match being one in which the computer solution overlays all parameters recorded during flight within the specified time interval and there is little difference between the flight maneuver and the computer generation. However, there 

were no good matches and only seven found to be acceptable. The other five maneuvers were impossible to match by model. Kempel and the team determined that the 

computer solutions didn't even remotely resemble the actual flight response of the 

HL-10. They concluded that they must not have been using an accurate mathematical model, leading them to examine once more the actual flight data. 

We decided to play the entire flight-recorded data back through the ground station, the team this time selecting parameters that would be grouped together. The team 
WINGLESS FLIGHT 

selected three families of specific data-accelerations, angular rates next to the control inputs, and information from control surface strain gauges. We then traced out 

these groupings as a function of time. The new approach gave the team the capability of looking at eight channels of data on each strip-chart. What we found was quite 

revealing. 

The inexperience of the team had shown in how it had earlier arranged the control-room strip-charts for the initial post-flight analysis. Real-time data hadn't been 

arranged in the best logical manner for accurate assessment of data families. With the 

data re-arranged, the ;earn found that, although of different parameters, each of the 

traces generally moved with the appropriate responses indicating the vehicle's motion. 

However, during certain portions of the flight, some of the traces would become blurry or fuzzy, especially the control surface strain gauges when a higher frequency disturbance occurred. When the data was lined up on a common time interval, many data 

traces displayed similar phenomena. 

A second but related discovery was that there had been two significant intervals 

when Bruce Peterson had commanded significant amounts of aileron, only to have the 

vehicle not respond until the angle of attack was reduced. Peterson was disturbed 

enough by the vehicle's response to control input that Kempel and the team decided 

to investigate it further. What they found was that each time the problem occurred, the 

angle of attack was above the range of 11 to 13 degrees, and that as the angle of attack 

decreased through this range, the ailerons suddenly became very effective, producing 

significant amounts (30 to 45 degrees per second) of roll angular rate. 

When the team computer-matched these two time intervals, the initial part of 

each response would not match. However, as the angle of attack was reduced to the 

point that the ailerons became effective, the mathematical model began to match the 

flight data. But why? 

As Kempel recalls, "We began to think that a massive flow separation was possible over the upper aft portion of the vehicle at the higher angles of attack, causing the 

control surfaces to lose a large percentage of their effectiveness. . . . This flow separation can be likened to the sudden loss of lift and increase in drag of a conventional 

wing as AOA [angle of attack] is increased and the wing stalls. As the AOA was 

decreased, the airflow would suddenly reattach and the controls would behave in their 

normal fashion. The more we looked at the data, the more plausible this theory 

seemed; although the wind-tunnel data did not indicate a problem to the degree that 

we had experienced in flight. The data also indicated a significant loss of lift-to-drag 

ratio above Mach numbers of 0.5 and AOA of 12 degrees. This finding further convinced us that the problem was caused by massive flow separation." 

At this point, Kempel and his team decided to share their preliminary findings 

with the NASA Langley engineers since, as Kempel said, the HL-10 was "their 
ANGRY MACHINES 

'baby."' The Langley team agreed to do more wind-tunnel tests immediately, using the 

0.063-scale, 16-inch-long HL-10 model. According to Kempel, the 1,angley team's 

decision seemed "highly unusual because, typically, wind-tunnel schedules are made 

at least a year and, sometimes, [several] years in advance."J As the Tangley team 

urged them to do, Kernpel and his team packed their data and hags and trareled to 

NASA Langley to work jointly on the situation. 

Bob Kernpel, Berwin Kock, Gary Layton, and Wen Painter of the Flight Research 

Center pthered around a table with 1,angIey's Bill Kemp, Linwood (Wayne) McKinny, 

Bob Taylor, and Tommy Toll in the building housing I,angleyYs 7-by-10-foot highspeed wind tunnel. Kenipel and his team, after presenting their data, theorized that 

the problem was caused by massive flow separation. Bob Taylor jumped up from his 

chair, angrily slammed his mechanical pencil to the floor, and let loose with a string 

of oaths. After he calmed down, Taylor said that he had earlier thought that this would 

be a He had had a gut feeling that the flow separation seen by the I,anglt-y 

team on the wind-tunnel model would be worse in flight, and he was upset with himself for not following his instincts as an aerodynamicist and adding preventative measures to the HL-10 design l~efore the rehicle was built. 

The discussion then turned to what could be done now. The Langley team agreed 

to give the problem its immediate attention, assuming responsibility for coming up 

with a remedy. Kempel ant1 his team left 1,angley more aware than they had been earlier of whj they were having a lateral control prohlem in flying the HL-10. They agreed 

that, until 1,angley came up with a solution, the HL-10 would not he flown. While they 

waited for word from Langley, they busied then~selves with solving the proltlems they 

hat1 detemnlined earlier (stick sensitivity and limit cycles), enlisting the help of 

Northrop in designing the electronic notch filter for eliminating the limit-cycle mode 

from feeding hack through the flight caontrol system. 

HL-10 as "Hangar Queen7' 

The HI,-10 was a "hangar queen" for the next 15 months, grounded after its first 

flight three days before Christmas 1966. During this time, flight safety began receiving more attention, to some extent due to the near crashes ancl temporary losses of control with the other lifting bodies. Adherence to flight schedules took a second priority 

to flight safety, benefiting the 11L-10 program. Bob KempeI was given free license to 

work without a time restraint in leading the effort to fix the vehicle's control problems. 

Throughout the winter and spring of 1967, members of the NASA Langley team 

continued to work on correcting the flow-separation problem, coordinating their efforts 

with those of Kempel and his team at the Flight Research Center. The Langley team 

came up with two possible ways to fix the prohlem, both modifications concentrating 

4. Ibid.., p. 26, for quotations 2 and 3. 
WINGLESS FLIGHT 

on changes to the outboard vertical fins. The first proposed modification involved 

thickening and cambering the inside of the fins. The second proposed slightly extending and cambering the leading edges. Langley ran a full set of hind-tunnel tests on 

both proposed modifications, sending the resulting data to Kempel and his team. 

Although the Langley team members gave their assessment of the mind-tunnel results, 

they left the decision of which motlification to use up to Kempel and the team at the 

Flight Research Center. 

Kempel recalls that once he hati the preliminary data from these wind-tunnel 

tests, he initiated his own extensive evaluation of the data. "Preliminaq data," 

Kempel clarifies, "was the wind-tunnel guys' way of telling us that they had worked 

most of their magic in data reduction, but that they still were not going to say that this 

was the last word.".; Kempel plotted all of the data from digital listings by hand. 

Although engineers today use computer plotting routines to do what Kempel in 1967 

had to do by hand, the approach made him and other team members intensely farniliar with the data, for the extensive process of hand-plotting meant they had to live with 

the data day in antl (lay out. 

During the summer of 1967, Kempel plotted all of the data for both proposed modifications as a function of angle of attack for constant Mach numbers. He niade all lot 

scales uniform to ease comparisons, plotting thousands of points in this way. Once the 

data was lined up antl compared, Kempel found there were some subtle hut significant differences between the Langley wind-tunnel data and the data set generated by 

the HL-10 simulator at the Flight Research Center. 

As Kempel explains it, "Some non-linearities in the original data were not present" in the Langley data. He hypothesized that "if these non-linearities indicated 

flow separation, then the lack of these would indicate no flow separation or separation 

to a lesser degree."h Based on that theory, Kempel backed using the second moclification proposed by Langley. He presented his hypothesis to his boss, aerodynamicist 

Hal Walker, and then to the management at the Flight Research Center. With their 

agreement and the concurrence of the NASA Langley team, Kempel and his team 

began making arrangements for the modification of the HL-10. 

In the early autumn of 1967, Northrop Norair was contracted to design and install 

the modification that would be the final configuration change to the HI,-10. Northrop 

and NASA decided that the modification would involve a fiberglass glove, backed hy 

a metal structure. Work on the glove continued through the autumn and winter of 

1967. 

As Kempel recalls, "In the NASA hangar, Northrop's Fred Erb shed his normal 

working attire-a suit-and donned coveralls to assist in the installation of the fiberglass glove. He was a senior-level engineer with over 25 years with Northrop, rolling 

5. [bid, p. 27. 

6. [bid., pp. 27-28. 
ANGRY MACHINES 

Attached flow I + 

Schematic showing HL-10 aerodynnmir modification (original drawing by Dale Reed, digital version by 

Dryden Graphics Ofie). 

up his sleeves and getting his hands dirty."7 "A real engineer!", Kempel might 

have added. 

By the spring of 1968, the HL-10 was nearly ready to end its stay as a hangar 

queen, with vehicle preparation then in its final stages. Changes in the configuration, flight controls, and internal systems were already finished. 

Gentry, Peterson, and the M2-F2 

Meanwhile, following Jerry Gentry's flight on 14 November 1966, the M2-F2 

was grounded five and a half months so that the LR-11 rocket-propulsion system 

could be installed by the lifting body's team under the leadership of Meryl 

DeGeer. Gentry made four glide tests in the M2-F2 hy 2 May 1967, conducting 

research maneuvers to define the vehicle's aerodynamic characteristics and 

preparing for planned rocket-powered supersonic flights. Having flown the M2-F2 

successfully several times, Gentry was by this time firmly established as an experienced lifting-body pilot, soon hecoming the Air Force's most active pilot in the 

joint NASA-Air Force lifting-body program.
WINGLESS FLIGHT 

A key member of the M2-F2 team, Gentry knew each crew member personally. Practical jokes abounded between them, and Gentry never once let anyone forget that he represented the Air Force on the project. During his early flights in 

1966, he had told the crew that he hated the zinc-chromate yellow-green color of 

the insides of the lifting bodies. Afterwards, during one of his flights, his flightline car, a 1954 Ford, was "borrowed" long enough to be painted entirely in zincchromate yellow-green at the NASA paint shop. 

In retaliation, Gentry and his Air Force cronies sliped over to NASA during 

one early morning to paste a large Air Force sign on the side of the HL-10, which 

originally had no markings indicating Air Force involvement in the program. 

When the NASA crew members arrived and saw the Air Force sign, they promptly removed it. Later, they had the last word, decorating Gentry's yellow-green Ford 

by pasting large "flower power" decals all over it, the decals then popularly in use 

mainly by the era's "flower children." 

By the winter and spring of 1966-1967, the two official lifting-body pilotsthe Air Force's Jerry Gentry and NASA's Bruce Peterson-were doing alternate 

flights in the lifting bodies. Since Peterson had flown the HL-10 for its maiden 

flight on 22 December 1966, it was Gentry's turn to fly the M2-F2 on 2 May 1967 

for its first flight with the rocket system installed. On this glide flight, his fifth in 

the M2-F2, Gentry reported that the weight increase from the installed rocket system had not changed the vehicle's control characteristics. However, he also confirmed what Milt Thompson and Bruce Peterson had reported on their previous 

flights: that if the M2-F2 is not flown properly, loss of roll control can occur 

quickly. 

In September of 1966, during the symposium of the Society of Experimental 

Test Pilots, Bruce Peterson had given a detailed description of the M2-F2's lateral control characteristics. Maneuverability "was not appreciably affected" as yaw 

and roll damper gains were reduced to zero during the first 180 degrees of 

approach on the fifth flight, he said. However, he felt at the time that "abrupt 

aileron or rudder inputs could readily induce Dutch roll oscillations"; and these 

"could be continuous and could seriously hamper the pilot in holding a bank 

angle." His strategy was to "nudge" the M2-F2 to the desired bank angle by using 

small 1ateraI control inputs. 

"Acceptable lateral control is achieved only by means of aileron-rudder interconnect since the adverse yaw due to aileron at most flight conditions results in 

roll reversal," he said. 
ANGRY MACHINES 

"The optimum interconnect ratio varies with angle of attack 

. . . and dynamic pressure. Consequently, unless the pilot is 

willing to change interconnect continuously ~hroughout the 

flight, roll effectiveness varies from sluggish to extremely 

sensitive, bordering on a pilot-induced oscillation. Even at 

the optimum interconnect ratio, the response to lateral control input is not smooth regardless of magnitude or rate of 

input. This is due to the initial rolling moment producoed by 

the rudder through the interconnect, which is the opposite of 

the desired roll direction. Vehicle response to lateral control 

input is always somewhat of a surprise to the pilot in terms 

of lag and resultant initial rate."8

Crash of the M2-F2 

On 10 May 1967, eight days after Gentry's glide flight, it was Bruce Peterson's 

turn for a glide flight in the M2-F2 with the rocket system installed. It had been 

eight months since Peterson's last six-minute glide flight in the lifting body, and 

this would be his third M2-F2 flight. 

All went well during the beginning of Peterson's flight on 10 May. He 

launched away from the B-52 at 44,000 feet, heading to the north, flying east of 

Rogers Dry Lake, and descended at a steep angle to 7,000 feet. Then, as he flew 

with a very low angle of attack, the M2-F2 began a Dutch roll motion, rolling from 

side to side at over 200 degrees per second. Peterson increased the angle of attack 

by raising the nose. The oscillations stopped, but now the M2-F2 was pointed 

away from its intended flight path. Realizing that he was too low to reach the 

planned landing site on lakebed Runway 18, Peterson was rapidly sinking toward 

a section of the lakebed that lacked the visual runway reference markings needed to accurately estimate height above the lakebed. 

At this moment, a rescue helicopter suddenly appeared in front of the M2-F2, 

distracting Peterson who was still stunned and disoriented from the earlier Dutch 

roll motions. He radioed, "Get that chopper out of the way." A few seconds later, 

he radioed, "That chopper's going to get me.'' NASA pilot John Manke, flying 

8. Quotations in tho paragraphs ahole from Brucr Peterson's comments in Miltoti 0. Thompson, 

Bn1c.e 4. Prterson, and Jerauld R. Centr)., "I.ifting Body Flight Trs~ Program," Society oj'Experimrrzta1 

Test Pilots, Technicnl R~r~ieu (Septrmher 1966): 4-5. 
WINGLESS FLIGHT 

M2-F2 after the crash, showing how the cockpit was held above the ground by the rollover structure. Bruce 

Peterson5 helmet is in the foreground. (NASA photo E67 16731) 

chase in an F-5D, assured Peterson that he was now clear of the helicopter, which 

had chugged off out of Peterson's flight path.9 

Trying to buy time to complete the flare, Peterson fired the landing rockets. 

The M2-F2 flared nicely. He lowered the landing gear, only one-and-a-half seconds being needed for the M2-F2's gear to go from up and locked to down and 

locked. But time had run out. The sudden appearance of the helicopter likely had 

distracted Peterson enough that he began lowering the landing gear half a second 

too late. 

Before the gear locked, while it was still half-deployed, the M2-F2 hit the 

lakebed. The weight of the vehicle pushed against the pneumatic actuators, and 

the landing gear was pushed back up into the vehicle. The round shape of the 

vehicle's bottom did not lend itself to landing minus landing gear. The result was 

more like a log rolling than a slide-out on a flat bottom. (By contrast, the shape 

of the HL-10 likely would have lent itself readily to a gear-up landing, had one 

been required. Langley engineers had even given serious thought to eliminating 

the HL-10's landing gear for spacecraft recovery.) 

9. Quotations from Hallion, On the Frontier, p. 159; Wilkinson, "Legacy of the Lifting Body," pp. 

57-60, but Dale Reed was watching the whole episode on a TV monitor from the control room, as pointed out below in the narrative, so he heard the comments first hand. 
ANGRY MACHINES 

As the M2-F2 contacted the ground, the vehicle's telemetry antennae were 

sheared off. As this happened, 1 and the other engineers in the control room 

watched the needles on instrumentation meters flick to null. Startled, we looked 

up at the video monitor in time to see the M2-F2, as if in a horrible nightmare, 

flipping end over end on the lakebed at over 250 miles per hour. It flipped six 

times, bouncing 80 feet in the air, before coming to rest on its flat back, minus its 

canopy, main gear, and right vertical fin. The M2-F2 sustained so much damage 

that one would have been hard pressed to identify it visually as the same vehicle. 

By all odds, Peterson could have been expected to have died in the crash. He 

was seriously injured. Assistant crew chief Jay King quickly crawled under the 

M2-F2 to shut off the hydraulic and electrical system. He found Peterson trying 

to remove his helmet. King unstrapped him and helped him out of the vehicle. 

Peterson was rushed to the base hospital at Edwards for emergency care. 

Afterwards, he was transferred first to the hospital at March Air Force Base near 

Riverside, California, and later, to UCLA's University Hospital in Los Angeles. 

The heavy metal cage-like structure around the cockpit-ironically, added to 

the M2-F2 by its NASA/Northrop designers simply to provide ballast and save 

their pride-was mainly what saved Peterson's life. Even with this added protection, his oxygen mask was ripped off as his head made contact with the lakebed. 

Each time the vehicle rolled, a stream of high-velocity lakebed clay hammered at 

Peterson's face. He suffered a fractured skull, severe facial injuries, a broken 

hand, and serious damage to his right eye. He underwent restorative surgery on 

his face during the ensuing months; however, he later lost the vision in the injured 

eye from a staphylococcus infection. 

He returned to the NASA Flight Research Center as a project engineer on the 

CV-990, F-8 Digital Fly-By-Wire, and F-8 Supercritical Wing. He continued to 

fly in a limited way on the CV-990 and F-111 and eventually became the Director 

of Safety, Reliability, and Quality Assurance. He also continued to fly as a Marine 

reservist. Later, he left NASA to serve as a safety officer at Northrop in the flight 

tests of the B-2 bomber and other aircraft. 

About two years after the crash of the M2-F2, the popular television series 

The Six-Million-Dollar Man began its six years of weekly programming, using 

NASA ground-video footage of the crash as a lead-in to each episode. The producers of the television series capitalized on Peterson's misfortune by inventing a 

"bionic man" (played by Lee Majors) who had missing body parts replaced with 

bionic devices. Colonel Steve Austin, the fictional television character played by 

Majors, had, like Peterson, also lost an eye in the crash. 

As can happen only in Hollywood, the fictional Austin gained a bionic eye 

with super powers. The television show also multiplied the injuries of Austin 

beyond those suffered in real life by Peterson, giving him two bionic legs and a 
WINGLESS FLIGHT 

bionic arm that provided him with super power and speed. Nevertheless, NASA 

pilot Bruce Peterson is the real-life model on which The Six-Million-Dollar 

Man is based. Due to the popularity of this television series, it's possible that as 

many Americans viewed the crash of the M2-F2 on television as later viewed the 

first televised NASA shuttle landings. 

The crash of the M2-F2 was the only serious accident that occurred during the 

twelve-and-a-half years of flight-testing eight different lifting bodies.10 Because 

of the popularity of the television program The Six-Million-Dollar Man, most 

people are more familiar with the solitary serious accident that occurred during 

the lifting-body program than they are with its extensive record of otherwise accident-free success. 

10. These were the M2-F1, M2-F2, M2-F3, HL-10, HL-10 modified, X-24A, X-24B, and the 

Hyper 111. 

CHAPTER 6 

BACKTOTHEDRAWINGBOARD 

The crash of the M2-F2 left us with no lifting bodies to fly for almost a year. When 

the M2-F2 crashed in early May 1967, the HL-I0 had been a hangar queen for over 

four months, and it ~ould remain grounded for another eleven months while its aerodynamic problems were fixed before its second flight. Bikle had grounded the M2-F1 

permanently, the "flying hathtub" that had launched the lifting-body effort four years 

earlier now destined to he a museum artifact. Another lifting body was in the works, 

the Air Force Flight Dynamic Laboratory at Wright-Patterson Air Force Rase having 

a contract with the Martin Aircraft Company of Middle River, Marylantl, for designing 

and building a piloted lifting hody originally designated the SV-5P and later known as 

the X-24A. However, it would be another two years before it was ready to fly. 

Despite the setbacks in lifting-hody flight testing, competition continued to 

flourish between the flight-test teams of the NASAIAir Force M2-F2 and the NASA 

HL-10. With the Air Force and three different NASA sites-Ames on the M2-F2 and 

Langley on the HL-10, each in conjunction with the Flight Research Center-ac-tively involved on the M2-F2 and in flight operations for the HL-10, the dynamic energy 

of their interaction could have been destroyed within the multiple organizational 

channels through which it had to travel. It was amazing to watch these teams cut 

across NASA and Air Force channels and remain unified, their first allegiance being 

to their shared lifting-body project. 

Rebirth of the M2-F2 

The crashed M2-F2 was pathetic-looking, nearly no skin panels without dents or 

damage. Rather than scrapping the M2-F2, John McTigue hat1 the hehicle sent to 

Northrop's plant in Hawthorne, California, where Northrop technicians put the battered vehicle in a jig to check alignment, having removed the external skin and portions of the secondary structure, and then removed and tested all systems and parts, 

an inspection process that took the next two months. Many parts such as valves and 

tanks were tested at the Flight Research Center's rocket shop. Meanwhile, the M2-F2 

team tackled the difficult problem of fixing the vehicle's control problems. Over the 

next 60 days, the NASA Ames team members, led by Jack Bronson, gave high 

priority to wind-tunnel tests for finding that solution. Using a make-shift model of 

the M2-F2, they tried five different approaches to fixing the with elevon 

adverse yaw. 
BACK TO THE DRAWING BOARD 

First, they tried canting the elevon hinge lines so that side force directly on the 

elevons would give favorable yaw into a turn. This approach failed, because there were 

still more pressure effects on the vertical fins that offset any favorable pressure on the 

elevons. 

Second, they tried an extra horizontal surface with two elevons attached between 

the right and left vertical tail tips, putting favorable pressures on the vertical tails that 

would reverse the yawing moments. This approach was abandoned due to its complexity and its structural problems. 

Third, they tried converting the elevons to a bi-plane arrangement with standoffs 

supporting a second horizontal surface above each elevon so that the original elevons 

and standoff surface would move as a control unit. This approach was abandoned 

because it did not produce the favorable pressure gradients they had hoped it would. 

Fourth, they tried extending the elevons aft of the body, away from the vertical 

fins. This approach succeeded in eliminating about half of the adverse yawing 

moments, although it also became apparent that pressure gradients were being affected upstream near the vertical tails from elevon deflection. 

Finally, they tried installing a center fin that would act as a splitter-plate between 

the right and left elevons, producing side forces that would counter those of the outer 

vertical fins. For example, following a right roll command by the pilot, the original 

M2-F2's right elevon trailing edge moved upward. The pressure field on the upper 

right side of the body would increase due to this deflection, pushing down on the right 

side of the body. This increased pressure would also push on the inner side of the right 

vertical tail, pushing the tail to the right and the nose to the left, resulting in adverse 

yaw. With the center fin installed on the M2-F2, however, this pressure would also 

push against the right side of the center fin, opposing the adverse yaw effects from the 

pressure pushing to the right against the right vertical tail and, as a result, canceling 

the moments of adverse yaw. 

Jack Bronson's team at NASA Ames ran wind-tunnel tests on center fins of various sizes. As expected, the larger ones produced more proverse (favorable) yaw than 

did smaller ones. Meryl DeGeer, the M2-F2 operations engineer at the Flight 

Research Center, was asked to provide a clearance drawing of the largest vertical fin 

that would fit under the B-52 pylon. As it turned out, the M2-F21B-52 adapter could 

not be used if a center fin were installed on the M2-F2, for it had a large beam running down the center. However, DeGeer and the Northrop designers decided that the 

HL-10 adapter-with a slight modification--could be used for both vehicles since it 

had been built to accommodate the center fin on the HL-10. NASA Ames tested the 

fin shown in DeGeer's drawing, and it worked. The fin not only neutralized the adverse 

yaw effects but it also produced a small amount of proverse yaw beyond what was 

needed to cancel adverse yaw. 

A conference called by Gary Layton was held at the NASA Flight Research 

Center, attended by team members from both NASA Ames and the Flight Research 

Center as we11 as the Air Force. Due to the wind-tunnel test results, the center fin was 

unanimously accepted by the attending team members as the way to fix the control 
WINGLESS FLIGHT 

problems on the M2-F2. The NASA Ames team then gathered a more complete set of 

data on the new configuration. The team at the Flight Research Center analyzed the 

Ames data that showed the elevons to have a small amount of proverse yaw, modified 

the M2-F2 simulator, and calculated new root-locus characteristics. 

Bob Kempel remembers making some root-locus calculations on the old and the 

new M2-F2 configurations at that time. He found the difference in controllability to be 

as extreme as that between night and day. The new configuration with the center fin 

had good roll control characteristics with no tendencies for problems in pilot-induced 

oscillation (PIO). Although Kempel was officially on the HL-10 team at the time, he 

had a vested interest in the M2-F2 from having done some analysis on it early in its 

development. Never happy with the lateral control-system design on the original M2- 

F2, he had aligned himself with the HL-10, which he originally considered the better 

of the two heavyweight lifting bodies. With the center fin added to the M2-F2, Kempel 

agreed that the vehicle could become a good flying machine. 

As their main mathematical tools in analyzing all motions made by an aircraft 

during flight, stability and control engineers such as Bob Kempel use La Place transforms, differential equations, and linear algebra. Winged aircraft normally have such 

typical motions as roll, spiral, and Dutch roll modes. Lifting bodies, on the other hand, 

can have a unique motion called a coupled roll-spiral mode, which Kernpel documented on the M2-F2 in September 1971 in a NASA report entitled, "Analysis of a 

Coupled Roll-Spiral-Mode, Pilot-Induced OsciIlation Experienced With the M2-F2 

Lifting Body."] Kempel explains that the oscillatory coupled roll-spiral mode results 

from a combination of non-oscillatory roll and spiral modes. When poor roll controls 

such as the M2-F2 elevons are used, PI0 problems result. 

The control problems in piloting a lifting body are somewhat like the control problems experienced by a lumberjack in maintaining his balance during the sport of logrolling, something I know a little bit about from growing up near the logging industry 

in Idaho. A log is similar to a lifting body in that both are very slippery in a roll, neither having anything like wings that work to resist the rolling motion in water, for the 

log, or in air currents, for the lifting body. A lumberjack wearing spiked boots has a 

pair of good controls on the log he's rolling. With constant attention, he can use his 

spiked boots to control the log's motion. Were the lumbe jack wearing instead a pair 

of ordinary slick-soled shoes, however, he'd have only a pair of poor controls to use. 

Even with constant attention, he'll eventually lose control of the log he's rolling and, 

when a wave (analogous to a side gust on a lifting body with poor controls) hits the log, 

he's going to get very wet. 

By 1967, we had flown two lifting-body configurations and were about to fly a 

third, the M2-F3, the rebuilt M2-F2 with the added center fin. The log-roller analogy 

1. R. W. Kempel, "Analysis of a Coupled Roll-Spiral-Mode, Pilot-Induced Oscillation Experienced 

With the M2-F2 Lifting Bodyv (Washington, DC: NASA Technical Note D-64%, 1971). 
- 

BACK TO THE DRAWING BOARD 

Schernciric sholcing the Jf2-F1, &12-F2 (4nd the If2 F3 (origincrl drazcing by Dnk Reed, digital version by 

nryrlerr Crophirs Ofjre). 

applies as well to the differences among the M2-F1, the M2-F2, and the M2-F3. The 

M2-F1 had the large "elephant ears", the external elevons, that provitIed good roll 

control, similar to the lumhe jack wearing the spiked boots. The "elephant ears" also 

served as flat surfaces that slow down, or damp, rolling motions, similar to what would 

happen if the lum1)erjac.k nailed a board to the log. Vhen we went from the M2-F1 to 

the M2-F2 configuration, we essentially deprived the luniberjack of his spiked boots 

and removed the board from the log, depriving him of the means fur good roll control 

and dan~ping. f hen we converted the M2-F2 to the M2-F3 configuration with the center fin, we essentially gave back to the lumberjach his pair of spiked l~oots, equipping 

him with the means for good roll control. However, our lumberjack would still have a 

slick log with no N-ay to slow down (damp) the rolling motions minus the board nailed 

to the log. Khat the board nailed to the log provides the lumberjack, a stahility augmentation systeni (SAS) on a lifting body provides the pilot, 110th helping to damp 

oscillations and other quick movements. 

Birth of the M2-F3 

Northrop was enthusiastic. about wanting to rebuild the M2-F2 into the M2-F3, 

strengthening th~ resolve of the NASA teams to seek approval from NASA Headquarters for continuing the M2 program. NASA Headquarters was reluctant about authorizing more M2 flight tests, but project manager John McTigue was not one to give up 

easilj. Eventually his tenacity succeeded in getting NASA's Office of Advanced 

Research ant1 Technology to authorize Northrop in March 1968 to continue its 
WINGLESS FLIGHT 

"inspection" of the wrecked lifting body. The Northrop team that had I~uilthe M2-F2 

was still intact, soon to be transferred onto other Northrop projects, so this was the last 

opportunity we hacl to have the vehicle rebuilt at low-cost, using the best possible 

Northrop team for the job. 

The lifting-body program was also fortunate to have the help of Fred DeMerritte 

to keep the effort going at NASA Headquarters. DeMerritte and McTigue had an 

unwritten agreement that they would proceed quietly at a steady pace until the 

M2-F3 was ready to fly. McTigue had Bikle to hack him up at the Flight Research 

Center, but DeMerritte was on his own at NASA Headquarters. There was no official 

authorization for conducting an M2-F3 flight program; however, DeMerritte managed 

to find a wray to continue sending money in incremental amounts to John McTigue to 

keep the "inspection" going until official approval was obtained. 

Just how tense the situation was around DeMerritte at NASA Headquarters in 

regards to the M2-Fb2/M2-F3 project is suggested by a conversation that Meryl DeGeer 

recalls having with DeMerritte on a visit the latter made to the Flight Research Center. 

DeMerritte privately asked DeCeer how things were going on the project. DeCeer 

said that everything was going fine but that if DeMerritte would give them some more 

money, they could have the M2-F3 ready to fly all the sooner. DeMerritte asked 

Deceer not to push him, for then he'd be forced to say no to the project. It was nearly ten months later-on 28 January 1969-that NASA Headquarters officially 

announced that the Agency would repair and modify the M2-F2, returning the vehicle to senrice as the M2-F3, a process that took three years and cost nearly $700,000. 

Since there wasn't enough money to contract out all of the work, most of the 

installation of systems was done by the "Skunk Works" at the Flight Research Center, 

similar to what had heen done with the M2-F1. However, McTigue was able to retain 

from Northrop five engineers arid nearly a dozen technicians to work with the Flight 

R~search Center in fabricating the M2-F3 from the remains of the M2-F2. 

Northrop's Fred Erl~ coordinatetf the Northrop technical effort while Meryl 

DeCeer, as NASA's M2-F3 operations engineer, headed up the rebuilding project at 

the Flight Research Center. Special design problems and parts that had to he manufactured at the Northrop facility were handled through Erl~. To keep costs down, as 

much of the rebuilding as possible was done in the FRC shops. Working from 

Northrop drawings, Lavern Kelly ant1 Jerry Reedy built new- vertical tails for the M2- 

F3 in the FRC sheet-metal shop, two sheet-metal workers from Northrop at times 

assisting the shop technicians. The FRC machine shop remanufacturetl broken parts, 

including the landing gear. Rocket, fuel-system, and plum1)ing parts were built in the 

Center's rocket shop. The FRC aircraft rlec.trica1 shop put together and installed the 

vehicle's wiring hundles and electrical systems. Besides the newT central fin, a numher of internal improvements and other additions were made to the M2-F3. For example, heavy components were moved farther fonvarcl, avoiding the need for nose ballast, 

and small changes in the cockpit area improved visibility ant1 access to the controls. 

For a cleaner installation, we also rotated the TAR-1 rocket engine 90-degrees. 
BACK TO THE DRAWING BOARD 

NASA hoped that the new hydrogen-peroxide jet-reaction roll-control system 

installed on the M2-F3 might be used as well on future lifting-body spacecraft so the 

pilot could rely on a single control system from orbit to landing, rather than the multiplicity of systems used on such aircraft as the X-15. NASA planned to use the 

M2-F3 as a testbed for research on the lateral control problems of lifting bodies. If we 

could eliminate the elevons and rudders, replacing them with reaction rocket controls, 

we would need only one flap on the bottom of the vehicle for longitudinal trim. 

According to Air Force pilot Jerry Gentry, the transformation of the M2-F2 into 

the M2-F3 changed "something I really did not enjoy flying at all into something that 

was quite pleasant to fly."2 

HL-10 Returns to Flight 

Meanwhile, after fifteen and a half months of wind-tunnel tests, simulation, control-system analysis, and modification of the outer tail fins, the HL-10 was returned to 

flight. Jeny Gentry flew the HL-10 for the second time on 15 March 1968, launched 

from 45,000 feet at Mach 0.65. From B-52 launch to touchdown, total flight time was 

approximately 4.4 minutes. 

"I think the whole Center came out to watch this flight," recalls Joe Wilson. 

"People were standing on the roof, by the planes [on the ramp, and at the edge of the] 

lakebed. I haven't seen so many observers for a first flight since I've been here. The 

day was almost absolutely clear and you could see the contrails of the B-52 and [the] 

chase [planes] . . . two F-104s, one T-38 and the F5D. On [the] drop, everything was 

O.K., and for a short time you could follow the contrails. The contrails began to pop 

in and out [of sight], and then were gone from view."3 

The flight plan called for mild pitch and roll maneuvers to 15-degrees angle of 

attack to evaluate the possibility of control degradation of the sort experienced during 

the first flight. To assess potential flare characteristics, Gentry executed a simulated 

landing flare to 2G at altitude. 

A camera had been installed on the tip of the vertical fin to provide in-flight 

photographs of the right inboard tip-fin flap and right elevon. These surfaces had been 

"tufted" so that a qualitative assessment of the aerodynamic flow field could be made 

from the photographs. "Tufting" involves taping the ends of short pieces of wool yam, 

called "tufts," on suspected problem surfaces of an aircraft for assessing the quality 

of airflow. If the flow is attached, the tufts lie flat in the direction of the flow across the 

surface. If the flow is separated, the tufts dance and flutter randomly. Generally, the 

conclusions following the flight were that the airflow did not separate significantly and 

2. The quotation also appears in Wilkinson, "Legacy of the Lifting Body," p. 61. 

3. Personal diary of NASA Flight Research Center employee Ronald "Joe" Wilson, entry for March 

15, 1968, copy available in the Dryden Flight Research Center History Office. 

116 
WINGLESS FLIGHT 

consequently that there had been no degradation of control. (When the airflow over 

control surfaces separates significantly, the control is degraded because it operates 

aerodynamically.) However, some over-sensitivity in pitch control was observed. 

In the debriefing room following the flight, Gentry said the vehicle felt solid. It 

had no problems in roll sensitivity, It had good longitudinal stability. He also said that, 

on turning to final approach, flare, and landing, the HL-10 was better than the F-104. 

He reported that he had put the gear down somewhere after 250 knots and had felt a 

sharp jolt as the nose gear touched down. 

