Captain Joe Engle is seen here next to the X-15-2 (56-6671) rocket-powered research aircraft after a flight. Engle made 16 flights in the X-15 between October 7, 1963, and October 14, 1965. Three of the flights, on June 29, August 10, and October 14, 1965, were above 50 miles, qualifying him for astronaut wings under the Air Force definition. (NASA followed the international definition of space as starting at 62 miles.) Engle was selected as a NASA astronaut in 1966, making him the only person who had flown in space before being selected as an astronaut. First assigned to the Apollo program, he served on the support crew for Apollo X and then as backup lunar module pilot for Apollo XIV. In 1977, he was commander of one of two crews who were launched from atop a modified Boeing 747 in order to conduct approach and landing tests with the Space Shuttle Enterprise. Then in November 1981, he commanded the second flight of the Shuttle Columbia and manually flew the re-entry--performing 29 flight test maneuvers--from Mach 25 through landing roll out. This was the first and, so far, only time that a winged aerospace vehicle has been manually flown from orbit through landing. He accumulated the last of his 224 hours in space when he commanded the Shuttle Discovery during STS-51-I in August of 1985. The X-15 was a rocket-powered aircraft 50 ft long with a wingspan of 22 ft. It was a missile-shaped vehicle with an unusual wedge-shaped vertical tail, thin stubby wings, and unique fairings that extended along the side of the fuselage. The X-15 weighed about 14,000 lb empty and approximately 34,000 lb at launch. The XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., was pilot controlled and was capable of developing 57,000 lb of rated thrust (actual thrust reportedly climbed to 60,000 lb). North American Aviation built three X-15 aircraft for the program. The X-15 research aircraft was developed to provide in-flight information and data on aerodynamics, structures, flight controls, and the physiological aspects of high-speed, high-altitude flight. A follow-on program used the aircraft as a testbed to carry various scientific experiments beyond the Earth's atmosphere on a repeated basis. For flight in the dense air of the usable atmosphere, the X-15 used conventional aerodynamic controls such as rudder surfaces on the vertical stabilizers to control yaw and canted horizontal surfaces on the tail to control pitch when moving in synchronization or roll when moved differentially. For flight in the thin air outside of the appreciable Earth's atmosphere, the X-15 used a reaction control system. Hydrogen peroxide thrust rockets located on the nose of the aircraft provided pitch and yaw control. Those on the wings provided roll control. Because of the large fuel consumption, the X-15 was air launched from a B-52 aircraft at 45,000 ft and a speed of about 500 mph. Depending on the mission, the rocket engine provided thrust for the first 80 to 120 sec of flight. The remainder of the normal 10 to 11 min. flight was powerless and ended with a 200-mph glide landing. Generally, one of two types of X-15 flight profiles was used: a high-altitude flight plan that called for the pilot to maintain a steep rate of climb, or a speed profile that called for the pilot to push over and maintain a level altitude. The X-15 was flown over a period of nearly 10 years--June 1959 to Oct. 1968--and set the world's unofficial speed and altitude records of 4,520 mph (Mach 6.7) and 354,200 ft (over 67 mi) in a program to investigate all aspects of piloted hypersonic flight. Information gained from the highly successful X-15 program contributed to the development of the Mercury, Gemini, and Apollo manned spaceflight programs, and also the Space Shuttle program. The X-15s made a total of 199 flights and were manufactured by North American Aviation. X-15-1, serial number 56-6670, is now located at the National Air and Space Museum, Washington DC. North American X-15A-2, serial number 56-6671, is at the United States Air Force Museum, Wright-Patterson AFB, Ohio. The X-15-3, serial number 56-6672, crashed on 15 November 1967, resulting in the death of Maj. Michael J. Adams.
