The X-planes are a series of experimental

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

aircraft An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...

and

rocket A rocket (from , and so named for its shape) is a vehicle that uses jet propulsion to accelerate without using any surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely ...

s, used to test and evaluate new technologies and aerodynamic concepts. They have an X designator within the US system of aircraft designations, which denotes the experimental research mission. Not all US experimental aircraft have been designated as X-planes; some received US Navy designations before 1962, while others have been known only by manufacturers' designations, non-'X'-series designations, or classified codenames. This list only includes the designated X-planes.

History

The X-planes concept officially came into being in 1944, as a joint programme involving the

National Advisory Committee for Aeronautics The National Advisory Committee for Aeronautics (NACA) was a United States federal agency that was founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved and its ...

(NACA), the

US Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

(USN) and the

US Army Air Forces The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...

(USAAF), in order to pursue research into high-speed aircraft.Miller 1983, p.9. NACA later became the

National Aeronautics and Space Administration The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the United States's civil space program, aeronautics research and space research. Established in 1958, it su ...

(NASA) and the USAAF became the

United States Air Force The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...

(USAF). Other organizations such as the Defence Advanced Research Projects Agency (DARPA) and the

US Marine Corps The United States Marine Corps (USMC), also referred to as the United States Marines or simply the Marines, is the Marines, maritime land force service branch of the United States Department of Defense. It is responsible for conducting expedi ...

(USMC) have also since sponsored X-plane projects. The first experimental aircraft specification, for a

transonic Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and Supersonic speed, supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach numb ...

rocket plane, was placed in 1945, and the first operational flight of an X-plane took place when the

Bell X-1 The Bell X-1 (Bell Model 44) is a rocket engine–powered aircraft, designated originally as the XS-1, and was a joint National Advisory Committee for Aeronautics– U.S. Army Air Forces– U.S. Air Force supersonic research project built by B ...

made its first powered flight nearly three years later at Muroc Air Force Base, California, now known as

Edwards Air Force Base Edwards Air Force Base (AFB) is a United States Air Force installation in California. Most of the base sits in Kern County, California, Kern County, but its eastern end is in San Bernardino County, California, San Bernardino County and a souther ...

. The majority of X-plane testing has since taken place there. X-planes have since accomplished many aviation "firsts" including breaking speed and altitude barriers, varying wing sweep in flight, implementing exotic alloys and propulsion innovations, and many more. New X-planes appeared fairly regularly for many years until the flow temporarily stopped in the early 1970s. A series of experimental hypersonic projects, including an advanced version of the

Martin Marietta X-24 The Martin Marietta X-24 is an American experimental aircraft developed from a joint United States Air Force–NASA program named PILOT (1963–1975). It was designed and built to test lifting body concepts, experimenting with the concept of ...

lifting body A lifting body is a fixed-wing aircraft or spacecraft configuration in which the body itself produces lift (force), lift. In contrast to a flying wing, which is a wing with minimal or no conventional fuselage, a lifting body can be thought of as ...

, were turned down. Eventually issues with the Rockwell HiMAT advanced UAV led to a crewed X-plane with forward sweep, the

Grumman X-29 The Grumman X-29 is an American experimental aircraft that tested a forward-swept wing, canard control surfaces, and other novel aircraft technologies. Funded by NASA, the United States Air Force and DARPA, the X-29 was developed by Grumman, a ...

, which flew in 1984. Some of the X-planes have been well publicized, while others, such as the X-16, have been developed in secrecy.Miller 2001, p. 209 The first, the

, became well known in 1947 after it became the first aircraft to break the

sound barrier The sound barrier or sonic barrier is the large increase in aerodynamic drag and other undesirable effects experienced by an aircraft or other object when it approaches the speed of sound. When aircraft first approached the speed of sound, th ...

in level flight.. Later X-planes supported important research in a multitude of aerodynamic and technical fields, but only the

North American X-15 The North American X-15 is a Hypersonic speed, hypersonic rocket-powered aircraft which was operated by the United States Air Force and the National Aeronautics and Space Administration (NASA) as part of the List of X-planes, X-plane series of ...

rocket plane A rocket (from , and so named for its shape) is a vehicle that uses jet propulsion to accelerate without using any surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely ...

of the early 1960s achieved comparable fame to that of the X-1. X-planes 8, 9, 11, 12, and 17 were actually

missile A missile is an airborne ranged weapon capable of self-propelled flight aided usually by a propellant, jet engine or rocket motor. Historically, 'missile' referred to any projectile that is thrown, shot or propelled towards a target; this ...

s used to test new types of engines, and some other vehicles were unoccupied or UAVs (some were remotely flown, some were partially or fully autonomous). Most X-planes are not expected to go into full-scale production; one exception was the

Lockheed Martin X-35 The Lockheed Martin X-35 is a concept demonstrator aircraft (CDA) developed by Lockheed Martin for the Joint Strike Fighter program. The X-35 was declared the winner over the competing Boeing X-32 and a developed, armed version went on to enter ...

, which competed against the

Boeing X-32 The Boeing X-32 is a concept demonstrator aircraft that was designed for the Joint Strike Fighter program, Joint Strike Fighter competition. It lost to the Lockheed Martin X-35 demonstrator, which was further developed into the Lockheed Martin ...

during the

Joint Strike Fighter Program Joint Strike Fighter (JSF) is a development and acquisition program intended to replace a wide range of existing Fighter aircraft, fighter, strike fighter, strike, and ground attack aircraft for the United States, the United Kingdom, Italy, C ...

, and has entered production as the

F-35 Lightning II The Lockheed Martin F-35 Lightning II is an American family of single-seat, single-engine, supersonic Stealth aircraft, stealth strike fighters. A multirole combat aircraft designed for both Air superiority fighter, air superiority and att ...

List

In the list, the date is that of the first flight, or of cancellation if it never flew.

Notes

References

Bibliography

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External links