X-15A-2 "Hypersonic Shutle" NASA

The ultimate manned research aircraft has to be the X-15. It is a plane that fired the imagination of many youth (including this one), spawned a number of astronauts, and gave high speed manned aviation research its final hoorahs.

Developed specifically to see how high and how fast a man and machine could travel in an aircraft, the first powered flight in September of 1959 with Scott Crossfield at the controls. He reached a speed of nearly 1,400 mph and an altitude of 37,000 feet on that flight. It actually was the 8th time he had been airborne in an X-15 for scheduled captive and free fall flights, but most of those ended back at base after systems failures.

Interestingly, this first powered flight was made in X-15 #2, while the last powered flight was made in October 1969 by aircraft #1. At that time it reached a height of 250,000 feet and a speed of 3,682 mph. In those ten years and 199 official flights, much was learned and much was modified on the X-15.

The ultimate version of the X-15 was the X-15A-2. This was aircraft #2 that had been damaged in an overweight landing that resulted in the aircraft landing gear collapsing and the aircraft rolling at touchdown. The NASA Pilot John McKay was injured and returned to test flying six months later, but his injuries were later the cause of his leaving NASA and test flying.

It was then decided to modify aircraft #2 by extending the fuselage to make room for more fuel and to allow it to carry external tanks for the initial boost phase up past Mach 2. Although it flew a number of flights above the design speed of Mach 6, the highest achieved speed was Mach 6.70 or 4,520 mph reached in October of 1967 with flight #188. This was with the aircraft coated in a white ablative material to protect the plane at high speed. The maximum altitude was achieved 354,000 feet on flight #91 in August of 1963. To be qualified for astronaut wings the pilot has to achieve an altitude of over 264,000 feet or 50 miles. Dozens of flights were made to that altitude and a number of X-15 pilots achieved their astronaut wings.

Only two of the three X-15s survived. During a November 1967 flight, #3 skewed sideways by overcorrection at a speed of Mach 5 while at 233,000 feet. It then entered a spin and when it reached lower levels the air pressure was enough to cause the plane to exceed maximum g loads and it disintegrated in flight, killing Air Force pilot Michael Adams. #1 is with the Smithsonian Collection and #2, the A-2, is with the USAF Collection at Wright-Patterson AFB in Ohio.

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