Spaceshipone. If it was not for open heart surgery in 2008, I bet Burt Rutan would have done the same thing with Spaceshiptwo with this simplicity at one trillionth part of the cost. Go big govt.
Burt Rutan is the Man! For years he's been on the cutting edge of aviation. I can remember getting my pilots license when I was in my teens and he had the EZ then the Long EZ designs. These things looked like a fixed wing airplane flying back wards and yet, they would out perform just about everything given the same power. My little Piper Archer had 160hp Lycoming and would cruise about 130 knots. That Long EZ on the same engine would be cruising at 180 knots and had a range of over 1500 miles! With the smaller 110 hp out of say a Piper 150-152, it will still do 160 and cruise for 2000 miles! Very efficient.