Bob Kempel, Wen Painter, and the rest of the team were as proud as peacocks following the second flight of the HL-10. When someone asked him what kind of problems had occurred on the flight, Kempel said there had been no problems at all, that 

the flight was a complete success from everyone's point of view. The sensitivity of the 

longitudinal stick, noted during the flight, was considered acceptable. 

The dynamics of the HL-10 in flight proved to be as good as had been indicated 

by the simulator. After the second flight, Kempel said, the HL-10 attracted the attention of the pilots. "From this point on, all the pilots wanted their shot at flying the HL10."4 

After pilots establish confidence in a new aircraft and have a little more time to 

evaluate things, they often change their opinions. The situation was no different with 

the HL-10. Although no major modifications were required, minor adjustments continued to be made to the HL-10 throughout the remainder of the program. The HL-10 

had 35 more successful flights, piloted by NASA's Bill Dana and John Manke and the 

Air Force's Jerry Gentry and Pete Hoag. 

F-104 Used in Pilot Training 

During 1968, pilots were becoming very dependent on the ground-based simulator for developing flight procedures and becoming as familiar as possible with the 

flight characteristics of the lifting bodies. Actual flight experience in the lifting bodies could not be relied upon to provide adequate pilot training because the typical 

flights were short-five to six minutes for glides, 10 to 15 minutes for rocket Aightsand weeks or even months separated flights. Furthermore, for the lifting-body pilots, 

the first launch off the B-52 hooks was like being thrown into deep water for the first 

time: you either swim or sink. 

In 1957-58, a young research pilot at the Flight Research Center by the name of 

Neil Armstrong-who, as a NASA astronaut, would later become the first human 

being to walk on the moon-had conducted a series of flights tests on the NASA 

F-104 designed to simulate low lift-to-drag-ratio flight experience. The technique 

4. Kempel, Painter, and Thompson, "Developing and Flight Testing the HL-10," p. 29. 
BACK TO THE DRAWING BOARD 

- 

118 

involved landing an F-104 "dirty," with power off ant1 with flaps, landing gear, ant1 

speed brakes extended.5 The pilots found it exciting to fly the F-104 this way, hut they 

had to be careful to avoid losing control of the aircraft. The pilots' choice later on in 

preparing for lo^ lift-drag flight and later for flying chase on lifting-body flights was 

clearly the F-104, a reliable aircraft that had the pilots' full confidence. 

The F-104, as it turned out. provided excellent training experience for pilots as 

preparation for lifting-body flights. The aircraft's high-speed landing gear and largespeed brakes could be used to duplicate lifting-body lift-to-drag characteristics. The 

aspect ratio of the F-104 was only a1)out 2.46 with a low-speed, clean configuration at 

a maximum lift-to-drag ratio of approximately 5.7. With the engine at idle, gear and 

flaps down, and modulation of speed brakes, the lift-to-drag ratio could he made to 

simulate each of the lifting-body configurations. In this sort of power approach at 170 

knots, the lifi-to-drag ratio was approximately 2.9. Thus, the lift-to-drag-ratio 

envelope of the F-104 essentially blanketed the lift-to-drag-ratio values of all of the 

lifting bodies. 

Chasing lifting bodies in the F-104, however, was not totally without risk, as experienced by NASA pilot Torn McMurtq. Chasing one lifting-body flight, McMurtry 

inadvertently entered an uncontrolled spin. This was serious because the F-104 was 

not known as an aircraft that could successfully recover from a spin. 

The incident occurred at 35,000 feet and 210 knots airspeed with gear down, flaps 

at takeoff, speed brakes out, and power at idle while McMurtry was maneuvering to 

join up with the lifting body. Maneuvering into position, McMurtry rolled to 45 

degrees of bank and sensed the aircraft starting to slice to the right while in heavy huffet with the nose up. The F-104 went into a spin. One of the other chase pilots, 

Gaq Krier, saw what was happening and radioed McMurtry, calling for full forward 

stick and full forward trim. The F-104 was in a flat uncontrolled spin directly over the 

Edwards maintenance and modification hangar, rotating to the right at about 40 to 50 

degrees per second. 

The aircraft made four or five full turns before McMurtry stopped the rotation by 

holding fill1 left rudder, neutral aileron, and stick and pitch trim at full nose-down. 

Recovery from the spin seemed very abrupt, completetl at approximately 180 knots 

and 18,000 feet. The engine did not flame out, and the only configwration change 

made during the spin was the retraction of the speed brakes. McMu~~ry held the nose 

down until the F-104 reached 300 knots and then pulled out at slightly over 4G, the 

bottom of the pull-out occurring at 15,000 feet. 

After the lifting body landed successfully, McMurtrj joined the other chase 

aircraft in the traditional fly-bj. Later, during the post-flight debriefing, discussion of 

5. Gene J. Matranga and Neil A. Armstrong, Approach and Landing Int,estigcction at Lift-Drug 

Ratios of 2 to 4 Utilizing a Straight-Ving Fighter Airplane (Edwards, CA: YASA TM X-31, 1959). 
WINGLESS FLIGHT 

the lifting-body mission seemed almost trivial in comparison with McMurtry's description of his experience in the F-104. 

From Analog to Digital Computer Simulation 

By the mid-1960s, flight simulation had become an essential part of flight 

research at the Flight Research Center.6 Even Paul Bikle, who had been somewhat 

skeptical of the early simulation work with the M2-F1, was beginning to recognize the 

importance of flight simulation in planning lifting-body flights. Ocer the three and 

half years of flight-testing the HL-10, three NASA simulation engineers-Don Bacon, 

Lany Caw, and Lowell Greenfield-were involved. Air Force Captains John Rampy 

ant1 John Retelle were later involved with the HL-10 simulator and stability 

and control. 

The HL-10 real-time simulator was primarily an engineering tool, not a pilottraining simulator per se. The simulator was fixed-base-that is, it had no cocekpit 

motion. It had an instrument panel similar to that of the fight vehicle as well as a 

pilot's control stick and rudder pedals closely approximating those of the actual aircraft. No visual displays were available, all piloting tasks being accomplished by 

using the instruments. The instrument panel included indicators showing airspeed, 

altitude, angle of attack, normal acceleration, and control surface position. A threeaxis indicator provided vehicle attitude and sideslip information. 

Both engineers and pilots used the simulation extensively. Engineers used the 

simulator for final validation of control-system configuration. Control gearing selection 

was aIways difficult with the fixed base. The wanted high sensitivity until they 

were airborne. Then, the simulation engineers had to decrease the gearing. Modem 

motion simulators of today have moving cockpits and give high fidelity to control gearing selection. 

The simulation was used later to plan each research flight mission, specifying 

maneuvers and determining flight profiles including Mach numbers, altitudes, angles 

of attack, ant1 ground track needed for mission objectives to be achieved. Emergency 

procedures were also practiced on the simulator, inducing various failure modes and 

selecting alternate landing sites. The pilots were relatively willing subjects once they 

knew they would be flying the actual mission, and the training paid large dividends. 

From this information, flight cards were assembled and distributed at crew briefings 

to all involved personnel, including chase and B-52 pilots, the mission controller, participating flight-research engineers, and NASA and Air Force managers. Coordination 

was critical to the success of each mission. 

The pilots were unanimous in reporting that, once in flight, the events of the mission always seemed to progress more rapidly than they had in the simulator. As a 

6. See Thompson, At thp Edge of Space, pp. 70-71. 
BACK TO THE DRAWING BOARD 

result, engineers and pilots experimented with speeding up the simulation's integration rates, or making the apparent time progress faster. They found that the events in 

actual flight seemed to occur at about the same rate as they had in the simulator once 

that simulation time was adjusted so that 40 simulator seconds was equal to about 60 

"real" seconds. Only the final simulation planning sessions for a given flight were conducted in this way. In his book, At the Edge of Space, Milt Thompson discussed how 

this difference between simulator seconds and seconds as perceived by pilots in actual flight was first discovered during the X-15 program, the first aircraft research program that made extensive use of simulation in flight planning and pilot training, and 

resolved by Jack Kolf who originated the concept of fast-time simulation, compressing simulator time to approximate time as it appeared in actual flight.7 

The first simulation of the HL-10 was done with the Pace 231R analog computers 

then in use at the Flight Research Center. The real capability of the analog computer 

was its ability to integrate differential equations. Because the equations of motion for 

the lifting bodies were differential equations-as are all equations of motion for aerospace vehicIes-the simulation engineers mechanized them on available analog computers. During the early to mid-1960s, digital computers were primarily used for data 

reduction, not for real-time simulation. Analog computers were fast, having no problems with cycle time. However, they left much to be desired when it came to mechanizing highly nonlinear functions common to aerodynamic data. Simulation engineers 

at the Flight Research Center could generate these nonlinear functions on analog 

computers-but only with great difficulty, patience, perseverance, and a lot of time. 

With the aerodynamic data for the modified HL-10, the simulation engineers 

wanted to mechanize the highest fidelity simulation possible, so they purchased a relatively high-speed digital computer to generate the nonlinear functions. They interfaced the digital and analog computers, using the analog system for the integrations, 

and moved into the world of hybrid computerization. This approach proved quite successful, allowing them to make fast, efficient changes to the aerodynamic database 

when they were needed. 

Although the program engineers were not aware of it, the simulation engineersDon Bacon, Larry Caw, and Lowell Greenfield--decided to experiment with moving 

all of the mathematical computations, including the integrations, to the digital computer. Afterwards, they gave a demonstration of an all-digital, real-time computer simulation. Program engineers Bob Kempel and Wen Painter couldn't tell the difference. 

Neither could the ~ilots Bill Dana, Jerry Gentry, Pete Hoag, and John Manke. 

The HL-10 program thus achieved another milestone, having successfully made 

the transition from simulation by analog computer to real-time simulation by digital 

computer. Today, analog computers have nearly gone the way of the dinosaur. At the 

Dryden Flight Research Center since the mid-1970s, virtually all flight simulation has 

been done by using high-speed digital computers. 

7. Ibid. 
WINGLESS FLIGHT 

Brown-Bagged Panic: Crashing the Simulator 

After the second flight of the HL-10 in March 1968, Jerry Gentry and John Manke 

alternated as pilots of the vehicle during eight more glide flights in subsonic 

configuration before the HL-10 was fitted with the rocket engine for supersonic flight 

in transonic configuration. The aerodynamics became quite different in the transonic, 

or "shuttlecock," configuration with the rudders moved outboard and the elevon flaps 

moved upward. Now that the flight envelope of the HL-10 was expanding to supersonic speeds at higher altitudes, everyone on the project was a little edgy, including 

the pilots. 

A diligent research pilot, John Manke didn't believe in wasting time when it came 

to practicing on the simulator for upcoming flights. One day, to practice for his first 

supersonic flight with the HL-10, he showed up during the lunch hour, bringing his 

bagged lunch with him. No program engineers were still in the room, and Manke was 

left alone with the simulator once the simulation engineer left for lunch after loading 

a data set into the simulator. However, inadvertently, the simulation engineer had 

loaded the wrong data set-a demonstration set, not used for flight planning, that had 

directional stability set at zero. 

Manke began simulated flight, unaware of the error. Achieving planned altitude 

for acceleration to supersonic speed, Manke pushed the nose over, toward zero angle 

of attack, and the vehicle became violently unstable in the lateral direction. The 

result? Manke "crashed" in the simulator. 

To a simulation engineer, "crashing" in simulated flight may seem no big deal, for 

the engineer may be primarily conscious of the fact that simulated flight is not real 

flight, but to a pilot who uses a simulator as a pre-stage to actual flight, "crashing" in 

the simulator can be a major big deal. With no program engineers around at the time, 

Manke expressed his concerns at once to NASA management. 

As a result, project engineers Bob Kempel, Berwin Kock, Gary Layton, and Wen 

Painter quickly found themselves in the "Bikle barrel," Bikle's wood-paneled executive office, trying to explain to Paul Bikle, Joe Weil, and several other members of the 

NASA management why they were trying to kill a perfectly good test pilot-a guy all 

the project engineers liked very much, even if he was from South Dakota. 

Kempel recalls feeling a long way from the office's door as a means of escape from 

this very uncomfortable meeting, a formidable barrier of high-level managers standing between it and the HL-10 project engineers. Once the feeding frenzy had abated, 

it occurred to the project engineers that the wrong data set must have being used. They 

explained the problem and followed up with a demonstration in the simulation lab, 

showing that with the correct flight data set loaded into the simulator, no dynamic 

instability occurred. 
BACK TO THE DRAWING BOARD 

From Rocket Power to Supersonic 

On 23 October 1968, Jerry Gentry attempted the first lifting-body powered flight 

in the HL-10. Unfortunately, the rocket failed shortly after launch. Propellant was jettisoned, and an emergency landing was made successfully on Rohamond Dq 1,ake 

located about 10 miles southwest of Rogers Dry Lake within the boundary of Edwards 

Air Force Base. A few weeks later, on 13 November, John Manke successfully flew the 

HL-10 for the first time in powered flight. 

Five months later, on 17 April 1969, Jerry Gentry flew the X-24A for its first 

flight. After the B-52 hat1 launched Gentry in the X-24A that day, it was mated with 

the HL-10 and then launchetl John Manke in the HL-10 for that vehicle's fifteenth 

flight. For the first and only time in lifting-1,otIy history, two flights in two different 

vehicles were launched the same day from one mothership. 

It's traditional, following a maiden flight, to douse the pilot. After Gently's first 

flight that day in the X-24A, during the party at the Edwards Officers' Club, someone 

decided the swimming pool could be used for Gentry's dousing. However, no one had 

noticed the pool was nearly empty. Fortunately, Gentry survived his shallow immersion with only a few cracked front teeth. 

A few weeks later, on a beautiful spring day in the Mojave Desert, John Manke 

made the world's first supersonic lifting-body flight in the HI,-10 on 9 May 1969. The 

flight plan for the first supersonic flight of the HL-10 called for launching approximatel) 30 miles northeast of Edwards AFB, igniting of three rocket chambers, rotating to a 20-degree angle of attack, maintaining that angle of attark until the pitch 

attitude was 40 degrees, and maintaining that pitch attitude until the vehicle reached 

50,000 feet. At that altitude, according to the flight plan, Manke would push over to a 

six-degree angle of attack anti accelerate to Mach 1.08, aftenvarcts changing angle of 

attack, turning off one rocket chamber, and maintaining a constant Mach number 

while gathering data. Landing was planned as a typical 360-degree approach with a 

landing on Runway 18. 

later, Manke reported that there had been no significant I)roblems during the 

fligllt and that generally everything had gone really well. Indeed, the actual flight went 

almost t~ntirely according to plan. On this historic seventeenth flight, the HL-10 actually rose to an altitude of 53,300 feet and achieved a speed of Mach 1.13, both slightly abobe the planning figures. 

Some special engineering etents preceded the first supersonic lifting-body flight. 

These included completely reviewing the wind-tunnel aerodynamic data and reassessing the predic-ted dynamic and \chicle controllability characteristics in transonic and 

supersonic flight regimes. Between Mach 0.9 and 1.0, the data indicated an area of 

low, and even slightly negative, directional stahility at angles of attack of 25.5 degrees 

and above. Predictions and the simulator showed acceptable levels of longitudinal ant1 

lateral-directional djnamic stahility at all angles of attack and Mach speeds. The 

engineering team also prepared a detailed technical Griefing that was presented to the 

NASA and Air Force management teams. 
WINGLESS FLIGHT 

The HL-10, like all lifting bodies, had very high levels of effective dihedral. This 

characteristic-along with positive angles of attack and accepta1)le levels of directional stability-ensured lateral-directional dynamic stability almost everywhere in 

the flight envelope. Before the flight, the HL-10 team demonstrated to project pilot 

John Manke that the HL-10 would exhibit this dynamic stability even if the static 

directional stability was zero or slightly negative, provided that the angle of attack did 

not approach zero. 

Bob Kempel recalls that the actual flight was probably not as exciting as the 

events leading up to it. From what Kempel remembers of the flight, it was relatively 

uneventful-except for the fact of going supersonic. Nevertheless, in his book On. the 

Frontier, Richard Hallion calls this first supersonic flight "a major milestone in the 

entire lifting-body program," adding that "the HL-10 [later] became the fastest and 

highest-flying piloted lifting body ever built."8 

Faster and Higher 

About nine months after Manke's first suprrsonic flight, during the 34th flight of 

the HL-10 on 18 February 1970, Air Force pilot Major Pete Hoag bested Manke's 

Mach 1.13, achieving Mach 1.86. Nine days later, on the 35th flight, NASA pilot Bill 

Dana took the HL-10 to an altitude of 90,303 feet. 

Hoag's Mach 1.86 in the HL-10 was, indeed, the fastest speed achieved in any of 

the lifting bodies. From B-52 launch to touchdown, the flight lasted 6.3 minutes. 

Except for the Mach number exceeding the preflight prediction, the flight was fairly 

routine. 

The HL-10 had been launched about 30 miles southwest of Edwards AFB, heatling 059 degrees magnetic, at 47,000 feet. According to flight plan, all four rocket 

chambers were ignited immediately after launch. The vehicle was rotated to a 23- 

degree angle of attack until a pitch attitude of 55 degrees was attained, that pitch attitude held until the vehicle reached 58,000 feet, followed by a pushover to zero 

G--angle of attack near zero-maintained until the fuel was exhausted. Predicted 

preflight Mach speed hat1 been 1.66 at 65,000 feet. However, Hoag achieved Mach 

1.86 at 67,310 feet. 

The fourth NASA research pilot to fly the HL-10, Bill Dana had flown the 199th 

and last flight of the X-15 in late October 1968, six months later making his first HL10 glide flight on 25 April 1969. When he took the HL-10 to 90,303 feet on 

27 February 1970, Dana not only flew the HL-10 higher than it had ever been flown 

before, he also set the record for the highest altitude achieved by any lifting body. 

From B-52 launch to touchdown, the flight lasted 6.9 minutes. 

8. Hdllion, Ort the Frontter, p. 162. See immediately b~lr~w in the narrati~e for the drtails Hallion 

is summarizing here. 
BACK TO THE DRAWING BOARD 

Dana's flight to maximum altitude was launched under the same initial conditions 

as Hoag's nine days earlier, except that launch was executed 2,000 feet lower (45,000 

feet) with pushover 9,000 feet higher (67,000 feet) to a seven-degree angle of attack 

held to Mach 1.15. Speed brakes were deployed at that altitude and speed, angle of 

attack then increasing to 15 degrees. According to the flight plan, maximum altitude 

was to have been reached at this point. What was achieved was Mach 1.314 and an 

altitude of 90,303 feet. The rest of the flight was fairly routine, except that touchdown 

was changed from Runway 18 to Runway 23 to avoid high crosswinds. 

HL- 10: Lift and Drag 

For success, any aerospace vehicle must have adequate controllability. The modified HL-10 had very good control characteristics. Equally important to the HL-10's 

success in the lifting-body program was its ability to generate and control lift, plus 

its relatively high lift-to-drag ratio in its subsonic configuration. As measured in 

flight with the landing gear up, the HL-10's maximum lift-to-drag ratio was 3.6, 

so its best subsonic glidepath angle was approximately -16 degrees (below the 

horizontal reference). 

The HL-10 and the M2-F2 can be compared in terms of their lift-to-drag characteristics, for although the two lifting bodies had considerably different configurations, 

their missions were similar. Maximum lift-to-drag ratio for the HL-10 was 14 percent 

higher than for the M2-F2. Although both vehicles had similar lift-curve slopes, the 

M2-F2 had a much lower angle of attack at a specific lift coefficient than the HL-10. 

Both vehicles initiated a 300-knot approach at a lift coefficient of approximately 0.15, 

resulting in a flight path angle of about -25 degrees for the M2-F2 and about -16 

degrees for the HL-10 and a landing approach at pitch attitude of about -25 degrees 

(nose down) for the M2-F2 and about -8 degrees for the HL-10. (The approach flight 

path angle of commercial airliners in 1990, by comparison, was about -3 degrees.) 

Never a problem for the lifting-body pilots, the steep approaches for landing 

were always breath-taking to watch, especially the particularly steep descents of 

the M2-F2. 

At about Mach 0.6, the lift-to-drag ratio of the HL-10 in transonic configuration 

was approximately 26 percent lower than it was in subsonic configuration. Since lowering the landing gear decreased the lift-to-drag ratio by about 25 percent, the common landing technique with the HL-10 involved flaring in the clean subsonic 

configuration, then lowering the landing gear in the final moments of flight. 

"Dive Bomber" Landing Approaches 

After its modification, the HL-10 was often rated by the pilots who flew it as the 

best flying lifting body in terms of turns and the "dive bomber" landing. approaches 

typical of the lifting bodies. On a rating scale of 1 to 10, with 1 being the highest rat- 
WINGLESS FLIGHT 

ing, the average of ratings for the HL-10 was a 2. Each pilot was asked to evaluate 

various piloting tasks or maneuvers during each of his flights. Following a flight, the 

pilot then completed a questionnaire involving numerical evaluations as well as comments. Of the 419 numerical ratings given on flights, 43 percent were 2, with 98 percent of the pilot ratings being 4 or better. The best possible rating, a 1, figured on 3 

percent of the ratings, while the worst rating received, a 6, showed up in only 0.7 percent of them. 

Following the modification, the HL-10 presented no serious problems in piloting. 

Pilots found it relatively easy to fly, the HL-10 landings being no more difficult than 

making a similar power-off landing approach in an F-104. To some, the steep and 

unpowered landing approaches seemed to be mere sport, a daring maneuver of little 

or no advantage. Often, until they have been apprised of the benefits, spacecraft 

designers and engineers have failed to appreciate the advantages of these steep, 

unpowered approaches. Air Force pilot Jerry Gentry, in fact, advocated this type of 

approach even for the F-104 in normal operations. Pilots found the high-energy, 

steep, unpowered approach to be safer and more accurate than the recommended 

low-energy approach for the F-104 because it allowed gentler, more gradual changes 

in altitude. 

What Gentry and other pilots found to be true in the HL-10 and F-104 had been 

known to be true for many years in terms of accuracy in the old dive bombers, where 

it was generally accepted that the steeper the dive angle, the greater the accuracy. The 

approach task in the HL-10 involved positioning the vehicle on a flight path or dive 

angle to intercept a preflare aim point on the ground, similar to the targeting task of 

the dive bomber. The difficulty of the HL-10's task was minimized by using a relatively steep approach of -10 to -25 degrees. 

There was never a problem in the HL-10 of being short on energy, because the 

approaches generally were begun well before the peak of the lift-to-drag curve-that 

is, at high speeds and relatively low angles of attack. Energy was modulated while 

arriving on the desired flight path by slowing, accelerating, or remaining at the same 

speed and using the speed brakes to make needed changes in the flight path. Speed 

brakes are critically important on any aircraft landing with power off, for speed brakes 

can be used much like a throttle to vary the parameters of the landing pattern. What 

is more, speed brakes add onIy minimal weight to the vehicle and require no fuel. The 

small emergency landing rockets installed on the HL-10 were used only for experimental purposes and during the first flight of the vehicle. On all later flights, the speed 

brakes were consistently used, instead. 

Later in the lifting-body program, many spot landings were attempted in the 

HL-10 because it was generally believed that unpowered landings on a conventional 

runway would one day be a requirement, as it is currently with the Space Shuttle. On 

those spot landing attempts, the average miss distance was less than 250 feet. This 

degree of accuracy in landing is a benefit of the high-energy, steep, unpowered 

approach typical of the HL-10 lifting body. 
BACK TO THE DRAWING BOARD 

Higher speed in the landing approach also provided better controllability of the 

vehicle. For example, a contemporary aircraft landing approach with high power and 

low speed was much more demanding on a pilot. During the low-speed approach to n 

canier deck, the aircraft was operating past the peak of the lift-to-drag-ratio curvethat is, at a relatively high angle of attack-where the vehicle's stability, 

controllabilit4; and handling qualities were degraded and where engine failure coultl 

he catastrophic. 

Although the pilots thought highly of thv HL-10 for its excellent control in turns 

and during the steep landing approaches, most of the pilots did not like the visibility 

they hacl from inside the vehicle. Even though the pilot was located far forward in the 

HL-10, the canopy had no conventional canopy bulge. What is more, the rails at the 

lowest extent of the plexiglass canopy were relatively high, providing a sideward fieldof-view depression angle of approximately 16 degrees to the right and somewhat less 

on the left, due to the canopy defrost duct. Pilots in the HI,-10 were supplied routinely 

with a squirt bottle of water to use in case the flow from the defrost duct wasn't 

enough to handle the fog of condensation obstructing their view during critical 

moments of flight. 

The plexiglass nose window provider1 excellent forward vision for navigation and 

maneuvering for touchdown. Unfortunately, the nose window was lens-shaped and, 

distorting distance like the wide-angle sideview mirrors on today's cars and trucks, 

gave the pilots the impression that they were higher off the ground than they really 

were. After one of his flights in the HL-10, John Manke reportetl that he had touched 

down before he wanted to, due to the distorted view out the nose window. Sorne pilots 

on their first flights in the HL-10 waited until they were critically close to the ground 

before they extencled the landing gear. Only the accumulation of actual flight experience in the HL-10 alleviated this problem for the pilots. 

Mysterious Upsets and Turbulence Response 

As one might imagine, all of the lifting bodies possessed some unique aerodynamic characteristics. One of the most unusual is what is called "dihedral effect." On 

conventional winged aircraft, the "dihedral" is the acute angle between the intersecting planes of the wings, usually measured from a horizontal plane. The "dihedral 

effect" is essentially the aerodynamic effect produced by wing dihedral that is related to the tendency of a winged aircraft to fly "wings level." It is also the effect which 

produces a rolling tendency proportional to the angle of sideslip (side gusts). Even 

though lifting bodies don't have wings, they possess very large amounts of dihedral 

effect, which means that a very large amount of rolling tendency is generated for small 

amounts of sideslip, the primary reason why lifting bodies were flown with "feet on the 

floor"-that is, with pilots deliberately keeping their feet off the rudder pedals. 

Rudder would induce sideslip, and the lifting bodies would respond primarily 

with rolls. 
WINGLESS FLIGHT 

Each of the lifting bodies experienced flight through turbulence which caused 

pilot anxiety out of proportion to the involved "upsets," or uncommanded disturbances 

of unknown origin. These upsets were so different from upsets as experienced in conventional winged aircraft that the pilots frequently became disturbed when encountering any turbulence in a lifting body. Aerodynamically, the lifting bodies were 

significantly different from winged aircraft and one might expect them to respond 

quite differently to turbulence, hut what we were experiencing was something 

entirely new and unknown. 

The pilots could not agree on what particular sensations triggered their anxiety, 

hut they said that they often felt on the verge of instability. Early in the lifting-body 

program, the pilots reported feeling that the vehicles Nere going to "uncork" on them. 

Once the pilots became convinced that there was no real instability and that the vehicle disturbances were caused by turbulence, they rode through the disturbances with 

little concern. 

The gust response of an unwinged vehicle is considerably different from that of 

winged aircraft. In conventional aircraft, turbulence primarily affects the vertical, felt 

in the seat of the pants. In a lifting body, turl~ulence primarily affects the horizontal, 

producing small amounts of sideslip disturbance, resulting in a high-frequency rolling 

sensation. This was particularly true at lower elevations where turbulence could be 

most severe. Following the crash of the M2-F2 in May 1967, the pilots became even 

more sensitized to upsets close to the ground, the crash of the M2-F2 during landing 

linked to the rolling motions from such an upset that temporarily disoriented the pilot. 

In turbulence at low elevations, the pilots felt they might be experiencing some 

impending dynamic instability in the vehicle, even though the engineers assured them 

that they were not. 

Mysterious upsets occurred at altitude as well, usually during the powered portion of a profile. The pilots found these upsets "spooky." The program engineers 

hypothesized that these upsets were caused by wind shears. Consequently, on one 

flight a movie camera was positioned on the ground directly beneath the planned 

ground track, since the LR-11 rocket motor always left a distinctive white trail of 

exhaust condensation, or contrail, in any and all atmosphere conditions. Just before 

launch, the upward-facing camera was turned on to record the launch, powered portion of the flight, and the pilot's radio transmissions. As the pilot flew the powered portion, he called out where the vehicle "felt squirrely" in the lateral direction. Later, 

playing the film showed that the vehicle had indeed encountered wind shears, as 

shown by the disturbed contrail, when the pilot had reported that the vehicle 

"felt squirrely." 

Over time and with experience, the pilots came to accept that the turbulence 

response of the HL-10 was considerably different from that of conventional winged 

aircraft and that the upsets did not mean that they were on the threshold of dynamic 

instability. This was new territory in aerospace exploration, one in which the liftingbody pilots and engineers found themselves having to separate the real from 

the imagined. 
BACK TO THE DRAWING BOARD 

Experiments with Powered Landings 

After its 35th flight, when all of the major program objectives had been met, the 

HL-10 was reconfigured for a powered approach and landing study conducted over 

two flights on 11 June and 17 July 1970. For the study, the LR-11 rocket engine was 

removed and three small hydrogen-peroxide rockets were installed. The objective was 

to study shallower glide angles during final approach. Ignited during approach, the 

rockets reduced the angle of approach from approximately 18 to 6 degrees. The 37th 

and final flight of the HL-10, piloted (like the 11 June flight) by Pete Hoag, was also 

the last of the powered approach flights in this study. 

The overall results of the study were negative, powered landings having no advantage over unpowered ones for the lifting body. Indeed, shallower powered approaches 

in the lifting body provided none of the benefits normally obtained in winged aircraft 

from powered landings. Another conclusion from the study was that the normal 

approach technique for any space re-entry vehicl-ven if equipped with airbreathing engines with go-around capability-should be to operate the vehicle as if it were 

unpowered, relying on the engines only if the approach were greatly in error. This conclusion proved to be of great influence later in the design of the Space Shuttle, especially the decision not to install landing engines on the Shuttle. Yet much credit for 

that decision should go to Milt Thompson, especially to his perseverance in campaigning vigorousIy for unpowered Shuttle landings. 

When we total up the flight time for the HL-10 in its 37 flights between 1966 and 

1970, we come up with 3 hours, 25 minutes, and 3 seconds. Was that enough time for 

us to prove the value of the lifting-body concept? We think so, especially every time 

we watch a Space Shuttle landing. 
CHAPTER 7 

WINGLESS FLIGHT MATURES 

Costing between two and three million dollars and involving 60 NASA employees, 

the rocket-powered lifting-body programs for the M2-F2, M2-F3, and HL-10 were 

major undertakings for the Flight Research Center. However, this effort seems small 

in comparison with the several hundred million dollars being invested by the United 

States at that time, mostly through the Air Force, in lifting re-entry technology. 

In the early 1960s, the Air Force funded several studies within the aerospace 

industry of winged-vehicle configurations, variable-geometry slender bodies, and 

high-volume lifting bodies. However, having less confidence in wingless designs, the 

Air Force committed several hundred million dollars to winged vehicles, most of this 

money channeled between 1960 and 1964 into two hardware programs, the manned 

Boeing Dyna-Soar X-20 and the unmanned McDonnell ASSET (Aerothermodynamic/elastic Structural Systems Environmental Tests) programs. 

In 1963, a major shift occurred within the Air Force regarding aerospace concepts, interest waning in the winged-vehicle concept as interest grew steadily in the 

concept of high-volume lifting bodies. By that time, we had had nearly a year of solid 

flight experience at the Flight Research Center with the M2-F1 lifting body, and I was 

spending most of my time developing and selling the supersonic lifting-body program 

to NASA management. Since November 1960, the Air Force had had the Martin 

Aircraft Company under contract for developing a full-scale flight-testing program of 

a lifting re-entry vehicle. By December 1963, Martin had selected the SV-5 configuration, following the results of wind-tunnel tests on various lifting re-entry designs. 

A high-volume lifting body, the SV-5 was the brain child of Hans Multhopp, an 

aerodynamicist at the Martin Aircraft Company. The SV-5 quickly became the centerpiece of a new Air Force program known as START (Spacecraft Technology and 

Advanced Reentry Tests). Established in January 1964, START consisted of dual 

programs-the unpiloted PRIME (Precision Recovery Including Maneuvering Entry) 

and the piloted PILOT (Piloted Lowspeed Tests). 

In early 1964, I visited the Martin Aircraft Company to gather information on the 

SV-5 and possibly gain some support from Martin and the Air Force in convincing 

NASA management to fund a supersonic lifting-body flight-test program. I met Hans 

Multhopp, introduced to me as Martin's chief scientist and the designer of the SV-5. 

A soft-spoken man with a heavy German accent, Multhopp seemed to be highly 

respected and admired by others in Martin engineering. After a conversation with him 

about the SV-5, I could understand why he was so highly respected, for his knowledge 

of aerodynamics and aircraft design was impressive. 

A former aeronautical engineer, Multhopp had worked during World War I1 for the 

Focke-Wulf Flugzeugbau in Bremen, Germany, first as head of the aerodynamics 
FINGLESS FLIGHT MATURES 

department and then as chief of the advanced design bureau. One of his projects at 

Focke-Wulf was designing, in conjunction with Kurt Tank, the Ta-183. Information on 

the Ta-183 design obtained by the Russians at the end of World Rhr IT greatly influenced the design of the Russian MIG-15 jet fighter. The Pulqui-11, a derivation of the 

Ta-183 design flown in Argentina after World Ear TI, had been huilt by former FockemTulf employees who had fled to Argentina. 

Whisked out of Germany at the end of World War IT, Multhopp went to work for 

the British at Farnborough. There, he designed the swept-wing British Lightning fighter, using calculation techniques he had developed. After four years, however, the 

British found his arrogance intolerable and he was sacked. He then became the chief 

scientist for the company that eventually became the giant American aviation and 

space contractor, Martin Marietta. 

Multhopp was able to convince Martin management as well as the Air Force thai 

the SIT-5 shape was superior to NASA's M2-F3 and HL-I0 shapes on the basis of six 

features. First, the SV-5 was a maneuverable lifting body with no essential surface 

components that would be destroyed on re-entry from orbit. Second, the vehicle had a 

hypersonic lift-to-drag ratio of 1.2 or better, permitting a lateral range of 1,000 miles. 

This feature would enable a recall to any preselected site at least once a day as well 

as emergency recall to a suitable location from every orlit. 

Third, the low-speed aerodynamics of the SV-5 were suitable for making a tangential landing without resort to automatic controls. Fourth, volumetric efficiency was 

as high as possible, the shape giving as much volume forward as possible for centerof-gravity control. The resulting configuration gave more room up front for the pilot 

and equipment. The center-of-gravity could then be positioned sufficiently forward to 

provide adequate vehicle control without resorting to an unstable vehicle with a negative static margin. Fifth, positive camber was includetl in the body, allowing trimmed 

lift conditions at lower angles of attack as well as a high subsonic lift-to-drag ratio of 

about 4.0. Sixth, in regards to pilot visibility, the ShT-5 cockpit canopy design was 

superior to that of the M2-F3 and the HI,-10. 

