An illustration of the X-51A Flight Test Vehicle

Imagine traveling from Orlando to Los Angeles in less than an hour. Commercial air travelers won’t be able to make that flight anytime soon, but West Palm Beach-based Pratt & Whitney Rocketdyne is working with the Air Force, Defense Advanced Research Projects Agency and Boeing on a breakthrough propulsion system designed to perform at Mach 6, more than 4,500 mph — three times faster than the Concorde.

“The program has been a huge success,” says Curtis Berger, director of hypersonic programs for Pratt & Whitney Rocketdyne.

Designing combustion systems for hypersonic (Mach 5 and above) speeds is difficult because the engine typically gets so hot that it burns up. But Pratt & Whitney Rocketdyne has designed a system that uses the fuel as both a coolant and a propellant. A standard, kerosene-type fuel is pumped through the engine casing, where it cools the engine structure. The system also breaks the fuel into smaller molecules that burn faster in the combustion chamber.

The temperature remains balanced in the engine, which has no moving parts and is made of conventional metals.

“It is aimed at multiple applications,” says Berger. One use may provide low-cost access to space, using a conventional jet engine to get off the ground before switching to supersonic combustion — called scramjet mode — at high altitudes.

In Air Force weapons applications, an unmanned missile-like vehicle dropped from a B-52 bomber would use a solid-rocket booster to power it to Mach 4.5. At that point, the booster would fall away, and the hypersonic combustion system would take over. Berger says that any commercial applications will come much later.

Pratt & Whitney Rocketdyne has been working on the X-51A scramjet demonstrator project since 2003. It conducted the first simulated flight last April and plans further tests this spring. Four actual flight tests will begin in late summer 2009.

Pratt & Whitney Rocketdyne X-1 scramjet engine in a High Temperature Tunnel.