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-2003-07-084 DFRC 

XB-70 

NASA Photo ECN-1814. XB-70A Valkyrie on ramp. 

The B-70 Valkyrie, with a planned cruise speed of Mach 3 and operating altitude of 70,000 feet, was to be the 

ultimate high-altitude, high-speed manned strategic bomber. Events, however, would cause it to play a far 

different role in the history of aviation. 

To achieve Mach 3 performance, the B-70 was designed to "ride" its own shock wave, much as a surfer rides an 

ocean wave. The resulting shape used a delta wing on a slab-sided fuselage that contained the six jet engines 

that powered the aircraft. The outer wing panels were hinged. During take off, landing, and subsonic flight, they 

remained in the horizontal position. This feature increased the amount of lift produced, improving the lift-todrag ratio. Once the aircraft was supersonic, the wing panels would be hinged downward. Changing the position 

1
Photo ED97-44244-3. XB-70 landing. 

of the wing panels reduced the drag caused by the 

wingtips interacted with the inlet shock wave. The 

repositioned wingtips also reduced the area behind the 

airplane's center of gravity, which reduced trim drag. 

The downturned outer panels also provided more 

vertical surface to improve directional stability at high 

Mach numbers. Attached to the delta was a long, thin 

forward fuselage. Behind the cockpit were two large 

canards, which acted as control surfaces. 

As impressive a technological feat as the B-70 represented, the aircraft was under development at a time 

when the future of the manned bomber was uncertain. 

During the late 1950s and early 1960s, many felt that 

manned aircraft were obsolete, and the future belonged to missiles. As a result, the Kennedy Administration ended plans to deploy the B-70. Two experimental XB-70A prototypes were under construction at 

North American Aviation when the program was 

canceled. 

At the same time there was growing interest in an 

American supersonic transport (SST). Jet airliners had 

cut flight times by more than half in comparison to 

propeller-powered aircraft. A Mach 2 or 3 SST would 

make a similar improvement over the new subsonic jet 

airliners. The Flight Research Center (FRC-now the 

Dryden Flight Research Center, Edwards, Calif.) had 

several SST studies underway during the early 1960s. 

NASA's Douglas F5D-1 was used for landing studies, 

a North American F-100C was modified to simulate 

SST handling qualities, a North American A-5A was 

used to simulate an SST for tests of the air traffic 

control system, and a Lockheed JetStar was modified 

as an in-flight SST simulator. 

The XB-70 Valkyrie seemed to be a perfect testbed for 

SST research. It was the same size as the projected 

SST designs, and used similar structural materials, 

such as brazed stainless steel honeycomb and titanium. 

Thus, the XB-70A's role changed from a manned 

bomber prototype to one of the most remarkable 

research aircraft ever flown. 

The XB-70A number 1 (62-001) made its first flight 

from Palmdale to Edwards Air F orce Base, Calif., on 

Sept. 21, 1964. Tests of the XB-70's airworthiness 

occurred throughout 1964 and 1965 by North American 

and Air Force test pilots. The Flight Research Center 

prepared its instrument package. Although intended to 

cruise at Mach 3, the first XB-70 was found to have poor 

directional stability above Mach 2.5, and only made a 

single flight above Mach 3. Despite the problems, the 

early flights provided data on a number of issues facing 

SST designers. These included aircraft noise, operational 

problems, control system design, comparison of wind 

tunnel predictions with actual flight data, and highaltitude, clear-air turbulence. 

NASA Ames Research Center, Moffett Field, Calif., 

wind-tunnel studies led engineers at North American 

Aviation in Downey, Calif., to build the second XB70A (62-207) with an added 5 degrees of dihedral on 

the wings. This aircraft made its first flight on July 17, 

1965. The changes resulted in much better handling, 

and the second XB-70 achieved Mach 3 for the first 

time on Jan. 3, 1966. The aircraft made a total of nine 

Mach 3 flights by June. 

At the same time, a joint agreement was signed between NASA and the Air Force to use the second XB70A prototype for high-speed research flights in 

support of the SST program, selected due to its better 

aerodynamics, inlet controls, and a much superior 

instrument package, compared to the first aircraft. The 

NASA research flights were to begin in mid-June, 

once the North American Aviation Phase I tests of the 

vehicle's airworthiness were completed. NASA research pilot Joe Walker was selected as the project 

pilot. The flights were to evaluate the aircraft on 

typical SST flight profiles, and to study the problems 

of sonic booms on overland flights. 

2
These plans went awry on June 8, 1966, when the 

second XB-70 crashed following a midair collision 

with NASA's F-104N chase plane. Joe Walker, F104N pilot, died in the accident. North American test 

pilot Al White ejected from the XB-70 in his escape 

capsule, but received serious injuries in the process. 

Co-pilot Maj. Carl Cross, who was making his first 

flight in the XB-70, was unable to eject and died in the 

crash. 

