NASA 

National Aeronautics and 

Facts

Space Administration 

Dryden Flight Research Center 

P.O. Box 273

Edwards, California 93523 

Voice 661-276-3449 

FAX 661-276-3566 

pao@dfrc.nasa.gov FS-2003-11-031 DFRC 

Research Airplane Program 

X-3 (center) and, clockwise from left: X-1A, D-558-1, XF-92A, X-5, D-558-2, and X-4. NASA photo E-2889. 

The Research Airplane Program was a joint research effort by the National Aeronautics and Space Administration 

(NASA--formerly the National Advisory Committee for Aeronautics or NACA) and the military services. It was conceived near the end of World War II to perform flight studies with a series of specially-constructed research aircraft in the 

then-unexplored transonic to low-supersonic characteristics of full-scale aircraft in flight. 

Although supersonic flight was first achieved in 1947, further research in the program resulted in notable increases in 

knowledge about the dynamics of piloted flight in winged aircraft at speeds up to and in excess of 4,500 miles per hour 

and at altitudes up to and greater than 350,000 feet. 

1
Two general categories of aircraft were obtained for the 

research airplane program: (1) those needed to explore new 

areas of performance, such as the X-1, D-558-1, D-558-2, 

X-1A, X-1B, X-1E, X-2, and X-15; and (2) those required 

to investigate the effects of different airplane configurations, such as the X-3, X-4, X-5, XF-92, and the XB-70. 

The outstanding contributions of this research program 

include providing important information on previously 

unexplored aircraft characteristics; validating the transonicsupersonic characteristics predicted by wind-tunnel tests 

and analytical techniques; and the intangible benefit of 

providing confidence in the achievement of safe, controllable, transonic-supersonic flight. 

X-1, 1946-1951 

The first of the rocket-powered research aircraft, the X-1 

(originally designated the XS-1), was a bullet-shaped airpl 

e that was built by the Bell Aircraft Company for the U.S. 

Air Force and the NACA. The mission of the X-1 was to 

XS-1-1 in flight in 1947. NASA photo E60-6204A. 

investigate the transonic speed range (speeds from just 

below to just above the speed of sound) and, if possible, to 

break the "sound barrier." 

The first of the three X-1s was glide-tested at Pinecastle 

Army Airfield, Fla., in early 1946. The first powered flight 

of the X-1 was made on Dec. 9, 1946, at Edwards Air 

Force Base, Calif., with Chalmers Goodlin, a Bell test pilot, 

at the controls. 

On Oct. 14, 1947, with Air Force Captain Charles "Chuck" 

Yeager as pilot, the aircraft flew faster than the speed of 

sound for the first time. Yeager ignited the four-chambered 

XLR-11 rocket engine after the B-29 air-launched it from 

under the bomb bay at 21,000 feet. The 6,000-pound thrust 

ethyl alcohol/liquid oxygen burning rockets, built by 

Reaction Motors Inc., pushed the aircraft up to a speed of 

700 mph in level flight. 

Yeager was also the pilot when the X-1 reached its maximum speed, 957 mph. Another Air Force pilot, Lt. Col. 

Frank Everest Jr., was credited with taking the X-1 to its 

maximum altitude of 71,902 feet. Eighteen pilots in all flew 

the X-1s. The number three plane was destroyed in a fire 

before making any powered flights. 

A single-place monoplane, the X-1 was 30 feet, 11 inches 

long; 10 feet, 10 inches high; and had a wingspan of 29 

feet. It weighed 6,784 pounds and carried 6,250 pounds of 

fuel. It had a flush cockpit with a side entrance and no 

ejection seat. 

D-558-1, 1947-1953 

A single-place, straight-wing, jet-powered aircraft, the D558-1 "Skystreak" was manufactured by Douglas Aircraft 

Company for a joint Navy/NACA flight research program. 

It was designed to investigate jet-aircraft characteristics at 

transonic speeds, including stability and control and buffet 

investigations. 

D-558-1 in flight. NASA photo E-713. 

The D-558-1 was roughly 35 feet long and 12 feet high, 

with a wingspan of 25 feet. It weighed 10,105 pounds when 

fully fueled. One Allison J35-A-11 turbojet engine powered 

the D-558-1, which took off and landed under its own 

power. 

