The crew of the planned Apollo 1 mission, astronauts Gus Grissom, Ed White, and Roger Chaffee (l-r), stand in front of the launch pad at Cape Kennedy days before they were killed during a launch dress rehearsal. A fire broke out in the cockpit on January 27, 1967, less than a month before their planned launch, quickly killing all three men. NASA found multiple problems with the spacecraft itself and with the overall design. An intensive effort to solve the problems led to the launch of the first manned mission, Apollo 7, 21 months later, and the first lunar landing nine months after that. [NASA]