Hyper-X project leader Vince Rausch with a model of the Hyper-X in a wind tunnel. The Hyper-X was the first jet aircraft designed to fly at more than 5 times the speed of sound, (Mach 5), in flight. Rausch had hoped to launch the Hyper-X, (black), on the tip of a Pegasus rocket, (silver). The aircraft and rocket then separate, and the unpiloted Hyper-X burns hydrogen fuel to fly at hypersonic speeds of up to Mach 10. The Hyper-X uses oxygen from the atmosphere for combustion, rather than having its own supply like a rocket. This increases its payload and range. Live testing began in 2001; today the project remains in limbo.