Mach 6 Scramjet Test Planned For December

Airmen successfully mated the X-51A WaveRider flight test vehicle to a B-52 Stratofortress last month at Edwards Air Force Base, CA. The fit check followed integration earlier in the month of the Pratt & Whitney Rocketdyne scramjet propulsion system into the X-51 at Air Force Plant 42 in Palmdale, CA.

The X-51 test vehicle is now back at the Boeing facility in Palmdale where additional systems integration and testing are taking place in preparation for its inaugural flight test in December, said Charlie Brink, X-51 program manager from the Air Force Research Laboratory's Propulsion Directorate here.

During the flight test, currently planned Dec. 2, the Air Force Flight Test Center's B-52 will carry the X-51A to 50,000 feet over the Pacific Ocean then release it. A solid rocket booster from an Army tactical missile system then will ignite and accelerate the X-51 to about Mach 4.5. Then, the supersonic combustion ramjet propulsion system will propel the vehicle for five minutes to more than Mach 6. Hypersonic combustion generates intense heat so routing of the engine's own JP-7 fuel will help keep the engine at the desired operating temperature.

Engineers expect a great deal will be learned about hypersonic flight during the nearly 300 seconds under scramjet power. The longest-ever previous scramjet test, lasted only about 10 seconds, Brink said. As the engine ignites it will initially burn a mix of ethylene and JP-7 before switching exclusively to JP-7 fuel.

"The heart of this aircraft is its engine," Mr. Brink said. "We're really breaking new ground in our understanding of hypersonic propulsion, but our four planned test flights will also enhance our knowledge of airframe-engine integration, high-temperature materials and other technologies. Together they will help us bridge air and space."

Data from the flight will be telemetered back to Edwards before the X-51A test vehicle plunges into the Pacific.

Two B-52 flights, one captive carriage and one dress rehearsal, are planned this fall prior to the X-51's first powered flight scheduled in December, Mr. Brink said.

The X-51A WaveRider program is a joint effort by representatives from the Air Force, DARPA, Pratt & Whitney Rocketdyne and Boeing.

FMI: www.af.mil