My first meeting with Hans Multhopp at Martin in early 1964 also turnetl out to 

be my last. After that visit, he seemed simply to clisapprar from public view. Later, 

when the X-24A was being llowm at Edwards Air Force Base as the final stage of the 

PTI,OT portion of the Sir-5 program, I Has surprised to learn that my .4ir Force c.01- 

leagues at Etlwards had never even heard of Hans Multhopp. At that time, there was 

still considera1)lr resenlment in this country about using Gennan engineers in 

American aerospace projects. Consequently, it became the usual practice to keep 

German engineers at low profile. However, this was not always true. A good example 

of an exception to this practice was Wirnher von Braun, who rose to high rank in 

NASA in fulI public view and made a significant contribution to our space pmgram. 

The PRIME unpiloted SV-5 program began in November 1964. The Space 

Systems Division of the Air Force Systems Commantl gave the Martin Aircraft 

Company a contract to design, fal~ricate, and test a maneuveral~le re-entry vehicle in 

order to demonstrate whether a lifting body could, in fact, be guided from a straight 
WINGLESS FLIGHT 

course and then returned to that course. Martin had already been studying lifting reentry vehicles for some time-the company had, after all, been in the Djna-Soar competition-and had invested more than two million hours in lifting-body studies. 

Martin Aircraft Company refined the SV-5 design into the SV-5D, an 880-pound 

aluminum vehicle with an ablative heat shield. The Air Force ordered four of the 

SV-5D aircraft, which it designated the X-23A. Between December 1966 and midApril 1967, the Air Force launched three of these vehicles atop Atlas boosters that 

blasted them at 14,900 miles per hour over the Pacific Ocean Western Test Range 

toward Kwajalein. The three vehicles performed so well that the Air Force canceled 

the fourth launch to save money. The PRIME project demonstrated that a maneuvering lifting body could indeed successfulIy alter its flight path upon re-entry. These 

tests also conclusively confirmed that lifting bodies were maneuverable hypersonic 

re-entry configurations. 

From SV-5P to X-24A 

As an expansion of Martin's PRIME work, the Air Force and Martin derived 

PILOT-a proposed "low-speed" (Mach 2) research vehicle that the Air Force could 

test for its supersonic, transonic, and subsonic-to-landing behavior. Martin designated the vehicle the SV-5P. 

Colonel Chuck Yeager, then commandant of the Edwards Test Pilot School, had 

been a fan of the lifting bodies since his flight in the M2-F1. At the time, he had told 

Paul Bikle that the first lifting body handled well and that he would like to have a few 

jet-powered versions to use for training future lifting-body pilots. After learning of 

what Yeager had said, Martin proposed the SV-SJ, a low-speed lifting-body trainer 

powered by a small turbojet, for use by the Air Force's test pilot school at Edwards. 

Nothing came of this proposal, although Martin built the shells for two such vehicles and even tried to entice MiIt Thompson to fly the SV-5J when it was completed. 

NASA had no interest in the vehicle, and Thompson was committed to supporting the 

objectives of the NASA lifting-body program. Calculations showed that the vehicle, 

because of its high drag and low thrust, would not only have marginal climb perhrmance but would actually be dangerous to fly. Nevertheless, Martin offered Milt 

Thompson $20,000 if, on his own time, he would simply get the vehicle airborne. 

Thompson offered to accept Martin's $20,000 if he could get it airborne by simply 

bouncing the SV-5J a few inches into the air by running it across a two-by-four on the 

runway. Martin didn't accept Thompson's "flight plan." 

Meanwhile, the SV-5P development was progressing smoothly. In May 

1966, the Air Force gave Martin a contract for building one SV-5P. Martin began 

development under the direction of engineers Buz Hello and Lyman Josephs. About a 

year later on 11 July 1967, Martin rolled out the SV-5P at its plant in Baltimore, 

Maryland. The Air Force designated the vehicle the X-24A. 
WINGLESS FLIGHT MATURES 

X-24A Crew and Wind-Tunnel Testing 

Selecting staff and crew for thp X-24A lifting-body project coincided with the 

winding down of the X-15 program. The X-24A gained experienced fight planners 

and flight-test engineers from both the X-15 and M2-F2 programs, including NASA's 

Jack Kolf and the Air Force's Johnny Armstrong, Bob Hoeq, Paul Kirsten, and David 

Richardson. Chief NASA flight planner for the X-15, Jack Kolf hecame project manager of the program under the direction of John McTigue. 

Norm DeMar became operations engineer for the X-24A. His crew included crew 

chief Jim Hankins; mechanics Chet Rergner, Me1 Cox, and John "Catfish" Gordon; 

inspector LeRoq Barto; avionics technician Ray Kellogg; instrumentation technicians 

Bill Bastow and Jay Maag; and, from Martin Aircraft Company, electrical engineer 

Bob Moshier and hydraulics and mechanical-systems engineer Jack Riddle. Wen 

Painter and Sperrp Rand's Ron Kotfilm worked on the vehicle's stability and 

augmentation slstem. 

On 24 August 1967, the X-24A was delivered to Edwards .4ir Force Rase. An 

experienced lifting-body pilot who had probed the instahility boundaries of the 

M2-F2, Jerq Gentry was assigned as project pilot. Although Paul Bikle and Jerry 

Gentrj were anxious to keep the X-24A on schedule, the vehicle did not fly for the 

better part of another two years. The vehicle was not released for program activity 

until 5 October 1967, when DeMar and his crew began preparing the X-24A for windtunnel tests at NASA Ames. 

Although the X-24A left Edwards on 19 February 1968, wind-tunnel testing at 

NASA Ames did not begin until 27 February, the extra days at the wind tunnel used 

to prepare the vehicle with a removable coating to simulate the ablative roughness that 

would be encountered after the heat of re-entrj. Roughness measurements from recovered PRIME vehicles were used in preparing this coating. Afterwards, the X-24A was 

wind-tunnel tested with two skin contfitions, with a clean metal skin and with the 

rough surface stuck to the skin with an adhesive. 

The rough surface seemed to cause a significant reduction in the lift-to-drag ratio 

for landing, a reduction that would, in turn, reduce the time available for correcting 

control inputs during actual landings on re-entry from space. These conclusions, 

along with other aspects of the wind-tunnel test data on the X-24A, were published a 

year later in a NASA report written by Jon S. Pyle and Lawrence C. Montoya, two engineers at the NASA Flight Research Center, entitled Effects of Roughness of 

Simrilated Ablated Material on Low-Speed Performance Characteristics of a 

Lifting-Body Vehicle.' However, flight tests at Edwards were planned for the vehicle only with a clean metal skin. 

1. Jon S. Pyle and 1aw.renc.e C. Montoya, ESfects of Roughness of Simulated '4blrctrd Material 

on Low-Speed Performance Characteristics of u Lifting-Body Vehicle (Wdshington, DC: NASA TM 

S-1810, 1969). 
Problems and More Problems 

After the X-24A returned to Edwards on 15 March 1968, DeMar and his crew 

began preparing it for flight. However, probIems began to appear that would slow them 

down. First, since the cockpit instrument panels had not been designed at Martin to 

he removable for check-out and maintenance, DeMar and his crew had to spend two 

months installing connectors on all electrical and pressure fittings in the panel. Next, 

when the hydraulic control system was operated, the actuators started leaking, so they 

had to change all of the servo valves. During hangar tests of the control system, when 

runaway control-surface oscillations were put in, structural feedback resulted, eventuallj traced to its origin through the soft actuator structural mounts. This problem 

occurred because Martin engineers-in their zeal to avoid having to add weight to the 

vehicle nose for balance-had designed the X-24A to be very light in its aft end, 

where the actuators were supported. 

Competition had sprung up earlier between the Martin designers of the X-24.4 

and the Northrop designers of the M2-F2, M2-F3, and HI,-10. The Martin designers 

knew that the Northrop designers had had to add either nose hallast or redundant 

structure in the noses of the Northrop-built lifting bodies to maintain center-of-gavitj, and they vowed that they would not do the same in their design of the X-24A lifting body. They claimed that one of the assets of the X-24A shape was that it offered 

more volume forward for the pilot, allowing heavy equipment to be installed in the 

nose. However, the Martin designers had been so frugal in weight control that the 

structure and actuators in the aft end of the X-24A were of minimum size and thicknesses. In fact, the aft end of the X-24A was so light that 140 pounds of ballast had 

to be added to it to balance the vehicle for flight. 

DeMar and his crew had to beef up the structure to eliminate the control-system 

djnamic feedback encountered in ground tests, and this process delayed the X-24A 

schedule substantiallj. According to DeMar, he was called into Bikles office almost 

weekly during this time to explain to Bikle and Gentry what was causing the latest 

delay. Even more delays came about as a result of the new wave of caution arid conservatism that had engulfed the Flight Research Center following the crash of the 

M2-F2 the year before. It had always been a tradition at the Center to have a Flight 

Review Board made up of engineers and technicians not involved in a project to recommend when a project's aircraft was ready for flight-testing. The Board formed to 

examine every detail of the X-24A, however, proved to be very picky. Extra tests on 

sjstems were needed to assure the Board that the tehicle was flight-worthy, further 

delaying the schedule. 

X-24A Glide-Flights, 1969-1 9 70 

After the X-24A finally was declared ready for flight, Jeny Gentry was set to pilot 

the vehicle in its first glide-flight on 17 April 1969, nearly two years after its roll-out 
WINGLESS FLIGHT MATURES 

Drawing illustrating the concept of shuttlecock stability of the X-24A transonic con&ration with extended 

control surfaces (original drawing by Dale Reed, digital version by Dryden Graphics Ofice). 

by Martin Aircraft Company. Gentry's first glide-flight of the X-24A turned out to be 

almost as hair-raising and exciting as Milt Thompson's and Bruce Peterson's first 

glide-flights respectively of the M2-F2 and HL-10. 

Milt Thompson had experienced a lateral-directional pilot-induced oscillation 

(PIO) in the M2-F2 at low angles of attack when he moved the manual rudder-aileron 

interconnect wheel the wrong way. Bruce Peterson had experienced pitch and roll 

oscillations in the HL-10, the result of flow separation on the outer vertical fins at high 

angles of attack. Because of this flow separation, the pitch and roll control in the 

HL-10 was ineffective. Jeny Gentry faced somewhat different problems on the first 

flight of the X-24A. 

The X-24A was more automatic and complex than either the M2-F2 or HL-10. 

First of all, roll control on the X-24A could come from either the lower split flap or 

the upper split flap. Roll control could be shifted from the lower to the upper flap in 

either of two ways: by scheduling an automatic biasing (shuttlecock configuration) of 

the upper flap for transonic flight, or by the pilot pulling back on the stick, resulting 

in retraction of the lower flap and extension of the upper flap. 

Eliminating the dependency on the pilot to set the rudder-aileron interconnect 

manually, the X-24A included an automatic system that changed the interconnect 

ratio as the angle of attack varied. For its first glide-flight, the X-24A was launched 

from the B-52 with its upper flap set at 21 degrees upward from the body's upper skin 
WINGLESS FLIGHT 

to give the lowest drag during the subsonic glide to landing. This setting meant that 

all roll control during the flight would conle from the lower split flap. 

The first flight of any air-launched lifting body is unique. With the vehicle's very 

rapid rate of descent, the pilot has only about two minutes to evaluate actual flight 

characteristics and determine that no serious deficiencies exist that could compromise 

a safe landing. During that same two minutes, the pilot also has to perform enough 

maneuvers in the aircraft to allow lift-to-drag performance and longitudinal trim to be 

determined, information that later will be compared with wind-tunnel predictions so 

that the second flight can be approached with an even higher degree of confidence. 

The launch of the X-24A from the B-52 into its first glide-flight was smooth. 

However, one minute into the flight, the automatic interconnect system failed, causing the interconnect to stick in one position. During the landing approach at two 

degrees angle of attack and 300 knots, Gentry experiences an uncomfortable lateraldirectional "nibbling." He said that the sensation was similar to one he had experienced in the M2-F2 with a characteristic that developed into a severe 

lateral-directional PI0 tendency with large bank-angle excursions. At approximately 

1,800 feet above ground, to stop the roll oscillation in the X-24A, Gentry increased 

the angle of attack to between four and five degrees, decreased airspeed to 270 knots, 

and used the landing rockets, a successful flare landing without rockets requiring an 

airspeed of 300 knots. 

Just before touchdown, the lower flaps were rate-limited, the maximum surface 

rate from the actuators being insufficient to follow the large commarids from both the 

roll rate-damper system and the pilot, which were in phase. During the flare, Gentry 

considered the longitudinal control to be good. However, due to actuator rate-limiting, 

the rate damper could not be fully effective during periods of surface rate-limiting. 

The result was that the vehicle's roll-rate excursions reached 20 degrees per second. 

Something obviously needed to be changed on the X-24A. Johnny Armstrong, Bob 

Hoey, the NASA engineers, and the Air Force engineers Captain Charles Archie, Paul 

Kirsten, Major John Rampy, Captain John Retelle, and Dave Richardson analjzed the 

flight data and concluded that the problems with roll oscillation and elevon actuator 

rate-limiting were caused by the failure of the automatic interconnect system. The 

poor handling qualities of the X-24A during the final approach were primarily the 

result of the higher-than-planned rudder-to-aileron interconnect that occurred when 

the automatic system failed. 

Once the interconnect system problem was corrected and with no other changes 

to the vehicle, Jerry Gentry piloted the X-24A on its second glide-flight. However, the 

same problem occurred, the lower flaps again becoming rate-limited on the final 

approach, even though the rudder-aileron system was working properly. 

Before the third glide-flight of the X-24A, the program's engineers conducted a 

considerable investigation by simulator to define the changes needed to improve the 

vehicle's flying qualities on final approach. Subsequent changes made to the control 

system included modifying the lower-flap control horns to approximately twice the 

maximum surface rate, modifj ing the rudder-aileron interconnect schedule with angle 
WINGLESS FLIGHT MATURES 

of attack, and increasing the control-stick force gradient and stick-damping in roll. 

More effective rate-damping gain settings in roll and yaw were defined. Although the 

X-24A's response to motion in turbulence could not be duplicated adequately in the 

fixed-based simulator, the X-24A engineering team concluded that the effect of turbulence significantly contributed to the control problem. 

Bob Hoey recalls that the most significant cause of the oscillations on the X-24A's 

first and second glide-flights was "an error in the prediction of the yawing-momentdue-to-aileron for the lower flap. The error was apparently caused by flow interference 

around the sting in the wind tunnel when the flaps were closed to nearly zero deflection. The flight data showed that the derivative was of opposite sign than predicted. 

Although we suspected the problem, we didn't measure this correct value until after 

fl[igh]t 2, when the pilot did some aileron doublets." 

In retrospect, Hoey concluded, "we were lucky on fl[igh]t 1." Not only had the 

interconnect stuck too high at 35 percent but even more proverse was the aileron 

derivative. These effects were additive, Hoey said. "Later analysis showed that Gentry 

was well into the predicted PI0 region on that approach, and his decision to slow 

down and use the rockets was a good one!"2

During Gentry's third glide-flight, he noticed considerable improvement due to 

the changes in the control system. However, he continued to be concerned about the 

vehicle's response in turbulence. Gentry did not begin to lose this concern until, during additional glide-flights, he became convinced that the motions he was sensing 

stemmed from "riding qualities" aggravated by turbulence rather than from any serious deficiency in handling qualities. The increased surface rates of the lower flaps, 

furthermore, prevented the reoccurrence of the earlier with rating-limiting. 

Nine more glides were made in the X-24A before the vehicle's first powered flight. 

X-24A Powered Flights, 1970-197 1 

By combining much larger fuel tanks with a lightrr-weight structure in the 

X-24A, Hans Multhopp and the other Martin designers theoretically achieved the 

potential for the X-24A to attain much higher speed and altitude than either the 

M2-F3 or the HL-10. All of the powered lifting bodies had the same type of rocket 

engine, the LR-11, with a maximum theoretical vacuum thrust of 8,480 pounds. In 

structure, the X-24A was nearly 200 pounds lighter than the HL-10 and 700 pounds 

lighter than the M2-F3. The X-24A also carried about 1,600 pounds more in fuel than 

did the HL-10 or M2-F3. Fuel-to-vehicle weight ratios for the three powered lifting 

bodies were 0.45 for the X-24A, 0.35 for the HL-10, and 0.33 for the M2-F3. The X24A seemed to have the potential for breaking lifting-body speed and altitude records. 

2. Typed comments of Robert G. Hoe) to Dale Reed in conjunction with h~s technical review of the 

original manuscript for "Wingle\s Flight," Sept. 1993. 
WINGLESS FLIGHT 

View of the X-24A showing eight retractt@control surjaces on the aft end of the vehicle in its subsonic, lowdrag configuration. (NASA photo E68 18769) 

Bob Hoey, however, felt that the maximum speed of the X-24A would not be 

greater than what had been achieved already with the other powered lifting bodies. 

"The reference area of the X-24A was 162 sq[uare] fleelt," he explained, compared to 

139 square feet for each of the other two powered lifting bodies, "so it was larger with 

more wetted area. The X-24A also required a larger wedge angle (more drag) for stability at transonic and supersonic speeds. This is a desirable feature while decelerating during an entry, but undesirable when trying to accelerate with a rocket." 

Actual X-24A entry, Hoey continued, would use 50 degrees of upper flap and 10 

degrees of outward flare on the rudder down to Mach 2, identical to the configuration 

of the PRIME vehicle that deployed a drogue chute at Mach 2. As speed decreased 

below Mach 2 in the X-24A, Hoey theorized, the upper flap and rudder bias would 

begin to program inwardly. "We used 40 degrees of upper flap and 0 rudder as our 

transonic/supersonic configuration," Hoey said, "a compromise in reduced shuttlecock stability in order to get lower drag and higher speed under power. Our simulation showed that we would only reach about Mach 1.7 for an optimum, full duration 

burn."3

Historic accounts including Richard P. Hallion's On the Frontier and The 

Hypersonic Revolution have suggested the X-24A had few, if any, negative points. 

3. Hoey, comments to Reed. 
WTNGLESS FLIGHT MATURES 

However, the X-24A's high reputation rests on the fact that the vehicle was not 

allowed to be flown in what might have been very uncontrollable flight regimes. Hans 

Multhopp and his fellow designers at Martin had designed the X-24A exclusively as 

a re-entry vehicle. It had not been designed to perform well in other situations, including being launched from a B-52, climbing to altitude, and diving to achieve a high 

Mach speed during rocket burn.4 

The X-24A had very serious angle-of-attack control limitations at transonic 

speeds. If the pilot increased angle of attack above about 12 degrees, he risked losing 

roll control clue to roll-reversal boundary. If the pilot continued increasing angle 

of attark in the X-24.4 to near 20 degrees, wind-tunnel tests and simtllations predictet1 the vehicle would depart in yaw from its intended direction due to lack of directional stability. According to these predictions, at these high angles of attack, neutral 

longitudinal stability also would occur. The X-24A also had a low angle-of-attack 

limitation, experiencing roll-reversal and pitch-instability problems at angles of 

attack lower than four degrees. 

Nevertheless, it can be said that the X-24A had no constraints in handling or stability for an optimum, maximum speed boost profile. "Although the stability boundaries were well defined by flight test," Bob Hoey said about the X-24A, this use of 

flight-testing being fairly traditional by the end of the X-15 and M2 programs, "they 

DID NOT constrain the optimized trajectory. . . . We had adequate margins on both 

sides of the boundaries to safely fly an optimized trajectory."j 

Flight research teams for the various lifting bodies always wanted their vehicle to 

surpass the speed and altitude records of earlier lifting bodies. The less restrictive 

control boundaries of the HI,-10 allowed its pilots to be able to fly more optimum-powered trajectories on speed and altitude missions than were allowed for the X-24A. The 

X-2414 team chose to see the HL-10's speed record as mainly a matter of luck, saying 

that on its speed mission the HL-10 clinibed and accelerated at lower altitudes with 

a tailwind, then climbed slightly into a jet-stream headwind that increased airspeed 

and added about 0.2 of its speed record of Mach 1.86. Perhaps partly in jest, the HL10 team replied that they had planned it that way and that perhaps the X-24A team 

ought to do the same. 

Nevertheless, the wave of caution that engulfed the Flight Research Center following the R12-F2 crash affected flight-planning for several years for the lifting bodies still being flight-tested-the HL-10, the X-24A, and eventually the M3-F3. As a 

4. Rlchard P. Hallion and John Id. ViteIl~, "The Piloted Lifting Body Demonstrators: Supersonic 

Predecessors to Hyperron~c and Lifting Reentry," Chapter 11: 'The Air Force and the Lifting Rod) 

Concept," pp. 893-945, esp. p. 922 of Hallion, ed., The FIypersonic Re~!olution: EI~J~ Case Studies 

in /he ffistorj- offepersonic Technohg ,2 ~019. Fiight-Patterson Air Force Base, OH: Aeronautical 

S) stems Dit. ision, 1987), Vol. 11; Halllon, On the Frontier, p. 164. 

5. Hoey, comments to Reed. 
WINGLESS FLIGHT 

result, much care was taken to avoid crossing any possible out-of-control boundaries. 

Carefully considered restraint characterized the planning of maximum speed and 

altitude missions for the X-24A. Flight safety was paramount. Program oljjectives 

would be met if the rocket-powered lifting bodies, including the X-24A, could be 

flown at supersonic speeds near or greater than Mach 1.5 in order to test re-entry 

glide performance. 

As ol~jectivity prevailed, the X-24A team decided not to tq to set speed and altitude records for the lifting bodies. Describing the X-24A team effort, Bob I-Ioey said, 

"We tried tn ice to get to the expected burnout point of 1.7 (actually 1.68 on the Flight 

Request). Both flights resulted in engine nlalfunctions. The X-24B program had 

already been approved, so we decided that the benefit of another tenth in Mach number was not worth the added risk to the vehicle and crew." As a result, "we stopped 

the X-24A program without ever flying a speed profile to burnout."G

Eighteen powered flights were made in the X-24A between mid-March 1970 and 

early June 1971. A typical X-24A powered flight lasted just under eight minutes, consisting of a two-and-a-half-minute rocket-powered flight followed b) a five-minute 

glide to landing. The vehicle's speed envelope in Mach number was expanclrtl in successive small steps separated at times by pauses for investigating problems affecting 

handling. Primary flight objectives were not met on the first five powered flights due 

to system failures following launch. 

Flight planning and crew preparation for the powered flights took considerably 

more time than had been required for the glide flights. Not only was the basic flight 

plan more complex for powered flight, but a large number of possible deviations had 

to be planned and practiced in simulation. Each X-24A pilot usually spent over 20 

hours in flight simulation in preparing for each flight. Furthermore, actual flight practice in the F-104 was also increased to include landing approaches to as many as five 

different runways. Each of the three X-24A pilots-NASA's John Manke and Air 

Force Majors Jerry Gentry and Cecil Powell-performed as many as 60 landing 

approaches during the two weeks prior to a flight. 

Generally, the primary objective of each powered flight was to perform data 

maneuvers near the planned maximum Mach speed, and this required precise control 

of the profile. Consequently, data maneuvers were generally limited to the angle-ofattack range required for profile control. To prevent the possibility of large upsetting 

maneuvers that could compromise the profile, all data maneuvers were done with the 

stability augmentation system engaged. The capability for individually operating the 

LR-11 rocket engine's four chambers made it possible to select a reduced thrust level 

upon reaching the desired test conditions to provide additional data time at quasisteady flight conditions. 

On 19 March 1970, Jerry Gentry piloted the X-24A in its first powered flight, 

reaching well into the transonic region by achieving a speed of Mach 0.87. After we 

6. Hoey, comments to Reed, underlining in the original. 

139 
WINGLESS FLIGHT MATURES 

analyzed the data from the first powered flight, there were two changes. First, the center-of-gravity in the X-24A was moved forward by removing 140 pounds of ballast 

from the tail. Second, to help reduce longitudinal control sensitivity, the upper flap 

was biased upward from 30 to 35 degrees above the aircraft's body surface-in effect, 

opening the shuttlecock. 

On the flights that followed, pilots John Manke and Cecil Powell steadily 

expanded the X-24A's performance envelope. During these flights, to increase directional stability, the shuttlecock was increased, biasing the upper flap upward to 

40 degrees above the body surface, and the rudders were moved outboard. To improve 

handling, we also increased yaw damper gain and the rudder-to-aileron 

interconnect ratio. 

Exactly 23 years after Chuck Yeager's first supersonic flight, on 14 October 1970, 

Manke piloted the X-24A on its first flight beyond Mach 1, reaching Mach 1.19 at 

67,900 feet. Less than two weeks Iater, Manke simulated a Space Shuttle approach 

and landing in the X-24A from an altitude of 71,400 feet. On 29 March 1971, Manke 

reached Mach 1.60 in the X-24A, its fastest research flight. However, the 28th and 

final research flight of the X-24A on 4 June 1971 was disappointing. Only two of the 

LR-11 engine's four chambers ignited, limiting the X-24A to subsonic speeds. 

1971: X-24A Ready for Space 

The only lifting-body configuration completely flight-tested from near-orbital 

speeds to subsonic landing was the PRIME (a predecessor of the X-24A, which had a 

slightly different configuration). The unpiloted PRIME vehicle demonstrated hypersonic maneuvering flight from Mach 24 to Mach 2.0, while the piloted X-24A demonstrated maneuvering flight from Mach 1.6 to landing. By 1971, the technology existed 

for initiating a rapid-turnaround, low-cost, low-risk program that could place a piloted lifting body into orbit, using a Titan I1 booster from the Gemini program. Had such 

a program come into being then, it would have resulted in the world's first lifting reentry to horizontal landing a decade before the Shuttle Orbiter. 

The last flight to the moon was to occur in December 1972, leaving two complete 

Saturn V-Apollo systems unused. One of these rocket-and-spacecraft systems would 

eventually be used in a joint AmericanISoviet space effort, the ApolloISoyuz orbital 

linkup. However, in 1971, there were still no plans for using either of the two Saturn 

V systems. A Northrop lifting-body engineer came up with the idea of using the vehicles for launching two lifting bodies into orbit. I thought it was a great idea. So did the 

NASA lifting-body project manager at the time, John McTigue. 

I prepared a briefing for Wernher von Braun, then in charge of the NASA Marshall 

Space Flight Center in Alabama, who was visiting Paul Bikle at the Flight Research 

Center. The briefing was about launching two lifting-bodylsaturn missions, carrying 

the HL-10 in the same space where the Lunar Lander had fit. The HL-10 would be 

modified for space flight with a heat-protective ablative coating to protect its aluminum structure. In the first mission, the HL-10 would be flown unpiloted back to 
WINGLESS FLIGHT 

earth from orbit. In the second mission, the HL-10 would be flown back by a pilot on 

board. Because of its maturity, the X-24A probably would have been a better choice 

than the HL-10. 

What made the concept attractive was the proven safety of the Apollo command 

module that would be used by three astronauts, one of whom would be the lifting-body 

pilot, for the launch and climb to orbit. During the first mission, the lifting-bodj pilot 

would transfer from the Apollo capsule to the cockpit of the lifting body, conduct prere-entry systems checks in the lifting body, and then return to the Apollo capsule. 

The astronauts would then send the lifting body back to Earth unpiloted for a runway 

landing. Later, the astronauts would themselves return safely to Earth in the capsule 

via parachute. 

The second mission would follow the successful completion of the first, only this 

time the lifting body would be flown by the astronaut/pilot bark from orbit for a runway landing. If the in-orbit cockpit checks of the lifting body proved to be unacceptable, the astronaut pilot could then simply return to earth with the other two astronauts 

in the Apollo capsule, as done in the first mission. 

In my presentation to von Braun, I used a large Saturn V-Apollo model that I had 

built from a commercially available plastic kit. I had substituted a model of the 

HL-10 for the Lunar Lander module and had even devised a model of an extraction 

arm for placing the lifting body in free orbit. There was enough room in the model for 

either the M2-F3 or the X-24A, had we chosen one of those vehicles for the mission. 

However, at the time, I had decided to use a scale model of the HL-10 to show the 

compatibility of the Saturn V-Apollo with existing lifting bodies. 

Wernher von Braun thought it was a fantastic idea. He told Bikle he woultl prepare the rockets at NASA Marshall if Bikle would prepare a lifting body at the Flight 

Research Center by adding an ablative heat shield to protect the vehicle's aluminum 

structure from the heat of re-entiy. Tmagine how I felt at that moment, if you will. I was 

sitting in a room with two of my heroes, making plans for the first pilotecl lifting reentry from space-many years before the Shuttle. 

Of course, I was disappointed when Paul Bikle said "no" to the project, even 

though I could respect why he had made that decision. He felt my idea was good, but 

he also believed it was a project beyond his experience and interest. Space was 

beyond his realm, and he was interested only in aircraft. Paul Bikle and Wemher von 

Braun had each demonstrated the ability to work outside the bureaucratic. process. 

Together, I had little doubt, they would have made the proposed project a success. 

And if they had, we might have been able to keep the momentum going in the liftingbody program-all the way to space. 

Although we still had another five years of flight evaluation to come on the M2-F3 

and X-24B lifting bodies, putting a piloted lifting body into orbit would have been a 

fitting conclusion to our first seven years of lifting-body flight research. However, voices of support for the Space Shuttle concept were already being heard, voices that all 

too soon became loud enough to drown out our vocalized advocacy for the lifting-body 

approach in space applications. Nonetheless, our efforts in the lifting-bod) program 
WINGLESS FLIGHT MAmRES 

had two very significant influences on the immediate future in terms of spacecraft. 

First, we established the concept of horizontal landing as feasible for spacecraft recovery. Second, we established the fact that landing unpowered spacecraft with gliding 

lift-to-drag ratios as low as 3.0 could be conducted safely and routinely. 

1969: Shuttle Concept Emerges 

It wasn't until 1969-after six years of lifting-hody flight at the Flight Research 

Center-that NASA's top-rank decision-makers and planners decided to switrh from 

parachute recoveries of piloted spacecraft to horizontal landings. Chief of engineering 

at NASA Johnson Space Center, Max Faget was one of the leading figures who, at the 

time, was still hanging on to the parachute concept in spacecraft recovery. In fact, it 

was in 1969, ~hile he was promoting the "Big G" concept for building a hig Gemini 

capsule that could carry 12 astronauts, that he became convinced that the concept of 

horizontal landing was good and immediately switched sides. Studies began at NASA 

Johnson Space Center on lifting bodies, delta-wing configurations, and a straight-wing 

vehicle with a conventional horizontal and vertical tail designed by Max Faget 

himself. Studies led by Gene Love at NASA T.angley evaluated candidates for the 

Shuttle configuration. 

Lifting bodies remained major contenders for the Shuttle configuration until two 

significant events took place in 1969. The first was the invention of the lightweight 

ceramic tile. The second was the mandate by Congress that the Shuttle design satisfy 

Air Force as well as NASA requirements, including the Air Force's requirements for 

hj personic lift-to-drag ratio and a full-access payload compartment about the size of 

a railroad hoxcar. 

The early ablator heat shields, developed for spacecraft such as the Apollo capsule, could he applied direc.tly to lifting bodies with much less weight penaltj than 

when applied to winged vehicles. However, with the invention of the lightweight 

ceramic tile by Lockheed Space Systems (later improved by Ho~ard Goldstein and his 

team at NASA Ames), winged vehicles constructed of such low-cost materials as aluminum could compete with the lifting bodies as candidates for space. Thin surfaces, 

such as those found on wings and tails, could be covered with the tiles, adtfing only 

mininlum weight. Minimum use of the heavier newly-developed csarbon-carbon tiles 

could also protect leading-edge high-heat areas of winged vehicles. 

Even though NASA had heen granted the responsibility for developing the 

Shuttle, Congress dictated to NASA that the Shuttle design also had to satisfy requirements of the Air Force, which called for a payload size ancl cross-range requirements 

roughly twice those of NASA. The typical hypersonic lift-to-drag ratios of the highvolume lifting bodies that we were flight-testing were between 1.2 and 1.5, which 

would havc served any of the projected NASA missions for hauling people and cargo 

to ant1 from orbit. However, the Air Force projected greater cross-range capal~ility 

requiring hypersonic lift-to-drag ratios as high as 2.0, a requirement that made winged 

vehicles more attractive as Shuttle candidates. 
WINGLESS FLIGHT 

The payload requirement of the Air Force was about 50,000 pounds to low orbit, 

to be contained in a compartment roughly 15 by 60 feet, or about the size of a railroad 

boxcar. Easy access to this compartment also required the use of full-size doors that 

could be opened in space. This requirement narrowed down the potential spacecraft 

shape to what basically resembled a rectangular box with lifting surfaces (wings and 

tails) attached to it, plus a rounded nose on the front and rocket motors on the back. 

Two basic shapes evolved for final consideration: Max Faget's configuration with 

unswept wing and tail surfaces, and a delta-wing design with a vertical tail attached. 

Studies continued through 1972, when NASA selected the delta-wing shape for 

the Shuttle. 

Phoenix Rising: From M2-F2 to M2-F3 

In the winter of 1970, two powered lifting bodies were in the air over Edwards Air 

Force Base and a third would enter flight testing by early June. Very popular with the 

pilots after its modification, the HL-10 was flown more times than any other of the 

rocket-powered lifting bodies, its final flight occurring 17 July 1970. Since the spring 

of 1968, it had been flown 36 times by four pilots-10 times by John Manke, nine 

times each by Bill Dana and Jerry Gentry, and eight times by Pete Hoag. The X-24A 

was about halfway through its two-year flight-test program by the spring of 1970, ultimately being flown 28 times-13 times by Jerry Gentry, 12 by John Manke, and 3 by 

Cecil Powell. 

The M2-Fl next to Shuttle prototype, Enterprbe, showing the comparative sizes of the two vehicles. The 

Space Shuttle with its delta wings was selected over a lifting-body shape for theJirst reusable launch vehicle, but later the X-33 employed a lifing-body con.ration. (NASA photo EC81 16288) 

143 
PI71NCLESS FLIGHT MATC'RES 

Like the mj thic phoenix rising from its own ashes, the M2-F3 emerged from the 

wrecked M2-F2 after a nearly three-year "inspection process" of the M2-F2 that had 

crashed on 10 Ma) 1967. Working closrly with the Northrop lifting-body crew in I,os 

Angeles, John McTigue parlayed resources from the shops at the Flight Research 

Center and Northrop along with about $700,000 from NASA Headquarters for this 

"inspection process," and by 2 June 1970, an essentially new rocket-powered lifting 

body-the M2-F3-was ready for its first flight. 

McTigue had kept costs down for the M2-F3 by means of several methods. For 

instance, he appropriated idle X-15 crews during the winter months when the X-15s 

could not fly because the normally dry lakebeds used for landing experimental aircraft 

were wet. He also had sheet-metal arid niac.hinetI structural parts made in NASA's 

shops to Northrop's drawings and specifications ant1 then sent to Northrop's 

Hawthorne facility for asseml~ly, a uniquely cooperative venture between a government agency and a contractor that involved a most cost-effective use of labor and facilities, keeping expenses to an absolute minimum. McTigue also had the full support of 

Paul Bikle, a man with a reputation for supporting thrifty approaches in flight 

research. 

