Quick answers
X-15 frequently asked questions
Short answers to the questions people ask most about the X-15. Follow the links for the full story.
What was the X-15?
The X-15 was a rocket-powered research aircraft built by North American Aviation for a joint NASA, US Air Force and US Navy program. Three were built, and they flew 199 times between 8 June 1959 and 24 October 1968 to study flight at hypersonic speeds and at the edge of space.
How fast did the X-15 fly?
The fastest flight was Mach 6.7, or 4,520 mph, flown by Pete Knight in the X-15A-2 on 3 October 1967 (flight 188). It remains the fastest speed recorded by a crewed, powered aircraft. The standard X-15 reached Mach 6.04 on 9 November 1961.
How high did the X-15 fly?
The highest flight was 354,200 ft (67.1 miles), flown by NASA pilot Joe Walker on 22 August 1963 (flight 91). Walker also flew flight 90 to 347,800 ft on 19 July 1963. These were the only two X-15 flights above the 100 km line.
How many X-15 flights were there?
There were 199 flights. X-15-1 made 81, X-15-2 (later the X-15A-2) made 53, and X-15-3 made 65. A 200th flight planned for November 1968 was cancelled.
Who flew the X-15?
Twelve pilots flew it: five from NASA (Neil Armstrong, Bill Dana, Jack McKay, Milton Thompson and Joe Walker), five from the Air Force (Michael Adams, Joe Engle, Pete Knight, Robert Rushworth and Robert White), one from the Navy (Forrest Petersen) and one from North American Aviation (Scott Crossfield).
Did the X-15 reach space?
By the US definition of 50 miles (264,000 ft), yes: thirteen flights by eight pilots went above it. By the international 100 km (62 mile) line used by the FAI, only Joe Walker's flights 90 and 91 did.
How was the X-15 launched?
It was carried under the wing of a modified B-52 (the NB-52A or NB-52B) and released at about 45,000 ft at more than 500 mph. The pilot then lit the rocket engine.
What engine did the X-15 use?
The first 24 powered flights used two Reaction Motors XLR11 engines of about 16,000 lbf in total. From 15 November 1960 the aircraft used the throttleable XLR99, which produced up to 57,000 lbf.
Did Neil Armstrong fly the X-15?
Yes. Armstrong flew seven X-15 flights between December 1960 and July 1962. His fastest was flight 64 on 26 July 1962, at Mach 5.74.
When did the X-15 program end?
The last flight, flight 199 flown by Bill Dana, was on 24 October 1968. A 200th flight planned for 21 November 1968 was cancelled on 20 December 1968.
Where can I see an X-15?
X-15-1 is in the Milestones of Flight gallery at the National Air and Space Museum in Washington, D.C. The X-15A-2 is at the National Museum of the United States Air Force. X-15-3 was destroyed in 1967. Painted displays stand at Edwards Air Force Base and elsewhere.
Can I fly the X-15 myself?
Yes. Project X-15 is a flight simulator that runs in your desktop browser: drop from the B-52, light the XLR99, climb toward 354,200 ft and land on Rogers Dry Lake.