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The X-planes are a series of experimental United States airplanes and helicopters (and some rockets) used to test and evaluate new technologies and aerodynamic concepts. Most of the X-planes have been operated by the National Advisory Committee for Aeronautics (NACA) or, later, the National Aeronautics and Space Administration (NASA), often in conjunction with the United States Air Force. The majority of X-Plane testing has occurred at Edwards Air Force Base.
Some of the X-planes have been well publicized, while others, such as the X-16, have been developed in secrecy. The first, the Bell X-1, became well known after it became, in 1947, the first aircraft to break the sound barrier in level flight. Later X-planes supported important research in a multitude of aerodynamic and technical fields, but only the North American X-15 rocket plane of the early 1960s achieved comparable fame to that of the X-1. X-planes 7 through 12 were actually missiles (used to test new types of engines), and some other vehicles were un-piloted (some were remotely flown, some were full-on drones).
Most X-planes are not expected to go into full-scale production; one exception was the Lockheed Martin X-35, which competed against the Boeing X-32 during the Joint Strike Fighter Program, and has entered production as the F-35.
Not all U.S. experimental aircraft have been designated as X-planes; some received U.S. Navy designations before 1962, while others have been known only by manufacturers' designations,[N 1] non-'X'-series designations,[N 2] or classified codenames.[N 3]
|Image||Maiden flight||Purpose and Notes|
|January 19, 1946||High-speed and high-altitude testing.|
First aircraft to break the sound barrier in level flight.
Proved aerodynamic viability of thin wing sections.
|June 27, 1952||High-speed and high-altitude testing.|
First aircraft to exceed Mach 3.
|October 27, 1952||Titanium alloy construction; low aspect ratio wings.|
Planned to test long-duration high-speed flight.
Incapable of reaching design speed, but provided insights into inertia coupling.
|December 15, 1948||Evaluated handling characteristics of tailless aircraft in the transonic speed region.|
|June 20, 1951||First aircraft to fly with variable geometry wings.|
|Not flown||Modified Convair B-36 for study of Aircraft Nuclear Propulsion; not built.|
NB-36H testbed tested reactor.
"Flying Stove Pipe"
|April 1951||High-speed testbed for ramjet engines.|
NACA, USAF, USN
|Upper air research vehicle and sounding rocket.|
|April 1949||Guidance and propulsion technology testbed.|
Assisted development of GAM-63 Rascal missile.
|X-10||North American Aviation|
|October 13, 1953||Testbed for SM-64 Navajo missile.|
|June 11, 1957||Testbed for SM-65 Atlas missile.|
|July, 1958||Advanced testbed for SM-65 Atlas missile.|
|December 10, 1955||Vertical takeoff and landing (VTOL) testbed.|
Evaluated tailsitting configuration for VTOL flight.
|February 19, 1957||VTOL testbed.|
Examined the vectored thrust configuration for VTOL flight.
|X-15||North American Aviation|
|June 8, 1959||Hypersonic (Mach 6.7), high-altitude (350,000 feet (110,000 m)) testing.|
First manned hypersonic aircraft; capable of suborbital spaceflight.
|Never flew||High-altitude reconnaissance aircraft project.|
"X-16" designation used as cover story.
|April 1956||Tested the effects of high Mach number reentry.|
|November 24, 1959||VTOL/Short take-off and vertical landing (STOVL) testbed.|
Evaluated the tiltwing concept for VTOL flight.
|November 1963||Tandem tiltrotor VTOL transport testbed.|
XC-143 designation proposed.
|Never built||Reusable spaceplane for military missions.|
|April 18, 1963||Boundary layer control testbed.|
|March 17, 1966||Quad ducted fan tiltrotor STOVL testbed.|
|December 21, 1966||Maneuvering atmospheric reentry effects testbed.|
Note: Designation never officially assigned.
|August 1, 1973||Low-speed lifting body handling testbed.|
Lifting body aerodynamic shape trials.
|December 6, 1955||Light autogyro for emergency use by downed pilots.|
DARPA, US Army, USN
Training glider for yaw-roll coupling
Quiet observation aircraft testbed.
|X-27||Lockheed||Never flew||High performance fighter prototype.|
|August 12, 1970||Inexpensive aerial policing seaplane testbed.|
DARPA, USAF, NASA
|1984||Forward-swept wing testbed.|
NASA, DARPA, USAF
|Never built||Single stage to orbit spaceplane prototype.|
DARPA, USAF, BdV
|1990||Thrust vectoring supermaneuverability testbed.|
USAF, USN, RAF
|September 2000||Joint Strike Fighter prototype.|
|Prototype never completed||Half-scale reusable launch vehicle prototype.|
|Never flew||Reusable unmanned spaceplane testbed.|
USAF, USN, RAF
|2000||Joint Strike Fighter prototype.|
|May 17, 1997||28% scale tailless fighter testbed.|
|April 7, 2006 (drop test)|
April 22, 2010 (orbital flight)
|Reusable orbital spaceplane.|
|1999||Lifting body Crew Return Vehicle demonstrator.|
|Classified||Unknown||Future Aircraft Technology Enhancements (FATE) program.|
Note: Designation never officially assigned.
|August 11, 1998||80% scale Space Maneuver Vehicle testbed.|
|Classified||Unknown||Maneuvering re-entry vehicle.|
|Classified||Unknown||Expendable liquid propellant upper stage rocket.|
|June 2, 2001||Scramjet hypersonic testbed (Mach 9.68) (110,000 ft).|
|Cancelled||F-22-based Multi-Axis No-Tail Aircraft thrust vectoring testbed.|
|May 22, 2002||Unmanned combat air vehicle (UCAV) demonstrator.|
|Cancelled||Naval UCAV demonstrator.|
|February 23, 2003||Naval UCAV demonstrator.|
|July 20, 2007||Blended Wing Body (BWB) testbed.|
|July 29, 2007||Compound helicopter|
Vectored Thrust Ducted Propeller (VTDP) testbed.
|24 November 2003||Canard Rotor/Wing testbed.|
|26 May 2010||Hypersonic scramjet demonstrator.|
|X-52||Number skipped to avoid confusion with B-52.|
|X-53||Boeing Phantom Works|
|November 2002||Active Aeroelastic Wing testbed.|
|Future||Supersonic transport testbed.|
|X-55||Lockheed Martin Skunk Works|
|June 2, 2009||Advanced Composite Cargo Aircraft (ACCA).|
Molded composite fuselage and empennage testbed.
|X-56||Lockheed Martin Skunk Works|
|2012||Active flutter suppression and gust load alleviation technology for potential use in future high-altitude, long-endurance (HALE) reconnaissance aircraft.|
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