US astronauts Virgil Ivan ‘Gus’ Grissom, Edward Higgins White II and Roger Bruce Chaffee were killed inside their Apollo 1 capsule on 27 January 1967 during a launch rehearsal at Cape Canaveral, Florida, USA. The fire was caused by a spark from an electrical fault which occurred in the capsule’s artificial atmosphere of pure oxygen. The internal pressure caused by the fire meant the crew could not open the hatch, which was designed to open inwards.