Boeing Preps for Mach 5 X-51A Flight

Unmanned flight demonstrator will put scramjet technology to the test.

X-51A WaveRider
X-51A WaveRider
Artist's conception of the X-51A WaveRider

Boeing on Tuesday was preparing to fly its experimental X-51A WaveRider, a scramjet-powered unmanned aircraft that is designed to travel at speeds above Mach 5 burning JP-5 jet fuel.

The Air Force planned to transport the aircraft under the wing of a B-52 bomber from Edwards Air Force Base in California to an altitude of 50,000 feet over the Pacific Ocean near Point Mugu. From there, the X-51A’s high-speed test flight -- at speeds in excess of 3,500 mph -- was planned to last 300 seconds, after which it was to splash down in the ocean.

Once released over the ocean, the X-51A will fall for several seconds before its booster rocket ignites, allowing the craft to gain its initial acceleration for about 30 seconds. The booster will then drop off, with the WaveRider accelerating to around Mach 4.5. After that, the X-51A’s jet-fuel-powered Pratt & Whitney Rocketdyne SJY61 scramjet engine will ignite, propelling the craft above Mach 5 at a height of 70,000 feet.

The WaveRider is so named because its engine allows it to ride on its own shockwave, Boeing said. The test flight picks up where a failed test left off last year. The X-51A maximum attainable speed is predicted to be above Mach 7.