DARPA has long been the source of some of the American military’s most advanced weapon systems, vehicles, and communication technologies, and now they’ve joined with Boeing to set their sights on the stars.  Last month, DARPA announced their selection of the Boeing Company to complete the advanced design work on their experimental space plane (XS-1) program.

The intent behind this initiative it simple: reduce the amount of time required to prepare a launch into low-earth orbit from the current timeline of months or even years down to just mere days.  According to the agency, doing so would require significant leaps in what we’re capable of in terms of ground operations and technological capabilities, but accomplishing this goal “would revolutionize the Nation’s ability to recover from a catastrophic loss of military or commercial satellites, upon which the Nation today is critically dependent.”

“The XS-1 would be neither a traditional airplane nor a conventional launch vehicle but rather a combination of the two, with the goal of lowering launch costs by a factor of ten and replacing today’s frustratingly long wait time with launch on demand,” said Jess Sponable, DARPA program manager.

“We’re very pleased with Boeing’s progress on the XS-1 through Phase 1 of the program and look forward to continuing our close collaboration in this newly funded progression to Phases 2 and 3—fabrication and flight.”

The XS-1 design calls for a fully reusable unmanned vehicle that is roughly the size of a business jet.  It will take off vertically like a rocket, and then obtain hypersonic speeds as it leaves the earth’s atmosphere.  Thus far, this all sounds quite a bit like SpaceX’s efforts to reuse rocket stages and its Dragon capsule, or like the still highly secretive Air Force X-37B, but the DARPA/Boeing initiative takes a significant departure from either of those platforms in its launch design: the XS-1 will use no external boosters or rocket stages to bring it to orbit.  Instead, Boeing’s ship will be “powered solely by self-contained cryogenic propellants.”

Aside from the mind-boggling challenge building a self-contained, fully reusable rocket-plane presents, Boeing and DARPA also have to contend with revolutionizing the recovery process and launch preparation stages of low-earth orbit trips.  They hope to do so by adopting the techniques already in use by the military for quick turnarounds on combat aircraft, such as using easily accessible subsystem components “configured as line replaceable units” wherever practical, to enable quick maintenance and repairs.

Despite the number of advances and new technologies required to make this goal attainable, DARPA isn’t starting from scratch on all the equipment they intend to use on the XS-1.  Some of the parts come from previous DARPA, NASA, or U.S. Air Force initiatives, like the Aerojet Rocketdyne AR-22 engine intended for use on the demonstrator.  That engine first saw orbital use as the now defunct space shuttle’s main engine.

DARPA and Boeing expect to begin demonstration flights as soon as the early 2020s, which means delivering payloads to orbit could soon become even more affordable than the already significant cost reductions anticipated by the likes of SpaceX and other private space ventures.  More importantly, it would allow the United States to quickly replace damaged or destroyed satellites our country and its military rely on for communications, GPS tracking, and the like.