posted on Nov, 22 2013 @ 11:26 AM
The SABRE engine can theoretically get up to mach 5 ... and that's out there in the "white world".
Perhaps someone could use the SABRE engines to get up to mach 5 at over 100,000 feet, then switch to a pair of areospike engines to achieve orbit.
Apparently arespike engines were strongly considered for the Space Shuttle's main engine...
I'm not sure if the SABRE engine would create the "doughnuts on a rope" effect, however.