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Apollo 13 (EVENT SEQUENCE (Oxygen (O2) tank designed and fabricated with…
Apollo 13
EVENT SEQUENCE
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NASA changed the design of the O2 tank to run on 65V power to improve compatibility with ground-based testing equipment
Apollo 13's O2 tank 2 was originally installed on Apollo 10's Service Module, but was removed in order for it to be retrofitted with the 65V components
During removal from Apollo 10's Service Module, the shelf carrying the O2 tank was dropped approximately 5cm due to the operator failing to observed the pin locking the shelf in place was still secured.
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Pre-flight testing required 50% of the contents of the tank to be expelled when in operational configuration, 8% was expelled during the initial testing. Additional testing was carried out using this procedure, and the tank failed each time.
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The internal heaters of the O2 tank were used by the engineers during this testing, which after approximately 8 hours.
The heating of the tank was not monitored by the testing engineers and the tank reached 538 degrees Celsius (for most of the 8 hour duration of the test).
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High temperature damaged the Teflon coating of the wiring on the fan motor (used to mix the O2 during flight) within the O2 tank.
As the tank would expel under these conditions and it would be faster than replacing the component, the decision was made that the O2 tank would be ok to be used on Apollo 13
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Unknowingly, the original (not retrofitted) 28V O2 tank was then assigned to the Apollo 13 Service Module.
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46 hours 40 mins in to flight, the oxygen tanks were again stirred
Apollo 13 launches, without significant issues (one engine burnt out sooner than expected).
Based on this suspicion the engineers modified the test in order to force the oxygen out of the tank to ensure the 50% expulsion of contents occurred, allowing them the pass the component for flight.
The Service Module panel blew off the spacecraft due to the pressure of the built up oxygen exceeding the structural strength of the Service Module.
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The exposed wiring likely short circuited and sparked, causing the Teflon wire-coating to ignite in the oxygen-rich tank
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explosion damaged O2 tanks 1 and 2, venting O2 into space.
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O2 required for breathing and to mix with hydrogen to operate the power systems on the service module
Mission Aborted, and modified with aim or safely returning astronauts to earth.
Improvised procedures required to be written and tested for manual course correction engine burns and Command Module start-up
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