By Marina Malenic

The X-51A Waverider will make its first hypersonic flight attempt tomorrow, the Air Force said last week.

A development effort involving the Air Force Research Laboratory, prime contractor Boeing [BA] and rocket engine manufacturer Pratt & Whitney [UTX] Rocketdyne, the X-51 is ready to for flight, the Air Force Research Laboratory (AFRL) at Wright-Patterson AFB, Ohio, said.

The unmanned X-51A is expected to fly autonomously for five minutes after it is released by a B-52 bomber off the southern California coast. It will be powered by a supersonic combustion ramjet or scramjet engine, accelerating to about Mach 6 and transmitting vast amounts of data to ground stations before breaking up after splashing down into the Pacific. There are no plans to recover the flight test vehicle.

“In those 300 seconds, we hope to learn more about hypersonic flight with a practical scramjet engine than all previous flight tests combined,” said Charlie Brink, X-51A program manager with AFRL’s Propulsion Directorate.

The longest previous hypersonic scramjet flight test performed by a NASA X-43 in 2004 was faster, but lasted only about 10 seconds, Brink said.

The 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.

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.

“This is an experimental X-plane and it’s a complicated test. We knew the original schedule was aggressive and we would need to be flexible,” Brink said. “It’s also expensive to keep a staff of engineers and support staff at the ready and then not be able to fly when supporting assets aren’t available. So we elected to make only one hypersonic try this spring and then pause for a few months to conserve funding.”

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. The X-51 test this spring is expected to be the longest duration air-breathing hypersonic flight ever conducted.

Two captive-carry tests were flown in December and January over the Point Mugu, Calif.-controlled test range. The X-51 is to be launched at 50,000 feet on the same flight path during the upcoming test.

A U.S. Navy P-3 will aid in transmitting telemetry data to both Naval Air Station Point Mugu and Vandenberg AFB, Calif.

Virtually wingless, the X-51 is designed to ride its own shockwave. The heart of the system is its Pratt Whitney Rocketdyne SJY61 scramjet engine, but other key technologies that will be demonstrated by the X-51A include thermal protection systems materials, airframe and engine integration, and high-speed stability and control.