DARPA Space Plane Project

[popcorn]

Basically a reusable 2nd stage.

https://defensesystems.com/pages/topics ... stems.aspx

Boeing to demo DARPA space plane

Boeing will build and demonstrate a prototype of a new class of hypersonic aircraft designed to provide quick access to low-Earth orbit.

The Defense Advanced Research Projects Agency selected Boeing's design for the next "fabrication" and "flight" phases of its Experimental Spaceplane-1 (XS-1) effort. The DARPA program seeks to create a "launch-on-demand" capability for smaller payloads while lowering launch costs by a factor of 10.

The reusable XS-1 would serve as a hybrid aircraft-space launcher capable of lifting payloads to the edge of space where an expendable upper stage would place satellites up to 3,000 pounds into polar orbits.

Launched like a rocket and powered by cryogenic propellants, program officials said the XS-1 space plane would reach hypersonic speeds before releasing its upper stage. The reusable first stage would then land on a runway to be readied for its next flight "within hours," DARPA said...

Boeing's prototype dubbed "Phantom Express" measures 100 feet in length with a wingspan of 62 feet. The single AR-22 engine would burn a mixture of liquid hydrogen and oxygen.

[zhangmdev]

VTHL / flyback booster will be unnecessarily heavy and complicated. Folks on NSF have little positive to say about XS-1

http://forum.nasaspaceflight.com/index. ... ic=32829.0

Just (re)use a Falcon 9 and call it a day, at least that will launch something meaningful into orbit.