Working under the direction of McTigue, Meql DeCeer had kept the original 

M2-F2 team intact and involved in the building of the M2-F3. The original M2-F2 

crew chief, Bill LePage, and mechanics Jay King and Bill Szuuralski continued on 

with the M2-F3. Although the M2-F3 resembled the M2-F2 externally, several systems had been modified, relocated, or added. The four-chamber LR-11 rocket engine, 

for example, was turned on its side so the lower flap could be retracted without having to build a bulge into the shape of the M2-F3's lower flap. Furthermore, heavier 

items were mo~ed forwarcl and lighter items were moved aft to help eliminate nose ballast used in controlling center-of-gravity. 

Some people consider the M2-F3 the "purest" lifting-body configuration, for it 

had no horizorital projections or tail surfaces that could be considered small wings of 

some sort. The other lifting bodies had canted fins projecting into horizontal and vertical planes. By 1970, we became convinced that any engineering information that we 

could produce from M2-F3 flight tests would be very valuable to those designing 

future spacecraft. Consequentl~, we decided to use the M2-F3 for conducting controlsystem research. 

The first lifting body, the lightweight M2-FI, had used a very basic mechanical 

control system of pushrods and cables moved solely by the pilot's muscles. There were 

no power systems such as hydraulics or electric actuators hecause the pilot didn't 

need them to fly the M2-F1. Only when the heavjweight lifting bodies came alongstarting with the M2-F2 which, fully fueled, weighed nearly ten times as much as the 

M2-F1-were hydraulic controls necessary to help the pilot move the control systems 

against the high pressures caused by high-speed flight. 

The high speeds of the heavyweight lifting bodies introduced another control 

problem common to all the heavyweights, the tentlency for overshoot or oscillation 

when the pilot made a control input. Although this problem tended to manifest itself 
WINGLESS FLIGHT 

in varying degrees, depending on the configuration, it arose from the high inertia 

(mass distribution) and low aerodynamic damping of these vehicles. To solve this 

problem, we added a rate-damping stability augmentation system (SAS) to all of the 

heavyweight lifting bodies. 

Figuratively speaking, the SAS worked like a very fast secondary electronic or 

robot pilot that shared control with the slower human pilot. Either "pilot" could move 

the control surface incle~endentl~. However, since many of our early stability augmentation systems were single-string or nonretfundant, we never allowed the "ro1)ot" 

to have more than 50 percent of the authority on the control system, not trusting it to 

have more control than the human pilot. We also limited the control authority 

mechanically to guarantee that the pilot would always have 50 percent or more control in case of electronic failure in the SAS. 

The primary task of the SAS was to respond to rate gyros by telling the control surfaces to oppose angular rate movements. We called this process "rate damping" 

because it slowed or resisted motions of the lifting body. Often, the SAS would oppose 

the pilot's control inputs, telling the control surfaces to move in the opposite direction 

to slow down the vehicle motions commanded by the pilot. To keep the pilot and the 

SAS from this kind of conflict, we designed a special washout circuit for the SAS, 

allowing the pilot to make normal-but not high-rate-turns. 

In transforming the M2-F2 into the M2-F3, we used the basic mechanical portion 

of the M2-F2's control system. However, we increased authority in the speed brake, 

modifying the rudders to allow 25 degrees of outboard deflection, and increased 

aileron deflection from 10 to 20 degrees. Yaw was controlled through the rudder pedals that deflected either of the two rudder surfaces on the outboard side of the two 

outer vertical fins. 

The primary manual control system in the M2-F3 was an irreversible dual 

hydraulic system. Pitch was controlled by moving the center stick longitudinally, positioning the lower flap. Roll was controlleil by moving the same stick laterally, differentially positioning the upper flaps. 

By adding a center fin to the M2-F3, we gained true roll control with differential 

body flaps, no longer having the vehicle's nose moving in the opposite direction from 

adverse aileron yaw, as had happened with the M2-F2. In essence, we eliminated roll 

reversal. Even though simulation with the new wind-tunnel data told us that the rudder-aileron interconnect was not needed once the center fin was added to the M2-F3, 

we kept the manual interconnect control wheel in the cockpit in case we wanted to use 

it during the flight-test program. 

Two vehicle configurations-subsonic and transonic-were used to provide adequate stability at transonic speeds and low drag (that is, an increased lift-to-drag ratio) 

for approach and landing. For shuttlecock stability at speeds higher than Mach 0.65, 

the upper body flaps were moved from the average position of 11.8 degrees to 20 

degrees upward from the body surface. Outboard biasing of both rudders was used 

solely as a speed brake-not for transonic shuttlecock stability, as was the case for the 

HL-10 and X-24A. 
WINGLESS FLIGHT MATURES 

Pilot desired rate 

Pilot desired rate 

Scherrruttc sho~ring how the l$ting-botlj. rontrol hystems differed. The W2-F3 uras a test-bed for four 

clifferent control systems including reaction controls (originnl clrawing by Duk Reed, digitul trersion by 

Dryden Grclphics Ofice). 
WINGLESS FLIGHT 

Three Experimental Control Systems Added 

To add reliability and flexibility to the electronic portion of the control system in 

the M2-F3, we eventually replaced the original single-string SAS of the M2-F2 with a 

triply-redundant Sperry electronic control system similar to the one used in the 

X-24A. We also added three new control systems to the M2-F3, supplemental to the 

basic system, using simple rate-damping controlled by the pilot's center stick. We 

used a second "sidearm" control stick in the cockpit for flying the M2-F3 with the 

three different experimental control systems. The pilot could always revert back to the 

basic center-stick control system by throwing a switch on the center stick or on the 

front panel. We planned to install these systems after the speed and altitude envelope 

for the M2-F3 had been expanded while using the basic center stick and SAS. 

The first experimental control system for the M2-F3 was a rate command augmentation system (CAS) in the roll and pitch axis, which we hoped would improve 

pilot control by smoothing out the configuration's nonlinear longitudinal aerodynamic 

characteristics. Conceptually, the CAS differed from the SAS normally used in the lifting bodies. Instead of sharing control of the control surface with the pilot and being 

capable of independent operation, as was the case with the SAS, the CAS received 

instructions from the pilot's control stick and then used gyro and other information to 

actually fly the vehicle for the pilot. For instance, if the pilot wanted a certain pitch 

or roll rate, he would move the side-stick accordingly. After receiving the electrical 

signals from the pilot's side-stick, the CAS would fly the M2-F3, avoiding overshoots 

and oscillations and steadying the vehicle at the angular rate the pilot had indicated 

by stick position. 

With lead and lag electronic networks, the CAS actually could do a better job than 

the pilot in flying a dynamically unstable aircraft. In 1970, however, we didn't trust 

electronics the way we do today. We gave the CAS only 50-percent authorit), the pilot 

retaining 50-percent mechanical authority so the pilot could control the M2-F3 with 

the center stick if a failure occurretl in the CAS. Today, high-speed aircraft routinely use command augmentation systems with 100-percent authority that are based on 

redundant digital computers. 

We added another feature to the CAS for maintaining a pilot-indicated angle of 

attack. The CAS woultl maintain constant angle of attack when the cockpit hold 

switch was engaged if the pilot's side-stick was in centered position. The side-stick 

had a detent switch so that when it was out of center, angle-of-attack hold was disengaged and a rate dependent on stick position was commanded until a new angle of 

attack was reached. Centering the stick would engage angle-of-attack hold. When 

angle-of-attack hold wasn't desired, the pilot could turn it off with the cockpit switch 

and then only rate command was operative. Another switch on the side-stick provided a vernier so that angle of attack could he changed without taking the stick out of 

detent. The pilot could regain center-stick control with the SAS at any time hy disengaging the CAS switch on the instrument panel or on the center stick. 
WIXGLESS FLIGHT MATURES 

The second experimental system installed in the M2-F3, a reaction-control rocket system, offered potential weight reduction and simplified design for potential future 

lifting-body re-entry vehicles. Such a vehicle could be greatly simplified if the same 

rockets used for maneuvering in space could be used for control during landing. Four 

90-pound-thrust hydrogen-peroxide rocket motors installed on the base of the M2-F3 

were designed to be operated in pairs, providing either rolling or pitching moments for 

roll and pitch control. 

The rockets could be operated only in two states-basic ON-OFF (or "bangbangw)--with no capability for variable thrust. Effective rolling or pitching moments 

could be achieved only by pulsing the rockets' burn times to produce the desired 

impulse for changing the vehicle's motion. At first, a pilot operated the rocket system 

by using a spring-loaded toggle switch on the right console. Later, we replaced the toggle switch with a side-arm controller--obtained surplus from an old World War TI formation stick-that enabled the pilot to use his right wrist rather than his fingers to 

operate the system to produce the necessary "beep-beep" or "bang-bang" motion. 

A third experimental system installed in the M2-F3 was a CAS to control the reaction-control rocket system. The ON-OFF scheme of controlling the rockets seemed 

crude and marginal, so the CAS was modified to control the rockets rather than the 

aerodynamic control surfaces. 

June 1970: Bomb on the Ramp! 

The flight-test program for the M2-F3 benefited from the experience gained in the 

M2-F2, HL-10, and X-24.4 flight-test programs. Meryl DeGeer served as operations 

engineer only through the first two glide flights of the M2-F3 and then was reassigned 

as operations engineer on the newly established YF-12A flight program at the Flight 

Research Center that involved three of the Lockheed Blackbirds, similar to the SR71A reconnaissance aircraft. Herb Anderson, who had been operations engineer on 

the HL-10 through its last flight, took over as M2-F3 operations engineer. 

Most of the time, preparations for the M2-F3 flight tests progressed smoothly, 

n~ethodicall~, and safely. However, an extremely dangerous incident occurred in June 

1970 as the M2-F3 was being prepared for a powered flight following four unpowered 

glides. While hanging under the B-52's wing, the M2-F3 was being fueled on the 

ramp. During the fueling operation, crew member Danny Garrabrant noticed liquid 

was spilling out of the liquid oxygen vent onto the ramp. 

Normally during fueling, the liquid-oxygen tank and the water-alcohol fuel tanks 

in the M2-F3 and other lifting bodies were protected by a "quad valve," a dual-redundant check valve that keeps the fuel from flowing into the liquid-oxygen tank. 

However, both sides of the valve failed on this occasion, allowing the fuel and liquid 

oxygen to mix, something that had never happened with any of the other lifting bodies. The mixture in the tanks immediately froze due to the temperature of the liquid 

oxygen (-270 to -290 degrees Fahrenheit), creating a bomb. The slightest jar could set 

off a gigantic explosion on the ramp under the fully fueled B-52. 
WINGLESS FLIGHT 

M2-F3 launched from B-52. (NASA photo EC71 2774) 

At once, Garrabrant sounded the alarm to his crew chief, Bill LePage. Herb 

Anderson and LePage immediately alerted the Air Force. The area was evacuated. All 

flights at Edwards Air Force Base were canceled, including all supersonic over-flights, 

for the jar from a sonic boom could trigger the explosion. 

Anderson and LePage then set out to defuse their bomb. Using padded tools and 

being extremely careful not to drop anything on the M2-F3's tanks, they eventually 

succeeded, but only after several very long hours of extreme danger to themselves and 

the aircraft. 

FEght-Testkg the M2-F3 

Project pilot Bill Dana flew the M2-F3 on 19 of its 27 flight missions, including 

the first three of four glide flights for determining how its characteristics compared 

with those of its predecessor, the M2-F2. Even though he had not flown the M2-F2 

since 1967, Jerry Gentry piloted the M2-F3 on his final lifting body flight in February 

1971. Two other pilots made the other 7 of the M2-F3's powered flights-four by John 

Manke and three by Cecil Powell. 

After the end of the vehicle's flight-test program in late 1972, Bill Dana helped 

write a pilots' report on the flight characteristics of the M2-F3 that included not only 

his own observations but also those of John Manke, Cecil Powell, and Jerry Gentry. 

Published in 1975, this final NASA report on the vehicle's handling qualities entitled 
WINGLESS FLIGHT MATURES 

"Flight Evaluation of the M2-F3 Lifting Body Handling Qualities at Mach Numhers 

from 0.30 to 1.61" was written by Bob Kempel and Alex Sim as well as Bill Dana.7 

This report was based on the pilot ratings for all flights and is the main source for the 

comments, details, and summarized results that follow. 

Beginning 2 June 1970 and ending I6 December 1971, the first 13 of the 27 flight 

tests were made using only the vehicle's center-stick system, with in-flight maneuvers 

to evaluate control characteristics with the SAS on and off. Maximum Mach speed for 

these flights was 1.27. After the thirteenth flight, the M2-F3 was grounded for six 

months-until July 1972-while the experimental control systems and side-stick 

were installed for evaluation during the final 14 flights. The last flight occurred on 20 

December 1972, the M2-F3 during the course of its flight-test program achieving a 

maximum speed of Mach 1.61 and altitude of 71,500 feet. 

Glide Flights and Landings 

During the first half of its flights, in glide and at subsonic speeds, the M2-F3 flew 

very well with the SAS on. Adding the center fin had made a dramatic change in the 

configuration, transforming the "angry machine" of the original M2-F2 into the very 

controllable and pleasant-to-fly M2-F3. The pilots reported that control in both longitudinal and lateral-directional axes was excellent with the rate-damping system (SAS) 

on. While the M2-F3 proved it could also be flown during glides with the SAS turned 

off in all axes, vehicle response was very sensitive and the pilots had to exercise great 

care to keep from over-controlling in both longitudinal and roll axes. According to the 

pilots, without the SAS, the M2-F3's nose would "hunt" up and down and roll maneuvers were "jerky." 

During landings from the glide flights, the M2-F3 demonstrated characteristics 

that distinguished it from the other lifting bodies. Of the three lifting-body shapes 

tested, the M2 possessed the lowest subsonic lift-to-drag ratio. This fact did not 

create traffic-pattern difficulties due to the careful planning that went into each flight 

to protide sufficient altitude for comfortable landing under both normal and 

emergency conclitions. 

The low lift-to-drag ratio, however, did require more of the pilot's attention on final 

approach and flare than had been needed with the HL-10. Flare speed caried from 

260 to 320 knots, but 260 knots proved insufficient to hold the airrraft off the ground 

while "feeling for the runway." About 290 knots of preflare airspeed gave a reasonable float time. However, the faster the final approach, the more romforta1)le it was for 

the pilot. Flare altitude also had to be carefully monitored for the vehicle to come level 

just above the ground, varying between 600 feet for final approach at 260 knots to 100 

feet for 320-knot approaches. 

7. Robert 8'. Ken~pel, William H. Dana, and Alex G. Sim, "Flight Evaluation of the M2-F3 Lifting 

Botl) Handling Qualities a( Mac11 Nulnl~et, from 0.30 to 1.61" (Fihhington, DC: NASA Technical Note 

D-8027,1975). 
WINGLESS FLIGHT 

Turbulence response in the M2-F3 resembled that of the HL-10 and X-24A. 

A side gust would cause a high-frequency roll oscillation that would damp out without pilot input, the type of response caused by the vehicle's excessivel) high amount 

of effective dihedral. At first, low-level turbulence would make the M2-F3 pilots 

apprehensive due to the unusual nature of the vehicle's response. As with the HL-10 

and X-24A, however, their apprehension decreased as additional experience showed 

that the unusual response did not mean the vehicle was on the threshold of divergent 

lateral oscillation. Nevertheless, we chose not to fly the M2-F3 on days when we 

expected high turbulence in the atmosphere over Edwards. 

Having made sixteen of the X-15 flights, including its last flight, Bill Dana tended to be disappointed with the M2-F3's speed brakes. Spoiled by the X-15's powerful 

speed brakes, he wasn't impressed with the lesser effectiveness of those on the 

M2-F3. Dana also did not like the vehicle's large nose-down pitching moment when 

the speed brakes were applied bj outboard biasing of both rudders. 

The flat upper deck of the M2-F3 challenged the pilots' visibility, requiring them 

to switch back and forth quickly between looking over the top side and looking down 

through the nose window at their feet. The biggest problem with visibility in the 

M2-F3 was visually judging altitude just hefore touchdown when the nose was at high 

angle. Historic accounts claim that fighter pilots during World War TI adapted well 

when they hat1 little or no forward visibility due to the long noses on that era's aircraft, 

compensating by using their peripheral vision. Using the nose window, especially during approaches to touchdown, the pilots of the M2-F3 adjusted just as successfully to 

limited forward visibility. 

Rocket-Powered Flight 

During the vehicle's first rocket-powered flight in late 1970, Bill Dana achieved 

the transonic speed of Mach 0.81. However, indications appeared shortly after launch 

that the M2-F3 had longitudinal problems transonically. Angle of attack drifted nearly uncontrollably due to a decrease in pitch stability and changes in trim as the Mach 

number increased. 

As speeds were gradually increased on each additional rocket-powered flight, the 

pilots discovered that the most longitudinal instability occurred near Mach 0.85, when 

they had difficulty controlling angle of attack. The center-of-gravity was moved forward with ballast added to the nose. Increasing the pitch damper gain, or sensitivity, 

to its maximum value also helped the pilot steady the vehicle. However, even with 

these changes, longitudinal stability (pitch control) was only marginally acceptable in 

the transonic speed range. Consequently, the longitudinal rate-damping system (SAS) 

was never turned off in this speed range. 

In contrast, the pilots rated the roll control of the vehicle at transonic speeds as 

very good. Just as at subsonic speeds, the M2-F3 could be flown with the roll and yaw 

damping system (SAS) turned off. However, as it had been in glide flights, the vehicle 

was very sensitive to roll control, and the pilots had to exercise great care to avoid 
WINGLESS FLIGHT MATURES 

over-controlling the M2-F3 at transonic speeds with the roll and yaw damping system 

turned off. 

At speeds between Mach 1.0 and 1.6, longitudinal control with the rate-damping 

system turned on was considerably better than it had been in transonic flight. 

However, the longitudinal control still wasn't as good as it was at subsonic speeds. We 

decided, consequently, that the longitudinal rate-damping system (SAS) should not be 

turned off at supersonic speeds, On the other hand, at supersonic speeds, the pilots 

felt comfortable about turning off the lateral-directional rate-damping system (SAS), 

for roll control was sensitive with this system operating and pilots had to be very cautious to avoid over-controlling in roll. 

After the side-stick and experimental control systems were installed in 1972, the 

final 14 flights of the M2-F3 evaluated them. Generally, the pilots were disappointed 

in the Command Augmentation System (CAS). Bill Dana had hoped the CAS would 

improve the vehicle's handling characteristics at transonic speed during the rocketburning phase. While the CAS did improve the longitudinal control in rate-command 

mode slightly, it was far from satisfactory. The pilots preferred not to use the angle-ofattack-hold mode, for it did not work well. Furthermore, the CAS did nothing to 

improve lateral control, already good using only the basic SAS. It seems we had cut 

costs too much in developing the CAS and had failed to optimize its potential. 

The sidearm controller selected for use with the CAS proved to be too 

rudimentary. One spring in the side-stick provided both force gradient and breakout 

force. Adjusting one required great care to prevent varying the other. Changing either 

parameter required disassenlbling the stick, threatening the integrity of the assembly. 

We should have located or developed an electric sidearm controller with external and 

independently adjustable force gradients and breakouts. 

The potential for improvement in the CAS was never fully achieved due to the 

poor physical characteristics of the side-stick plus the system's requirement that the 

pilot wear a pressure suit, which not only limited mobility but also aggravated the negative effects of the side-stick. Nevertheless, the potential for the CAS was recognized. 

In spite of its drawbacks, the system was a welcomed addition to the M2-F3. 

The ON-OFF, or "hang-bang," rocket reaction-control system was first tried in roll 

with poor results. Manual control of the rockets was too responsive, resulting in jerkj 

flying. Longitudinal control was not even tried for fear of losing control of the M2-F3. 

In the reaction-control system with CAS, the pilot's side-stick was a proportional 

control with the stick's position commanding an angular roll rate. Tested in flight, the 

CAS responded to pilots' input command, firing the rontroI rockets with pulses timed 

to give the desired results in changing or holding the vehicle's angular rate. The system worked beautifully without moving the aerodynamic control surfaces. Bill Dana 

rated the s~stem as excellent. The system's reflected the level of achievement 

from appljing experience with previous systems first developed at the Flight 

Research Center hack in the days before the NACA became NASA, experience that 

was then applied on the rocket-boosted F-104 zoom aircraft and even later on the 

X-15 and Lunar Landing Research Vehicle. 
WINGLESS FLIGHT 

A refinement on this rocket-control system eliminated unwanted yaw moments 

when applying roll control. The system worked almost perfectly in this mode when 

rockets were needed only to change roll rates. In the longitudinal mode, however, 

excessive use of the rockets was needed when the vehicle got out of trim by adjusting 

the longitudinal aerodynamic flap. A further refinement of the system, had we had the 

time and money to implement it, would have been to combine the longitudinal reaction-control rockets with the body's longitudinal flap in an automatic control system. 

The M2-F3 flight-test program was almost over, and we were nearly out of money. So 

we took what we had learned from the M2-F3, wrote our technical reports, and left the 

potential for application of what we had learned in the hands of the designers of future 

spacecraft.8 

8. Kempel, Dana, and Sim, "Flight Evaluation of the M2-F3;" and Alex G. Sirn, "Flight-Determined 

Stability and Control Characteristics of the M2-F3 Lifting Body Vehicle" (Washington, DC: NASA 

Technical Note D-7511, 1973). 

CHAPTER 8 

LIFTING-BODY RACEHORSES 

By 1969-1970, the lifting-body program had become a major activity at the 

NASA Flight Research Center, Ames, and Langley. The Air Force Flight Test Center 

was vigorously supporting the flight-test part of the program for the M2-F3, HId-10, 

and X-24A. However, T was becoming concerned that a disproportionate amount of 

our effort was going into supporting only one type of lifting body. 

The M2-F3, HL-10, and X-24A were configurations with high volumetric efficiencies, best suited for shuttle-type missions in deploying satellites and in canying 

cargo and people to and from earth orbit. All three had hypersonic lift-to-drag ratios 

between 1.0 and 1.4, permitting a potential cross-range capability of 700 to 1,000 

miles-that is, they could range from 350 to 500 miles to either side of the orbital path 

during re-entry. They also had adequate lift-to-drag ratios for landing. 

To me, the M2-F3, HL-10, and X-24A were the lifting-body "plow-horses," and 

I was becoming interested in a different kind of lifting body, a class of vehicles I considered the "racehorses." The shapes of these lifting bodies had high fineness ratios 

with long pointed noses and flat bottoms. The more efficient of these shapes had 

hypersonic lift-to-drag ratios as high as 3.0, allowing a total cross range of 3,000-the 

ability to range 1,500 miles to either side of the orbital path. A hypersonic vehicle 

with a lift-to-drag ratio greater than 3.0, of course, would be considered at the top of 

its class in performance. 

The "racehorse" class of lifting bodies could be used for special missions where 

flexibility was required, being able to land anywhere on earth on short notice. 

However, the slender shapes would not lend themselves to serving as efficient cargo 

containers. While these vehicles would have high aerodynamic efficiencies at hypersonic speeds, they wouldn't perform well at landing speeds and likely would need 

some sort of deployable wings to land. 

Two of these "racehorse" shapes were the Hyper I11 developed by NASA Langley 

and the FDL-7 developed by the Air Force Wright Flight Dynamics Laboratory in 

Dayton, Ohio. There is some question about whether the Hyper TIT and the FDL-7 

were true lifting-body configurations since they both had small deployable wings used 

for landing. Both can be called special forms of the lifting body, however, since the 

small wings would be stowed during most of the projected re-entry flight before landing. Another of the lifting-body features that each possessed was that, even with the 

wings deployed, the body still dominated the aerodynamics of the total configuration. 
LIFTING-BODY RACEHORSES 

m- 

/ 

2000- 

Cross 

raw, 

mlles 

1000 - Standard Biconlc 

0 1 2 3 

Hypersonic 97w 

Graph shotcing rross range distances in miles plotted against hypersonic lift over drag for several vehicles 

returning from orbit. Notice that the "race-horse" v~hicksuch as the X-2JB and Hyper 111 have thegrecltest cross-range capability--round 2,500 miles. 

Model-Testing of Lifting-Body Spacecraft 

By 1969, I was outside the mainstream of the on-going lifting-body program at the 

Flight Research Center, busy looking at new concepts and projects further into the 

future. Using the excellent radio-control equipment then becoming available to 

model-airplane hobbyists, I teamed up with Dick Eldredge to conduct sev~ral experiments in flying models of experimental spacecraft. We worked with what was called 

the "de-coupled mode" in which the basic re-entry vehicle is flown down to a certain 

point and then converted to a landing configuration by deploying either a gliding 

or wings of some sort. 
WINGLESS KIGHT 

Eldredge had been the first research engineer to join my M2-F1 lifting-body team 

seven years earlier, and I still thought of him as my "little buddy." Although we had 

remained in contact with each other throughout the lifting-body buildup program, 

since the early days of the M2-F1 we had not had the time to brainstorm together 

about new ideas. This situation began to change after I got out of management with the 

lifting-body program in 1965 and, by 1969, I was free to think about new ideas again. 

Over the years 1 have often compared the relationship between me and Dick 

Eldredge with that of the Wright Brothers. I thought of Eldredge as being a sort of 

brother off whom I could bounce ideas and from whom I could get constructive feedback, much as the Wright Brothers did between themselves during the first part of 

their career. Even the progressive changes in our careers bore some resemblance to 

those experienced by Orville and Wilbur Wright. At first, the Wright Brothers treated 

aeronautics as a hobby and had fun. All innovation begun early in their career 

stopped, however, once they became businessmen and project managers. They had no 

time for experimentation or research once they entered competition with Glen Curtiss 

and others and became involved with legally protecting their wing-warping and other 

patents. By that time, aviation was no longer fun for the Wright Brothers. It had 

become serious business. 

I have noticed that the same changes often occur within the careers of many innovative individuals who are motivated by fun as well as the satisfaction they receive 

from creating something that has never existed before. When these people enter the 

business world, they often become unhappy, their productivity diminishing. I believe 

I made the right decision when I took Paul Bikle's advice in 1965 and got out of 

management with the lifting-body program. When I returned to engineering, I essentially returned to the realm of innovation. 

As I learned from my own experience over the years, NASA Headquarters operates in such a way that priority and attention tend more easily to be given to large and 

costly projects. Experiments or projects by two people or a small group generally do 

not fit into the scheme of things at NASA Headquarters. In fact, until a project has 

been supervised by NASA Headquarters, pondered for some time there, and then officially blessed, it usually is not considered important by headquarters people. 

Nevertheless, the small projects that result from brainstorming at the NASA centers are often exciting for those who originate them and literally love the work they do. 

I don't think, on the other hand, that most managers at NASA Headquarters trust those 

who have too much fun while working. In fact, these managers coined the term 

"hobby-shop projects" for referring disparagingly to projects originating outside of the 

mainstream and controI of the master plan. 

Dick Eldredge and I, however, were intrigued with the idea of doing the first 

flight-testing of a sleek "racehorse" configuration with a pointed nose, a design we 

believed would give superior performance at hypersonic speeds. As we continued our 

radio-controlled model flying of lifting-body spacecraft, we tested models of both the 

"racehorse" Hyper I11 and the "plow-horse" M2-F2, using a Rogallo Limp Wing gliding parachute for recovery. 
LIFTING-BODY RACEHORSES 

R'e also designed and built a special twin-engined, 14-foot model mothership for 

canying the lifting-body models to altitude and launching them, much as was being 

done with the B-52 for the full-scale lifting bodies. I!$+ envisioned future space missions where there might be a need to use the vehicle's hypersonic lateral cross-range 

capability to reach a meadow in Alaska, for example, and land the vehicle there softly and slowly by means of a gliding parachute for some covert military mission. Our 

imaginations also came up with a mission that used the hypersonic lateral range of the 

vehicle to take an injured astronaut back to earth, landing in a field near the hospital 

best able to provide the care needed. 

One of us would flj the mothership by radio-control with the lifting-body model 

attached to its belly with a hook activated by remote control. The other would take 

charge of the experimental lifting body, flying it after air-launch on its own aerodynamics, then controlling it through steering control lines to a landing on its 

gliding parachute. 

We found that the Hyper IIT's extremely low lift-to-drag ratio of 2.5 made it 

impractical to land without either a gliding parachute or deployable wings. We experimented with three types of deployable wings for the Hyper 111. The first was a pair of 

switchblade wings that pivoted out of slots in the lower part of the body. The second 

was a one-piece wing that pivoted in the center and was stowed in the upper portion 

of the body, the right half of the wing exiting from a forward slot on one side and the 

left half exiting from a rearward slot on the other side. With this second type of wing, 

after rotating 90 degrees, the final configuration for landing was a straight wing mounted high on the body. 

The third type of wing we tried was the Princeton Sailwing that had been tested 

in the NASA Langlej full-scale wind-tunnel on a conventional glider fuselage. The 

Sailwing involved two D-shaped spars stowed in two slots in the body and deployed 

like a switchblade wing, with trailing edge cables pulling taut from a tip rib and 

stretching upper and lower fabric membranes from the spar to the cable. The fabric 

surfaces would then curve upward, like sails on a boat, forming a cambered airfoil and 

producing positive-lift airflow over the wing. 

Hyper I11 and Parawing 

Our second type of deployable wing-the one-piece pivoted design-proved to be 

the best of the three for actual flight. NASA Langley conducted wind-tunnel tests on 

the Hyper I11 without the wing up to Mach 4.6, followed by tests with the 

wing tleployed at subsonic speeds. I put together a plan for building a full-scale vehicle at low wing-loading similar to the M2-F1. However, I proposed to fly it without a 

pilot onboard. The idea of flying unpiloted vehicles at the Flight Research Center was 

unpopular, especially with the pilots. Paul Bikle would approve the plan only if I 

would build the vehicle so that a cockpit could be installed for a pilot to fly it after the 

initial tests were completed. Later, an X-15 type of canopy would be added slightly 

forward of the wing to balance the piloted version. 
WINGLESS FLIGHT 

In spite of the success of the on-going rocket-powered lifting-body program, 

NASA Headquarters still was not tolerant of programs as small as that of the original 

lifting body, the M2-F1. For this reason, I was very interested in developing a flighttest approach with the pilot doing the early hazardous flight tests in a simulator-type 

cockpit on the gound. This approach would put us in a better position later for getting approval for the more expensive piloted flight tests. 

I managed to convince Paul Bikle that this approach had merit and we ought to 

give it a try. However, the idea went over like a lead balloon with the pilots. In the end, 

I had to turn once again to Milt Thompson for help. Even though Thompson had 

retired from flying, he was intrigued with the idea and offered to flj the Hyper I11 from 

a ground-based cockpit. 

By this stage in 1969, I had two projects developing at the same time. The gliding parachute tests that Dick Eldredge and I had been doing with spacecraft models 

had attracted the interest of the NASA Johnson Space Center. I discussed our use of 

the limp Rogallo parachute in recovering spacecraft models with Max Faget, Johnson's 

director of engineering who had played a major role in designing crewed spacecraft 

starting with Project Mercury.1 Not yet accepting horizontal landing as appropriate for 

the next space mission, Faget at the time was still backing gliding parachute concepts 

such as the "Big G," a twelve-astronaut version of the Gemini space capsule with one 

astronaut steering the capsule to flare and landing at a ground site. 

While talking with Faget, I offered to develop a one-pilot test vehicle that could 

be launched from a helicopter and used to test a pilot's ability to fly the vehicle while 

looking through the viewing ports typical of spacecraft. I suggested we fly the vehicle 

at first by radio-control with just a dummy onboard until it was determined to be safe 

to flj. Faget just happened to have a borrowed Navy SH-3 helicopter that was being 

used to practice fishing Apollo astronauts out of the water. Enthusiastic about my idea, 

Faget offered to let us have the helicopter for a month, plus enough money to buy 

large-sized Rogallo Parawings for the project. 

Paul Bikle approked our Parawing Project, as it was called, and assigned NASA 

pilot Hugh Jackson to it. Although he was the new kid on the block among the other 

NASA pilots, Jackson was considered the resident expert in parachuting, having parachuted four or five times. At best, Jackson was lukewarm about participating in the 

Parawing Project. He likely accepted the assignment because he wasn't yet allowed to 

fly the NASA research aircraft. 

Dick Eldredge designed the vehicle for the Parawing Project. It was built in the 

shops at the NASA Flight Research Center. Since we were experienced scroungers 

and recyclers by this time, we used surplus energy struts from the Apollo couches in 

the vehicle to soften the load on the pilot in hard landings. The M2-F2 launch adapter 

not being used with the B-52, we used its pneumatic hook-release system to launch 

1. See Henry C. Dethloff, Sz~ddenly Tornorro~r, Canze . . . '4 History oJth~ Johnson Spnra Ce~iter 

(Xashington, DC: NASA SP-4307, 1993), esp. pp. 6245. 
LIFTING-BODY RACEHORSES 

the vehicle from the side of the SH-3 helicopter. For the test configuration, we used a 

generic lifting-body ogive shape with Gemini viewing ports. We attached landing 

skids with energy straps to an internal aluminum structure containing the pilot's 

Apollo couch. A general-aviation auto-pilot servo was used to pull down on the parachute control lines. The pilot used a small electric side-stick to control the servo. 

The plan was that before putting a pilot onboard, we would launch the lifting-body 

with the dummy in the pilot's seat off the side of the helicopter, deploy the parachute, 

then steer the vehicle to the ground by radio-control, using model-airplane servos to 

move the pilot's control stick. We even tied the dummy's hands in its lap so it would 

not interfere with the control stick. Measured accelerations in the dummy and on the 

airframe were transmitted to the ground to record shock loads as the parachute opened 

Hyper 111 with single-piece, pivot wing installed. Flexible Princeton sailwing is on the ground to be installed 

for future tests (never perjormed), and one of the fabricators of the Hyper 111, Daniel C. Garrabrant, is 

standing next to it. (NASA photo E69 20464) 

and the vehicle made ground contact. By moving the pilot's stick directly with the 

radio-controlled servos, we qualified the entire control system downstream of the 

pilot's control stick. 
WINGLESS FI,TGHT 

Dick Eldredge stayed with the Parawing Project until the system had been qualified for piloted flight following 30 successful radio-controlled flights. Hugh Jackson 

was getting ready to make his first flight in the vehicle when the NASA Johnson Space 

Center decided that the next piloted space program would not make use of a gliding 

parachute system but would use a horizontal-landing spacecraft instead. I think 

Jackson was relieved when he heard this news that made his flight unnecessary. A few 

months later, he left the pilots office at the NASA Flight Research Center. 

Hyper I11 Team 

Meanwhile, Dick Fischer had himself assigned as the operations engneer on the 

Hyper 111. Fischer had other aircraft obligations, but his bosses agreed to the assignment after I had accepted the decision of management at the Flight Research Center 

that the Hyper I11 program would be conducted on a low-priority basis. A long-time 

friend of mine and a model-airplane flying buddy, Dick Fischer was also an excellent 

designer of home-built aircraft who restored antique aircraft in his spare timr. 

