X-51A Scramjet Demonstrator Program: Waverider Ground and Flight Test

Supersonic combustion ramjet scramjet propulsion is a significant advancement in air-breathing propulsion technology. The X-51A WaveRider research vehicle recently set new aviation speed records by employing a scramjet engine in a specialized airframe designed to operate at hypersonic airspeeds. The X-51A was an unmanned scramjet demonstration vehicle designed and developed by the consortium of Air Force Research Laboratory AFRL, Defense Advanced Research Projects Agency DARPA, The Boeing Company, Pratt Whitney Rocketdyne and the National Aeronautics and Space Administration NASA to meet the requirements of the United States Air Force USAF WaveRider program. The overall test objective of the X-51A program was to demonstrate a scramjet engine using endothermic hydrocarbon fuel, by accelerating a vehicle up to Mach 6 after the vehicle was boosted to the altitude and airspeed conditions required for engine start. Four X-51A vehicles were built and flown, but only the fourth and final X-51A flight accomplished on 1 May 2013 was fully successful. On that flight the X-51A traveled more than 230 nautical miles in just over six minutes reaching a peak airspeed of approximately Mach 5.1 with a record-setting 210 seconds of air-breathing hypersonic flight. Overall, X-51A flight tests demonstrated the feasibility of an air-breathing scramjet-powered vehicle using hydrocarbon fuel. Flight tests showed the vehicle could successfully be boosted to reach the required conditions for scramjet engine start and the engine could sustain supersonic combustion during autonomous flight operations. The process of preparing to conduct X-51A flight tests was extremely meticulous, in part due to unique constraints of the X-51A test vehicle. This paper presents the attention to detail that was required for the proper planning and execution of X-51A flight tests.