The first flight of the aircraft, of which three were built, 

was on April 14, 1947, with Gene May, Douglas test pilot, 

at the controls. Its maximum speed of 650.8 mph, then a 

world record for turbojet powered aircraft, was achieved by 

then-Maj. Marion Carl, U.S. Marine Corps, on Aug. 25, 

1947. 

D-558-2, 1948-1956 

Three D-558-2 "Skyrockets" were built by Douglas for 

NACA and the Navy. The mission of the D-558-2 program 

2
was to investigate the flight characteristics of a swept-wing 

aircraft at high supersonic speeds. Particular attention was 

given to the problem of "pitch-up," a phenomenon often 

encountered with swept-wing configured aircraft. 

The D-558-2 was a single-place, 35-degree swept-wing 

aircraft measuring 42 feet in length. It was 12 feet, 8 inches 

D-558-2 in flight. NASA photo E-713. 

in height and had a wingspan of 25 feet. Fully fueled it 

weighed from about 10,572 pounds to 15,787 pounds 

depending on configuration. 

The first of the three D-558-2s had a Westinghouse J34-40 

jet engine and took off under its own power. The second 

was equipped with a turbojet engine replaced in 1950 with 

a Reaction Motors Inc. LR8-RM-6 rocket engine. This 

aircraft was modified so it could be air-launched from a 

P2B-1S (Navy designation for the B-29) carrier aircraft. 

The third Skyrocket had the jet engine and the rocket 

engine but was also modified so it could be air-launched. 

The jet engine was for takeoff and climbing to altitude and 

the four-chambered rocket engine was for reaching supersonic speeds. The rocket engine was rated at 6,000 pounds 

of thrust. 

The D-558-2 was first flown on Feb. 4, 1948, by John 

Martin, a Douglas test pilot. An NACA pilot, Scott 

Crossfield, became the first person to fly faster than twice 

the speed of sound when he piloted the D-558-2 to its 

maximum speed of 1,291 mph on Nov. 20, 1953. Its peak 

altitude, 83,235 feet, a record in its day, was reached with 

Lt. Col. Marion Carl at the controls. 

X-4, 1950-1953 

The X-4, a single-place, swept-wing, semi-tailless aircraft 

was designed and built by the Northrop Aircraft Compnay 

for NACA. It had no horizontal tail surfaces and its 

mission was to obtain in-flight data on the stability and 

control of semi-tailless aircraft at high subsonic speeds. 

The two X-4 aircraft were 23 feet long, 14 feet high, and 

X-4 in flight. NASA photo E-713. 

had wingspans of 26 feet. They weighed almost 8,000 

pounds at takeoff. 

The X-4 was initially powered by two Westinghouse XJ30 

turbojet engines and then by J30 turbojet engines with 

1,600 pounds of thrust each. These engines boosted the X-4 

up to speeds of 630 mph and up to altitudes of 43,300 feet. 

The aircraft's maiden flight was on Dec. 16, 1948, with 

Charles Tucker, a Northrop test pilot, at the controls. 

The X-4 helped demonstrate that tail surfaces are important 

for proper control effectiveness in the transonic speed 

range, and was also used to investigate the characteristic 

problems of tailless airplanes at low speeds, such as 

marginal longitudinal stability and control. 

X-5, 1950-1954 

The X-5 was the first aircraft capable of changing the 

sweep of its wings in flight. It was a single-place jetpowered aircraft, measuring 33 feet, 4 inches in length with 

a wingspan of 20 feet, 9 inches (with the wings swept back 

60 degrees). The wings could be swept back 20 to 60 

degrees. The X-5 weighed 9,875 pounds when fully fueled. 

Its mission was to study the effect of wing-sweep angles of 

20 to 60 degrees at subsonic and transonic speeds. Results 

X-5 in flight. NASA photo E-17351. 

3 
from these tests provided some of the design background 

for the F-111 and the Navy F-14 tactical aircraft. 

Two X-5s were manufactured by Bell Aircraft. The X-5 

was powered by an Allison J35-A jet engine with a static 

thrust of 4,900 pounds. The maximum speed was 705 mph. 

The aircraft was equipped with an ejection seat. 

The first flight was completed on June 20, 1951, with Jean 

Ziegler, a Bell test pilot, at the controls. 

Results of the research program verified NASA windtunnel predictions for the reduced drag and improved 

performance resulting from increasing the wing sweep as 

the aircraft approached the speed of sound. Even the 

unfortunate spinning characteristics of the X-5 yielded a 

wealth of data for determining poor aircraft spin design. 

