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EDWARDS AIR FORCE BASE, Calif. — An X-51A Waverider flight test vehicle successfully made the longest ever supersonic combustion ramjet-powered hypersonic flight today off the Southern California coast.
The more than 200-second burn by the X-51’s Pratt & Whitney Rocketdyne-built air breathing scramjet engine accelerated the vehicle to Mach 5. The previous longest scramjet burn in a flight test was 12 seconds in a NASA X-43.
Even before sifting through volumes of telemetry data transmitted by the X-51, Air Force officials called the test, the first of four planned, an unqualified success. The flight is considered the first use of a practical hydrocarbon-fueled scramjet in flight.
"We are ecstatic to have accomplished the most significant of our test points on the X-51A’s very first hypersonic mission," said Charlie Brink, X-51A program manager with the Air Force Research Laboratory at Wright-Patterson Air Force Base, Ohio. "We equate this leap in engine technology as equivalent to the post-World War II jump from propeller-driven aircraft to jet engines."
The X-51 departed about 10 a.m. from Edwards Air Force Base, carried aloft under the left wing of an Air Force Flight Test Center B-52H Stratofortress. Then, flying at 50,000 feet over the Point Mugu Naval Air Warfare Center Sea Range, the Waverider was released. Four seconds later an Army Tactical Missile solid rocket booster accelerated the X-51 to about Mach 4.8 before it and a connecting interstage were jettisoned. The launch and separation were normal, Mr. Brink said.
Then the X-51’s SJY61 engine ignited, initially on a mix of ethylene, similar to lighter fluid, and JP-7 jet fuel then exclusively on JP-7, the same fuel that once powered the SR-71 Blackbird before its retirement. The flight reached an altitude of about 70,000 feet and a peak speed of Mach 5.