Together, Fischer and I recruited Bill "Pete" Peterson, a control-system engineer 

on the X-15 program, to help design the control system for the Hyper 111. Peterson had 

worked earlier for Honeywell in Minneapolis, designing the adaptive control system 

for the X-15. As a Honeywell employee, he had come initially to the Flight Research 

Center during the X-15 flight tests to help NASA with operating the X-15's control 

system. He was then hired by the Flight Research Center to continue working with the 

control system on the X-15 and other aircraft. Peterson managed to find time to help 

us with the Hyper 111, despite the fact that he was involved with four other aircraft at 

the Flight Research Center at the time. 

On the Hyper 111, I managed to use volunteers in the same way I had originally 

with the M2-F1, thanks to the influence of Paul Bikle. As in the days of the M2-F1, 

we found that NASA supervisors were tolerant when engineers such as Pete Peterson 

wanted to work on volunteer projects like the M2-F1 or Hyper 111 and could do so 

while still meeting their obligations on assigned projects. 

Dick Fischer designed the structure of the Hyper 111, and the vehicle was built in 

the NASA shops. When finished, it was 35 feet long and 20 feet wide at the tail surfaces. The fuselage was basically a Dacron-covered steel-tube frame, the nose 

was made out of molded fiberglass, and the four tail surfaces were constructed of 

aluminum sheet-metal. The aluminum wing was built from the wing kit for an 

HP- 1 I sailplane. 

Frank McDonald cut and fitted the steel-tube body, and Howard Curtis did the 

welding. NASA aircraft craftsman Daniel "Danny" Garrabrant-a highly skilled 

builder of model aircraft and of home-built wooden and aluminum full-size 

sailplanes-assembled the wing for the Hyper 111. Lavern Kelly assembled the vehicle's sheet-metal tail surfaces. 

Many of the people who worked on the M2-F1 worked as well on the Hyper 111, 

including aircraft inspector Ed Browne and painter Billy Shuler. We worked closely 
LIFTING-BODY RACEHORSES 

with the NASA fabrication shops to get the Hyper 111 structure completed without 

interfering with the shops' work on other, prioritized projects. With the X-15 program 

winding down, I managed to recruit even more talented volunteers to work part-time 

on the Hyper 111, including crew chief Herman Dorr and mechanics Willard Dives, 

Bill Mersereau, and Herb Scott. 

Our skills in scrounging and recycling came in handy in building the control system for the Hyper 111, which was composed of an uplink from a Kraft model-airplane 

radio-control system. The control surface on each of the two elevons was driven by a 

surplus miniature hydraulic system from the Air Force's PRIME lifting-body program. 

The hydraulic system was a battery-driven pump that had run two actuators for the 

elevons on the PRIME vehicle. 

Peterson cleverly designed the system to operate from either of two Kraft 

receivers, depending on the strength of the radio signal at the top or bottom of the 

Hyper TIT, one receiver mounted on the top and the other mounted on the bottom of 

the vehicle. If either receiver malfunctioned or picked up a bad signal, an electronic 

circuit switched to the other receiver. Signals from the operating receiver controlled 

the two elevon surfaces driven by hydraulic actuators. A talented hydraulics engineer, 

Keith Anderson modified the PRIME hydraulic actuator system for the Hyper 111. 

In case we lost control during the flight tests, we mounted an emergency parachute-recovery system in the base of the vehicle. It consisted of a drogue chute that 

fired aft, extracting a cluster of three paratrooper-type chutes that would lower the 

vehicle onto its landing gear. The Northrop support contract still in effect, I managed 

to get the help of Northrop's Dave Gold for a few weeks. A top parachute designer, 

Gold had tione most of the detailed design of the parachute system used on the Apollo 

spacecraft. Gold and John Rifenberry from the NASA pilots' life-support shop worked 

steadily for two weeks at the sewing machines in Rifenbeq's shop ~hile completing 

the vehicle's parachute-recovery system. The Flight Research Center's expert on 

pyrotechnics, Chester Bergner assumed the responsibility for the drogue firing system. 

We tvsted the emergency parachute-recovery systenl by putting the Hyper 111 on 

a flatbed truck and firing the drogue extraction system while we were racing across the 

dq lakebed, but a weak link kept the three main parachutes from jerking the Hyper 

111 off the truck. We then tested the clustered main chute by attaching it to a weight 

that equaled that of the Hjper 111 and dropping it from a helicopter. We were very fortunate that the emergency parachute-recolery system never needed to be used. 

With the help of Don Yount as instrumentation engineer and Chuck Bailey and 

Jini Duffield as instrumentation technicians, a 12-channel FMIFM down-link telemetering systenl recorded data and drove instruments in the ground cockpit. Assembled 

by Ton1 McAlister, the ground cockpit was made out of plywood and looked somewhat 

like a Romn (;hariot when it was hauled out to the Ianding site on a two-wh&letltrailer. The instruments in the ground cockpit Here identical to those in our fixed-base 

simulator. In the center of the display, an artificial-horizon ball intlicated roll, pitch, 

heading, and sideslip. Other instruments in the ground cockpit showed air speed, altitude, angle of attack, and control-surface positions. 
WINGLESS FLIGHT 

First Flight of the Hyper I11 

Bruce Peterson piloted the borrowed Navy SH-3 helicopter that towed the Hyper 

TJI aloft for its first flight on 12 December 1969. A Marine Corps pilot before joining 

NASA, Peterson continued to fly helicopters and jet fighters in the Marine resenTes on 

a restricted basis following the M2-F2 crash that cost him his vision in one eye. After 

the crash, Peterson also flew support aircraft during various NASA flight-research 

missions, although he was not allowed to fly the actual research aircraft. The first flight 

of the Hyper IT1 was the last lifting-body mission in which Bruce Peterson and Milt 

Thompson would directly participate. 

After liftoff, with the Hyper TIT attached to the helicopter at the end of a 400-foot 

cable, Peterson had a difficult time getting the Hyper TIT to track straight on the end 

of the tow-line. Afterwards, we realized that we should have installed a small drag 

chute on the Hyper TI1 that could have been jettisoned after launch. As Peterson 

struggled to get the vehicle to track straight, Milt Thompson sat in the ground 

cockpit located beside the planned landing site on the lakebed, relaxed and smoking 

a cigarette. 

After starting and stopping forward flight several times during the climb, Peterson 

eventually got the Hyper TI1 to stabilize in a forward climb. When Peterson radioed 

that he was ready to launch, Thompson flipped his cigarette onto the lakebed and 

hunched over the controls, intently ready to fly the Hyper 111. Peterson towed the 

Hyper 111 to 10,000 feet above the dry lakebed, where the Hyper 111 was released from 

the tow-line by an electric cargo hook. For this first flight, the Hyper 111 was flown with 

the wing fixed in deployed position, the configuration that would be flown in a final 

low-speed approach and landing after re-entry from space. 

Peterson dropped the Hyper 111 in forward flight on a downwind path with a 

northerly heading, Thompson controlling the Hyper I11 from the ground cockpit. 

Thompson flew the vehicle in a glide three miles north, guided it into a 180-degree 

turn to the left, and then began steering it the three miles to the planned landing site. 

During the straight portions of the flight, Thompson had performed research doublet 

and oscillation maneuvers so we could extract aerodynamic data following the flight. 

Since Thompson was flying strictly by instrument flight rules in the ground cockpit with his head down, I asked Gary Layton in the control room at the Flight Research 

Center to watch a radar plot board and guide Thompson by radio to landing position. 

Layton had often helped lifting-body pilots in this way in the past as they steered to 

landing sites on the lakebed runways. Since we had no experience yet in landing 

unpiloted vehicles at the Flight Research Center with the use of onboard video, we 

had not installed a forward-looking video camera in the Hyper 111. Dick Fischer was 

standing beside Thompson in the ground cockpit to take control of the Hyper 111 just 

before the landing flare, using the model-airplane radio-control system's box during 

the landing-flare maneuver to touchdown. 
LIFTING-BODY RACEHORSES 

Although the sky over Edwards Air Force Base is often clear, on this particular 

day in December, the sky was hazy with moisture. While the Hyper TIT could be seen 

from the ground cockpit when it was overhead, it could not be seen through the haze 

when it was slanted at an angle three miles away. Without visual contact with the 

Hyper 111, Fischer had to rely on Thompson's comments to know how the vehicle was 

flying, Thompson steadily watching the gauges in the cockpit. 

On the final approach to landing, with Thompson calling out altitudes, Fischer 

strained to see the Hyper I11 through the haze. As the Hyper 111 broke through the 

haze at about 1,000 feet, Dick said, "I see it!" Thompson replied, "You've got it!" and 

switched control to Fischer's model-airplane control box. 

Noticing no response from the vehicle as control was transferred, Fischer deliberately input a roll to verify that he indeed had control before he executed the landing flare. Still monitoring the gauges, Thompson told Fischer that the vehicle was 

rolIing left, and Fischer replied that, yes, he had commanded it to roll. Now certain 

that the vehicle was responding to his control, Fischer used the pencil-sized control 

sticks on his box to bring the Hyper I11 level and complete the flare to a soft landing. 

The Hyper 111 slid safely to a stop on its three skids, landing on the lakebed in front 

of Fischer and Thompson in the ground cockpit. 

We were gratified by the successful first flight of the Hyper 111, having gotten the 

flight scheduled at our last possible opportunity for using the SH-3 helicopter before 

it was returned the next day to the Navy. Later, as quoted in a paper that I presented 

at an ATAA conference, Thompson described his experience flying the Hyper 111 from 

the ground cockpit. 

"During nIy first attempts to change the vehicle's heading," Thompson said, "the 

vehicle appeared to be marginally stable or even unstable in roll. Vehicle motions in 

response to roll-control input seemed to be erratic and much too rapid when compared 

to the simulation. When faced with a situation of this type in a flight or in a simulator, I have always found the best procedure is to let go of the control stick momentarily to determine whether the vehicle is inherently stable. The Hyper I11 motions 

damped immediately after the stick was released, indicating adequate levels of stability and damping. I had simply been over-controlling and exciting a pilot-induced 

oscillation. The over-controlling resulted from much higher roll-control effectiveness 

than had been predicted."Z

The lift-to-drag ratio of the Hyper 111 turned out to be lower than expected. Rather 

than 5.0 maximum, it proved to be 4. Thompson had had to stretch the glide as much 

as possible to bring the Hjper 111 close enough for Dick Fischer to be able to see it 

and land it. Twice, as Thompson pointed out, the flight had shown that a research pilot 

2. R. Dale Rrrd, "RPRVs: The First and Future Flights," Astronautics & Aeronazrti;rs 

12 (April 1974): 31-32. 
WINGLESS FLIGHT 

could use actual flight experience to compensate for significant deficiencies in or 

departures from predicted aerodynamic characteristics. 

Before the flight, Thompson had worried that the lack of motion cues, particularly during short-period motions of the vehicle, might hurt his performance in piloting 

the Hyper TI1 from the ground cockpit. "This apprehension was quickly dispelled 

once the vehicle was launched," Thompson said. "It seemed very natural to fly the 

gauges, just as in the simulator, and respond to what I saw rather than what I felt." 

What Thompson found surprising were his reactions during the flight. "I was really stimulated emotionally and physically, just as in actual first flights," he said. After 

noting that he had made the first flights in such "strange kehicles" as the 

Paresev and the M2-F1, he said, "Flying the Hyper 111 from a ground cockpit was just 

as dramatic." 

In explaining how the experience differed from flight simulators, Thompson said, 

"I have flown many different simulators with and without motion and visual cues, 

including centrifuge and airborne simulators. Although some provided a lot of realism, none stimulated me emotionally. I always knew I could hit the reset button, or in 

the airborne simulators, turn the vehicle back to the conventional testbed aircraft 

characteristics. There was no question with the Hyper 111. I, and only I, had to fly it 

down to the landing location." 

According to Milt Thompson, his experience in flying the Hyper 111 "tends to confirm the theory that responsibility rather than fear for personal safety is the real driver of physiological response."3

NASA Headquarters Says CCN~3' to Hyper 111 Piloted Flights 

Our single flight of the Hyper 111 produced good aerodynamic data and demonstrated that the vehicle was safe to fly. By early 1970, I had located in Arizona the 

ideal aircraft for launching the Hyper I11 in a piloted flight program, an Air Force 

Albatross SA-116B seaplane with low flight time that had never been in the water, had 

no corrosion, and was in excellent condition. The aircraft was available to NASA as 

Air Force surplus. The Albatross had sufficient structure, control authority, and performance capability for carrying the Hyper TII aloft under its wing at the 2,000-pound 

drop-tank location for air launch at 15,000 to 20,000 feet. 

Paul Bikle asked NASA Headquarters to substitute the Albatross for the C-47 

currently in use at the Flight Research Center as a utility aircraft. Trading the C-47 

for the Albatross on a one-to-one basis would involve no additional cost to aircraft 

operation at the Flight Research Center. We could also make better use of the 

Albatross than the C-47, for only the Alltatross could serve a dual purpose, being used 

as a utility aircraft when it wasn't being used in air launches. 

3. Quotations from the precedirtg four paragraphs all in Reed, "RPRVs," p. 32. 

165 
LIFTING-BODY RACEHORSES 

Retired M2-Fl, Hyper III, and remote control models on display. (NASA photo EC70 2450) 

Bikle's request was turned down. By 1970, NASA Headquarters was caught up in 

the throes of internal politics, flexing its muscles as it cut authority within the various 

NASA centers for planning their own research. Without a launch vehicle such as the 

Albatross, the Hyper I11 would never achieve piloted flight. In this way, the Hyper I11 

fell victim to political currents within NASA Headquarters. 

The Hyper I11 program had three strikes against it. First, it was too low-cost to get 

the attention and support of NASA Headquarters. Second, it had been flight-tested as 

an unpiloted vehicle first, taking away some of the luster it would otherwise 

have had if first flown as a piloted vehicle. Third, it was a variable-geometry 

configuration, making it less competitive in weight and complexity than the simpler 

lifting-body configurations. 

Paul Bikle was very upset when NASA Headquarters rejected his request for the 

Albatross. He saw the Albatross as a tool for the Flight Research Center and, as the 

director of the Center, he felt he should be able to select his own tools, especially 

when a tool was not going to cost NASA extra money. At the time, I think he was also 

seeing the writing on the wall, sensing that he no longer fit in the more bureaucratic 

NASA of the 1970s. It was only about a year later-on 31 May 1971-that Paul Bikle 

retired from NASA. 
Schernntic showing the X-ZJ/I ronrrrsion to the X-24B. This wns n cost-snving nppmtrch to us<, the snme systenls for both rorJigurcttions. 

A Racehorse of Another Color: the X-24B 

While we were still involved with the Hjper TIT, Alfred Draper and others at the 

Air Force Flight Djnamics 1,al)oratory in Ohio had come up with an idea for recycling 

the X-24A 1)y wrapping a new shape around it. The) found that the new configuration 

coul(1 achieve hypersonic* lift-to-drag ratios near 2.5, putting it into the same "rarehorse" category of lifting hodj as the Elqper TTT which, before its wing was drplojecl 

for landing, had a hypersonic lift-to-drag ratio near 3.0. The other lifting l)odies--thc 

M-2, HL-10, and X-24A-had hypersonic lift-to-drag ratios betwren 1.2 ancl 1.4. 

A distinct adtantage over the IIyper TIT was that the new X-24A urap-aroundshape designatetl the FDT,-8 could achiece a landing lift-to-drag ratio of at least 4.0 

without \ariaI,le geometry. The more slender shape of the Hyper IT1 gave it the higher hypersonic lift-to-drag ratio of the two lifting-bodj shapes. Hwever, the Hj-per TI1 

had a landing lift-to-drag ratio near 2.0, rnaking it necessaq to use a cleplolal)le wing 

to bring the vehic.lr7s subsonic lift-to-drag ratio up to near 4.0 for landing. 

A1 Draper and his colleagues at the ,4ir Force Flight namics 1,ahoratot-y 

l~clie\ecl that flat-1)ottomrd pointed shapes like the FD1,-8 woulcl prove to 1,e useful 

not only for sustained hypersonic-cmise aircraft using air-breathing propulsion hut 

also for unpowered boost-glide orbital re-entry vehicles capable of landing at 1 irtual1) any conhenient airfield. Furthrrnmore, the long flat under-surface of the FDL-8 

nould make an ideal conlpression ramp for the inlet of a future supersonic conm1)ustion ramjet engine operating at speeds tip to Matsh 8. 
1,IFTING-BODY RACEHORSES 

At Edwards, NASA director Paul Bikle and Bob Hoey, manager of the Air Force's 

lifting-body program, endorsed the idea. Always attuned to thrift, Rikle was in favor 

of ideas that saved government money by getting the most research out of each dollar 

spent, the same reason why he had readily endorsed my ideas for saving money by 

recycling rocket engines and sharing launch aircraft with other programs. 

,4t this point, a critical stunlhling block appeared. Major General Paul T. Cooper, 

chief of research and technology development for the Air Force, rejected the idea of 

using the X-24A as a basis for the test shape that would later be designated the X24B. Clearly opposed to the entire flight-test concept, he asked that the proposal be 

reviewed by a joint panel of the Air Force Scientific Advisory Board and the National 

Academy of Sciences. A1 Draper and Bob Hoey briefed the panel on the concept. The 

panel concluded that the Air Force could not afford to do without the project. Thus 

securely endorsed, the plan advanced rapidly. 

By the erid of -4ugust 1970, the directors of both the NASA Flight Research 

Center and the Air Force Flight Test Center at Edwards had agreed that such a program was worthwhile. However, Air Force Systems Command delayed approving the 

program until suitable arrangements had been made for joint funding by NASA and 

the Air Force. Paul Rikle asked John McTigue to work with Fred DeMerritte at NASA 

Headquarters to come up with the money needed to get the program started. Thanks 

to the teamwork of McTigue and DeMerritte, NASA transferred $550,000 on 11 March 

1971 to the Air Force to initiate acquisition of the aircraft. The Air Force pledged a 

similar amount. Finally, on 21 April 1971, the director of laboratories for Air Force 

Systems Command approved the program. On 4 June 1971, the X-24A completed its 

last flight. 

On 1 Janualy 1972, the Air Force awarded the modification contract to the Martin 

Marietta Corporation. A month later, on 4 February, Grant L. Hansen, the Air Force's 

assistant secretary of research and development, anti John S. Forster, Jr., the director 

of defense research and engineering, signed a memorandum of understanding 

between the Air Force and NASA on conducting the X-24B program as a joint 

Air Force/NASA lifting-body venture. The memoraridum was also signed by 

George M. Can; NASA's deputy administrator, and Roy P. Jackson, NASA's associate 

administrator for advanced research and technology. The memorandum marks the official beginning of the X-24B program. Modifying the X-24A into the X-24B meant that 

the new research aircraft would cost only $1.1 million. The same vehicle, built from 

scratch, might have cost $5 million. 

At the Air Force's Arnold Engineering Development Center, hypersonic wind-tunnel tests on a model of the X-24R indicated that the proposed shape performed well 

at those speeds. As usual, the big question was what would happen to performance 

when the vehicle decelerated to much lower velocities. Many, including Fred 

DeMerritte, expected surprises as the kehicle passed through the transonic range. 
WINGLESS FLIGHT 

X-24B as delivered to Edwards. Notice that the original X-24A is completely disguised inside of the X-24B 

shape. (NASA photo E73 25283) 

X-24B Shell Arrives at Edwards 

On 24 October 1972, the X-24B shell built around the structure of the X-24A 

arrived at Edwards Air Force Base, delivered by Martin Marietta's Denver plant. 

Systems for the X-24B were delivered separately. The structure had grown an additional 10 feet in span and 14.5 feet in length. It weighed 13,800 pounds at launch, the 

X-24A having weighed approximately 12,000 pounds. The X-24B had a 78-degree 

double-delta planform for good center-of-gravity control, a boat-tail for favorable subsonic lift-to-drag ratio, a flat bottom, and a sloping three-degree nose ramp for hypersonic trim. The sides of the forebody aft of the canopy were sloped 60 degrees relative 

to the Y-plane (lateral, or left-to-right, axis). 

The aerodynamic design features of the X-24B were quite distinct from those of 

the X-24A. Like the earlier lifting bodies, however, the X-24B also used several offthe-shelf components. Portions of its landing gear, control system, and ejection system came from the Northrop T-38, the Lockheed F-104, the Martin B-57, the 

Gmmman FllF, the Convair F-106, and the North American X-15. It had an LR-11 

rocket engine and Bell Aerosystem landing rockets. 

Although the basic systems in the X-24B were the same as those in the X-24A, 

several upgrades and additions were made in the propulsion system, control system, 

and nose landing gear. The LR-11 rocket engine was modified, the vacuum thrust 

increased from 8,480 to 9,800 pounds by increasing chamber pressure and adding 
1,TFTTNG-BODY RACEHORSES 

nozzle extensions. The engine started at a lower thrust lekel uith thrust increasetl after 

the engine was sta1)ilized. 

Ti+o outltoartl ailerons were added to the eight caontrol surfaces that had heen on 

the X-21.A. The HI,-10 also had ten control surfaces (the subject of the standing joke 

that HI,-10 stood for "Hinge Line Ten"). Thr tuo new control surfaces on the X-24B 

were used only for roll control uith a plus or minus five-degree pitch bias feature. 

Ur~like the X-24A, the X-24B's split upper and lower body flaps were not used for roll 

control. The pitch control arid shuttlecock hiasing of the X-24B, however, were the 

same as on the X-24A. The triplj-redundant rate-damping system used in the X-24A 

was retained in all three axes on the X-24B ~ith tariahle gain control by the pilot. 

Most of the other control system features of the X-24B, including the hjdraulic power 

supplj and rudder hiasing linked to the body flap hiasing for transonic stability, were 

the same as on the X-24A. TIie biasing on the X-24R could also be used bj the pilot 

for speed brake control. 

Basicallj the same automatic aileron-rudder interconnect system was used in 

110th the X-24B arid the X-24A, although the sjstem in the X-24R had more flexibility in operation. The amourit of interconnect bas autonlatically programmed as a function of angle of attack. As in the X-24A, the pilot could select two interconnevt 

angle-of-attack schedules, a high-gain one for transonic-supersonic conditions and a 

lower-gain one for control at suhsonic speetls. The pilot could also use a manual interconnect mode as backup to the automatic scheduling or for special test maneuvers. 

The X-24B rvtained the T-38 main landing gear that had been used in the X-2414. 

How-ever, unlike the X-24A, the X-24R used a modified Grumman F-IIF-1F nose 

gear. The combination resulted in an unusual arrangement of landing gear, similar to 

ljut not as extreme as that on the X-15. The main gear on the X-24B was significant1j aft of the landirlg center of gravitj, ant1 thr three-point attitude was nose low. 

The landing gear was a quick-acting (approximately 1.5 secontls) pneumatic system. 

The main gear tleployrd fonvartl, the nose gear aft, minimizing not onlj the movement 

in the center of gra\ itj but also the change in longitudinal trim. From the cockpit, the 

pilot could actuate the landing gear onlj to the down position. 

While the cockpit controls ant1 instruments were basicallq the same in both the 

X-24A and X-2 tB, the X-24B alone had an F-104 stick-shaker. The shaktlr actuated 

at 16 degrees angle of attack lo warn the pilot that the vehicle was approaching an 

area of reduced pitc.h stability. Later in the X-24B flight-test program, to pro\ ide additional sideslip monitoring for the pilot, an audio sideslip warning system was atlded. 

X-24B Team: Preparing for Flight Tests 

Following the end of the X-24A flight-test program on it June 1971, the X-2 1A 

crew, led by operations engineer Norm DeMar, was tlisbanded for 16 months while 

hlartin Marietta was contrac~tetl arid the X-24A was transformed into the X-24B. 

During this time het~vccn the disbanding of the X-24A crew and the formation of tht. 

Y-2ZB crm, DrMar lost his X-24A crew chief, Jirr~ Hankins, to thv neu Digital-FIj- 
BJ-Fire (DFRW) progani that, using an F-8 fighter as a test-bed, ~ould create the 

worltl's first fully digital fl1-hj-m-ire aircrdft (i.e., one ~tithout a mechanical hack-up 

system). In the F-8 fighter used in tllp DFRT program was a repr~~anin~ed version 

of the computer used earlier to control the Apollo Lunar T.andirig Yehicle, another 

example of the sort of cost-savings practiced at the Flight Researcall Center 1)j recycling equipment from earlier projects into new- ones. 

Man) of the X-24R crew recruited 1)) Nom~ Dr.Mar hatl cxuperience 14 it11 rocketponerecl aircraft, having 1)taen on the crews of either the X-244 or the X-15. Cliarlej 

Russell, a crew chief on the X-15, becanie crew chief for the X-24B. Tliree of the X24A tnrchanics-Me1 Cox, John Gordon, and Ray Kellogg-were assigned as well to 

the X-24R crew. Other X-24B crew members inclirtletl inspecator Bill Bastow, instrumentation inspector Dick Blair, and aircraft inspector Gaston Moore. 

DeMar atid the X-24B crew managetl to install systems in the X-24R and prepare 

for systenis tests 1)~ Fel)ruarS 1973, just three and a half months after Martin Marietta 

hatl tleli~eretl tlle X-24R as an empty shell. Rather than full-5t.ale wind-tunnel tests, 

a T eq detailed set of eleven types or grountl and raptitre-flight tests was sc-hetluled 1)) 

the two X-24B program managers, NAS.4's Jack Kolf anci the Air Force's Johnny 

Armstrong, to be done during the six months Iwtween Fe1)ruary and r\ngust 1973 

befort. the first glide flight. 

During strucatural resonance tests on the X-24R.s control system, we fount1 an 

unaccepta1)le resonance in the ailerons. It was a purely mechanical resonance, sustained solelj b) the acatuator and its linkage. To eliminate it, we adtIed a niechanical 

damper to the actuator's servo valve. 

We ran goutit1 kiljration tests on the horizontal and vertical tail surfaces to 

verifq flutter clearance margins. Since tlie results were significant1 j diffrhrrnt froni tlie 

predicted matlieniatical model user1 t)y Martin Marietta, w-e reran the flutter analjsis 

using tlie experimeritall~ determined moilel data, finding flutter margins to 

he adequate. 

To esta1)lish the relationships hetween applied loads and strain gauge responses, 

we did strucatural loads c.alihration tests on all ten mova1)le control surface~s as well as 

on the left fin and strake. For use later in interpreting flight results, we also measured 

the outputs of strain gauges and derived the appropriate load equations. 

As hatl been done on the earlier lifting bodies, the X-24R was hung at diffrrent 

angles to tl~termine the vehicle's center of gravit), then crosscheckrtl by weighing tlie 

veliic.le while it was l~alancecl on each wheel and tipped at larious angles. We usetl 

tlic "rocking ta1)le" technique to determine pitch and roll inertias. The vehicle was 

also hung on a (.able and oscillatetl, using springs attacahed at Ijoth ends of the 

~ehicle, to determine yaw inertia and the product of inertia, tlie coupling I~etween roll 

and 1 aw. 

On the X-24R, we expected very high landing-gear loads during X-15-like "slapdown" landings due to its long nose, fbrwartl center-of-gal itj relative to the location 

of the main gear, and its increased weight-1,800 pounds more than the X-2414. 

To pro\ itle adtlitional tire capal)ilitj, we had selcctrd 12-p1) T-38 tires for the X-2 1R, 
T,lFTIKG-BODY RACEHORSES 

rattler than the 10-ply tires used on the X-24A. During dynamic load tests on the tires 

at \X7right Patterson Air Force Base, however, the tread repeatedly separated from the 

tire casing at the anticipated loading. Later tests showed that shaving the tread from 

the tire through the first ply resulted in satisfartorj tire performance. As a result, we 

decided that a new set of shaved tires would be used for each flight of the X-24B. 

During hag-load tests on the main gear, we found that the down-load lock 

released when predicted drag loads were applied, ~hich coultl result in gear collapse 

cluring landing. The crew reworked the locking device so that it would maintain a 

securely locked position. 

We did "slap-down" tests on the nose gear to verify the strength of the new hackup structure as well as the energy-absorbing capability of the nose gear and new 

metering pins in the X-24B. For these drop tests, we elevated the nose of the vehicle 

with the main tires restrained and then released the vehicIe from increasing heights. 

To produce appropriate nose-gear drag loads, we rotated the nose tires with a spin-up 

device prior to each release. During these tests, the struc-ture and nose-gear performance proved to be satisfactory. 

Flutter while the X-24B hung in p-e-launch position under the wing of the B-52 

could cause structural failure on the B-52. Therefore, vibration tests were conducted 

on the B-52 ~ith the X-24B hanging in launch position that assured us that no flutter 

would occur in flight from the B-52's wing, the lifting-1)ody adapter, or the X-15 pylon. 

We ran a series of taxi tests with incremental increases in speed to test for nosegear shimmy, which we felt was possible due to the X-24B's nose-gear steering that 

made it distinctly tlifferent from the other lifting bodies. The other lifting bodies had 

had nonsteerable dual nose wheels that avoided all possible shimmj prot-jlems. Our 

primary concern with the X-24R.s nose-gear steering was that the nose gear or 

backup stn~cture might fail if severe \himmy occurred in the nose gear at touchdown 

on the first flight, given the dynamic load added to the already high landing loads that 

we e-ipected. 

Eight taxi runs were made at speeds from 40 to 150 knots, using the main LR-11 

rocket engines as well as the 500-F)ound hydrogen-peroxide rockets intended to help 

the pilot during the landing flare. The 1.50-knot run across the lakehed runway was 

made using approximately 4,000 pounds of thrust from tho 1.R-11 chanihers. Even at 

150 knots, the nose-gear steering and handling characteristics of the X-24B 

were found to be satisfactory, with no shimmy in the nose gear. However, lateral (-enter-of-gravitj was offset two inches cluring the test run, the liquid-oxjgen tank on the 

left side outwc.igliing by 1,000 pouncls the alcohol fuel tank on the right, making the 

X-24T3 l)ull to the left. The pilot was able to compensate for the offset with intermediate riglit ])raking. 

VCi. made a final taxi test to 80 knots on the take-off runway with the X-24B hanging uncle1 thr R-52. Both acceleronieter measurements and comments from the pilot 

verified that the ride was smooth and no problems coultl be pretlictetl. 

During the capti\e-flight test of the X-~ICR, Me had to exercise niuch greater care 

thdn we hat1 in captii e-flight tests of the other lifting bodies, for the pilot of the X-24B 
VETINGI,ESS FLIGHT 

coul(1 not ejec-t while the vehicle was matetl to the B-52. To obtain acceptable loads 

on the forward hook of the X-15 pylon, we located the X-24B adapter further aft under 

the pylon than we had with the other lifting bodies, a design compromise based on the 

proven safe operation of the X-24A. 

If there hat1 Le~n a problem during the captive flight, X-24B pilot John Manke 

would hace had to launch hefore he could have ejected safely. The B-52 was flown as 

slowly as possible during the climb to 30,000 feet, where stnrctural resonance tests 

were conducted at speeds higher than possible on the ground. Since tl~e X-24R was 

~ithin gliding clistance of the dr} lakebed during these tests, Marike could have landed the vehicle if it had broken loose or had had to he launched, hut no pro1)lerus 

occurred (luring the single captive flight. 

Flight Tests of the X-24B 

On 1 August 1973, John Manke pilotetl the X-24B on its first glide flight, launching from the R-52 at 40,000 feet, coasting eal-thw-ard at 460 miles per hour, performing a series of maneuvers to establi5h handling qualities, and executing a practice 

landing flare approach before making a 200-mile-per-hour landing on the lakebed. On 

the flight, the same flight-test maneuvers and evaluations were done that had heen 

done on flights of the earlier lifting bodies. During the series of glide flights that 

followed, Manke and Major Michael V. I,ove, the Air Force X-24R project pi lo^, 

checked the vehicle's performance in a variety of configurations. 

On 15 November 1973, John Manke piloted the X-24R in its first powerecl flight. 

Tjpical flight time in the X-24R was seven minutes, longer than in the other lifting 

hodies. As had don? before flights in the earlier lifting I)odies, Manke and Love 

completed pre-flight practices of numerous simulated approaches in the T-38 and 

F-104 aircraft. Bj the end of the X-24B project, lifting-hod} pilots had flown more 

than 8,000 such simulated approaches in support of the entire lifting-body program. 

On 25 October 1974, during the sixteenth flight of the X-24B, 1,ove reached the 

aircraft's fastest flight speed, Mach 1.75-or 1,164 miles per hour. On 22 May 1975, 

Manke made the X-24Bb highest approach arid landing, coming down to the lakehetl 

from 74,100 feet-more than 14 miles above the ea~-th's surface. 

Love and Manke were pleasantly surprised bj the handling qualities of the X-24B 

at all speed ranges, both with and ~ithout engaging the control dampers in the stahility augmentation syslen~. Even in turbulence, the X-24B flew surprisingly well. In 

subsonic handling qualities, the X-24B earned the ver) high rating of 2.5 on the Cooper-Harper pilot rating scale. In short, the X-24B was considered a fine airrraft. 

Manke and Love saitl the handling characteristics of the X-24R c-ompared favoraldy with those of the fighter aircraft, the T-38 and F-104. The X-24B's handling ant1 

riding qualities in tur1)ulence during the final approac+h werr sup~rior to those of the 

earlier lifting hodies. The high dihedral effect of [he other lifting 1)otlies hat1 created 

tlisconcerting roll upsets for pilots due to sideslips in turl~ulence. With its low values 

in effeco~ive dihedral, the X-24B rotle turhulenre with rnore of a side-to-side motion 
LIFTING-BODY RACEHORSES 

X-24B simulatingfuture Shuttle landings. The F-104 chase plane is behind and to the (pilot$) right of the 

X-24B. (NASA photo EC75 4914) 

that the pilots found more acceptable. The pilots also found the vehicle's dampers-off 

handling qualities in the landing pattern to be excellent, commenting that they could 

not believe the dampers were off.4 

Despite the fact that the X-24B was 1,800 pounds heavier than the X-24A, it had 

achieved a top speed of Mach 1.75 due to the lower configuration drag of the X-24B 

and a 15 percent increase in thrust from the uprated LR-11 engines. Although the X24A had reached Mach 1.6, it very likely could have achieved Mach 1.7 had its testflight program not been cut short to build the X-24B. 

X-24B Simulations of Future Shuttle Landings 

By the time that the Space Shuttle was well into the design phase, space mission 

planners wanted to know if such unpowered re-entry shapes with low lift-to-drag ratios 

could land successfully on asphalt or concrete runways. Convinced that the 

X-24B could successfully execute such an approach and landing, John Manke had 

recommended even earlier that the X-24B make a series of landings on Runway 

04/22, the main 15,000-foot concrete runway at Edwards. For John Manke, Mike 

4. See John A. Manke and M. V. Love, "X-24B Flight Test Program," Society of Experimental Test 

Pilots, Technical Review 13 (Sept. 1975): 129-54. 
WING1,ESS FLIGHT 

I,ove, and other pilots, such a (lemonstration seemed important for developing the 

confidence needed to proceed with similar landings of the Space Shuttle. 

