Boeing X-51
| X-51 | |
|---|---|
 |
|
| Artist's concept of X-51A during flight | |
| Role | Robotic flight demonstrator |
| Manufacturer | Boeing |
| First flight | 26 May 2010 |
| Status | Flight testing |
| Primary user | United States Air Force |
| Number built | 4 |
The Boeing X-51 (or X-51 WaveRider) is an unmanned research scramjet aircraft for hypersonic flight at Mach 5 (3,300 mph; 5,300 km/h), an altitude of 70,000 feet (21,000 m). The aircraft was designated X-51 in 2005. It completed its first powered hypersonic flight on 26 May 2010. After two unsuccessful test flights, the X-51 completed a flight of over six minutes and reached speeds of over Mach 5 for 210 seconds on 1 May 2013 for the longest duration powered hypersonic flight.
Waverider refers in general to aircraft that take advantage of compression lift produced by their own shock waves. The X-51 program was a cooperative effort by the United States Air Force, DARPA, NASA, Boeing, and Pratt & Whitney Rocketdyne. The program was managed by the Aerospace Systems Directorate within the U.S. Air Force Research Laboratory (AFRL). X-51 technology will be used in the High Speed Strike Weapon (HSSW), a Mach 5+ missile planned to enter service in the mid-2020s.
In the 1990s, the Air Force Research Laboratory (AFRL) began the HyTECH program for hypersonic propulsion. Pratt & Whitney received a contract from the AFRL to develop a hydrocarbon-fueled scramjet engine which led to the development of the SJX61 engine. The SJX61 engine was originally meant for the NASA X-43C, which was eventually canceled. The engine was applied to the AFRL's Scramjet Engine Demonstrator program in late 2003. The scramjet flight test vehicle was designated X-51 on 27 September 2005.
In flight demonstrations, the X-51 is carried by a B-52 to an altitude of about 50,000 feet (15 km; 9.5 mi) and then released over the Pacific Ocean. The X-51 is initially propelled by an MGM-140 ATACMS solid rocket booster to approximately Mach 4.5 (3,000 mph; 4,800 km/h). The booster is then jettisoned and the vehicle's Pratt & Whitney Rocketdyne SJY61 scramjet accelerates it to a top flight speed near Mach 6 (4,000 mph; 6,400 km/h). The X-51 uses JP-7 fuel for the SJY61 scramjet, carrying some 270 lb (120 kg) on board.
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