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First Flight: June 8, 1959

Mission: High speed research aircraft used to provide information on thermal heating, high speed control and stability, and atmospheric re-entry.

Major Accomplishments: Holds both speed (Mach 6.72) and altitude 67.08 miles) records for winged aircraft.

Power Source: One (1) Reaction Motors (Thiokol) XLR99-RM-2 throtteable liquid fuel (liquid hydrogen, liquid oxygen) rocket. 57,000 lb. (25,855 kg) thrust. (First flights were made with two (2) Reaction Motors LR11-RM-5 engines at 8,000 lb. (3,630 kg) thrust each.)

Wing Span: 22 ft (6.7 m)

Length: 52 ft, 5 in (15.98 m)

Weight: Approx. 14,000 lbs (dry); 34,000 lbs (fuelled)

Maximum Achieved Speed: 4,534 mph (Mach 6.72)

Maximum Achieved Altitude: 354,200 ft. (67.08 miles)

Additional Information:  The X-15 was made primarily from titanium and stainless steel. The airframe was covered with Inconel X nickel, an alley which could withstand temperatures up to 1,200 degrees F. Because the X-15 was often subjected to temperatures higher than 1,200 degrees, the plane was often covered with a pink ablative material (MA-25S) which could "boil" away, carrying the heat with it (this material was covered with a white material that protected the MA-25S while the X-15 was in transit).

The rear tail was movable, and was pivoted for control at altitudes where the air was sufficient to control the craft. The tail also contained air-brake surfaces. At higher (non-atmospheric) altitudes, control was provided by 12 hydrogen peroxide jets, 4 in the wingtips and 8 in the nose.

All flights were conducted from Edwards Air Force base. The X-15 was dropped from a B-52 bomber "mother plane" at an altitude of 45,000 feet, and a speed of 500 mph. The plane was then piloted following a predetermined flight path, and landed on Rogers dry lake bed.

The plane was incapable of conventional (runway) take-off due, in part, to its unique landing gear. Just before landing, the lower half of the bottom tail section was jettisoned, and two landing skids were deployed. The nose contained conventional two wheel landing gear.

3 X-15's were built. The second was involved in a landing crash in November, 1962 and was rebuilt. Modifications to this model included large external fuel tanks for higher speed flights. It was this plane, in X-15A-2 configuration (see picture below) that set the speed record of mach 6.72, which stands to this day.

X-15A2 with external fuel tanks, white ablative paint, and mock-up of "Scram-Jet" engine. The Scram-Jet engine project was never completed, and only the non-functional mock-up was flight tested. The Scram-Jet mockup is on display at the US Air Force Museum in Dayton Ohio.


The final X-15 flight was conducted in November 1968, having completed a total of 199 missions.


The 3rd X-15 built was destroyed in a fatal crash in November, 1967. The surviving examples are housed at the Smithsonian Air and Space Museum (Washington DC) and the United States Air Force Museum (Dayton Oh). The Air Force Museum model is displayed on the floor, and the viewer has direct access to the plane (though the museum enforces a no-touch policy). This plane is also displayed with the "scram-jet" mock-up, an engine that would have been attached to the the lower tail section to provide higher altitude and speed performance. The program was cancelled before a working model was deployed.


X-15 Pictures

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Website Author: Nick Portwin (portwin@easynet.co.uk)

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Date Last Modified: 31 07 1999