X-37 unmanned spaceplane exists now without any fancy SABRE engines: http://en.wikipedia.org/wiki/Boeing_X-37 http://en.wikipedia.org/wiki/Boeing_X-37 The las

X-37 unmanned spaceplane exists now without any fancy SABRE engines: http://en.wikipedia.org/wiki/Boeing_X-37 http://en.wikipedia.org/wiki/Boeing_X-37 The last one was sent up on Decemember 2012 and its still up there. Probably not as cost-efficient, but, there is an unmanned spaceplane in production, but its a secretive DoD project so we don't know too many details nor will it be used for non-military applications.