XF-92A, 1951-1953 

XF-92A in flight. NASA photo E-17346. 

The XF-92A was this country's first delta-wing aircraft. It 

was flown to obtain data on the flight characteristics of a 

delta-wing aircraft in the transonic speed range. 

It was a single-place aircraft, 42 feet, 5 inches long and 17 

feet, 8 inches high, with a wingspan of 31 feet, 3 inches. 

The XF-92A took off and landed under its own power 

using an Allison J33-A jet engine, equipped with afterburner capability. 

The XF-92A was built by the Consolidated Vultee Aircraft 

Company (Convair). Stability and control, pitch-up, and 

lift/drag measurements obtained from the XF-92A helped 

build up the technology that was used to develop such 

delta-wing aircraft as the F-102, F-106, B-58 and other 

high-performance aircraft. 

X-3, 1953-1955 

A single-place jet aircraft, the X-3 had a slender fuselage 

and a long tapered nose. Its primary mission was to investigate the design features of an aircraft suitable for sustained 

supersonic speeds. 

X-3 in flight NASA photo E-17348. 

Douglas Aircraft built the only model of the X-3 ever 

produced. It was 66 feet, 9 inches long; 12 feet, 6 inches 

high; and had a wingspan of 22 feet, 8 inches. Two 

Westinghouse J34 turbojets, equipped with afterburners, 

powered the X-3. It was capable of takeoff and landing 

under its own power. 

The top speed of the aircraft was just under the speed of 

sound. A secondary purpose of the X-3 was to test new 

materials such as titanium, and it also contributed to the 

development of aircraft tire technology. 

X-1A, X-1B, & X-1D, 1953-1958 

The X-1A, X-1B, and the X-1D were growth versions of 

the X-1. They were almost 5 feet longer, almost 2,500 

pounds heavier and had conventional canopies. The X-1A 

and X-1B were modified to have ejection seats. 

Their mission was to continue the X-1 studies at higher 

speeds and altitudes. The X-1A began this research after 

the X-1D was destroyed in an explosion on a captive flight 

X-1A in flight over lakebed. NASA photo E-2490. 

before it made any research flights. On Dec. 12, 1953, 

Yeager flew the X-1A up to a speed of 1,612 mph (almost 

two-and-a-half times the speed of sound). Then on Aug. 26, 

1954, Major Arthur Murray took the X-1A up to an altitude 

of 90,440 feet. Those two performances were the records 

for the X-1 program. Later the X-1A was also destroyed 

after being jettisoned from the carrier aircraft because of an 

explosion. 

4
X-1B on lakebed. NASA photo E-4097. 

The X-1B was fitted with 300 thermocouples for exploratory aerodynamic heating tests. It also was the first aircraft 

to fly with a reaction control system, a prototype of the 

system used on the X-15. The X-1C was cancelled before 

production. 

All three of the Bell Aircraft-manufactured planes had 

6,000-pound thrust, XLR-11 four-chambered rocket 

engines. The XLR-11 was built by Reaction Motors, Inc. 

The aircraft were all air-launched from a carrier aircraft. 

X-2, 1954-1956 

The X-2 was a swept-wing aircraft designed to fly three 

times as fast as the speed of sound. It was flown to investigate the problems of aerodynamic heating and stability and 

control effectiveness at high speeds and altitudes. 

The X-2 was a single-place airplane with wings swept back 

40 degrees. It was 37 feet, 10 inches long (fuselage only); 

11 feet, 9 inches high; and had a wingspan of 32 feet, 3 

inches. It was constructed primarily of K-Monel (a nickel 

alloy) and stainless steel. It had an ejectable nose capsule. 

X-2 in flight. NASA photo E-2822. 

The X-2 was powered by an XLR25-CW two-chambered 

rocket engine. The Curtiss-Wright-manufactured engine 

was throttleable and had a thrust of from 2,500 to 15,000 

pounds. Two X-2s were made for NACA and the Air Force 

by Bell Aircraft. They were air launched from a B-50 

carrier aircraft. 

One X-2 (no. 2 aircraft) was destroyed in an explosion on a 

captive flight before it made any powered flights. The 

other X-2 (no. 1 aircraft) went on to perform as predicted 

including making a flight on Sept. 7, 1956, with Air Force 

Captain Iven Kincheloe at the controls to an altitude of 

126,200 feet. Twenty days later the X-2 program ended 

when Air Force Captain Milburn Apt piloted the X-2 to its 

highest speed of 2,094 mph (over three times the speed of 

sound) before it went out of control and crashed. Apt was 

killed in the crash. 