The deaths of Walker and Cross, and the destruction 

of the second XB-70 had major consequences for the 

research program. The second XB-70 had been selected for the Phase II tests, which were to be conducted jointly by NASA and the Air Force. With this 

aircraft now destroyed, only the first aircraft was 

available. Given the aircraft's shortcomings, the Air 

Force began to doubt that it would be able to meet the 

Phase II test goals. 

The first XB-70 was undergoing maintenance and 

modifications at the time of the accident to its sister 

ship. It did not fly again until Nov. 3, 1966. Col. Joe 

Cotton piloted it, while NASA research pilot Fitzhugh 

Fulton served as co-pilot. The flight reached a top 

speed of Mach 2.1. Between November 1966 and the 

end of January 1967, a total of 11 joint Air Force/ 

NASA research flights occurred. Cotton, Fulton, and 

Van H. Shepard of North American Aviation were 

crewmen on these flights. A top speed of Mach 2.57 

was the highest attained during the remainder of the 

XB-70 program. 

These flights were made as part of the National Sonic 

Boom Program. The XB-70 flew at differing altitudes, 

Mach numbers, and weights over an instrumented test 

range at Edwards. The "boom carpet" area was determined and the overpressure measured on two specially 

constructed housing units. The tests showed that a 

large aircraft, such as the XB-70 or the projected SST, 

could generate overpressures high enough to cause 

damage. Moreover, when the XB-70 made a turn, its 

shock waves converged, and often doubled the overpressure on the ground. 

Following these tests, the XB-70 was grounded for 

maintenance that lasted 2 1/2 months. The Air Force 

had concluded by that point that the XB-70 program 

should be turned over to NASA as soon as possible. 

Photo EC68-2101. XB-70A on ramp. 

FRC director Paul Bikle and Air Force Flight Test 

Center (AFFTC) commander Maj. Gen. Hugh Manson 

created a joint FRC/AFFTC XB-70 operating committee on March 15, 1967. This was patterned on similar 

committees established for the X-15 and lifting bodies. 

The NASA XB-70 program continued to receive Air 

Force assistance, in terms of aircraft support and Air 

Force test pilots. 

The first NASA XB-70 flight occurred on April 25, 

1967, by Fulton and Cotton. By the end of March 

1968, another 12 research flights had been completed. 

The pilots included Fulton, Cotton, and Shepard, as 

well as Lt. Col. Emil Sturmthal and NASA research 

pilot Don Mallick. The flights acquired data to correlate with an Ames ground-based SST simulator and 

the JetStar in-flight SST simulator at FRC. Other XB70 research goals were to measure its structural response to turbulence; determine the aircraft's handling 

qualities during landings; and investigate boundary 

layer noise, inlet performance, and structural dynamics, including fuselage bending and canard flight 

loads. 

The XB-70 underwent modifications after a final 

flight on March 21, 1968. During research flights, the 

XB-70 pilots had frequently experienced trim changes 

and buffeting during high-speed, high-altitude flights. 

These resulted from clear-air turbulence and rapidly 

changing atmospheric temperatures. For a specialized 

research aircraft, these characteristics were little more 

than annoying; on a commercial SST, however, they 

3
NASA Photo ECN-792. XB-70A during take-off. 

would be uncomfortable for the passengers, increase 

the pilots' workload, and shorten the structural fatigue 

life of the SST. 

The XB-70 was fitted with two small vanes for the 

Identically Located Acceleration and Force (ILAF) 

experiment. The vanes rotated 12 degrees at a rate of 

up to 8 cycles per second. This induced a structural 

vibration in the XB-70 at a known frequency and 

amplitude. The XB-70's accelerometers detected the 

disturbances, then signaled the aircraft's stability 

augmentation system to damp out the motion. When 

XB-70 research flights resumed on June 11, 1968, the 

ILAF proved its ability to reduce the effects of turbulence and atmospheric temperature changes. 

Despite the accomplishments of the XB-70, time was 

running out for the research program. NASA had 

reached an agreement with the Air Force to fly research missions with a pair of YF-12As and a "YF12C," which was actually an SR-71. These represented a far more advanced technology than that of the 

XB-70. In all, the two XB-70s had logged 1 hour and 

48 minutes of Mach 3 flight time. A YF-12 could log 

this much Mach 3 time in a single flight. 

The final XB-70 research flight occurred on Feb. 4, 

1969. Fulton and Sturmthal made a subsonic structural 

dynamics test and ferry flight. The XB-70 took off 

from Edwards and flew to Wright-Patterson Air Force 

Base, Ohio, where the aircraft was put on display at 

the Air Force Museum. The first XB-70 made 83 

flights totaling 160 hours and 16 minutes, while the 

second XB-70 logged 46 flights in its brief life, 

totaling 92 hours and 22 minutes 

4