X-15 Flight 91 was an August 22, 1963 American crewed sub-orbital spaceflight, and the second and final flight in the program to fly above the Kármán line, which was previously achieved during Flight 90 a month earlier by the same pilot, Joseph A. Walker. It was the highest flight of the X-15 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 support plane over Smith Ranch Dry Lake, Nevada, 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 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, 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. Unofficial altitude record set for class. Highest altitude achieved by X-15.