Defence

A US Air Force, Boeing and Pratt & Whitney team plans to test fly the newly designated X-51A hypersonic scramjet demonstrator in 2009 at target speeds close to Mach7. The X-51A is a descendent of earlier efforts including the Advanced Rapid Response Missile Demonstrator and the liquid hydrocarbon-fuelled scramjet engine developed under the USAF’s HyTech programme.

“It’s not a missile, but a propulsion demonstrator intended to validate the operation and performance of a scramjet engine in an operating environment as close as possible to reality,” says P&W Space Propulsion hypersonic and combined-cycle programmes manager Joaquin Castro. Ground tests of the X-51A will begin late this year, with flight tests in 2009. The latter will culminate with a series of sorties in which a 4.3m (14.1ft)-long vehicle powered by the actively fuel-cooled research engine will be accelerated by a solid rocket to a scramjet ignition speed of M4.5. The approximately 635kg (1,400lb) vehicle is then expected to accelerate to between M6.5 and M7.