By Marina Malenic

An X-51A Waverider flight test vehicle successfully made the longest ever supersonic combustion ramjet-powered hypersonic flight off the California coast this week, the Air Force announced following the test.

Launched a day later than expected due to discovery of a ship steaming in international waters underneath restricted airspace in the vicinity of the X-51A’s potential splashdown zone, the aircraft was accelerated to Mach 5 by its airbreathing scramjet engine on May 26.

“We are ecstatic to have accomplished most of our test points on the X-51A’s very first hypersonic mission,” said Charlie Brink, program manager with the Air Force Research Laboratory at Wright-Patterson AFB, Ohio. “We equate this leap in engine technology as equivalent to the post-World War Two jump from propeller-driven aircraft to jet engines.”

The 200-second hypersonic flight was the longest ever; a 12-second NASA X-43 flight in 2004 was the previous record.

The X-51 launched from Edwards AFB, Calif., under the left wing of a B-52 Stratofortress test aircraft. Flying at 50,000 feet over the Point Mugu Naval Air Warfare Center Sea Range, the vehicle was released. Four seconds later an Army Tactical Missile solid rocket booster accelerated it to about Mach 4.8 before it and a connecting interstage were jettisoned. Then the X-51’s SJY61 engine ignited.

The flight reached an altitude of about 70,000 feet and a peak speed of Mach 5, according to Air Force officials. After about 200 seconds of engine operation, a vehicle anomaly occurred and the flight was terminated. The flight was expected to last 300 seconds. Engineers are working to identify the cause of the problem, according to the Air Force.

“Now we will go back and really scrutinize our data,” Brink said. “No test is perfect, and I’m sure we will find anomalies that we will need to address before the next flight.”

A development effort involving the Air Force Research Laboratory, prime contractor Boeing [BA] and rocket engine manufacturer Pratt & Whitney [UTX] Rocketdyne, the program has produced four Waverider test vehicles.

Four flights in quick succession are still planned, according to the AFRL. However, program officials said this will be the only hypersonic flight attempt this fiscal year, a change from the original test plan which was to fly in December 2009 then three more times in 2010.

The first X-51 flight was originally scheduled for October 2009 but was delayed to March 2010 because the B-52H aircraft that will launch the X-51 was not available. Both government and industry officials have said that weather also played a role in the delays. Because of the high importance of data collection, clear weather is a prerequisite for test success.

Hypersonic technology has potential applications in the fields of high-speed weapons, intelligence, surveillance and reconnaissance and space missions. Hypersonic speed describes velocities upward of Mach 5, or five times the speed of sound.