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X-15 North American
High-Speed Research Aircraft

The X-15 remains the fastest and highest flying manned aircraft ever flown, and is regarded by many as the most important research plane in history. The X-15 emerged from a combined US Air Force and US Navy request for a research aircraft to reach altitudes of 250,000 ft and speeds exceeding Mach 6. The design featured a long slender fuselage with fairings along the side containing fuel and early computerized control systems. Thick fins were placed on the aft fuselage to provide directional control, and the bottom fin was ejected shortly before landing to provide clearance for the landing skids.

The X-15 was carried aloft by a modified B-52 bomber before its rocket engine powered it to the very edge of the atmosphere. The improved X-15A-2 was extensively modified with heat-resistant coatings and large external fuel tanks so that it could fly even higher and faster than earlier examples.

Though the Air Force and Navy funded the project, NACA, later NASA, was in charge of the flight test program. Despite some early accidents, nearly 200 flights were made between 1959 and 1968 allowing NASA to collect data vital to the design of the Space Shuttle.

Data below for X-15A
Last modified 28 August 2010

First Flight

(X-15A) 10 March 1959 [carried by B-52 but not released]
(X-15A) 8 June 1959 [unpowered glide]
(X-15A) 17 September 1959 [powered flight]
(X-15A-2) 28 June 1964

CREW: one: pilot



Wing Root unknown
Wing Tip


Length 50.00 ft (15.24 m)
Wingspan 22.00 ft (6.71 m)
Height 13.50 ft (4.12 m)
Wing Area 200 ft (18.58 m)
Canard Area

not applicable

Empty 13,000 lb (5,895 kg)
Normal Takeoff unknown
Max Takeoff 34,000 lb (15,420 kg)
Fuel Capacity internal: unknown
external: unknown
Max Payload


Powerplant one Reaction Motors XLR-99 rocket motor
Thrust 57,000 lb (253.6 kN) at sea level
70,000 lb (311.4 kN) at peak altitude

Max Level Speed (X-15A) 4,160 mph (6,695 km/h)
(X-15A-2) 4,520 mph (7,274 km/h) at 102,100 ft (31,120 m), Mach 6.72
Initial Climb Rate unknown
Service Ceiling (X-15A-2) 354,200 ft (107,960 m)
Range 215 nm (400 km)
g-Limits unknown

X-15A Original design first powered by an 8,000 lb (35.6 kN) thrust XLR-11 rocket engine; 3 built
X-15A-2 Second X-15A rebuilt following a landing accident, featured a longer fuselage, external fuel tanks, and heat-resistant surface; 1 converted


United States (US Air Force)
United States (NASA)



  • Boeing North American X-15 site
  • Chant, Christopher and Taylor, Michael J.H. The World's Greatest Aircraft. Edison, NJ: Chartwell Books, 2006, p. 284, North American X-15.
  • Donald, David, ed. The Complete Encyclopedia of World Aircraft. NY: Barnes & Noble, 1997, p. 706, North American X-15.
  • Dryden Research Center Photo Gallery
  • Miller, Jay. The X-Planes: X-1 to X-45. Hinckley, England: Midland Publishing, 2001, p. 172-203, North American X-15 and X-15A-2.
  • Pima Air & Space Museum X-15 site
  • US Air Force Museum X-15 site
  • Winchester, Jim. Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft. San Diego, CA: Thunder Bay Press, 2005, p. 184-185, North American X-15.

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