Archive: Three astronauts die in Apollo 1 tragedy
6 April 2011 Last updated at 09:29 BST
Three US astronauts died on January 27 1967 after a fire swept through the Apollo 1 spacecraft on the launchpad at Kennedy Space Center in Florida.
The fire spread quickly in the oxygen-filled atmosphere of the command capsule, with the crew dying of smoke inhalation and burns.
The crew of flight commander Gus Grissom, Edward White and Roger Chaffee, were taking part in a test run for the launch of the first Apollo mission.
Despite a full investigation, the precise origin of the fire was never clearly determined.
In the aftermath of the event, the BBC's aerospace correspondent Reg Turnill gained access to a mock-up of the capsule at Nasa's Mission Control in Houston, Texas, to see why the three men failed to escape.
First broadcast 8 February 1967.