The U.S. military has long sought quick, low cost access to space along with the ability to operate a satellite launcher like a commercial airliner making daily roundtrips.

The Defense Advanced Research Projects Agency (DARPA), which launched an experimental space plane program in 2013, recently settled on a winged design that would be propelled by a version of Aerojet Rocketdyne’s AR-22 engine originally used as the main engine for the American space shuttle.

Prime contractor Boeing Co. said it is applying automation technology developed during testing of the X-37B shuttle to its Phantom Express prototype selected by DARPA.

A key step in the DARPA spaceplane program was verifying propulsion technology. A test engine was ignited ten times in ten days last summer at NASA’s Stennis Space Center in Mississippi, demonstrating the ability to repeatedly fuel, inspect and re-ignite the engine within 24 hours.

Along with quick turnarounds, the goal of DARPA’s XS-1 (Experimental Spaceplane) program is reducing per-flight cost to less than $5 million. Key requirements include the ability to launch a reusable first stage capable of hypersonic speeds and a smaller second stage to boost payloads up to 5,000 pounds into low Earth orbit.

The vehicle would “further break the cost of launch into space, in particular satellite launch,” according to Boeing CEO Dennis Muilenburg.

“This idea of being able to launch, return, turn the vehicle [around in 24 hours] and launch again the next day, and do it ten days in a row, is going to fundamentally revolutionize our access to space,” Muilenburg asserted.

With current satellite launches easily exceeding $40 million a pop, Muilenberg predicted the DARPA program seeks to bring launch costs down to “single-digit millions” of dollars.

“We’re looking at order-of-magnitude cost reductions” for launching military satellites, the Boeing chief told the next generation of aerospace engineers at Purdue University’s School of Aeronautics and Astronautics last week.

In announcing Boeing’s selection to build the XS-1, DARPA noted that the reusable unmanned vehicle roughly the size of a business jet would take off vertically like a rocket but would not require an external booster. The AR-22 engine burning cryogenic propellants would boost Phantom Express to a suborbital altitude at which point an expendable upper stage would deploy payloads to polar orbit.

The reusable spaceplane would then bank away and return to Earth landing on a runway, similar to the X-37B and the space shuttle. Among the differences is that the XS-1 would be ready to fly again, “potentially within hours,” DARPA said.

At least a dozen test flights are currently scheduled for as early as 2020. The successful firing of the AR-22 engine over a ten-day span was a key milestone in deploying the reusable spaceplane, program officials said.

By: DocMemory
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