Today is the anniversary of one of the darker days in the history of space exploration. On this day in 1967, three astronauts boarded an Apollo command module to conduct a series of launch and training drills, in anticipation of a February 27th launch. Tragically, the module suffered an internal fire that killed all three astronauts and destroyed the spacecraft.

Their names were Virgil I. “Gus” Grissom, Edward H. White II, and Roger B. Chaffee.

The name “Apollo I” was the unofficial name of the mission, chosen by the crew. In commemoration, the name was made official by NASA historians in April.

A cause for the fire was never conclusively identified, but an analysis of the command module did discover a large number of design flaws. The consensus was that the fire was the cumulative result of several small problems. Development of the Apollo program was delayed for twenty months while the flaws in the command module design were examined and corrected. The first successfully manned flight of an Apollo spacecraft was in October of 1968, by Apollo VII.

This tragedy almost ended the Apollo program. During the follow-up investigation, there was evidence of political corruption and poor project management by both NASA and it’s relevant contractors. These issues were eventually deemed to be separate from the engineering problems that doomed Apollo I, and the Apollo program was allowed to continue. However, stricter quality review protocols were put in place. The Senate oversight committee had concluded that NASA had become over-confident, and by extension, careless. This has proven to be a pattern that NASA periodically falls into.

The Apollo program would later carry humans to the moon, and became the backbone of the Skylab program. The Orion program, currently in development, is in many ways an update of Apollo.