DARPA's conceptual image for its XS-1 spacecraft

Slowly but surely, DARPA's XS-1 Experimental Spaceplane is becoming more than a bundle of nice ideas. The agency has just chosen the companies that will square off in the first phase of the unmanned craft's design program, most of which are recognizable names in the space business. Boeing is partnering with Jeff Bezos' Blue Origin on one version of the ship; Masten Space Systems is teaming up with XCOR on another, and Northrop Grumman is cooperating with Virgin Galactic. All three groups will have to submit initial designs before DARPA can move on to a second phase, so we're still far, far away from seeing an XS-1 in orbit. But hey, it's progress -- and the companies involved are skilled enough that a cheap, highly reusable spaceplane should become a practical reality.