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Scramjet engine flight tests to start this fall

Air Force’s long-range goal for futuristic aircraft is access to space

Ty Greenlees/Staff Photographer Charlie Brink, manager of the Air Force's X-51 "Waverider" scramjet research project stands with a scale model of the hypersonic aircraft. Staff photo by Ty Greenlees

ENLARGE PHOTO

Photos: Air Force's X-51 'Waverider'

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By John Nolan, Staff Writer Updated 11:38 PM Saturday, May 9, 2009

This fall, the Air Force will send a futuristic-looking aircraft roaring out over the Pacific Ocean at nearly five times the speed of sound in its first flight test of a scramjet engine.

Officials hope the engine eventually will provide a speedier transition between conventional aircraft in the atmosphere and rockets in outer space for deployment of satellites, and reconnaissance or strike missions.

“The long-range goal of this for the Air Force is access to space,” said Charlie Brink, an Air Force Research Laboratory propulsion directorate official who manages the X-51 program from Wright-Patterson Air Force Base.

The X-51 aircraft sent aloft on Oct. 27 will be sped up by an Army missile booster to at least Mach 4.5, the minimum speed at which the air-breathing scramjet engine operates, before the scramjet kicks in and accelerates the vehicle to at least Mach 6 — six times the speed of sound. The Air Force Research Laboratory expects that the aircraft will fly for about five minutes before crashing into the Pacific (shipping is to be alerted ahead of time). The other three X-51s are to suffer similar watery fates.

The October flight — and three separate test flights planned in early 2010 — are designed to demonstrate the practicality of using the air-breathing scramjet engine to power and control an aircraft at hypersonic speeds (Mach 5 or greater). The $246.5 million development program has been under way since December 2003.

That price tag includes the four X-51s and their engines, the government support, and research ongoing at Wright-Patterson and Edwards Air Force bases in conjunction with industry partners.

The X-51 aircraft has been dubbed the “Waverider” because it stays aloft, in part, with lift generated by the shock waves of its own flight.

The Boeing Co.-built vehicle will to burn JP-7 jet fuel for the Air Force test. That is a change from the National Aeronautics and Space Administration’s initial 2004 flight test of a hydrogen-based scramjet engine which reached speeds of Mach 9.6, or nearly 7,000 mph, powering an aircraft known as the X-43.

A B-52 from Edwards Air Force Base, Calif., will carry the assembly to 50,000 feet to get the test flight under way.

Brink compares the work of developing the scramjet — to complement aircraft turbine engines and rockets — with aviation’s earlier transition from propellers to jet engines. Air Force leadership will decide the scramjet program’s next step, depending on how the project turns out, Brink said.

Partners include NASA, Defense Advanced Research Projects Agency, Boeing Advanced Network and Space Systems, and Pratt & Whitney Rocketdyne.

Program notes

Scramjet engine development was a spinoff of the government’s now-abandoned effort to develop a national aerospace plane, a project begun during the Reagan administration and continued into the 1990s.

Scramjets use the forward motion of an engine to compress air for fuel combustion. Pratt & Whitney has built scramjet engines for four of the X-51 aircraft for the flight tests in October 2009 and January-March 2010. The engines are made of a nickel alloy and are cooled during flight by their own fuel.

Propulsion Directorate

The mission of the Air Force Research Laboratory’s propulsion directorate is to provide advanced propulsion technologies for U.S. military services. The technologies are developed through partnerships with industry.

About 30 government workers and 20 contractor employees at Wright-Patterson are supporting the work of five core researchers overseeing the X-51 program from the propulsion directorate there. Under the government’s $210 million contract with Boeing and Pratt & Whitney, much of the project work is being done in California and Florida.

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