It's really too bad no one thought to use David Criswell's (now
expired) patent #4,836,470 as the basis for an X-Prize vehicle.

See:

http://patft.uspto.gov/netacgi/nph-P...l+AND+IN/david
aka


An oblique all wing SST can continuously vary from a high-lift
configuration to a ballistic configuration by simply changing the cant
of the engine as the wing gains speed and altitude while losing fuel
mass. (There need be only one engine -- a rocket engine.) Fitting
three guys inside the wing would be rather awkward but it could be
done.