50 years ago, the Apollo program began with a deadly tragedy

On March 21, 1966, NASA announced its crew selection for the AS-204 mission — the first crewed mission in the program aimed at reaching the moon.

Astronauts Virgil "Gus" Grissom, Edward H. White II and Roger B. Chaffee were chosen to carry out a 14-day low orbital test of the Apollo Command/Service Module, with a launch date of Feb. 21, 1967.

The men were well suited to the task. Grissom was a decorated fighter pilot and veteran of projects Mercury and Gemini, White was the first American to perform a spacewalk during Project Gemini and Chaffee had served with both men as the capsule communicator for the Gemini 4 mission.

As the astronauts spent months training for their mission, the Command/Service Module was tweaked, modified and finally mated to its Saturn launch vehicle at Cape Canaveral's Launch Complex 34.

There's always a possibility that you can have a catastrophic failure, of course; this can happen on any flight; it can happen on the last one as well as the first one. So, you just plan as best you can to take care of all these eventualities, and you get a well-trained crew and you go fly.

On January 27, 1967, the astronauts reported to the launch pad for a "plugs-out" test to see how the spacecraft operated on internal power.

See photos from the Apollo fire below:

The test was not considered hazardous, as there was no fuel present and all pyrotechnic systems were disabled.

The three astronauts were strapped into the cramped module, the hatch was sealed and the spacecraft was pressurized with a pure oxygen atmosphere.

The astronauts were running through a checklist of preparations when a power surge sparked a fire.

The fire spread rapidly in the pure oxygen environment, and the high pressure in the cabin made the egress hatch virtually impossible to open. Within seconds, Grissom, White and Chaffee asphyxiated and died.

NASA and both houses of Congress conducted exhaustive investigations into the incident and crewed missions were halted for months.

Extensive design changes to the Command/Service Module were implemented, and stringent safety protocols were implemented.

From this day forward, Flight Control will be known by two words: Tough and Competent. Tough means we are forever accountable for what we do or what we fail to do. We will never again compromise our responsibilities... Competent means we will never take anything for granted.... These words will remind you of the price paid by Grissom, White, and Chaffee. These words are the price of admission to the ranks of Mission Control. ---- NASA Flight Director Gene Kranz, speech to Mission Control

Grissom and Chaffee were buried at Arlington National Cemetery and White was buried at West Point Cemetery.

At the request of the astronaut's widows, the mission designation was officially changed from AS-204 to Apollo 1.