X-15 Flight 91
|Mission type||Test flight|
|Operator||US Air Force/NASA|
|Mission duration||11 minutes, 8.6 seconds|
|Distance travelled||543.4 kilometers (337.7 mi)|
|Apogee||107.96 kilometers (67.08 mi)|
|Launch mass||15,195 kilograms (33,499 lb)|
|Landing mass||6,260 kilograms (13,800 lb)|
|Dry mass||6,577 kilograms (14,500 lb)|
|Members||Joseph A. Walker|
|Start of mission|
|Launch date||August 22, 1963, 18:05:57UTC|
|Launch site||NB-52A #52-003, Edwards
Dropped over Smith Ranch Dry Lake
|End of mission|
|Landing date||August 22, 1963, 18:17:05UTC|
|Landing site||Rogers Dry Lake, Edwards|
X-15 Flight 91 was a 1963 American human spaceflight mission, and the second and final flight in the program to achieve sub-orbital spaceflight—a flight over 100 km in altitude—which was previously achieved during Flight 90 a month earlier. It was the highest flight of the X-15 program. It was the first flight of a reused spacecraft, as plane number three flew the previous sub-orbital flight on July 19. This mission was piloted by Joseph A. Walker on August 22, 1963, with the air-launch occurring 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 manned 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.
|Pilot||Joseph A. Walker
- 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
On this flight, Joe Walker became the first person to enter space twice. He had a maximum speed of 3,794 MPH 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. 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 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.
- Jenkins (2000), p. 119
- Goodwin, Robert (2000). X-15: the NASA mission reports, incorporating files from the USAF. Burlington, Ontario: Apogee Books. ISBN 1-896522-65-3.
- Jenkins, Dennis R. (2000), Hypersonics Before the Shuttle: A Concise History of the X-15 Research Airplane, NASA Technical Reports, NASA, hdl:2060/20000068530; Document ID: 20000068530
- Price, A. B. (1968), Thermal protection system X-15A-2 Design Report, NASA Technical Reports, NASA, hdl:2060/19680016245; Document ID: 19680016245
- Stillwell, W. H. (1965), X-15 research results with a selected bibliography, NASA Technical Reports, NASA, hdl:2060/19650010561; Document ID: 19650010561
- Watts, Joe D. (1968), Flight experience with shock impingement and interference heating on the X-15-2 research airplane, NASA Technical Reports, NASA, hdl:2060/19920075739; Document ID: 19920075739