If we had gone with the X-20
AKA, Dyna-Soar, like the USAF wanted in the early 1960s, perhaps
the Space Shuttle disasters would never have happened and everyone
would be in a win-win situation.
But no, we wanted to beat the Soviets so we went with their cannon
ball concept and set aside the X-15 tests for years. Even von Braun
was advocating a space plane in the early 1950s, had we listened.
http://history.nasa.gov/SP-4209/ch3-1.htm
