To orbit, a space craft needs to achieve a velocity of 7.75 Km/sec, or 27,900 Km/hr, or 44,900 MPH at an altitude of 250 Km or just over 150 mi.
Burt Rutan's SpaceShipOne achieved a velocity of zero MPH at an altitude of 100 km, or just under 67 mi.
That is the difference between a space craft and a thrill ride.
Oops, math error:
27,900 Km/hr is correct, but should translate to 17,100 MPH, not 45,000! Main point still stands.
Further, the Space Shuttle has to re-enter the atmosphere and scrub off that 17,000 MPH, while SpaceShipOne re-entered the atmosphere at 0 MPH. That expains why SpaceShipOne didn't need very much heat shielding.