In Januarj 1974, the X-24R research suhconiniittee had approved Manke's proposal. Afterwards, Manke and Love began a three-week flight program, flying the 

F-104 and T-38 in lantling approaches approximating those of the X-24R. Manke 

alone made over 100 of these approaches. 

The payoff came on 5 August 1975. Manke launched in the X-24B from the R-52 

mothership, climbed to 60,000 feet, hegan his descent, an(1-seven minutes after 

launch-touched down in the X-24B precisely at the planned target landing spot, 

5,000 feet down Runwaj 04/22. Aftenvarc14, Manke said, "We now knot+ that concrete 

runway landings are operationally feasible and that touchdown accuracies of + [plus 

or minus] 500 feet can be expected."i Assisting landing accuracy, Manke commented, were the distance markers and geographic features along the concrete runway, not 

characteristic at the time of the lakehed runways. Two weeks after Manke's first runway landing, Love ctuplicated the feat in the X-24B. 

These precise touchdourns demonstrated to the Shuttle program that a configuration with a comparatively low lift-to-drag ratio could land accurately without power, 

thereby convincing Shuttle authorities that they coultl dispense with the airl~reathing 

jet engines originally planned for the Orbiters. The resultant retfuction in weight 

added significantly to the Shuttle's payloatl. 

Of all the vehicles flight-tested during the twelve years of the lifting-body program, the X-24B had the highest landing lift-to-drag ratio, 4.5. Next highest was the 

X-24A at 4.0, then the HL-10 at 3.6. Lowest among the lifting bodies was the M2-F3 

with a landing lift-to-drag ratio of 3.1. Because of its relatively high lift-to-drag ratio 

plus good control characteristics, the X-24B was considered 1)y the pilots to be very 

comfortable to land without power. The lifting-body pilots also considered the M2-F3 

acceptable in landing charac.teristics, although the M2-F3 required more of the pilot's 

attention in landing, due to having less time from the flare to setting the wheels down 

on the runway. 

By the end of the X-24R program, we had gained witlespread experience with the 

unpowered landing characteristics of lifting-body configurations over a range of la~itling aerodjnamic perfornmance. In its maximlim "dirty" configuration-with flaps, 

deployerl lantling gear, speed l~rakes, and lo\\ levels of thrust-the F-104 had been 

used to train pilots in landing approaches for both the X-IS and lifting-hodp programs, 

beginning in 1959 uith NASA pilots Neil Armstrong (of Apollo farnr) and Joe Walker. 

During the course of these F-104 flights, the aircraft woul(1 be landed in the worst liftto-drag configuration-with flaps, gear, and speed 1)rakes extentled in idle powerthat approached a maximum lift-to-drag ratio of 2.5. Later tests conductt~tl by Rob 

Hoej and the Air Force pilots conc1iidt.d tllat landing without aids, a vehicle with a 

5. Ibid., p. 140. 
LIFTING-BODY RACEHORSES 

maximum lift-to-drag ratio of 2.5 bordered on the totally unacceptable-that is, a 

landing $+here the risk of crashing is highest. These test results in the F-104 served 

as a benchmark for the Flight Research Center while evaluating the different flighttested lifting-body configurations for future space operations. 

Landing performance and safety were critical as well in terms of the ablative heat 

shields used for re-entry vehicles before the development of such new heat-protection 

materials as the lightweight silicon tiles. Wk tailored the concept of the lifting body as 

a re-entry vehicle to the use of the ablative heat shields, the technology current at the 

time. As a result, landing performance and safety were linked to how the roughness 

resulting from the burned arid melted ablative heat shields would affect the aerodlnamic drag of the lifting bodies. 

VC'e had excellent data from flight tests at hypersonic speeds made during the 

X-15 program to use in predic-ting the magnitude of this effect for the lifting bodies, 

available in Lawrence C. Montoya's Drag Characteristics Obtained from Several 

Configurations of the MocliLf2ed X-1.5-2 Airplane up to Mach 6.7.6 The report 

compares the drag characteristics of a clean-surfaced X-15 with an X-15 flo~n with 

an ablative coating. We also had the results of a similar test done on the X-24A during the full-scale wind-tunnel testing of the vehicle at NASA Ames. Although the X24A was later flight-tested at the Flight Research Center only with a clean metal skin, 

the wind-tunnel testing of the X-24A with a coating simulating the ablative roughness 

typical after the heat of re-entry showed a significant reduction for the vehicle in landing lift-to-drag ratio. This reduction, in turn, would reduce significantly the time a 

pilot would have for making corrections in control during an actual landing of a 

lifting-body re-entry vehicle. 

When we used the ablative roughness data from the X-15 and the X-24A tests to 

calculate the aerodynamics of lifting bodies with ablative roughness, we found that 

some lifting-body configurations previously found to be acceptable for flight would 

become unacceptable as re-entry vehicles with ablative roughness. The ablative 

roughness after the heat of re-entry would cause the drag of lifting bodies to increase 

between 15 and 30 percent, lowering the lift-to-drag performance. As a result, for 

example, the 3.1 lift-to-drag ratio of the M2-F3 would be lowered to less than 2.5, 

making the M2-F3 unacceptable as a re-entry vehicle unless considerable care were 

taken to use the correct heat-protection materials in certain places, such as carboncarbon rather than ablative material on the leading edges. Likewise, the HL-10's liftto-drag ratio of 3.4 would drop to a ratio that would make it barely acceptable in 

re-entry. With ablative roughness added, the only lifting bodies that would retain adequate lift-to-drag ratios would be the X-24A and X-24B. 

When Bill Dana made the last powered flight of the X-24B on 23 September 1975, 

the lifting-body program drew to a close. After Dana's flight, six pilot familiarization 

6. Lawrence C. Montoya, Drag Characteristics 0btairzedfronr Several Configurations ofth~ 

,Norhi~dX-ls'-Z .4irplr1ne up to .Mach 6.7 (Washington, DC: NASA TM X-2056, 1970). 

1 76 
WINGLESS F1,IGHT 

glide flights were made in the X-24B by Air Force Captain Francis R. Scobee and 

NASA's Einar Enevoldson and Tom McMurtry. On 26 November 1975, piloted 11y 

McMurtry, the X-24B completed its 36th and final flight. Through the spring of 1976, 

before being sent to the Air Force Museum, the X-24B remained in residence at 

Edwards Air Force Base, resplendent in its blue and white paint scheme. 

CHAPTER 9 

WINGLESS FLIGHT LIVES ON 

'Klien Tom M(8Murtrj landed the X-248 for the la51 time in No\en~l~er 1975, 

NASA's lifting-1)otly program officially eniled. Yet the legacy of winglesi flight has 

lived on, continuing to have a significant impact on the design ant1 techriology of current arid developing \chicles. In the 1980s and 1990s, the lifting-botl) legacy went 

international as Russia, Japan, and France began to design ant1 test lifting bodies. 

During the earl) 1990s, the USA began to dt.velop lifting-1)odj designs for use as 

spare-station transports, as spacecraft, anti as a future replacement of the current 

Space Shuttle. 

Today, meanwhile, the original lifting-hody \~ehic.les flight-~ehtetl at the NASA 

Flight Research Center in the 1960s arx1 earl) 1970s are all in museums, in outcloor 

mounted displa)~, or in the process of heing restore(1 for future pul~lica clisplays. 

The first lifting 1)otl)-the M2-F1, fontfly dubt)ed "the fl)ing 1)athtub"-was 

stored out(1oors at N4SA Drjden for several years. It Isas daniagr~rl when it has blown 

over by the wind, but it was in the process of heing restored as these lines were writtm. Several of the craftsnlen who built the M2-F1 have contributed their time ant1 

lahor in restoring it to its exact origillal condition. E\entually, the M2-F1 may conceivablq join the M2-F3-the third lifting hodq, built from the crashed M2-F2-at the 

Snlithsonian National Air and Space Museum in Washington, D.C., where the M2-F3 

now hangs from the ceiling. 

The HL-10 is currently on display outdoor5 at NASA Dryden, mounted atop a 

petlestal. Earl~er, the HL-I0 hat1 been se~erel) (lamaged when it was dropped b) a 

crane that has lifting it off a truck for displa) at the 1,os Angeles Museum of Science. 

The nose antl vertical tails were smashed when the HL-10 hit the ground. Fortunatel), 

no one was hurt in the accideni. However, those of us who had worked on the liftingl)ody program were unclerstantlahly upset with the Museum's crane crew and handlers, 

given the HI,-1% illustrious flight-test record of 37 flights ~vithout mishap or damage. 

Jerq Reed) and his expert team in NASA Dqden's "Skunk Qkrks" sheet-metal shop 

repaired the HI,-10, tloing the work in their spare time. Rcxitorctl to its original condition, the HI,-10 was carefully and sturdily mounted on its current prdrstal tlisplaj 

at NASA Dryden, nevrr again to be lifted t)y a crane. 

For several )ears, the Hyper I11 was stored outtloors at NASA Drjden, along with 

the M2-Fl. Fully restored by the Air Force, the Hyper 111 now hangs from the ceiling 

in the Air Museum at Castle Air Force Base near Merced, California. 

The X-24R is in the Air Force Museum at Wright Patterson Air Force Base in 

Daj ton, Ohio. The original X-24A was converted into the X-24B, hut to show what the 

X-24A looked I~ke, amocketl-up SV-SJ configured as the X-24A is displayed next to 

the X-24B. ASSET antl PRIME, rerovered following surcessful re-entries, are also 

tlisplajed near the X-24R. 

- 

- 
WINGLESS FLIGHT LIVES ON 

M2-F1 being disassembled for restoration in 1994. People from viewerk left to right: Bill Dana, Dale Reed, 

Dan Garrabrant, Dick Fischer, and Dick Klein, all of whom participated in the original lifting-body 

program. (NASA photo EC94 42484-2) 

Lifting-Body Concept Goes International 

The NASA lifting-body program has been well documented in about 100 technical reports on the program's 222 flights and 20,000 hours of wind-tunnel tests. Many 

of these publications are unclassified. The Soviet Union purchased copies of these 

reports from NASA Headquarters in Washington, D.C., then designed its own lifting 

body. In 1982, the Soviets flight-tested an unpiloted, 10-foot-long, subscale version of 

their lifting body, the BOR-4, including a maneuvering re-entry over the Indian Ocean 

from space orbit. The flight test of the BOR-4 closely resembled that of our PRIME 

(X-23) vehicle in 1966. The main difference between the two was that the BOK-4 was 

parachuted into the Indian Ocean for ship recovery, while the PRIME had been 

snatched from the air by a C-130 to avoid a splash down in the Pacific Ocean. There 

is no information available yet on whether the successor states of the former Soviet 

Union continued their work in the 1980s into larger-scale lifting bodies. 

Other than the Soviet flight experiments with the BOR-4, very little lifting-body 

design activity seems to have occurred in the 1980s. In the United States, the ShuttIe 

satisfied all requirements for space flight. Even though the Soviets had built a copy of 
our Shuttle, the) flew it only once (unpiloted) and continued to re14 on parachute 

recovery for their spacecraft. 

As the concept of an International Space Station emerged in the United States and 

other countries, however, interest revived in lifting-body configurations. 

Countries involved in or entering space exploration accepted that the International 

Space Station was required if mankind were to maintain a presence in space in 

preparing to send human beings to Mars and other planets or to revisit the moon. 

Smaller vehicles costing less to operate would be needed over many decades for the 

International Space Station. The small, compact shapes of lifting-body configurations 

began to show up on engineering sketch pads and drawing boards for use as space ferries or emergency lifeboats. 

Other countries entering the realm of space technology have also demonstrated 

interest in lifting bodies for various projected space missions. For example, the 

Japanese conducted hypersonic re-entry flight tests with parachute recovery during 

February 1997 of the HYFTXX, an unpiloted lifting body. The French also have indicated that they are doing mission studies using lifting bodies. 

HL-20 Lifting-Body Space Ferry 

During 1990-1995, NASA Langley conducted studies on a new lifting-body 

shape designated the HL-20, designed to meet the projected need for a low-cost transportation system to ferry personnel between Earth and future space stations. As part 

of the NASA Langley study, personnel at North Carolina Agricultural and Technical 

University and North Carolina State University built a full-scale mockup of the 

HL-20 in 1990. 

nesigned to carry ten people into orbit and back, the HI,-20 would be considerably smaller and lighter than the present Shuttle, the large size of the Shuttle being 

unnecessary for many of these future missions involved with transporting personnel to 

and from space stations and with delivering supplies to space stations. The projected 

HL-20 would be only 31 feet long and weigh 32,448 pounds, considerably smaller and 

lighter than the Shuttle, which is about 122 feet long and weighs over 171,000 pounds 

without its propellants, external tank, and solid rocket boosters. The HL-20 would be 

boosted into orbit by a Titan 111 rocket system, a system smaller than the Shuttle's 

rocket system. 

National Aerospace Plane, the X-30 Lifting Body 

During the first half of the 1990s, while NASA Langley was conducting studies on 

the HL-20, several government organizations including NASA were conducting substantial studies on the design of a National Aerospace Plane (NASPIX-30) capable of 
WINGLESS FLIGHT IdVES ON 

taking off from an aircraft runwaj, fljing into space, and returning to Earth for a landing on an airport runway-all ~ithoi~t theuse of rocket I~oosters. Of tht, various configurations studied, a fo~m of lifting hody emerged that ir~tegi-ated a hypersonic 

air-1)reathing propulsion system M ithin the vehicle's shape. However, the NASP stutlj 

was terminated in 1994, when it was conclutlt~d that the high-temperature materials 

ant1 air-breathing prop~~lsion technology required for such prolongetl high speeds 

within Earth's atnioiphcre noultl take many more years to mature than hall originally 

been estimatecl. 

Ne~ertht~less, N.4SA contitlued efforts on its own towanl de\elol,ing a space 

transportation sjstem that woultl eventuall~ replace the Shuttle. Opting to stay with 

rockel-~)ropulsion sjsterns, NA4SA required a design that would etnphasize maximum 

efficiency, combining a veq efficirnt single-stage-to-ohit vehicle with an ad\anced 

rocket-engine sqsten~ 1)uilt into the vehicle's shape. 

From X-33 to Venturestar 

In 1994, NASA solicited proposals from the aerospace industry for designing and 

1)uilding a highly efficient single-stage-to-orhit vehicale to rrplatae the Shuttle. Three 

proposals were submitted, one each from McDonnell Douglas, Rockwell Aerospace, 

and Lockheed Martin. 

M(.DonneIl Douglas submilted a design for a lifting 1)otlj that took off ierticallj 

and lantfed verti(*ally on its tail. The design was reminiscent of Disneylantl's Future 

Space Ride, lier re niillions of tourists have sat in a simulator cabin watching a screen 

showing the spacecraft lifting off a launch pad and returning to the pat1 on landing, a 

procedure very simiIar to that shown in the Buck Rogers movies of the past. 

MrDonnell Douglas built ant1 flew a scale model of its proposetl DC-X rocket to prove 

that it could indeed take off and land vertically on its tail. 

Rockwell Aerospace proposed a design tha~ was a conservative but highlj refined 

remake of the current Shuttle. The proposed vt~hicle hat1 wings, could Le propelled 

into space xerticallj without drop-off lwosters, and could land horizontally. 

Ry contrast, the design proposed 1)) Lockheetl Martin pushed the state-of-the-art 

in rocket propulsion, integrating a rocket Inotol design within the shape of a liftinghody spacecraft. NASA decidecl that this proposal reduced risk more than the other 

two alternatives. AS a result, NASA awartled a contract valued at ahout $1 1)illion from 

1996 through 2000 to the Locklieetl Martin Skunk Vorks in Pal~ntlale, California, for 

building and flight-testing the X-33, a 67-foot-long prototype model of tlie projec-ted 

127-foot-long JTerltureStac The X-33's emptq weiglit will l)e ahout one-ninth that of 

VentureStai. The 2,186,000-pound lift-off height of the proposed V~ritureStar is about 

one-half of the 4,500,000-pountl lift-off weight of the Shuttle. 

Acc.ording to Dap id Crie, then manager for high-speed programs at the Z,ot.kheecl 

Martin Skunk Works, his firm had put together a design that would launc-11 irerticallj 

like a rocket and larlcl horizontally like an airplan?. Lockheed Martin hat1 tlec,itlrd 

against a horizontal take-off because tlie weight of the undercarriage woul(1 limit the 
WINGLESS FLIGHT 

X-33 Advanced Technology Demonstrator designed to demonstrate injlight the new technologies needed for 

a Reusable Launch Vehicle for the 21st century. The X-33 employs a lifling-body shape. (NASAphoto EC96 

43631-2) 

payload severely. Vertical landing was rejected because the vehicle would have to 

carry fuel for landing throughout flight.1 

Wings were also eliminated during the design process. Although a lifting body is 

not as efficient as a winged aircraft at producing lift, the advantage of a lifting-body 

design for VentureStar is that-minus fuel and payload-the vehicle will be very light 

when landing back on Earth, light enough to land on an 8,000-foot-long runway, which 

is shorter than those found at most major airports today. Another significant feature of 

the lifting body is the large amount of storage area. 

The X-33 prototype as well as VentureStar will use the "aerospike" rocket engine 

developed by the Boeing Company's Rocketdyne Division of Canoga Park, California. 

Whereas conventional rocket engines have round bell-shaped nozzles, the aerospike 

engine uses the changing ambient air pressure as the rocket ascends to regulate the 

1. See, e.g., Bill Sweetman, "Venture Star: 21st Century Space Shuttle," Popular Science (October 

1996): 4% "Reusable Launch Vehicle," in Spinof1996 (Washington, D.C.: NASA, [1996]): 30-31 for 

printed accounts of the X-33 and Venture Star plans, which were still in the developmental stages as this 

account was written. David Urie read this section for the author and expressed his satisfaction with its 

accuracy. In addition, Stephen D. Ishmael, Deputy Manager for X-33 Flight Test and Operations, representing NASA at the Lockheed Martin Skunk Works in Palmdale, read the section and offered some 

changes that have been incorporated in the narrative. 
WINGLESS F1,TGFIT LIVES ON 

shape of the exhaust plume. The conventional nozzle, on the other hand, operates at 

its highest level of efficiency onlj at a single altitude. 

In the 1960s, Rocketdjne developed a rounded aerospike nozzle, leading to the 

"linear aerospike" engine in 1972, with the gas stream exiting along the surface of a 

rectangular wedge rather than around a round spike-shape. Its designers hoped that 

NASA would use the new engine to power the Shuttle, but NASA opted at that time 

for a more conservative design. The engine fairlj much sat on the shelf until Urie and 

his colleagues at Lockheed Martin mated it with a lifting-body design in creating the 

X-33 ant1 Venturestar's initial designs. 

Seven of the linear aerospike engines will be arrayed across the entire trailing 

edge of VentureStar, the engines blending into the lifting-body shape. According to its 

designers, this arrangement will cause less drag in descent than that caused by a cluster of conventional engines. As with most rockets, VentureStar will be steered during 

ascent by vectoring engine thrust. However, unlike conventional rockets that move on 

g~mbals, Venturestar's engines are fixed, the rockets' automatic flight-control system 

adjusting the throttle on each engine's upper and lower modules to steer the vehicle. 

Beneath the rocket's carbon-fiber skin, tanks on each side carry liquid hjdrogen. 

A smaller tank in the nose contains liquid oxygen, which mixes with the hydrogen for 

combustion. Located in the niitldle of the vehicle is a 45-by-15-foot payload bay. 

The vehicle has been designed to lift 40,000 pounds of payload to low Earth orbit 

arid 25,000 pounds to the higher orbit occupied by a space station, most of the liftoff 

weight consihting of the liquid hjdrogen and oxygen propellants. With the airframe, 

engines, and flight-control systems making up only nine percent of the proposed \chicle's 2.2 million-pound liftoff weight, science writer Rill Sweetnian has said 

VentureStar is "roughly equivalent to a 20-pound racing bike carrying a 200-pound 

rider."2

I,aunching VentureStar should be dramatically different from today's space 

launches of the Shuttle, with consideral~lq savings in tirne and materials as well as 

increased safety. iTentureStar will not use the solid rocket boosters that, with the current Shuttle, must be fished out of the ocean and rebuilt after each Shuttle fllght. 

Furthermore, Venturestar will use a metal heat shield, eliminating the 17,000 hours 

of between-flights maintenance currentlj involved in checking and replacing heatresistant ceramic tiles on the outer surface of the Shuttle. 

Because of the large surface area of the lifting bodh its designers expec-t 

Venturestar to re-enter Earth's atmosphere more gently than does the current ShuttIe. 

Unlike the Shuttle's maneuvering thrusters, which use hjpergoIic. propellants that 

ignite on contact with one anothel; VentureStar will use onlj liquid hydrogen and oxygen for propellants. Unlike the Shuttle, VentureStar will have no hydraulic system, 

using electricallj powered flight controls, doors, and landing gears. 

2. Sneelman, "Venture Slar." p. 46. 
WINGLESS FLIGHT 

Currentlq, Shuttle launches can be delayed when NASA engineers discover a 

glitch in a satellite payload already loaded onto the launcher. VentureStar bypasses 

this potential problem by using a self-contained canister as a payload hay. The satellite's manufacturer will load it into the canister, test it, and deliver it to the NASA 

launch site. 

The currently cumbersome job of assembling the Shuttle vehicle on a vertical 

tower is eliminated with VentureStar, for the vehicle will have no boosters or external 

tanks. This will allow VentureStar to be checked out in a hangar, like an airplane. 

Furthermore, VentureStar is expected to be safer than today's rockets, its design 

reducing the potential for catastrophic problems. While conventional rockets are 

doomed if an engine fails in flight, VentureStar's engines have a thrust reserve for 

emergency use. If one of VentureStar's seven engines should fail on liftoff, the engine 

opposite it would shut down to balance the spacecraft, the remaining five engines then 

throttling up to cany the vehicle safely into orbit. 

Employing a reusable rocket in the design of VentureStar is not only safer but 

friendlier to the environment. Its exhaust is comprised of water vapor, not the chemical wastes produced by a solid rocket, and there are no spent boosters to create a trail 

of debris behind the rocket. 

Flight-testing the X-33 prototype is expected to resolve certain critical issues 

before Lockheed Martin begins to build the full-scale VentureStar, For instance, 

although the X-33 will not fly to orbital speed, it will fly fast enough to test the aerodynamics and metal heat shield under realistic conditions. 

As in the X-15 and lifting-body programs between 1959 and 1975, NASA Dryden 

will play a major role in flight-testing the X-33. The plan is to begin flight-testing the 

X-33 at Edwards Air Force Base (AFB) in 1999. The X-33 is expected to reach Mach 

3 on its first flight before landing at one of the small dry lakebeds northeast of Edwards 

AFR. Fifteen flight tests are planned at speeds up to Mach 15, mostly between 

Edwards AFB in Southern California and Malmstrom AFB near Great Falls, Montana. 

Designing and building VentureStar is expected to begin in 2000, and the partners in the venture hope it will fly in 2004 as a commercial vehicle. The second 

VentureStar, ready for flight by 2006, might be the first to cany astronauts. Tf 

VentureStar proves it can fly as often as is currently projected, possibly only three or 

four vehicles would need to be built. Once VentureStar is fully operational, there likely will be a number of VentureStar launch and recovery sites around the world, each 

site considerably smaller than today's launch sites." 

3. Sweetman, "Venture Star," p. 47; "Rrusak)lr 1.aunc.h Vehicle," Spinoff 1996, p. 31. 

185 
WINGLESS FLIGHT LIVES ON 

Space-Station Rescue Vehicle 

In 1992, I met up again with my old friend John Kiker at an annual international 

parachute conference in San Diego, California. Years ago at the NASA Johnson Space 

Center, Kiker had been responsible for developing the parachute systems used in the 

Gemini and Apollo programs. He had long since retired from NASA but was working 

part-time as a consultant to NASA on the design of parachute systems for spacecraft. 

Kiker introduced me at the conference to Rob Meyerson, the young engineer who 

at that time headed parachute research and development at the Johnson Space Center. 

Over lunch, Meyerson told me that there was interest at the Johnson Space Center in 

developing a lifeboat that would remain attached to the International Space Station for 

use in case of a need for emergency evacuation. 

Ideally, Meyerson said, the lifeboat would be totally automatic in flight, from deorbit through re-entry and landing. Something more efficient than the Russian Soyuz 

two-to-three-person re-entry vehicle, recovered with a symmetrical parachute, was 

desirable. The ideal space-station lifeboat for Meyerson and his colleagues at the 

Johnson Space Center would use a guidance system allowing personnel to quickly 

punch landing coordinates into the lifeboat's onboard computer before or after boarding the vehicle. After the lifeboat had separated from the space station, onboard computers would fire the retro rockets at the right time during orbit for landing at the 

designated site on Earth. 

Dale Reedpictured with the X-38 technology demonstrator for a crew return vehicle from the International 

Space Station and the subscale model used in a test program for the X-38. (NASA photo EC97 44152-5) 
WINGLESS FLIGHT 

A lifting-1)ody design woultl allow the lifeboat to flj (luring re-entq to a landing 

site 700 to 800 miles left or right of the orbital path. After the vehicle had deceler~ited to sul~sonic speed at about 20,000-feet altitude, a series of parachutes woul(1 he 

cleployed-symmetrical deceleration cohutes followed 1)y a large, rectangular-shaped, 

gliding parafoil parachute. With a gliding ratio of about 3.5 to 1, the parafoil parachute could be steered left and right bj two lines attached to winches inside the \ ehicle. Global Positioning System (GPS) satellites would provide na~igation to the 

landing site. 

At an altitude of about 1,000 feet, the on1)oard computer would command a lanrling pattern with a tlownwind leg, hase, and final approach into the wind. Using a sonar, 

radar, or laser altitude ground sensor, thr computer would then commatltl both uinches to reel in the trailing edges of the parafoil parachute. Nekt, a landing flare maneuver uould reduce the parachute sink rate from ahout twent) fret per second to less 

than five feet per second. With a parachute loatling of about two pounds per square 

foot, the no-wind gliding speed would be about 40 miles per hour, blowing at toucbhdown to less than 30 miles per hour. Such low speed at landing ~ould allow the rehicle to touch down off-runway, such as on any flat field free of obstarles. 

After Meyerson had related this information to me, I mentioned that 1 11ad been 

involved in some model flight tests of this concept in 1969 at the NASA Flight 

Research Center, except we had used the limp Rogallo Parawing gliding parachute 

with lifting-1)odj shapes rather than the parafoil gliding parachute (see Chapter 8). 

Fascinated by the idea of GPS guidance, I told Meqerson that I woul(1 like to prove the 

concept by air-launching a lifting-body model as I had in 19G9. After Mejerson 

returned to the Johnson Space Center, hr had $150,000 sent to NASA Dl-).den so that 

I coul(1 put together a team to demonstrate the recovery concept using a 

subscale model. 

During the spring of 1992, we began the test program. B) the end of summer, 

using a team of four and working part-time, we hat1 achiexed fully autonomous flight, 

including flared lantling into the wind at a predeterminecl landing site in the Mojave 

Desert. Alex Sim served as NASA research project engineer. I did thr design work and 

flight-planning. Jim Murray handled the electronics and data analysis. David Neufelcl 

not only did the parachute rigging and packing but also senlet1 as radio-control pilot 

when the autonomous giding system was disengaged during tle\relopmental 

flight-testing. 

Neufelrl became so enthusiastic about his role as pilot that he took skq-di~ing 

lessons to learn more ahout controlling parafoil parachutes. He made onlj two staticline jumps during his skj-diving lessons, hut both were stand-up landings in the center of the 600-foot circle used as a landing zone. I asketl him whj he hadn't made more 

jumps. He told me that he had learned from the two jumps all that he needetl to learn 

about piloting the model, so why push his luck? 

To study the feasihilitj of the system, 1c-p used a flight motlel of a spacecraft in the 

generic shape of a flattened 1)iconic (an ol~ject shaped like two cones uith their 1)ases 

together). The model weighted al~out 150 pountls and was flown under a commercial 
WINGLESS FLIGHT LIVES ON 

ram-air parachute. Key elements of the system included GPS navigational guidance, 

flight-control computer, ultrasonic sensing for terminal altitude, electronic compass, 

and onboard data-recording. 

The vehicle was developed and refined (luring the flight-test program. It completed autonomous flight from an altitude of 10,000 feet and a lateral offset of 1.7 miles, 

ending with a precision flare and landing into the wind at the predetermined site. At 

times during autonomous flight, wind speed nearly equaled vehicle airspeed. We also 

evaluated several novel techniques for computing winds postflight. In September 

1993, we pu1)lished the results of these tests in NASA Technical Memorandum 4525, 

The Development and Flight Test of a Deployable Precision Landing System 

for Spacecraft Recoz~e ry .~ 

This was the first time I had worked with a fully autonomous air vehicle. I found 

myself talking to it as if I were coaching an onboard student pilot. As the model 

reached a planned turning point in the sky, I would say to it, "Now turn! Now turn!" 

As it approached for landing, I found mjself telling it, "Now flare! Now flare!" 

Meyerson discussed the results of our model testr with John Muratore, an engineering colleague at the Johnson Space Center. Muratore had recently become famous 

for organizing a "pirate team" that developed a low-cost spacecraft control room by 

using personal computers. His control room had just been pressed into service to 

operate the Shuttle in flight, saving NASA millions of dollars through fewer controllers 

and substan~ially lower maintenance costs on computer and display systems. 

Muratore became veq interested in the lifeboat concept and presented it to NASA 

Headquarters, enhancing his proposal by selecting a tried-and-proven lifting-body 

shape-that of the X-24A-for the lifeboat development program. The X-24A was the 

only lifting body that hat1 been proven in flight from near-orbital speeds to horizontal 

landing. Although the unpiloted X-23 PRIME had demonstrated maneuvering flight 

from orbital speeds down to Mach 2, it was the X-24A that had then demonstrated 

flight from Mach 2 to subsonic landing speeds. 

His selection of the X-24A lifting-body shape also saved on costs, avoiding the 

need to develop a new spacecraft shape. NASA Heatlquarter:, bought the idea that 

Muratore would prove the concept in low-cost steps to help in making management 

decisions for later steps leading to launching a prototype into space. 

Muratore telephoned me to see what I thought atlout the proposal and stipulation, 

especially tthether I thought NASA Dryden would be willing to qupport the Johnson 

Spare Center in a low-cost, full-scale flight demonstration of the lifting-hocly parafoilparachute-recovery concept. I said that during the lifting-body program, the NASA 

4. 41e\ G S~nl, James E Murra), Da\ld Neufeld, and R Dale Rercl, The Det*elopment und Flight 

Teat of u Dc~~~loycrble Precision Idartding System for Sparrtruft Rerot-ery Pdshlngton, D C.. 

NASA Tkf 452.5, 1993) Rot11 John Muratore, U4SY- projec t manager for the X-38 at the John+an Spare 

Center and E~lllarn I1 (R111) Dana, Drjdenh chirf rngneer ant1 formerl~ft~ng-lmd\ p~lot, read IIII~ chapter, as did Grdy Creerh, Dqden aerospace projects ~r~lt.r The narratne ha< been lrnpro~etl In seve~dl 

I)lc~(.es h) the~r cornrn~nt- 
WINGLESS FLIGHT 

Flight Research Center had spent twelve years proving lifting bodies in horizontal 

landing. Consequently, NASA Dryden tended to be biased in favor of landing lifting 

bodies horizontally on runways rather than using a gliding-parachute landing. Later, 

during a telephone conference among Muratore, NASA Dryden director Ken Szalai, 

and Szalai's management st&, this bias became apparent, especially with Bill Dana, 

one of the world's most experienced lifting-body pilots, now serving as Szalai's chief 

engineer. 

Muratore explained to Szalai and the others that studies at the Johnson Space 

Center had clearly shown that the lifeboat concept utilizing parachute recovery was 

the most effective in cost and time for rescuing astronauts from the International 

Space Station. During the studies, Muratore's team had considered several different 

basic schemes, including a capsule and a horizontal-landing mini-shuttle. With a capsule, to land at an acceptable site, astronauts might have to wait as long as 18 hours 

in orbit, substantially increasing life-support requirements for the vehicle. With a 

mini-shuttle, on the other hand, the tail would lose control authority, "blanked" by the 

high angle of attack during re-entry into Earth's atmosphere, requiring complicated 

maneuvering engines. 

Muratore also explained the added costs involved with both the ocean recovery of 

parachuted capsules and the horizontal landing of high-speed lifting bodies. The first 

involves the high cost of maintaining ocean ships to rescue the capsules. The second 

involves the maintenance of long runway landing facilities. 

X-38 suspended under the pylon that would attach it to the B-52 mothership for later captiveflights and 

launches. Note that the X-38 has an X-24A shape. (NASA photo EC97 44105-29) 

189 
WINGLESS FLIGHT LIVES ON 

X-38 suspended under B-52 0008 on its first captiveflight, July 30,1997. (NASA photo EC97 4416316) 

To keep lifting-body landing speeds low, Muratore explained that the vehicles 

would have to be either lighter or larger in size for the same weight. However, the 

larger lifting bodies would not be compatible with current rocket launch systems, such 

as the Ariane 5, Titan 4, and possibly the Atlas 2AS, Delta 3, H-2, Proton D-1, or 

Zenit as well. The 24-foot-long X-24A, for instance, had usually landed after fuel 

exhaustion at a weight near 6,000 pounds, although Bill Dana said he once made an 

emergency landing in the M2-F3 with a gross weight of 10,000 pounds. 

To be compatible with boosters, Muratore said, the lifting-body spacecraft recovery vehicles must be kept small but weigh 16,000 pounds or more due to internal systems and payloads. A lifting body with such high density would normally require 

extremely high horizontal landing speeds, too high to be acceptable to Muratore's 

lifeboat designers. However, the use of a large parafoil gliding ~arachute could reduce 

landing speeds to a very low 40 miles per hour, opening up the potential for off-mnway landings around the world. 

Szalai's team agreed to commit NASA Dryden to helping Muratore and the 

Johnson Space Center with the program. Szalai asked how Dryden could help. 

Muratore asked that it furnish and operate its B-52 for launching the Johnson Space 

Center's experimental vehicle at Edwards AFB. Szalai agreed. 

According to the agreement, Dryden would design and build a wing pylon so its 

B-52 could cany the experimental vehicle aloft. Besides operating the B-52, Dryden 

would also furnish its ground and hangar facilities and be responsible for personnel 
WINGLESS FLIGHT 

ant1 range safety. Johnson Space Center, on the other hand, would he rrsponsil)le for 

designing and fal~ricating the experimental vehicle or vehicles. In this u-a]-, a new lifting-1)otly flight-test program-the X-38--came to NASA Drjden, its first in nearly 

tw enty years. 

