US, Jan 27, 2017: Fifty years ago today, January 27, 1967, tragedy struck NASA's proposed first manned flight of the Apollo capsule when a fire engulfed the craft during a routine test on the launchpad.

All three American astronauts on board died in the fire: Lt. Col. Virgil "Gus" Grissom, Lt. Col. Edward White II and Roger B. Chaffee.

The tragedy stunned the nation, and it temporarily stalled NASA's push to meet then-president John F. Kennedy's deadline to reach the lunar surface by the end of the decade

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A NASA probe and congressional hearings concluded previously unidentified fire hazards existed inside the capsule, and the subsequent decision to pressurize it entirely with oxygen created an extremely combustible environment. The hatch opened inward, which made it difficult for the crew to open it and escape.

After the deadly accident, hundreds of changes to the capsule were made, and NASA instituted myriad safety procedures. The redesigned capsules used a mixture of oxygen and nitrogen, reducing the fire risk. A new hatch was designed that could be opened in just five seconds.

Only 21 months later, NASA sent humans back into space aboard Apollo 7. And less than a year after that, Neil Armstrong and Buzz Aldrin landed Apollo 11 on the moon.

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