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Apollo 13 was 178,000 miles away from Earth in the vast limitless thing we call outer space when oxygen tank number 2 exploded.  Unfortunately, the explosion ruptured oxygen tank number 1, and blew the cover off the service module bay number 4.  They were losing oxygen rapidly, which meant survival chances were very slim.  NASA believes that the switches for the oxygen tank heater welded shut, and the temperature that was supposed to be in the -300 to -100 degrees F. rose to almost 1000 degrees F.  But since the thermostat gauges were designed to measure only up to 80 degrees, neither NASA nor the astronauts noticed this extremely high temperature.  The high temperature emptied all the oxygen out of the tank.

At approximately 10:06 PM on April 13, a usual stir of the oxygen tank was performed, but the wires of the fan that performed the task were exposed, and since they were in pure oxygen, they caught fire and caused the whole tank to explode.  The astronauts heard a loud noise, and a jolting.  The craft lost power and was losing fuel.  As they were communicating with Houston, one astronaut looked out the window and saw a gas leaking out into space that he knew could only be one thing: oxygen.

So basically what happened was that the oxygen tank blew up and damaged the spacecraft's fuel and oxygen supplies.  They could not land on the moon, but returned safely to Earth with no harm done.

After NASA knew the general details of what happened, they did everything imaginable to keep the astronauts safe.  They worked day and night and used everything they knew to bring the astronauts back to the safety of Earth.

NASA had to make several very important decisions that came with many risks.  Here is a basic timeline of what they did:

  • Instructed astronauts to move to Lunar Module because Command Module had lost power
  • Decided how to get back: turn around or go around moon
    • Go around moon - risk not enough oxygen, power, water, etc.
    • Turn around - risk not enough fuel, fuel line could be damaged, might not be able to turn around
  • Decided to go around moon
  • Turned off everything not needed in Lunar Module - heat, power, light, etc.
  • Lined up craft with Earth - risk of missing Earth because they had no navigational computer

    The NASA team used the moon's gravity to 'slingshot' the craft back to Earth.  But for the 10 minutes that the astronauts were behind the moon, they lost contact with Earth, and everyone waited for what seemed like forever for an astronauts' voice to break the silence.