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X-51 MAKES HISTORIC HYPERSONIC FLIGHT

The X-51A Waverider, shown here under the wing of a B-52 Stratofortress, is set to demonstrate hypersonic flight.  Powered by a Pratt & Whitney Rocketdyne SJY61 scramjet engine, it is designed to ride on its own shockwave and accelerate to about Mach 6.  (U.S. Air Force graphic)

An X-51A Waverider successfully launched from the left wing of a B-52 Stratofortress May 26. The X-51A has been touted as a “leap in engine technology equivalent to the post-World War II jump from propeller-driven aircraft to jet engines.” (U.S. Air Force graphic)

EDWARDS AIR FORCE BASE, Calif (AFNS) -- An X-51A Waverider flight-test vehicle successfully made the longest supersonic combustion ramjet-powered hypersonic flight May 26 off the southern California Pacific 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.

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 most of our test points on the X-51A's very first hypersonic mission," said Charlie Brink, an 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 launched at about 10 a.m. from here, carried under the left wing of an Air Force Flight Test Center B-52 Stratofortress. Then, flying at 50,000 feet over the Point Mugu Naval Air Warfare Center Sea Range, it 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.

Hypersonic flight, normally defined as beginning at Mach 5, five times the speed of sound, presents unique technical challenges with heat and pressure, which make conventional turbine engines impractical. Program officials said producing thrust with a scramjet has been compared to lighting a match in a hurricane and keeping it burning.

"This first flight was the culmination of a six-year effort by a small, but very talented ... development team," Brink said. "Now we will go back and really scrutinize our data. No test is perfect, and I'm sure we will find anomalies that we will need to address before the next flight. "But anyone will tell you that we learn just as much, if not more, when we encounter a glitch."