X-15 Flight 91 was an August 22, 1963 American crewed

sub-orbital spaceflight A sub-orbital spaceflight is a spaceflight in which the spacecraft reaches outer space, but its trajectory intersects the atmosphere or surface of the gravitating body from which it was launched, so that it will not complete one orbital re ...

, and the second and final flight in the program to fly above the

Kármán line The Kármán line (or von Kármán line ) is an attempt to define a boundary between Earth's atmosphere and outer space, and offers a specific definition set by the Fédération aéronautique internationale (FAI), an international record-keeping ...

, which was previously achieved during Flight 90 a month earlier by the same pilot,

Joseph A. Walker Joseph Albert Walker (February 20, 1921 – June 8, 1966) (Capt, USAF) was an American World War II pilot, experimental physicist, NASA test pilot, and astronaut who was the first person to fly an airplane to space. He was one of twelve pilots ...

. It was the highest flight of the

X-15 The North American X-15 is a hypersonic rocket-powered aircraft. It was operated by the United States Air Force and the National Aeronautics and Space Administration as part of the X-plane series of experimental aircraft. The X-15 set speed ...

program. Flight 91 was the first internationally recognized spaceflight of a reused spacecraft, as Walker had also flown plane number three on the previous sub-orbital spaceflight over the Kármán line on July 19. The flight was air-launched from a modified

Boeing B-52 Stratofortress The Boeing B-52 Stratofortress is an American long-range, subsonic, jet-powered strategic bomber. The B-52 was designed and built by Boeing, which has continued to provide support and upgrades. It has been operated by the United States Air ...

support plane over Smith Ranch Dry Lake,

Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...

, United States. Walker piloted the X-15 to an altitude of 107.96 km and remained weightless for approximately five minutes. The altitude was the highest crewed flight by a

spaceplane A spaceplane is a vehicle that can fly and glide like an aircraft in Earth's atmosphere and maneuver like a spacecraft in outer space. To do so, spaceplanes must incorporate features of both aircraft and spacecraft. Orbital spaceplanes ten ...

to that time, and remained the record until the 1981 flight of Space Shuttle ''Columbia''. Walker landed the X-15 about 12 minutes after it was launched, at

Rogers Dry Lake Rogers Dry Lake is an endorheic desert salt pan in the Mojave Desert of Kern County, California. The lake derives its name from the Anglicization from the Spanish name, Rodriguez Dry Lake. It is the central part of Edwards Air Force Base as its ...

, Edwards Airforce Base, in California. This was Walker's final X-15 flight.

Crew

Mission parameters

*Mass: 15,195 kg fueled; 6,577 kg burnout; 6,260 kg landed *Maximum Altitude: 107.96 km *Range: 543.4 km *Burn time: 85.8 seconds *Mach: 5.58 *Launch vehicle: NB-52A Bomber #003

Mission highlights

On this flight, Joe Walker became the first person to enter space twice. He had a maximum speed of 3,794 mph (6,106 km/h) and a maximum altitude of 354,200 feet. Second and final X-15 flight over 67 miles.Jenkins (2000), p. 119 Unofficial altitude record set for class. Highest altitude achieved by X-15. Last flight for Walker in X-15 program. Number 1 left RCS nozzle froze up. First flight with altitude predictor instrument (needed calibration). The mission was flown by X-15 #3, serial 56-6672 on its 22nd flight. Launched by: NB-52A #003, Pilots Russell Bement & Lewis. Takeoff: 17:09 UTC. Landing: 18:56 UTC. Chase pilots: Wood, Dana, Gordon and Rogers. The X-15 engine burned about 85 seconds. Near the end of the burn, acceleration built up to about 4 G (39 m/s²). Weightlessness lasted for 3 to 5 minutes. Re-entry heating warmed the exterior of the X-15 to 650°C in places. During pull-up after re-entry, acceleration built up to 5 G (49 m/s²) for 20 seconds. The entire flight was about 12 minutes from launch to landing.

Notes

References

* * * * * {{North American X-15 1963 in spaceflight 091