Deke Slayton was one of the first seven Mercury astronauts. When the Air Force grounded him, he rejoined NASA as a civilian, becoming the head of America's Astronaut Corps. It was Deke who selected the crews who flew the Gemini, Apollo and Skylab missions and who made Neil Armstrong the first man on the moon. Here he reveals his inside knowledge of how the U.S. manned space program really worked. Photos.