When NASA's first fatal spacecraft accident occurred 50 years ago, it happened not in deep space but right on the launch pad. The three men set to blast off on Apollo 1 -- rookie astronaut Roger Chaffee and veterans Virgil "Gus" Grissom and Ed White. "Hey! We've got a fire in the cockpit!" yelled one of the astronauts. Horrified engineers watched on their screens as smoke filled the cabin while White desperately attempted to release the cumbersome hatch. "We have a bad fire! We're burning up!" came another screaming transmission from the cockpit. Then silence.