DARPA's Phantom Express experimental spaceplane has taken a step closer to flight with Aerojet Rocketdyne's AR-22 booster rocket engine successfully completing 10 test firings in 240 hours. Based on the Space Shuttle main engine, the new variant is designed for rapid recycling as part of an effort to create an aircraft-like launch vehicle that can send satellites into orbit as rapidly as airliners leave airports.

The Experimental Spaceplane program is a being developed as a partnership between DARPA and Boeing, with the aim of both speeding up the launch of orbital payloads and bringing down costs. The idea is for the spaceplane to launch small satellites of 3,000 lb (1,361 kg) for US$5 million apiece at a rate of 10 flights in 10 days.

To achieve this, the unmanned, autonomous Phantom Express lifts off vertically from a launch pad. After reaching hypersonic velocity, it goes into a sub-orbital trajectory to the edge of space, where it releases a piggyback second stage to send the payload into orbit. The key to the spaceplane is an updated version of the AR-22 engine. It burns a mixture of liquid hydrogen and liquid oxygen to produce over 375,000 lb of thrust for at least 100 seconds.

From June 26 to July 26 at NASA's Stennis Space Center, Aerojet Rocketdyne carried out 10 test firings interspersed with inspections and data reviews. The purpose was to demonstrate that it's feasible to recycle the engine fast enough after each flight to be ready for the next one, as well as improve the design for the operational variant.

"Aerojet Rocketdyne has continued to refine the reusable engine technology we originally developed for the Space Shuttle program," says Eileen Drake, Aerojet Rocketdyne CEO and president. "With the AR-22 we are taking reusability to the next level and have demonstrated that daily, affordable access to space is within reach."

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