By Marina Malenic

The Air Force, along with contractors Pratt & Whitney Rocketdyne [UTX] and Boeing [BA], are studying the details of last week’s record-setting scramjet flight–the first and only planned launch this year of the X-51 Waverider.

“We were 95 percent successful,” Charles Brink, U.S. Air Force Research Laboratory (AFRL) program manager, said during a June 1 teleconference with reporters.

The X-51A was launched over the Pacific on May 26, but the scramjet engine ran for only 200 seconds at Mach 5 or “just under” Mach 5, instead of the planned 300 seconds beyond Mach 6, Brink explained. The vehicle was destroyed in flight when it began to slow down and telemetry was lost.

Brink said the cause of the slower than expected flight speed and duration remains unknown but that it’s “safe to say that the engine was not the cause of the failure.” He noted that it could just have been “a fluke in the particular vehicle that we flew.”

The team now plans to spend at least 30 days analyzing the data.

A development effort involving the Air Force Research Laboratory, prime contractor Boeing and rocket engine manufacturer Pratt & Whitney Rocketdyne, the program has produced four Waverider test vehicles. However, further test flights are on hold because delays in last month’s flight have eaten away at test funds. The original plan was to fly in December 2009 then three more times in 2010.

Brink said an Air Force request for additional funding in Fiscal 2012 is possible but that existing flight test funds in next year’s budget could suffice. He said a decision would be made shortly.

“We moved to stretch out the program to maintain the critical skills to October or November. This success may open other coffers,” he added.

The program has spent $246.3 million since its FY 2004 start, which includes about $210 million in contracts to Pratt and Boeing, according to Brink. Remaining funds were used to pay for Air Force and Navy test assets, NASA wind tunnels and supercomputers, and other government-furnished equipment.

Brink also praised the Air Force Flight Test Center at Edwards AFB, Calif., for “putting us on point” for the May 26 launch. The test center provided the B-52 aircraft that carried the Waverider under its wing until launch.

The flight was the first using a hydrocarbon-fueled scramjet in which the fuel is used to cool the engine, and the heat is used to crack the fuel so that it will burn when injected into the supersonic flow. The thermal equilibrium achieved allows the engine to operate for as long as it has fuel.

The flight control software provided by Boeing “performed perfectly,” said Joe Vogel, the company’s program manager for the project. “There is no smoking gun, but we will figure out what the issue is and fix it.”

Brink said last month’s test is a “huge advance to the state of the art of the technology,” which is expected to someday revolutionize space lift systems, high-speed weapons, and intelligence, surveillance and reconnaissance. Hypersonic speed describes velocities upward of Mach 5, or five times the speed of sound.