Disturbing audio from inside space capsule during the Apollo 1 disaster

Audio has revealed what happened inside the cockpit of the disastrous Apollo 1 mission.

The mission had been due to launch on February 21 1967, and NASA was carrying out rehearsals for the launch ahead of the historic expedition.

Tragically during one of the rehearsals on January 27 disaster struck when a fire broke in the cockpit.

This killed all three crew members on board; Command Pilot Gus Grissom, Senior Pilot Ed White, and Pilot Roger B. Chaffee, as well as destroying the command module.

A subsequent investigation found that the cause of the fire had been electrical, and it had spread to the presence of a combustible nylon material in the cabin as well as the high pressure oxygen atmosphere in the command module.

Not only that, but it was also found that the mission had not been considered to be of a high safety risk.

This was because it was a rehearsal, and the Saturn rocket itself had not been fuelled.

The interior of the command module after the fire. (Heritage Space/Heritage Images via Getty Images)

Audio from inside the cockpit has revealed the final communications from the crew, who encountered problems as soon as they stepped in.

The test was delayed due to some minor issues, before an electrical surge was detected 'in the AC bus 2 voltage readings'.

The audio was captured by a microphone which had been worn by one of the crew, and posted to Twitter by the account @Morbidful.

An astronaut can be heard saying: "Hey! There's a fire in the cockpit."

A few seconds later a second voice is heard saying: "We have a bad fire."

The astronauts can then be heard shouting for several seconds, before the audio finally cuts out.

A memorial to the three crew who died. (Bill Ingalls/NASA via Getty Images)

The NASA Space Science Data Coordinated Archive reported that the last communication from the crew ended '17 seconds after the first indication of the start of the fire'.

The hatch was opened around five minutes later, and would have taken around 90 seconds under ideal conditions.

Tragically this proved too late for the three crew members on board.

NASA made a number of changes to their design following the disaster.

This included switching the pure oxygen atmosphere for one consisting of a mixture of oxygen and nitrogen, similar to what is now used in deep scuba diving.

The hatch was also modified so that it could also be opened from the inside.