One of the worst tragedies in the history of spaceflight occurred on January 27, 1967 when the crew of Gus Grissom, Ed White, and Roger Chaffee were killed in a fire in the Apollo Command Module during a preflight test at Cape Canaveral. They were training for the first crewed Apollo flight, an Earth orbiting mission scheduled to be launched on 21 February. They were taking part in a "plugs-out" test, in which the Command Module was mounted on the Saturn 1B on the launch pad just as it would be for the actual launch, but the Saturn 1B was not fueled. The plan was to go through an entire countdown sequence.
At 1 p.m. on Friday, 27 January 1967 the astronauts entered the capsule on Pad 34 to begin the test. A number of minor problems cropped up which delayed the test considerably and finally a failure in communications forced a hold in the count at 5:40 p.m. At 6:31 one of the astronauts (probably Chaffee) reported, "Fire, I smell fire." Two seconds later White was heard to say, "Fire in the cockpit." The fire spread throughout the cabin in a matter of seconds. The last crew communication ended 17 seconds after the start of the fire, followed by loss of all telemetry. The Apollo hatch could only open inward and was held closed by a number of latches which had to be operated by ratchets. It was also held closed by the interior pressure, which was higher than outside atmospheric pressure and required venting of the command module before the hatch could be opened. It took at least 90 seconds to get the hatch open under ideal conditions. Because the cabin had been filled with a pure oxygen atmosphere at normal pressure for the test and there had been many hours for the oxygen to permeate all the material in the cabin, the fire spread rapidly and the astronauts had no chance to get the hatch open. Nearby technicians tried to get to the hatch but were repeatedly driven back by the heat and smoke. By the time they succeeded in getting the hatch open roughly 5 minutes after the fire started the astronauts had already perished, probably within the first 30 seconds, due to smoke inhalation and burns.