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The X Programs

Source: Draft X-33 Environmental Impact Statement

APPENDIX A; HISTORY OF THE X-PLANE PROGRAM

The U.S. X-Plane Program has evolved from being the first rocket-powered airplane to break the sound barrier (the X-1 on OctoberÜ14, 1947) and included over 30 different major research designs, although not all were developed into flying prototypes (Hallion 1984, Miller 1988, DFRC/EAFB 1994-A/B, and DFRC/EAFB 1995). As the program progressed, other non-rocket-powered experimental aircraft were built and tested. These aircraft included: a range of vertical takeoff and horizontal landing vehicles; smaller, propeller-driven reconnaissance vehicles; and a series of unmanned missile testbeds of both single and multistage designs. Although the program grew to include conventional propeller-driven aircraft, all designs had in common the aspect of being highly valuable research tools for advancement of aerodynamics and astronautics.

Accomplishments of the X-Plane family have been many. The program included: (1) the first aircraft to break the sound barrier; (2) the first aircraft to use a variable-sweep-wing in flight; (3) the first to fly at altitudes in excess of 30,000, 60,000, and 90,000 m (100,000, 200,000 and 300,000Ãœft); (4) the first to use exotic alloy metals for primary structure; (5) the first to test gimbaled jet and rocket engines; (6) the first to use jet-thrust for launch and landing; (7)Ãœthe first to fly three, four, five, and six times the speed of sound; (8) the first to test boundary-layer-airflow control theories over an entire wing at transonic speeds; (9) the first to successfully complete a 180Ãœdegree turn using a post-stall maneuver; and (10) the first missile to reach an intercontinental flight range.

The majority of testing for the X-Plane family has occurred at Edwards Air Force Base (formerly known as Muroc Army Airfield). Hosts within Edwards include the Air Force Flight Test Center and Dryden Flight Research Center. Other sites which have served as X-Plane testing sites include: Langley Research Center and Ames Research Center; various Government owned ships; White Sands Missile Range, New Mexico; Wright-Patterson Air Force Base, Ohio; Cape Canaveral Air Station, Florida; Pinecastle Air Force Base, Florida; Buffalo, New York; and the National Aviation Facilities Experimental Center in Atlantic City, New Jersey. Edwards has seen more X-Plane programs and test flights than any other similar facility in the U.S.

As with every research program testing prototype equipment, the X-Plane Program has not been without technical glitches and equipment failures. Since the beginning of the programís manned flight operations in 1946, approximately 15 major accidents and 4 fatalities (pilots) have been associated with manned vehicle tests. Three of these fatalities were from the X-2 Program, flown between 1952 and 1956, and the remaining fatality happened in 1967 during an X-15 research flight. Stringent range safety controls have resulted in no civilian property damage losses or fatalities being reported as a result of any X-Plane Program accident. Given the overwhelming number of test flights, the small number of accidents which resulted in loss of aircraft or life can be considered a remarkable program achievement. Table A-1 provides key information about each plane tested in the X-Plane series of vehicles.

Another member of the X-Plane Program would be the X-33. As a reusable spaceplane, the X-33 continues the research line developed by various components of the X-Program, such as the X-10 which tested cruise missile components; the X-12, the Atlas B missile which tested one-and-one-half propulsion staging and obtained the first intercontinental flight distance for a U.S. missile; the X-15 which explored the problems of space and reentry at high speeds (Mach 6) and altitudes; the X-17 which explored high Mach effects on reentry vehicles; and the X-23A which was the first maneuvering lifting reentry vehicle. The X-17 was a multistage rocket design which transported various reentry vehicle configurations to very high altitudes to examine their reentry characteristics. The X-23A was launched by a modified intercontinental ballistic missile and utilized a ìlifting bodyî design to glide back to earth. Information acquired from the X-23A was instrumental in later development of the Space Shuttle.