For l)uil(ling three full-scale fiberglass models of the X-38 lifting I)otlj, the 

Johnson Space Center contracted with Sraled Composites, Inc., Burt Rutan's little airplane factoq in Mojave, California, not far from Edwards AFB. The three kehicles 

includetl one without fins for launching from a C-130 plus two with fins and control 

surfaces for launching from the B-52. 

In the spring of 1995, uith the assistance of the Arnly, the first ~ehicle was 

launchetl from a C-130 over the parachutt.-testing range at Yuma, Arizona. An eutracntion chute pullet1 the finless lifting-hody on an aluminum cargo pallet rearward from 

the C-130. Tmmetliatelj after launc.11 from the C-130, a pro1)lem developed with the 

cargo pallet and the parachute rigging. The pull from the extraction chute deformed 

the cargo pallet, causing parachute rigging deflections. Out-of-sequence line cutter 

and parachute deployments followed. The parachute sjstem became entangled, and 

the first X-38 cehicle was tlestroyed on ground contact. 

Scaled Composites, Inc., completed the other two X-38s in the fall of 1996, drlivering them to the Johnson Space Center for systems installation. Flight tests began at 

NASA Dq (fen in the summer of 1997. 

Bj the end of 1997, it is hoped that a successful flight demonstration can be 

made-launching an X-38 from the B-52 at 45,000 feet, the X-38 then fljing as a lifting hotlj in controlled flight down to 20,000 feet, where a series of pilot c.hute4, drag 

chutes, and the large 7,300-square-foot parafoil gliding parachute will deploj. The 

X-38 woul(1 then Ite steered and flared autonomously to a landing site on the dry 

lakebed at Edwards 4FB. 

Following successful flight demonstrations from B-52 launches, Muratore plans a 

follow-on vehicle huilt of aluminum with a shdl of graphite-cyanate ester epoxy. 

Improved and larger Shuttle-tierived t~lankets and tiles will provitle thermal protection to the vehicle's stiffer composite structure. The plan is to launch this vehicle into 

orhit in 2000 from the Space shuttle. After this vehicle is successfully recoveretl from 

orhit, the plan is to build four to eight mission vehicles designecl to carry astronauts 

ant1 service the International Space Station. 

A Lifetime of Excitement and Adventure 

Little did I know in 1962-as I was flying those paper models of lifting 1)otlies in 

the hallrvays at NASA Dryden and later the first balsa models on a ranch east of 

Idancaster in California-that I would see major flight-test and spacecraft lifting-body 

programs come into being within the drc.ac1e. Still less ditl I know then that, as these 

programs came into being, I would get to know and have the opportunit) to work \+ ith 

the greatest minds and human spirits in aerospace-from designers of airplanes ant1 

spacecraft to the lwst pilots, flight crews, and technicians in the world. 
WINGLESS FLIGHT LIVES ON 

Our work during the 1960s and early 1970s in developing and flight-testing the 

first experimental lifting bodies has had a highly significant influence on decisions 

guiding the course of events in the space program. For instance, the decision to develop the Shuttle as an unpowered glider was heavily influenced by our flight experience 

at the NASA Flight Research Center with the lifting bodies. Because lifting-body 

landings had proved that unpowered landings were not only safe but reliable, the 

Shuttle design did not include the extra weight of deployable turbojet engines 

necessary for powered landings. The reduced weight increasing the Shuttle's carrying 

capacity significantly. 

There are now immediate and direct applications on the horizon for lifting-body 

vehicles. Although a lifting-body configuration has not yet emerged as an operational 

vehicle, that reality is getting very close and is now within sight. Wingless flightboth in and out of Earth's atmosphere-is now a firm and substantiated technology, 

thanks to the hard work and dedication of the men and women involved with the lifting-body concept during the 1950s, 1960s, and 1970s. Most of us who were involved 

at that time are today retired or nearing retirement, passing the legacy of wingless 

flight on to the next generation of engineers, scientists, technicians, pilots, and astronauts. Our legacy exists in detail for this new generation, recorded in numerous technical reports and flight-test records. The young engineers of today, who will carry flight 

innovation into the 21st century, can make solid and informed decisions in considering a wingless configuration for future space systems. 

In writing this book, I wished to give the new generation something that isn't 

always obvious when reading technical reports and flight-test records. I wanted them 

to know that those reports and records were produced by real people with very human 

feelings who shed much sweat, some tears, and even some blood in arriving at the 

facts and data that might seem coldly detached from human realities on the printed 

page. When I recall the very high risks we sometimes took during the twelve years of 

initial lifting-body history, I know for certain that we could have spilled much more 

blood than we did. I prefer to think that even as we were pushing things to the edge, 

we were smart enough not to fall off and needed only a little luck to protect us 

from ourselves. 
APPENDIX 

Lifting Body Flight Log 

Part One: Light Weight, M2-F1 

Light Weight Lifting Body Flight Log (M2-F1) 

Date 

3/1/63 

4/5/63 

4/23/63 

811 6/63 

8/28/63 

8/29/63 

8130163 

9/3/63 

1017163 

1019163 

GRD Air Pilot 

Tuw Tow 

2 Thompson 

11 Thompson 

10 Thompqon 

I Thompson 

1 Thompson 

I Thompson 

2 Thompson 

2 Thompson 

1 Thompson 

1 Thompson 

Free Flight 

Sec 

None 

None 

0:00:13 

0:02:00 

0:22:09 

0:02:25 

0:04:42 

0:04:50 

0:01:26 

0:01:51 

Tow 

Vehirle 

PONTIAC 

PONTIAC 

POhTIAC 

R4D 

R4D 

R4D 

R4D 

R4D 

R4D 

R4D 

Tow Vehicle 

Pilot Remarks 

First Ground Tow 

First Airborne Time 

First Frrc Flight 

Mallick/Dana First Air Tow 

Mallick/Dana 

Mallick/Dana 

MallickDana 

MallickDann 

ButchartIDana 

HaisenlcKay 

10/23/63 1 Thompson 0:03:00 R4D ButchartlMrKay 

Thompson 0:0?:45 

Thompwn 0:01:00 

Yeager 0:01:35 

Peterson 0:03:15 

Thompson 

Peterson 0:0.1..44 

Yragrr 

Yragrr 

!dallirk/McKayl 

Butchart 

Dana/Mall irk 

DanalMallick 

DanalMallirk Bwkr Main Wheels 

DanaJMrKay 

DanaMcKay 

DanalMcKay 

DanflvKay 
2 h7alli1.L 

2 Thompqon 

1 Prtrrson 0:02:25 

2 Thompson 

3 Percrson 0:08:00 

2 Pttrrson 0:O L:OR 

1 Thompson 

3 Pt.tr.rson 0:W:jO 

1 Thompson 

1. Thompson 

1 Tllompson 

4 Tllompson 

3 Sorlic. 0:06:00 

1 Thompson 

2 Sorlir 0:04:30 

1 Tllompson 

1 D;ln;i 

1 Grntry 0:00:09 

3 Thompson 

1 Tllompson 

2 Tllompson 

1 Thompson 

2 Tllornpsnn 

1 Pc.lrrson 0:M:OO 

3 Pttrrson 0:0~1:00 

Grntq1 Gc-ntr) 

Project C.incclled 1)) Ptrctl Riklc. 

R in 

R lD 

R in 

R4n 

RID 

R rn 

R4D 

R 1D 

RID 

RlD 

R ID 

R ID 

RID 

RlD 

R In 

R ln 

R lD 

R bD 

R in 

n In 

RlD 

RID 

R 1.n 

RlD 

RID 

POUT1 \C 

RlD 

D;lr~a/\l(.liay 

R~~t(.t~i~~-t/reterson 

Ri~tc,hartKlurver Fir1.11 I.;lnciir~g Ro~.kt.t 

~i~tc~l~artllilurrrr 

Rt~t~l~irrtKlurr-er 

B~rtcl~;~riNclia) R~,~.krt 1.alltling Asst. 

Da~tOeterron 

Da~~afilaist 2- Flts, Roi.kt.tx rsc~tl 

Danflrtt~rson 

Dar~aIflaiselKalk~~r 

Da~lalPeirrson t\irspe~'d CaIiI). 

Rutcf1'1rt1Ffaisr 

Rut(.hart/retcrhor, 

Ili~i,t*/Pt*tt*rson 

Prttrs~)n/Haise 

FIaist~Klurrrr 

lIairt~/KIuever 

IIaisvKlurver I st SIon, RIIII 

P~tt*rso11/[7i1isr 

flais~./Ptlerson 

Pc~~t~rsor~ll~aise 

FIai~rIPt~t(~rson 

Pt.t~.r~onmi~tc.l~art 

ButchartlFult~~r~ 

Rut~~hartlFult~~t~ 

Firlal Car TOW 

R~lt~~lr;~~~t/F~iltcrn 211l SIUW Roll 

NI)II.: There were opproximairl! 10 tons 11). the. Pontaic,, 11ut not all ~IC thrm wrrr rrronlrd. 

Colirl)ilt,(l 1)) nttt! I.ovr, ron\rrte(l to Pagrmahvr fomlat It! Dennis DaCruz 
l&7NGLESS FLIGHT 

Part Two: Heavy Weights, M2-F2, M2-F3, HL-10, X-24A, X-24B 

Pilot 

Thompson First I.iftinp 

n(xl) [TJnj Fr~*c.-flight 

Thompwn 

Thompson 

Thnmpson 

Thompson 

Sorlie 

Peterson 

Sorlic. 

Sorl i t, 

C;entrY 

Gentr) 

Grntry 

Cel~tr~ 

Pctrrwn 

Sorlir's last Ifl flighl 

G~ritry'h 1st TJR flight 
APPENDIX 

Manke Manke's I st WR flight 

Manke 

Gentry 

Gentr) X1.R-I1 Engine 

Ill~ldl~f'l~ 

Manke 

Gentr) 1st Powered Flt., 

Eng. Malf., Landed 

Rosamond 

Mankr 3 Tries to Light 

Engine 

Gentry 

Genlry 

Manke 

Dana 

Gentry 

Manke 

Glide Flight 

Dana's 1st UR Flight 

Glide Flight 

1st Supersonic IJR 

Flight 

Dana 

Manke 

Hoag 

Manke 

Dana 

Manke 

Hoag's 1st IB Flight 

1st 4-chambered 

Flight 

Cenlrj 

Dana 

Gentry 

Mdnke 

Genlr) 

hag 

Manke 

Glide Flight 

Glide Flight 

Manke'z 1st X-24 Flight 
WINGLESS FLIGHT 

HT,- 10 

HI.-10 

X-24A 

HL-I0 

HI.-10 

X-24A 

HI.-10 

HL- 10 

HI.-10 

H1.- 10 

X-24A 

HIT10 

X-2412 

X-24A 

X-24A 

X-24A 

M2-F3 

HI.-10 

Dana 

Hoag 

Gentr) 

Dana 

IToag 

Gentr). 

Dana 

Hoag 

Dana 

Hoag 

Gentry 

Dana 

Gentry 

Manke 

Grr~trj 

Manke 

Dana 

Hoag 

Mankr 

Hoag 

Dana 

Gentry 

Manke 

Gentry 

ManktManke 

Dana 

Gentry 

Glitlr Flight 

Glide Flight 

Fastest Ill3 flight 

Highe.;~ IJR flight 

I st Powered X-24 Flight 

Only 2 Charnbtzrs Lit 

1st M2-F3 Flight 

I,ift/Drag Powered 

Approach 

Iloag'sIF~1.-10's 

Last Flight 

Only 2 Charntrers Lit 

1st Supersonir X-24 

Flight 

Highest X-24 Flight 
APPENDTX 

11/25/70 Dana 1st M2 -F3 Powered 

Flight 

1/21/71 Manke 

2/4/71 Powell Powell's 1st LIB 

Flight 

2/9/71 Gentry Gentry's 1st 

M2-F3Aast I/B Flights 

2/18/71 Manke 

2/26/7 1 Dana 

3/8/71 Powell 

312917 1 Manke 

5/12/71 Powell 

Only 2 Chambers Lit 

Fastest X-24 Flight 

Delayed Light of 

Rocket Chamber 

5/25/71 Manke 

61417 1 Manke 

Only 3 Chambers Lit 

Only 2 Chambers 

Litht X-24 A Flight 

7/23/71 Dana 

8/9/7 1 Dana 

8/25/71 Dana 1st Supersonic M2-F3 

Flight 

912417 1 Dana Engine Malfunction, 

Fire, Rosamond 

Landing 

11/15/71 Dana New Jettison Location 

Checkout 

1211 17 1 Dana 

1211 617 1 Dana 

7/25/72 Dana 

Only 2 Chambers Lit 

1st Command 

Augmentation 

System Flight 

8/11/72 Dana 

8/24/72 Dana 

9/12/72 Dana Engine Malfunction, 

Small Fire 

9/27/72 Dana 

10/5/72 Dana 100th Lifting Body Flight 
WING1,ESS FLIGHT 

Manke's 1 st M2-F3 Flight 

Powell 

Powrll 

Dana 

iI1ghe5t ancl last 

h12-F3 Fllgllt 

Mankr 

Firht Glidr Flight of 

X-24B 

klank~ 

blanke 

Manke 

1nlt.e 

Mankr 

hfanke 

I.ove 

Mankr 

I.ovels 1-1 IJB F11gh1 

1.t Y-24R P~WP~PII Flight 

Max. Spt.t~dK-24R Fligl~t 
APPENDIX 

X-24B 4/18/75 Manke 1.204 795 57,900 

X-24B 8/5/75 Mankr 1.190 773 GO,000 1st Runway 

1anding.Alarike's 

1.451 Flight 

X-24R 8/20/75 Love 1 .,5W 1,010 72,000 RunwayIandingllr)vc's 

last Flight 

X-24B 1019175 Enrvoldson 0.705 450 45,000 Enel oldson's 1<t IJB 

Fltght 

X-24R 10/21/75 Scubre 0.696 262 45,000 Srober's 1st IJR Flight 

X-24R 11/12/75 Enr~oltlson 0.702 t.56 45,000 Eneloldson's Iast 

T/R Flight 

Y -24R 1/1/75 Scol~ee 0.700 4610 45,000 Scobr~'c T~bt IlU Flight 

X-21R 11/2(575 UcM~rtq 0.713 460 35,000 M~Murtr)'~ 1.as1 UB 

FIightll~bt X-24R Flight 

* Approximate 

Assrnible(1 from a compilation t)y Jack Koif and .kppenrlix N of Richard P. IIallion, On the Frontier: 

Flight Rrs~rrrch at Dryclcm, 1946-1981 (Wasliir~ton, D.C.: NAS,Z SP-,4303, 1984); formatted in Pagrn1akc.r l,y 

Dennis DaCruz. 
GLOSSARY 

al~lation Themma1 process where the surface melts or vaporizes at high 

temperature, thereby ahsohing heat created aerodynamically. 

aldator Surface material that will melt or vaporize to absorl) heat. 

active cooling Process whereby a heat-c~otlrluctive fluid circulates hetween a hot 

and cool region, drawing off heat. 

ADP Ad~ranced Development Projects-a Lockheed group lo(-atetl in 

California. 

AF or USAF United States Air Force. 

AFB Air Force Rase. 

AFFTC Air Force Flight Test Center. 

AFSC Air Force Systems Command, an Air Force major commantl tluring 

the period of this narrative. 

analog In the context of this book, a computer in a simulator that 

computer solves equations of motion using analogous electrical circuits; that is, 

it expresses data in terms of measurable quantities, such as voltages, 

rather than 1)) nun11)rrs as a digital computer does. 

AOA Angle of Attack: direction of relative wind with respect to an 

aircraft's longitudinal axis. 

Apollo NASA program to land a hurnan on the moon ant1 return to eartli. 

ARC NASA Ames Research Center. 

ASD Aeronautical Systems Division (.4ir Force). 

aspect ratio The ratio of squared ailfoil length (span) to total airfoil area or 

of airfoil length to its mean chord (distance from leading to trailing 

edge). Thus, an airfoil of high aspect ratio is relativclj long with a 

relatively short chord, whereas one of low aspect ratio is 

romparativelj short and stubbj. 
attitude The position or orientatiotl of an aircraft or spacecraft with relation to 

its axes and some reference line or plane. 

1)allistic Adjec-tive descarihing the path of a l)ody launc*hrtl into a trajectot-y 

%here it is suI)je(-t on]) to tlie forces of grab it) and drag. 

hallist ir a;i.iglit divitled 1)j the drag coefficie~~t time5 thc. frontal arm. 

coeffic.ient 

Iwnk angle :lngle hetween the of an aircraft's wings and the horizon 

I)oat-tail Shapr of the rear of a ichictle hose cross set-tion decreases from the 

center to the aft end. 

C-130 Four-enginc., lulf~oprop-porvrletl transport airplane. 

capsule A helf-co~ltainecl, symmrtrical c*ontainer cal~able of 3afel) entering 

thc earth's atnlosphere from orl,ital or higher speetls. 

CD Drag coefficient. -4 non-tlimensional parameter for measuring drag. 

c.g. Center of gravity-an imaginary location within an ol~jecthat 

identifie5 its ccAuter of mass. 

crranlir tilt.5 Snlall 1)locks of rigid ~llaterial (primarilj silica) attachetl to tlie 

outside of a gliding re-entr) \~tiir.lr that prevent thy heat generatetl 

by re-entry specds from reaching the \-?hi(-le strucaturr. 

chase planes Aircaraft used to fl) close to research airplanes for purposes of 

provicIing thv rescarc-h pilot t\itlt an adtlitional set of eyes for safet) 

pu1-poses. 

chord The straight-line distance fro~l~ the leatling to the trailing edge of an 

airfoil s~1c.h as a wing. 

1,ift coeffic.ient. A non-dimensional parameter for measuring lift. 

Lift coefficaient diviclecl 1)y wing loading. X non-(limensional 

para~nrtc~r that allow4 the glide pet-fornlance of several aircraft to 1)t~ 

compared at the same airspeed. 
WIKC1,ESS FLIGHT 

control laws The relationship between the pilot's coniniancls and the a(-tual 

control surfac.e (aileron, elwon, etc.) movements protlucecl 1q a flight 

control spstrnl. 

cross range The i1isttinc.e that can 1)e achieved hy a re-rntq- vehicle (as it entvrs 

the atmospher~) in a direction perpendicular to that of the initial 

er1tl-y path. 

damp To slow (1015-n. 

tlerouplr niotle An entry concept that uses a tlifferent tlec-eleration method for entry 

than for lantling. 

delta wing A wing that has a triangular shape when 1-iem-eti from al~ove. 

digital Adjective descril)ing a mechanism, sucli as a computer, that 

expresses data in discrete, numerical digits. 

dihetlral Effvcat on lifting bodies of sitfeslip, producing roll. 

Don Department of Defense. 

doublet An aircraft control rnovement from neutral to a tlrflec.trtf position that 

is held, then returned in the opposite direction I~ack to the origitlal 

neutral position. 

drag A force that rt~sists motion ant1 is protluced 11) fi-ication within the 

atmosphere. 

Dutch roll A complex oscillating motion of an aircraft involving rolling, yawing, 

and sitleslipping-so-nan~ed from the resemhlancr to the 

characteristic. rhythm of an ice skater. 

Dyna-Soar Short for Djrialnic Soaring. karne of a host-glide research program 

that was canceled in 1963 hefort. its first flight. The aircraft 

designation was X-20A. 

effective ,An aircraft aerodynamic vharacteristic that makes the airplane 

dih~ilral roll (rotate around the lotigitudinal axis) when a sitleslip or side gust 

is encoi~ntercd. 

eyeballs-in ,4 tlescriptive term used to identify the direction of a force due to 

acceleration. 
GLOSSARY 

F-104 Air Force century series fighter Luilt hy Lockheed and used as a 

chase and research airplane at the Flight Research Center for 

many years. 

FDL The Air Force Flight Dynamics 1,al)oratory loca~cd at the 

mi-ight-Patterson Air Force Base in Dayton, Ohio. 

FDL-7 Seventh re-entry cdesign created at the FDL. 

FDL-8 Eighth re-entry design created at the FDL. 

fincness ratio The ratio of 1)odj length to body width of an aerodynamic shape. 

flight cards A type of (.heck list in card form used by pilots and other crewT 

members to track events in a plannetl flight test. 

flight path The path of a moving ohject, usuall~ measured in the vertical plane 

relative to the horizon. 

fly-by-wire A flight control concept that uses only elecatrical signals between the 

pilot's stick and the control surfaces. 

FRC The NASA Flight Research Center locatecl at Etlwarcls, California. 

From 1954 to 1959, the designation of this organization was the 

NACA and then the NASA High Speed Flight Station. In 1976, it 

became the NASA Hugh L. DTden Flight Research Center. 

frontal area The area of an ohject as projected onto a plane perpendicular to the 

flight tlirection. 

Sensiti\ itj with respect to flight caontrols or a sta1)ility augmentation gnln 

system. 

FI! per TIT A light-weight, unpiloted ,eliiclc built 1)y the NASA FRC and 

patterned after the FDL-7 sl~apc. 

h> personic Cliaracterizetl hy speeds of Mach 5 or greater. 

jack points Designated points marked on the untlrrsidr of an aircraft wing to 

 up^+-art1 with a hjdraulic jack for the purpose of cali1)rating 

stniin gages inside the wing structure. 
WINGLESS FLIGHT 

LaRC The NASA T,angley Research Center located in Hampton, Virginia. 

I JD Lift-to-drag ratio. 

Lift A force on an oI>ject produc.ed 1)y aerodynamic reaction aith the 

atmosphere as the o1)jec.t moves; it acts perpentlicularly to the 

flight direction. 

limit cycle A run-away oscillation of an aircraft control surface that occurs when 

the sensitivity (gain) of the automatic. htabilization s) stem is too high. 

lower flap A small nlechanical arm attached to a lifting t)od) lower flap control 

control horn surface to which an actuator control rod is attached. 

LOX Liquid Oxygen. 

Mach num1)er The ratio of an object's speed to that of sound. An o1)ject reaches 

Mach1 when it flies at the speed of sound; Mach 2 is tuice the 

speed of sound; and so forth. 

Mercury First U.S. manned space capsule program. 

MLRV Manned Lifting Re-entrq Vehicle. An earlj NASA Langley Research 

Center lifting 1,ody design. 

moment A tendency to cause rotation about a point or axis, as of a control 

s~~rface about its hinge. 

MOU Memorandum of Understanding-usually a simple document with 

signatures stating the agn.cxd-upon responsibilities l~etween two or 

more organizations. 

MSL Mean Sea Levrl. 

NACA National Atlvisol-y Committee for ileronautics. 

NASA National Aeronautics and Space Administration. 

neutral A fiigh~ contlition in which an aircraft that is clistur1)etl in pitch 

longitudinal continues to rotate away from the initial angle of attacak at a constant 

stat~ility angular rate without wturning. 
GLOSSARY 

A type of alllator (see a1)ove) that rnairltains its external climensions 

~vhile melting or vaporizing. 

nose-wheel The point in an aircraft take-off nlaneuver at which the pilot 

rotation romman(1s the aircraft to rotate its nose upnards, increasing lift so as 

to tfepart the grounrl. 

notch filter An elec.tronica filter in an aircraft's automalic control sjstem to 

remove or obstruct unwanted frequencies ~ithin anarrow hand to 

prexerlt them from causing prol)lems ~tith the s~stcn~. 

on-the-street The time whrn an agency advertises (in a request for proposals) that 

a new job or contract is plar~netl. 

Slang tenn usetl to clesc~ri1)e the 15 percent increase in thrust that was 

availalde on the X-24R rocket engine as compared with that used on 

previous lifting 1)odies. 

Pllotecl 1,Ow speed Test. Early tlesignation for what 1)ecame the 

X-24A program. 

Pilot Tt~tluc.ed Oscillation-a situation iri flight in which a pilot 

ca11ses an aircraft to ost.illate ahout the intended pat11 of flight hy 

making excessive control inputs. 

Angular displacement of a vehic-le suc*h as an aircraft ahout the 

lateral asis (i.r., nose up or nose down). 

The author's ten11 for clllll)l)} lifting 1)odies that are capallle of 

carrying large pavloatls but hare ~llortcar hjpcrsonic cross ranges 

than race horses (~thic.11 see). 

Pregnant A C-97 cargo airplallc. modified to carry an oversizetl cargo. 

Guppy 

Precision Recover). 1ttc.lutling Maneuvering Entry. Earl) designation 

for what became the SV-SD or X-2.3 program. 

projected The arm of an ot~jject as projcc*trd onto a horizor~tiil plane parallel 

area with the flight tiirec.tion. 

PSTS Prop~~lsion S! stem Tcsi Stancl. 
TIRG1,ESS FLIGHT 

race horse The author's term for streamlined, slender lifting 1)otlivs with smaller 

payload capacaitj than the plow horses (which see) hut with ver) high 

hypersonic cross ranges. 

radiative A type of cooling that radiates heat away from a cooling hot surface. 

ramjet A type of jet engine without an} mechanical compressor, comprised 

of a specially shapetl, open tube into w1iic.h the air necessary for 

com1)ustion is forced ant1 then compressetl 1)) the forward niotion of 

the aircraft. 

rate liniited Term indicating the masinium angular rate at which an actuator can 

drive an aircraft control sutface. 

Real Stuff Term (derived from Tom %'olfe's The Right Stuff) to d~scribe tlie 

qualities of p~o~le who create and senice aircraft or spacecrafi for 

experin~ental flights rather than fly them. 

retrofire Short-tern~ rocket ignition with the thrust pointed in tlie (lire(-tion of 

flight so as to reduce the speed of an orbiting o1)jec.t and to initiate 

entq. 

Reynolds A nondirnensional parameter representing tlie ratio of ~nonientunl 

number forces to viscous forces about a bod) in fluitl flou-, as in tlie 

atmosphere; nanird for English scitnti.st Osl~orne Rejnolds 

(1842-1912); among other applications the ratio is ital to tlie use 

of wind tunnels for scale-nlodel testing, as it provides a basis for 

extrapolating the test data to full-sized test vehicles. 

Right Stuff A term first coinvtl 1)) Tom %blfe in his hook of the same titlr. It 

refers to the qualities posse3setl b!- pilots and astronauts \+ho flj 

esperin~erital aircraft or spacecraft. 

Rogallo Wing 4 n-ing-like prachute tlesign that enables tlie paracl~uting o1)jec.t to 

move forward as \+ell as descencl. 

1-01 1 Rotational movement of an aircraft or similar 1)otly ahout its 

longitutlinal axis. 

roll reversal An adverse aircraft design conclition in tzliicsli an aircraft rolls in 

the opposite direction from that commanded I)] the or 

control surfaces. 
GLOSSARY 

rotation speed The minimum speed at which a pilot can rotate the aircraft nose 

upward (lift the nose wheel off the runway) during a take-off roll. 

RPV Remotely Piloted Vehicle-a vehicle controlled through radio links 

by a pilot not in the vehicle. 

RTD Research and Technology Development-an Air Force Organization. 

SAMSO Space and Missile Systems Organization-an Air Force organization, 

part of AFSC during the period covered 11y this narrative. 

SAS Stability Augmentation System-electronic control components 

designed to augment the stability of an airplane. 

second A vehicle that has benefited from the previous design, development 

generation and trsting of a similar vehicle. 

vehicle 

self-adaptive Adjective describing a flight control concept that samples, then 

alters, internal electronic signals to compensate for changing flight 

conditions. 

semi-ballistic Adjective describing a state in which an ol~ject is subject to small 

aerodynamic forces in addition to the forces of gravity 

and inertia. 

Shuttle The winged vehicle developed by NASA and its contractors to serve 

as a Spare Transportation System to carry cargo to and from earth 

orbit. 

side-arm A two- or three-axis control stick mounted on the side of the cockpit 

cont roller and operated by a pilot's wrist movements. 

sideslip A sideways movement of an aircraft away from the initial flight path. 

simulato~ A partial aircraft cockpit connected to an electronic computer; it 

allows a pilot to replicaate to a significant degree the flight of an 

airplane. 

Skunk Works Popular term for a small, highly efficient tiesign and fabrication 

organization capahle of creating innovative prototype aircraft in a 

short period of time. The Lockheed Advanced Dehelopment Projects 

group was the first organization to use the term "Skunk Works" 

officially to describe its organization. 
WING1,ESS FLIGHT 

span The distance from tip to tip or root to tip of an airfoil siich as an 

airplane's wing. 

spiral A natural aircraft charac.teristic8 that allows thtb vehic*le either to 

stability remain in level flight or to return thereto tvhen upset in roll or bank 

angle. 

Sputnik 1 Thy first man-made ohject LO 1,e placed in earth orbit (1,). the Soviet 

Union on 4 O(.tober 1957). 

strain gage An instrument used to measure the strain or distortion in a menil~er 

or test specimen (such as an aircraft struc.tural part) that is 

su1)jected to a force. 

st rakes Wing-like appendages at the aft end of an aircraft that pro1 ide lift or 

aclcled stal~ility; also long. flat surfaces attached to the ext~rior of an 

aircraft's hkin and aligned with the local free-stream contlitions. 

Basic configuration of a re-entry vehicle that let1 to the SV-SP 

(X-24A) and SV-SD (PRIME). 

Jet-powered version of the SV-5 configuration. Two were built but 

neither was flown. 

swashplate A mechanical plate with a universal joint giving it freetlorn to pivot 

in any tlirection ahout one point. Multiple attachnlent points for 

control rods in the plane of the plate allo~+-etl flexibility for c1ifft.rr.nt 

controls in the M2-F1 lifting hody. 

test-1,ed A ronventional aircraft that has been equipped with some new11 

aircraft designed internal or external components for in-flight testing. 

Thor-Delta A two-stage rocket using a Thor 1st stage and a Delta 2nd stage. 

triply Adjectit e describing the conccspt of using three parallel components 

retlun(1ant to accomplish a single function, with automatic, dr-selection of any 

faulty component. 

tufts Short segments of yam or string taped to an aerodynamic surface to 

alIow airflow characteristics to hc observed directl] or pllotograplled. 

1 olunletric The ratio of total volume to the surfacr area of a three-tlimensional 

efficiency shape. A sphere has the highest volumetric efficiency of any shape. 
GLOSSARY 

wedge angle The angle of the aft c-ontrol surfaces relative to the flight direction. 

Large angles produce shuttlecock-like stability. 

wetted skin The total exposed surface area of any shape. In an aircraft, this 

area is all skin area exposed to the outside airstream. 

wing loading Vehicle weight divided by the area of the wing. 

X-24C A follow-on proposal to the X-24B to test advanced air-breathing 

propulsion. 

yaw Motion of an aircraft or sirnilar vehicle about the vertical axis 

(i.e., nose left or right). 

Y-plane Lateral (left to right) axis of an aircraft or flight vehicle. 
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Test Program." AFFTC TD-71-10, August 1972. 

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Times (Dec. 4, 1989): B-3-4. 

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Progress of the X-15 Project. Papers Presented at LangleY Aeronautical I,al)oratory, 

0c.t. 25-26, 1956. 

Grosser, M. "Builtling the Gossamer Al1)atross." Technology Review, 83 (Apr. 

1981): 52-63. 

Hallion, Richard P. The Ily~wrsonic Revoh~tion: Eight Case St~rtlies in the 

History of Hypersonic Technology. 2 vols.; Wright-Patterson Air Forcr Base, Ohio: 

Special Staff Office, 1987. 

-, On the Frontier: Flight Research at DrS..tlen, 1946-1981. Vi'ashington, 

D.C.: NASA SP-4303, 1984. 

, Test Pilots: T11e Frontiersmen of Flight. Viashington, D.C.: Smitl~sonian 

Institution Press, 1981. 

Horton, Victor IT., Eldretlge, Richard C., and Klein, Richard E. "Flight-Drte~mined 

Lob-Si)eetl 1.ift ant1 Drag Characteristics of the Light\veigI~t M2-Fl lifting Rody." 

VEishington, D.C.: NASA TN D3021,1965. 

Tliff, Kenneth 1: "Parameter Estimation for Flight Vehit*les." Jor~rncil of Guidance, 

Control, crnd Dyrzcrrnics 12 (Sept.-Oct. 1989): 609-622. 
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Report 36'27, 1982. 

Kernpel, Kober-t lT: "A~ial~sis of a Coupled Roll-Spiral-Mocle, Pilot-Intluced 

0sr.illation Experienced Kith the M2-F2 Lifting Body." %'ashington, D.C.: NASA 

Technical Note D-6496, 1971. 

-? Dana, Killian~ H. and Sim, iZlrx G. "Flight Ecaluation of thr M2-F3 Lifting 

Rot1 Handling Qualities at Mach Numbers fro111 0.30 to 1.61." Washington, D.C.: 

NASA Technical Note D-8027, 1975. 

, Painter, Werteth D., and Thompson, Miltoll 0. "Developing and Flight Testing 

the HL-10 Lifting Body: A Precursor to the Space Shuttle." Vhshington, D.C.: NASA 

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Sci~nce (July 1978): 66-69. 

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Experimental Tvzt Pilots, Technircll Review 14, Ko. *t (1979): 232-dZ.3. 

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D.C.: NASA RP-1138, 1985. 

Marik~, John A, atid Love, M.V. "X-24B Flight Test Program." Society of 

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R'iishington, D.C.: NASA TM X-2056, 1970. 

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Ames Aeronautical Laboratot-), 1958. 
WINGLESS FLIGHT 

Pyle, Jon S. ant1 Montoja, Lawrence C. Effects of Roughness of Simulated Ablated 

Material on Low-Speed Performance Characteristics of a Lifring-Body 

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Reed, R. Dale. "High-Flying Mini-Sniffer RPV: Mars Round?" Astronautics & 

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Sim, Alex G., Murray, James E., Neufeld, David, and Reetl, R. Dale The 

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Spacecraft Recovery. Washington, D.C.: NASA TM 11.525, 1993. 

Sini, Ales G. "Flight-Determined Stahility and Control Charac.teristic.s of the M2-F3 

1,ifting Body Vehicle." Wkhington, D.C.: N4S4 Technical Note D-7511, 1973. 

Sn~ith, Harriett J. "Evaluation of the 1,ateral-Directional Stability ant1 Control 

Characteristics of the 1,ightwight M2-Fl 1,ifting Body at 1.o~ SF)ertls." V~asliingtoll, 

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Kilkinson, Stephan. "The Legacy of tl~r Lifting Rotly." Air &- Space (April/Maq 

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ABOUT THE AUTHOR 

R. Dale Reed is an aerospace engineer I+ it11 a ha(-helor of science tlegwr in merlianical engineering from the Univcrsitj of Idaho. He ltegan working at w hat later l,ecsame 

the NASA Dryden Flight Research Centrr as a research engineer in 19.53. F-le conduc-tetl aerodynamic loads research on the X-IF,, X-5, F-100, and D-558-11 aircraft 

ant1 performet1 aerodjnamic heating measuremrnts on thy X-15 1)efore he 1)egan 

tleveloping, atl~ocating, ant1 impleme~iting the lifting-lrodq flight research program 

that he writes al)out in this Iwok. Before his retirement from iTXS.4 in 1985, he won 

four NL4SA awards ranging from the Exceptional Serhicr Medal to an Associate FellowAward. 

