Under a DARPA/U.S. Air Force program, Boeing is making the X-51A hypersonic demonstrator aircraft, with the aim of making the first test flight in 2009. Pratt & Whitney Rocketdyne is making the X-1 JP-7 jet-fuel scramjet engine for the X-51A, which is also known as the WaveRider, because effectively it will surf the shock wave of compressed air that the aircraft creates in front of it as it flies at speeds well in excess of Mach 5. Credit: Pratt & Whitney