X-1E, 1953-1958 

The no. 2 X-1 was modified and redesignated the X-1E. 

The modifications included adding a conventional canopy, 

an ejection seat, a low-pressure fuel system of increased 

capacity, and a thinner high-speed wing. 

X-1E on lakebed. NASA photo E-1920. 

The X-1E was used to obtain in-flight data at twice the 

speed of sound, with particular emphasis placed on investigating the improvements achieved with the high-speed 

wing. These wings, made by Stanley Aircraft, were only 3 

- 3/8-inches thick at the root and had 343 gauges installed

in them to measure structural loads and aerodynamic 

heating. 

The X-1E used the XLR-11 rocket engine to power it up to 

a speed of 1,471 miles per hour and to an altitude of 73,000 

feet. Like the X-1 it was air-launched. 

X-15, 1959-1968 

The X-15 was a rocket-powered aircraft roughly 50 feet 

long with a wingspan of 22 feet in its original configuration. The no. 2 aircraft was later modified to become the 

X-15A-2. 

5
First flown in 1959, the three X-15 aircraft made a total of 

199 flights. Flight maximums of 354,200 feet in altitude 

and a speed of 4,520 mph were obtained. The final flight 

X-15 #2 just after launch. NASA photo EC88-0180-1. 

occurred on Oct. 24, 1968. The X-15 was manufactured by 

North American Aviation (NAA). 

It was a missile-shaped vehicle with an unusual wedgeshaped vertical tail, thin stubby wings, and unique side 

fairings that extended along the side of the fuselage. The X15 weighed about 12,295 pounds empty and approximately 

31,275 pounds at launch. The rocket engine, the XLR-99, 

was pilot-controlled and was capable of developing 57,000 

pound of rated thrust. It was manufactured by the Reaction 

Motors Division of Thiokol Chemical Corp. Before that 

engine was installed, the aircraft was powered by two 

XLR-11 rocket engines. 

The X-15 research aircraft was developed to provide inflight information and data on aerodynamics, structures, 

flight controls, and the physiological aspects of high-speed, 

high-altitude flight. The aircraft was later used as a testbed 

to carry various scientific experiments beyond the Earth's 

atmosphere. 

For flight in the dense air of the lower atmosphere, the X15 used conventional aerodynamic controls such as vertical 

stabilizers to control yaw and horizontal stabilizers to 

control pitch when moving in synchronization, or roll when 

moved differentially. 

For flight in the thin air outside of the appreciable Earth's 

atmosphere, the X-15 used a reaction control system. Eight 

hydrogen peroxide thrust rockets located on the nose of the 

aircraft provided pitch and yaw control. Four of them on 

the wings (two on each wing) furnished roll control. 

Because the X-15 consumed a large amount of fuel, it was 

air launched from a B-52 aircraft at 45,000 feet and a speed 

of about 500 mph. Depending on the mission, the rocket 

engine provided thrust for the first 80 to 120 seconds of 

flight. The remainder of the normal 10- to 11-minute flight 

was without power and ended with a 200-mph glide 

landing. 

Generally, one of two types of X-15 flight profiles was 

used--a high-altitude flight plan that called for the pilot to 

maintain a steep rate of climb, or a speed profile that called 

for the pilot to push over and maintain a level altitude. 

X-15 Flight Summary 

X-15 pilots in chronological order with total flights:

 • A. Scott Crossfield, NAA, 14

 • Joseph A. Walker, NASA, 25

 • Robert M. White, USAF, 16

 • Forrest S. Petersen, USN, 5

 • John B. McKay, NASA, 29

 • Robert A. Rushworth, USAF, 34

 • Neil A. Armstrong, NASA, 7

 • Joe H. Engle, USAF, 16

 • Milton O. Thompson, NASA, 14

 • William J. Knight, USAF, 16

 • William H. Dana, NASA, 16

 • Michael J. Adams, USAF, 7

The fastest speed (basic aircraft) was 4,104 mph on flight 

number 1-30-51 (taking place on June 27, 1962) with pilot 

Joe Walker. 

The fastest speed with tanks was 4,520 mph (Mach 6.7) on 

flight 2-53-97 with pilot William Knight (taking place on 

Oct. 3, 1967). 