Following his formal retirement, Mr. Reed went to work for a 1aric.t) of contracetors ant1 is today again worki~ig at Dqrlen, now as a contract enginrer. 111 his long 

career, he has pul~lishetl 14 technical reports and a number of periotlical articleh. He 

has also tukrn out four patents and managrd 19 programs. IIe is currentlq working 

actively with the X-38 program tlescrihtxcl in these pages. 

INDEX 

Ablative coatings, 176 

Ae~odjnarnic forces, 58,71,102,104,112, 

117, 121, 127; tufting to assess, 116; 

tlihrdral effect, 126 

A(~rotherniodjnamic/elasti(- Strut-tural 

Sj sterns Environmental Test (Asset), 8-9 

Air Force, 8; attitudes ahout lifting bodies, 

8, 65, 87, 111, 129; cancellation of 

Dj na-Soar, 8; Air Force Flight Dynamics 

Ial)oratory, 111, 167; Space Sjslems 

Dic ision of SJ hterns Comnland, 130; 

requirements for Space Shuttle, 142-1113; 

Scientific Advisory Roartl, la; Sjstems 

Command, 168; Arnold Engineering 

Deceloprnent Center, 168; Museum, 177, 

179 

Air Force Flight Test Center (,4FFTC), x, 

75,95, 149, 155; division of responsihility with the FRC, 75,87; competition and 

teainwork with the FRC, 111-112; nmway 04/25! at Edwal.ds AFB, 174 

All~atross SA-1 16R, 165-166 

Algranti, Joseph S., 47 

Allen, H. Julian "Harvey," 9 

Ames-Dryden Flight Research Facility, 5 

Ames, Milton, 65 

Ames Research Center, vii, 41,66, 11 1; as 

Ames Aeronautical Laltoratory, 9; ~intl 

tunnels, 17, 23, 41-45, 58, 80-81, 92, 

111-1 12, 132; and dirigiI>les, 41; interest 

in lifting bodies, 9, 65, 69; objection to 

"elt,phdnt ean," 67; shuttlecock stahilit!, 

(33; concern ahout sensitivity to gusts 

with center fin, 68,84; and ceramic tiles, 

1 42 

Antlerson, Arthur S., 95 

Anderson, Herhert, 95,148-149 

Antlerson, Keith E., 162 

Apollo Pi.ogram, 10; computer for Apollo 

1,unar Tanding Vehicle, 171 

Archie, Charles, 135 

Amistrong, Johnny G., 87, 132, I71 

Annstrong, Neil A., 47; and 10% lift-to-drag 

flights on F-104, 11 7-1 18,175 

Anriy, 191 

B-29 niothership, 6 

B-50 mothership, 6 

R-52 rnothe~shi~~, GG, 67 87-88, 88 ill., 89 

ill., 95, 122-123, 134, 150 ill., 189 ill., 

191; adaptt~r for launching liftir~g bodies, 

67,82; ~ind-tunnel tests, 82; adapter for 

HL-10 and M2-F3, 112; fi~st launches 

frorn for pilots, 117; captive flight for X21B, 171-172; captive flight for X-38, 

190 

Bacon, Donald, 95, 119-120 

Bail?], Charlcs H., 162 

Ballistic capsulrs, 8-10 

Bang-1)ang controls, 148 

Barnes, Florence "Pancho," 5 

Barto, LeRoj E., 132 

Bastow, IXilliarn J., 132, 171 

Bearce, Bolden "Bud," 34 

Recker, John V., 69 

Bergner, Chester F., 83, 132, 162 

Big "G," 159 

Rikle, Paul F., vii, x, xiii ill., xiv-xvi, n, 17, 

19, 21, 27, 53, 67, 75, 76, 83, 95, 133, 

258; Riklr Barrt.1, uv, 121; Ilalicie%, 24; 

and Pontiac tow-aehicle, 39; courageous 

decision, 48; openness and honest], 49; 

low-cost approach, 55; grounding of M2- 

F1, 62; relationship M ith Richard 

Homer, 73; career, 87; support of 
INDEX 

Mc.Tigle on "inspection" of hT2-F2, 1 1 5; 

and nimher vorl Rraun, 140-141; ant1 

replacement of C-47 with AlI)atross, 

165-166; rrtirt~n~ent, 1fh; ant1 X-24B, 

168 

BilIett.1, Orion B., 50, 53, 83, 89 ill. 

Bi.s~>linghoff, Raymond, 65, 72 

Blair, Richunl L., 9.5, 171 

Blunt-nosed rrentq \ehicalm, 9 

Boeing Company, Rocketdj ne Di\ ision, 

183-184 

BOR-(1 So\ iet liftirlg l)ody, 180 

Branch, 11% ing. 75 

Braan, acrnher von, 140, 1/11 

B~.ieglel), Clw, 21 -2.3 

Rn)nson, Jat-k, G7, 1 1 1-1 12 

Browne, E(1cvarcl F., 20 ill., 43, 161 

Rnlno, John M., 80 

C-130 transport, 180,191 

Can; George M., 168 

Cates, Aritlrew C. "Jack," 83,95 

Caw, Iawrence J., 95,119-120 

Crntcr fill, nertl for, 68 

Clifton, Williatrl D., 80, 93 

Congress, 5 1 

Control surfaces, 23-24, 29-31, .72 ill., 71, 

79-80, 83-85, 102-104, 104 ill., 116- 

11 7, 135, 137 ill., 1 1-.5, 170 

Contml systrnis, st^ Fligl~t Co~it~ul 

Cooper, Paul T., 168 

Cornell Aemna~ttic.al Label-ato13, 83 

Conlm family, 3-4 

Cox, Mel, 132, 171 

Cn)-sl)j, Jim, 82 

Cross range cal>ahilitirs, 155-156, 156 ill. 

Cuttih, Howard J., 20, 161 

Dana, V'iIlit1111 IT., x~iii, mi ill., xxii, 31-32, 

83, 117, 1/19, 151-152, 180 ill., 

189, 190; as mission controller, 50, 52, 

55; alt it ~irle reconl, 123-1 24: repo1-t on 

M2-F3, 119-150; final f~o~veretl lifting1)odq flight, 1'76 

Data analysis in "good oltl (lays," 5.5, 103 

DC-X, 182 

DeCeel; hler-41 D., 20, &, 80-82; and test of 

M2-Fl rjrc-tion scat, 47; installation of 

1,R-11 on M2-F2, 10 1; centcAr fin for hf2- 

F3 and clearance with B-52,112; hl2-F3 

operations enginee~, 11 5, 1/1.1, 1.R 

DrMal; Norman E., 82, 132-133, 170 

DeMerri~te, Fred, 66, 79; p~c,fers HL-10 

and M2-F2 ot7er 2 M2-F~s, 69; angeement ~~itl~ M(,Tigue on M2-F2 "inspection," 115; furltling of X-243, 168 

Div~s, Willard E., 162 

Dorr, Pasc.hdl H., 162 

Do~.dj, 41, 7 

Drape]; 4lfrt~1, 167-1 68 

Di~den, Hug11 I,., vii, 5 

Dr) dcn Flight Research Crnter, r-ii, 5; 

ethos, ix-x, xi, xv, 17, 19, 21, -18, 72, 73, 

102-103, 122, 133, 171; role in X-33 

flight wsean-11, 185; role in X--38, 187- 

191; see also Flight Re5earc.l-i Crritrr 

Duffieltl, Jm~es A., 162 

Durrett, Johri, 87 

Djna-St~ar, ax, 8, 129 

Ed~~ar(ls, Jo1111 WT., 95 

Eggers, Alfred J., vii, 9, 1 1, I G-17, 19, G9 

Eldrrdge, Ric.har(1 C., vii, 12-16, 13 ill., 22, 

29,43- K, 1.56-1 Gl ; report authol; 41,62 

F,nevol(Tson, Eitiar, mii, xviii, xuiv-m, 177 

En$. Joseph H., xvii, xviii, xxii, 59 

Erl), Fwd R., 72, 103, 115 
WINGLESS FT'TGHT 

F 

F-SD Skjlancaer, 107, 116 

F-8 Digital Flj -Bj -Wire proganl, 170-1 71 ; 

cost savings, 171 

F-104 Starfighter, 90,91 ill., 116-1 19, 174 

ill.; low lift-to-drag flights, 117-118; 

steep approaches, 125; reaction coritrols, 

152; sinrulating lifting 1)oc-lies, 173, 175; 

simulating X-15, 175 

F-1109, 7 

Faget, Maxinie A., 9, 142-143, 159 

FDT ,-7, 1 55 

FDT,-8, 167 

Fischtxr, Richard F., 161, 163-164, 180 ill. 

Flight control surfac~es, see control surfaces 

Flight control sjsterns, 15,23-24,29, 135- 

136, 144-143, 146 ill., 150-153; see also 

sta1)iIity augmentation system; bangbang tlefinetl, 1/48 

Flight research, 57; as compared with 

wind-tunnel research, 58 

Flight Research Center (FRC), vii, ix, 5; 

"Skiunk Wi)rks," 12, 16-17, 20, 11.5; 

"Wright Ric-jcsle Shop," 21, 32; di~ision 

of responsi1)ilitj \$it11 the AFFTC, 75; 

working relationship w it11 Northrop engineers, 77-7% rocket shop and h12-F2 It' ~nspection," 111; Flight Review Boanl, 

133; caution after crash of M2-F2, 133 

Forster, John S.. Jr., 168 

France, 179 

G 

Garcia, David L., 95 

Garral~rant, Daniel C., 148-149, 160 

ill., 161 

Gemini Program, 8 

Gentry. Jrraul(1 R., uviii, mi ill., 59-62, 78, 

83, 91-92, 104-105, 117, 121 ff., 1.39- 

1 M, 143; roll of M2-F1, 60-62; suhsevent career and honors, 62; on M2-F2 

dropping from R-52,82; on M2-F.3 compared with M2-F2, 116; on modifietl HI,- 

10, 11 7; project pilot on Y-244, 

132-1 36; final lifting-l>otfj flight, 149 

Glohal Positioning Sj stem, 187 

Gold, Da~e, 162 

Goldstein, Howarcl, 1.22 

Gordon, John A. "Catfish," 132, 171 

Gossamer Alhdtn)s.;, 1 4-15 

Gossamer Condor, 14 

Green, Robert G., 20 ill. 

Grcenfield, Love11 R., 95, 119-120 

Grieshaber, Alfred S., 80 

H 

Haise, Fret1 K, Jr., wii, xviii, xxii, 51, 59, 

60,83-84 

Hakes, Ralph C., 72 

Hallion, Ric-hart1 P., 137; quoted, 123 

Hamilton, Emmet, 35 

FTamilton, Grierson M., 20 ill. 

Hanej, Pat, 95 

Hankins, James D., 132,170 

Hansen, Grant I,., 168 

Harper, Robert, 82- 

Harris, Alher-t B., 95 

Hello, Ruz, 131 

High Speed Flight Research Station, 3 

High Speed Flight Station, 5 

HIJ-10 lifting lx)tly, xi, xii ill., 66, 97 ill., 

121-128; de\ elopment , 69-73; shape, 

70-71; fin arrangement, 71; statement of 

work and contract, 71-72; components, 

72; cost, 72; wind-tunnel testing, 79,81, 

92; control surfaces, 71, 79-80; limited 

Air Force involvement, 92, 1 11 -1 12; 

simulation, 92; marginal lateral-clirectional control characteristics of unmcxlifietl vehicle, 95-97; firrt flight, %-98; 

post-flight analysis, 98-102; htal)ility 

augmentation system, 99; grounding for 

1.5 months, 99; modificaation, 102-104, 
INDEX 

104 ill.; adapter for B-52, 112; return to 

flight, 116117; length of flights, 116, 

123; controllahilitj, 117, 124; minor 

a(Ijustrnents, 1 1 7; first supersonic liftirigbody flight, 122; stability, 122-123; 

speed antl altit~lcle records, 123; general 

characteristics, 124; compared to M2- 

F2, 124; pilot ratings, 124-125; spot 

landings, 125; powered approach ant1 

landings, 128; total flight time, 128; 

plans for space flight, 143-141; total 

flights antl final flight, 143; shuttlecock 

stal~ilitj, 145; on display at NASA 

Dry den, 179 

HL-20 lifting Ixxly, 181 

Hoag, Peter C., xxiii, xxiv, 11 7, 143; spec1 

recon], 123; poor visil~ilitj for pilot, 126; 

powered approach and landings, 128; 

landing lift-to-drag ratio, 175 

Hoej, Ro1)et-i G., 87, 92, 93 ill., 132, 135, 

136,138,175; ant1 X-24R, 168 

Homer, Richard, 73 

Horton, Victor I%:, 20, 31, 37, 44, 59-60, 

89; report author, 41, 62; finds tow 

hcwk, 46 

Huxman, Joseph D., 89 ill. 

HYFIEX, Japanese liftirig bcxl), 181 

Hjper TIT, xi, xii ill., 155, 160 ill., 161-1s; 

166 ill.; components, 162; at Castle Air 

Force Rase, 179 

Iliff, Kenneth W., 25-26,33,&7; use of root 

locus on R.12-F1 control system, 31, 36- 

37; data analysis on M2-F1, 45, 49-50, 

52, 57, 58; con~parison of wind-tunnel 

with flight data, 58-59; parameter estimation, 59; concein ahout lateral control 

on M2-F2, 68, 84; data analjsib for M2- 

F2 and other vehic-les, 68 

International Space Station, 181, 186 ff. 

Jackson, Hugh M., 159, 161 

Jackson, Roy P, 168 

Japan, 179,181 

Johnson Space Center, 8,47, 66, 70, 142, 

159, 186 ff.; control ronrn, 188; partnership on X-38, 190-191 

Joint FRC/AFFTC Lifting-BodJ.. Fliglit Tbst 

Committee, 75 

Josephs, 14 man, 131 

Juanita's ha]; 53 

KdrmAn .n ortex, 44 

Kellogg, Raymond J., 132, 171 

Kelly, IaJknl K, 11.5, 161 

Remp, Rill, 10'2 

tienipel, Robert XI, 26, 95, 11 7, 121, 123; 

as author of report, 95-Xi; analjrsis of 

unmotlified HT,-10, 99-1 03; on M2-F3, 

113; report on M2-F2, 11.3; rppor-t on 

M2-F3, lrt9-150 

Kenjon, Georg~, 66,67 

Kiker, John, 74, 1% 

King, Jay L., 80,&3,89 ill., 108, 144. 

Kirsten, Paul, 132, 135 

Klein, Rirliartl E., 20, 180 ill.; report 

author, 1.1,6'2; and test of M2-F1 ejection 

seat, 47 

Kock, Bemin, 82,89,95,102,121 

Kolf, Jack L., 120, 171; fast-time simulation, 120; X-24A, 132 

Kotfilm, Ron, 132 

Kramer Prize, 13-14 

Krier, Gary, 118 

Tangley lenticular fxwl), 14 ill., 14 

Langley Research Center, vii, 53, M, 11 1 ; 

iritercst in lifting i)odics, 65, 69-70; as 
WINGLESS FLIGHT 

mother center, 69; design of HL-10, 71, 

79-80, wind-tunnel tests, 79, 82, 95, 

102-103,158; solutions to the problem of 

the unmodified HTrlO, 102-103; HL-20, 

181 

hub, Georgene, 95 

Layton, Garrison P., Jr., 93-94, %, 102, 

112,121,163 

IxPage, William R., 80-81,83,144,149 

Lifting body, definition, vii; concept, 9-10; 

design and test by Russia, Japan, and 

France, 179 

Lifting-body program, passim; beginnings, 

x; nature, xii; objectives, 66, aerodynarnic heating 71; thermal protection 

research, 71; teamwork, 11 1-1 13; roll 

control, 113-114; lengths of flights, 117 

(and see individual vehicles); uniqueness, 127; significance, ix, 128, 142, 

175,179-192; cost and size, 129 

Lightning fighter, 130 

Linear aerospike rocket engine, 183-184 

Link, William K., 83, 95 

Linn, Charles C., 20 

Little Joe solid rockets, 73-74 

Lockheed Martin Skunk Works, 182-185 

Lockheed Space Systems, 142 

Lockwood, Millard I., 83 

lave, Eugene, 65, 69, 79; and studies of 

Shuttle configurations, 14.2 

Love, Michael V., xviii, xxiv, 173-175; 

fastest X-24B flight, 173 

Lovett, John W. "Bill," 95 

Ir)wder, Clyde E. "Ernie," 23 

1,R-8 rocket engine, xi 

LR-11 rocket engine, xi, 66,136,139,169; 

rotation in M2-F3, 115; contrail, 127 

Lunar Landing Research Vehicle, 47, 140; 

ejection seat, 47; reaction controls, 132 

MI-I, half cone, 14 ill., 15 

M2 design, vii 

M2-F1 lifting body, viii ill.. ix, xi, xii ill., 13 

ill., 22 ill., 32, 42 ill., 51-52 ill., 55 ill., 

143 ill., 166 ill.; model, 11-12; shape, 14 

ill., 15; initial teams, 16-23; analytical 

team, 23-28; motto for project, 17; "flying 

I~athtub," 19; cost, 19; design, 19-21,23; 

fabricators adjacent to designers, 21; 

wooden shell, 22-23, 32; flight controls, 

23-24,29,36-38, 144; sin~ulator, 28 ill.- 

31; wheels and nose gear, 31; steel skeleton, 31-32; plexiglass canopy, 32; time to 

construct, 32; weight, 33, &, in Ames 

wind tunnel, 43-45, 58; eliminating a 

KhAn voortx, a, flight research, 46- 

62; ejection seat, 46-47, 61 ill.; structural loads, 46; instrumentation, 49; contml 

room, 49; mission controller, 50; first airtow, 50-53; as expentfable vehicle, 53; 

damage to landing gear, 5G; replacement 

of landing gear, 56; types of maneuvers, 

57; length of flights, 58, lifting-body pilot 

checkout, 59-0; grounding, 62; significance, 62-63; comparison with M2-F2 

and -FB, 114 and 114 ill.; restoration, 

179, 180 ill. 

M2-F2 lifting hd4, ix, xi, xii ill., 67-69,88 

ill., 91 ill.; no "elephant ears," 67; shuttlecock stability, 68, need for center fin, 

68, 84; deb elopment, 67-69, 71 -73; 

statelllent of work and contract, 71-72; 

components, 72; cost, 72; and Little Joe 

rockets, 74; cockpit design, 78; rollout, 

80; overall design and size, 80; stability 

augmentation system, 80, 83; ejection 

seat, 80; comparison with M2-F1, 80; 

wind-tunnel tests, 80-82; steep descent, 

82, 124; angry qualities and crash, 83- 

85,88, 105-111, 107 ill.; rudderlaileron 

interconnec-t ratio, 84 ill.; hst flight, 87- 

88, installation of LR-1 I, 104; "inspection," 11 1-114, 144; (*omparison with 

M2-F1 and -F3, 114 and 114 ill.; com- 
INDEX 

parison with M2-F3,116,145; comparison with TTL-10, 124; concerns abut 

safety for other lifting bodies following 

crash, 138-139 

MZF3 lifting My, xii ill., 144-153, 149 

ill., 150-153; conversion from M2-F2, 

111-115, 144; center fin, 112-113; 

adapter for B-$2, 112; comparison with 

M2-F1 and -F2,114 and 1 14 ill.; cost of 

conversion, 115; rotation of T,R-11 mket engines in, 115,144; hytlmgen-peroxide roll-control system, 116; Gentry's 

comparison with M2-F2, 116, 144; cost, 

144; team, 144; control system, 144-147, 

150-153; speed hake, 145; reaction 

controlb, 148; bonil> on ramp incident, 

148-149; total missions, 149; flight 

records and last flight, 150; comparison 

with HL-10 and X-24A, 150-151; landing lift-to-drag ratio, 175; in 

Smithsonian, 179 

Mag, Hen17 J. "Jay" IV, 132 

Majors, Lee, 108 

Mallick, Donald L., mlii, xx, 50, 55 ill. 

Manke, John A., miii, xxii-xxiv, vxiii ill., 

97,106,117,121 ff., 139-140,143,149, 

173-175; firr;t supersonic lifting-body 

flight, 122; highest X-24B fight, 173 

Manned Lifting Re-ent~y Vehicle, 69 

Marshall Space Flight Center, 141 

Martin Aircraft Company, 53, 111, 129- 

132,134,136 

Martin Maric.tta Corp., 168-169, 171 

Mauimurn likelihoori estimator, see parameter estimation 

MciZlistcr, Thomas ,4., 162 

McCready, Paul, 14 

McDonald, Frarlk C., 161 

McDonnell Douglas, 8, 182 

McKay, John B., 50-51 

hlcKinnj, Lin~vood "Wayne," 102 

Mc-Murtry, Thomas C., xviii, xw, 118-119, 

177; final lifting-btxly flight, 177, 179 

McTigue, John, 72, 76 ill., 77,95-96, 132, 

14; "inspection of M2-F2," 11 1-1 15, 

144; hacked up by Bikle, 115,144; funding of X-21B, 168 

Mercuq Program, 8,lO; "man in a can," 70 

Mersereau, William TI., 95, 162 

Meperson, Rob, 186-187 

MTG-15,130 

Mingele, Ed, 32 

Mode1 "mothership," 158, 166 ill. 

Models, remote control, 166 ill. 

Montoya, Lawrence C., 132,176 

Moore, Gaston, 171 

Moshier, Bob, 132 

Multhopp, Hans, 129-130, 136 

Muratore, John, 188-191 

Muroc Flight Test Unit, ix, 3 

Murray, Janles E., 187; report author, 

188 n. 

National Acadenly of Sciences, 168 

National Adbisory Committee for 

Aemnautic.~, 9-10 

National Aeronautics and Space 

Administration Headquarters, 54; Office 

of Advanced Research and Technology, 

65, 79, 114-1 15; approval of motlifiration to V2-F2, 115; decision on Shuttle, 

143; and "hobby-shop projects," 157; 

assertion of authority, 166 

National Aerospace Plane, 181-182 

Neufeltl, David, 187; report author, 188 n. 

Nichols, &orge H. Jr., 20, 49 

North American Aviation, 72 

North Carolina Agricultural and Technical 

University, 181 

North Carolina State University, 181 
WINGLESS FLIGHT 

Northrop Corporation, xii, 53, 72-73, 77, 

102, la; Norair Division's method of 

producing HL-10 ant1 M2-F2, 73; working relationship with Flight Research 

Center personnel, 73, 77-79,95; modification of the HL-10,103; "inspection" of 

M2-F2, 11 1, 1 14-1 15; adapter for R-52, 

112; help ~ith Hyper III, 162 

0 

Orahoal, John, 20 

P 

P2B, 6 

Painter, Weneth D., 17,82,83,89,95,97- 

98, 102, 117, 121, 132; insistence on 

further analysis of HL-10 data, 98, 

100 ill. 

Parameter estimation, 59 

Parawing project, 1,59 

Paresev, 16, 54-55 

Partnerships, x, xii; see also Air Force 

Flight Test Center, Northrop, Martin, 

Ames Research Center, I,angley 

Research Center, Johnson Space Center 

Paulson, Jack, 65, 79 

Peterson, Bruce A., ix, xviii ff., 54.-57, 55 

ill., 57, 72, 78,83-84,91, 92, 96-99; on 

characteristics of M2-F2,105-106; <,rash 

of M2-F2, 106-1 11; injuries, 107; subsequent career, 108; piloting SH-3, 163 

Peterson, Bill, 161 

Pilot-induced oscillation, xvii 

Piloted Lowspeed Tests (PILOT), 129, 131 

Pontiac tow-vehicle, 33-39 

Powell, Cecil William, xviii, xxiv, 139-140, 

143,149 

Precision Recovery Including Manruvering 

Entry (PRIME), 129-131,140,180,188 

Program managers, 48, 72, 76 ill., 77 , 87, 

92., 93 ill., 95-96, 132, 135, 136, 138, 

140,175 

Pyle, Jon S., 57; report, 132 

R 

R4D Gooney Bird, xi, 21,46,50-51,51 ill., 

54 ff. 

Rainey, Robert, 65,66,79 

Rampy, John, 1 19,135 

Raspet, Aug~st, 12 

Reaction controls, 152 

Real stuff, 48 

Reed, Donna (wife of Dale), vii, 15 

Reed, R. Dale, vii, viii ill., xxv-xxvi, 1-3, 6, 

8, 13 ill., 22, 29, 43-46, 66, 129-130, 

155-161, 180 ill., 186 ill.; anti genesis of 

lifting-body program, 11-15; as opportunist, 27; data analysis on M2-F1, 45; 

compliment, 49; denied Yeager's request 

to roll M2-F1,57; as design engineer, 67; 

cost cutting, 67; concern about yaw on 

M2-F2, 68; heads team to write statement of work for M2-F2 and HI,-10, 

71 -72; career decision, 77; on contmllability of M2-F2,84; steps down as liftingMy project engineer, 92-93; work with 

remotely-piloted vehicles, 95; ancl idea of 

putting a lifting body in space, 141; 

report author, 188 n. 

Reedy, Jerry S., 1 15 

Reeves, John E., &3,95 

Remotely piloted vehicles, 158-159, 

163-165 

Rrsearch pilots, xvi ff., 25-26, 118, 135, 

165; see also pilots' names 

Retelle, John, 119, 135 

Reusable Iaunch Vehicle, sre X-33 

Richardson, David, 132, 135 

Riddle, Jack, 132 

Rifenbeq-, John R., 162 
INDEX 

Right Stuff, 48 

Rockwell Aerospace, 182 

Rogallo Wing, 16, 159 

Rogerr Dry Lake, 3-5,106, Runway 18,52, 

87,96,97 ill., 122; Runway 23, 124 

"Root locus," 26,31,36-37, 113 

Russell, Charles X, 95, 171 

Russia, see Sotiet Union 

Rutan, Burt, 191 

Ryan, Bertha M. 26-28,28 ill., 36,38, 53, 

87; data analysis on M2-F1, 45, 49-50, 

52, 57; work with simulator, 27, 58, 68; 

data analysis for M2-F2 and other vehicles, 68,81,84 

S 

Saltzman, Edwin J., 57 

Saturn 140 

Scaled Composites, Inc., 191 

Scobee, Francis R. ("Dick"), xvii, xviii, xxv, 

177 

Scott, Herbert E., 162 

Separating the real from the imagined, 127 

SH-3 helicoptpr, 159, 163-165 

Shimp, Jerry, 95 

Shuler, Billy R., 20,161 

Sim, Alex G., 1=W, report on M2-F3, 149- 

1 .W; and X-38,187; report author, 188 n. 

Simulators, 7,27,30 ill.-31,58-59,87,92, 

95-96, 99, 117, 119-121, 135-136; 

T-33A as simulator, 83 ; pilots rrlaxed in, 

9; coniparison of data frvm with windtunnel data, 99-100, 103; F-104 as simulator for lifting Wirs, 118; from analog 

to digital, 119-120; fast-time simulation, 

120; hybrid computerization of, 120; 

comparison with ground cockpit for 

RPY 165 

Sitterle, George, 95 

Six -Million-Dollar Man, The, ix, 108-109 

Smith, Glynn E., 49 

Smith, Harriet J., 26-27,27 ill., 36, 38,53; 

data analysis on M2-FI, 45, 49-50, 52, 

57; writer of report, 58-59,63; work with 

simulator, 27, 58, 68, data analysis for 

M2-F2 and other vehicles, 68,M 

Smithsonian Air and Space Museum, 179 

Sorlie, Donald M., xviii, xx, xxii, 59,62,83, 

91 

Soviet Union, 179-1 80, 186 

Soyuz re-entry vehicle, 186 

Spacecraft Technology and Advanced Reentry Tests (START), 129; Precision 

Recovery Including Maneuvering Entry 

(PRIME), 129-131; Piloted Tawspeed 

Tests (PILOT), 129, 131 

Space Shuttle, 13 ill., 63; Enterprise, 74; 

approach-and-landing tests, 74; influence of lifting bodies on, 128, 142, 175; 

tiles, 142; Air Force requirements for, 

142, 143; shown with M2-F1, 143 ill.; 

size and weight, 181, 182 

Sparks, Ralph H., 35 

Speed brakes, use on unpowered landings, 

125 

Spencer, Bernard, 65 

Speny Rand, 132 

Stahility Augmentation Systems, 80, 83, 

98-99, 114, 145-148 

Sterks, Pete, 12 

Straup, Bill, 34 

Strutz, Larry, 95 

SV-5, (23, 111, 129-131; compared to M2- 

F3 and HL-10, 130; proof that lifting 

bodies were maneuverahie hypersonic 

re-entry configurations, 131 

Sweetman, Bill, 184 

Syhertson, Clarence, 19,67 

Szalai, Kenneth J., 189, 191 

Szu~alski, Boleslaw "Bill," 141 

T-33A jet trainer as simulator, 83 
WINGLESS FLIGHT 

T-37 jet trainer as chase aircraft, 51 ill., 51- 

s2 

T-38 Talon jet trainer, 116; simulating lifting bodies, 173, 175 

Ta-183, 130 

Taylor, Boll, 1 02 

Taylor, 1,awence m., Jr., 25, 83; and 

"human transfer function," 2.5; and "root 

locus," 26, 31, 36-37; home-built wind 

tunnel, 58-59; parameter estimation, 59 

Thiokol, Reaction Motors Division, x, xi 

Thompson, Dick, 74 

Thompson, Mickey, 35n.4,38 

Thompson, Milton O., vii, xvii-xx, xix ill., 

16-17, 43-45, 47-43, 54, 55 ill., 57, 59- 

60,72,78,&7-85,91; and X-15, Paresev, 

16; and simulation, 27, 29, 51-52, 87, 

89; ant1 cbontrol system for the M2-F1, 

29-31,36-38; geatness as test pilot, 31, 

89; and M2-F1 ejection-seat tests, 47; as 

chief engineer, 49; first air-tow of M2-F1, 

50-53; author of At the Edge of Space, 

53; concern about sensitixity to psts 

with renter fin of M2-F2, 68, 105; last 

lifting-hcly flight, 90-91; as chief of the 

research projects office, 90; bails out of 

F-104, 90-91; campaign for unpowered 

Shuttle landings, 128; ant1 SV-SJ, 131; 

and Hyper TIT, 1 59, 163-165 

Tiles for re-entry, 142 

Toll, Thoman A., 47; ant1 X-15, 47, 102; 

and M2-F1 as not representative of a 

spacecraft, 48; on controlla1)ility of 

M2-F2,84 

Veith, Rohrrt G., 80 

\'ensel, Joseph R., 46-47,61,83 

w 

Walker, Haroltl J., 103 

Walker. Joe (guide), 4-5 

Walker, Joseph A. (pilot), 4-5, 175 

Pkbh, James E., 54 

Weher Compan); G,80 

Weil, Joseph, 92, 121 

Pllite Sands rocket testing fac.llity, 73 

Vlitesitfe, P51ter IT:, 33-36, 38, 39 

TVilliams, Walter C., xiv, 8 

Filson, Ronaltf J. "Joe," 116 

Wind-tunnel data as compared with flight 

research data, 58-59, 62-63, W-102, 

136 

Wind-tunnel vs. simulation data, 99-100, 

103 

Wt~lfe, Tom, 48 

Women "computers," 7 

%bn~en engineers, 53 

Xbng, Thomas J., 9n.4 

Wood, Jarnes K., xviii 

X 

X-l,6, 7,66 

X-2,6, 58 

X-4,6 

X-5,6 

X-15, xi, xiv, 24, 47, 66, 77; control room, 

xvi, 7-8, 50; simulator, 27; sensors, 49; 

partips, 53; weight, 66; speed and thnist 

with T,R-1 I engines, (h; wiritl-tunnel 

testing, 82; last flight, 123; reaction controls, 152; aL)lative coating, 176 

X-20, see Dyna-Soar 

X-23, see Precision Recovery Tilcluding 

Maneuvering Entq (PRIME) 

X-24A lifting bodj, xi, uii ill., 11 1, 122, 

131-143,137 ill., 141 ; beginnings a SV5P, 131; wind-tunnel testing, 132; tram, 
132; deliterq to Etlsrartls, 132; prol)le~ns, 

133,13.5; glide fl~ghts, 133-136; powered 

flights, 136-140; shuttlecock stal~ilitj, 

134 lll., 1f1.5; configuratior~, 134; control 

problelns and corrections, 135-136; 

comparison with M2-F3 and HI,-10, 

136-137; tlesiped e.iclusive1~ as reentry vehicle, 138; lirni~ations, 137-138; 

concerns alx~ut safety, 138-139; length of 

flights, 139; changes of configurations, 

1-1.0; first supersonic flight, 110; total 

flights, 1 t3; conversion to X-24B, 167 

ill., 167-170; last flight, 168; fastest 

speed, 174.; lanclil~g lift-to-drag ratio, 

175: provides shape for X-38, 188 

Y-24B lifting bod}, is, x+i ill., 167-1 77, 169 

ill.; conversion from X-24A, 167 ill., 

16'7-170; comparison with Hjper 111, 

167; cost. 168; climensions and shape, 

167 ill., 169; componrllti, 169-1 70; control surfaces, 170; main landing gear, 

170; nose gear, 170; tires, 171 -172; 

ground tebts, 171-173: captite-flight test, 

172-173; lengths of flights, 173; fastest, 

highest flights, 173; handling qualities, 

17.3; simulating Shuttle landings, 174- 

175, 174 ill.; lantling lift-to-drag ratio, 

175; aldatite coating, 176; in Air Forre 

Museum, 177,179 

X-30,181-182 

X-3.3 Advanced Tevhnoloa Demolistrator, 

182-18.5, 183 ill. 

X-38 Tecbhnology Demonstrator, 186 ill., 

187-191, 189 ill.; fint csaptite flight, 190 

ill.; first launch, 191 

XB-70, xv 

XF-92,G 

X1.R-11 rocket engine, see I,R-11 

XLR-99 rocket engine, xi 

XS-1 rocket airplane, .ti 

Yeager, Charles E., v, xi, xvii, svii ff., 54--57, 

55 ill.; greatness as trst pilot, 31; illfluence on X-24s, 57,131 

YF-12A "Blac.kl)irtI," 143 

Zero-zero rjec-tion seat, 46-47 
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~~~

~~~
-9.k 

THE NASA HTSTORITER1ES 

- &eb+ 

Center Histories NASa SP-1.300 

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1946-1 981 (NASA SP4303,1984) 

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Dawson, Virginia P. Engines and 

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Hansen, James R. Spaceflight 

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Corliss, William R. NASA Sounding - 

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-