In practice, this means Boeing is now building a unmanned, reusable hypersonic jet with the goal of running ten test flights over ten consecutive days by the year 2020 -- a program that's designed to prove that the XS-1 will be able to launch satellites into low-earth orbit on short notice. "The XS-1 would be neither a traditional airplane nor a conventional launch vehicle but rather a combination of the two," DARPA's Jess Sponable explained in a press release. "With the goal of lowering launch costs by a factor of ten and replacing today's frustratingly long wait time with launch on demand."

The XS-1 will manage this feat by flying to suborbital heights without boosters before deploying a disposable, secondary rocket to push its payload into orbit. Better still, the spaceplane will be able to take a second satellite up within hours of delivering the first. Well, that's the plan anyway -- the project is still years away from being finished, and the earliest on-ground engine tests won't start until 2019 at the earliest. Until then, we'll have to settle for DARPA's concept video, which admittedly, is still pretty cool.