The highest altitude was 354,200 feet (67 miles) on flight 

3-22-36 (taking place on Aug. 22, 1963). 

The total distance flown was 41,763.8 miles (statute). 

The total flights of the X-15 was 199 between 1959 and 

1968. 

Hours above Mach (cumulative):

 • Mach 1-18 hours, 16 minutes, and 28 seconds;

 • Mach 2-12 hours, 10 minutes, and 44 seconds;

 • Mach 3-8 hours, 51 minutes, and 33 seconds;

 • Mach 4-5 hours, 58 minutes, and 52 seconds;

 • Mach 5-1 hours, 25 minutes, and 33 seconds;

 • Mach 6-1 minutes and 18 seconds.

Total: 30 hours, 14 minutes, 57.2 seconds 

6 
XB-70, 1966-1969 

The XB-70 was the world's largest experimental aircraft. It 

was capable of flight at speeds of three times the speed of 

sound (roughly 2,000 mph) at altitudes of 70,000 feet. It 

was used to collect in-flight information for use in the 

design of future supersonic aircraft, military and civilian. 

XB-70A taking off. NASA photo E-16695. 

The major objectives of the XB-70 flight research program 

were to study the airplane's stability and handling characteristics, to evaluate its response to atmospheric turbulence, 

and to determine the aerodynamic and propulsion performance. In addition there were secondary objectives to 

measure the noise and friction associated with airflow over 

the airplane and to determine the levels and extent of the 

engine noise during takeoff, landing, and ground operations. 

The XB-70 was about 186 feet long, 33 feet high, with a 

wingspan of 105 feet. Originally conceived as an advanced 

bomber for the U. S. Air Force, the XB-70 was limited to 

production of two aircraft when it was decided to limit the 

aircraft's mission to flight research. The first flight of the 

XB-70 was made on Sept. 21, 1964. The number two XB70 was destroyed in a mid-air collision on June 8, 1966. 

Program management of the NASA-Air Force research 

effort was assigned to NASA in March 1967. The final 

flight was flown on Feb. 4, 1969. 

Designed by Rockwell International, the XB-70 had a long 

fuselage with a canard or horizontal stabilizer mounted just 

behind the crew compartment. It had a sharply swept 65.6-

percent delta wing. The outer portion of the wing could be 

folded down in flight to provide greater lateral-directional 

stability. The airplane had two windshields. A moveable 

outer windshield was raised for high-speed flight to reduce 

drag and lowered for greater visibility during takeoff and 

landing. The forward fuselage was constructed of riveted 

titanium frames and skin. The remainder of the airplane 

was constructed almost entirely of stainless steel. The skin 

was a brazed stainless-steel honeycomb material. Six 

General Electric YJ93-3 turbojet engines, each in the 

30,000-pound-thrust class, powered the XB-70. Internal 

geometry of the inlets was controllable to maintain the 

most efficient airflow to the engines. 

XB-70 Flight Summary 

XB-70 pilots in chronological order and number of flights 

as pilot and co-pilot:

 • Alvin White, NAA, 49 as pilot, 18 as co-pilot

 • Joseph Cotton, USAF, 19 as pilot, 43 as co-pilot

 • Van Shepard, NAA, 23 as pilot, 23 as co-pilot

 • Fitzhugh Fulton, USAF and NASA, 31 as pilot, 32 as

 co-pilot

 • Carl Cross, USAF, 1 as co-pilot

 • Donald Mallick, NASA, 4 as pilot, 5 as co-pilot

 • Emil Sturmthal, USAF, 3 as pilot, 7 as co-pilot

The first flight was on Sept. 21, 1964, with White and 

Cotton as crew. 

The final flight was on Feb. 4, 1969, with Fulton and 

Sturmthal as crew. 

The fastest flight in terms of miles per hour was on Jan. 12, 

1966; the speed was 2,020 mph with White and Cotton as 

crew. 

The fastest Mach flight was on April 12, 1966; it achieved 

Mach 3.08 with White and Cotton as crew. 

The highest flight was on March 19, 1966; it attained 

74,000 feet with White and Shepard as crew. 

The total flight time was 252 hr and 38 min. The breakdown of flight time was:

 * Subsonic, 145 hr and 28 min;

 * Mach 1-2, 55 hr and 50 min;

 * Mach 2-3, 49 hr and 32 min;

 * Mach 3, 1 hr and 48 min.

7