There were two components to the problem; first, getting the ship and crew on the fastest route home and second, conserving consumables, power, oxygen, and water. However, sometimes one component interfered with the other.
Conserving Resources; Preserving Life
As an example, the guidance platform needed to be aligned. (The venting substance had played havoc with the ships attitude.) However, powering up the guidance platform was a heavy drain on their limited power supply.
The conservation of consumables had already begun with the shutting down of the Apollo 13 CM. For most of the rest of the flight, it would only be used as a bedroom. Later, they powered down all of the systems in the LM except those required for life support, communications, and environmental control.
Next, using precious power they could not afford to waste, the guidance platform was powered up and aligned.
Mission control ordered an engine burn that added 38 feet per second to their velocity and return them to a free-return trajectory. Normally this would be a fairly simple procedure. Not this time, however. The descent engines on the LM were to be used instead of the CM’s SPS and the center of gravity had changed completely.
At this point in time, had they done nothing, their trajectory would have returned them to Earth approximately 153 hours after launch. A quick calculation of consumables gave them less than an hour of consumables to spare. This margin was far too close for comfort.
After a great deal of calculating and simulating at Mission Control here on Earth, it was determined that the Lunar Module’s engines could handle the required burn. So, the descent engines were fired sufficiently to boost their speed up another 860 fps, thus cutting their flight time to 143 hours.
Chilling Out Aboard Apollo 13
One of the worst problems for the crew during that return flight was the cold. Without power in the CM, there were no heaters to maintain cabin temperatures. The temperature in the CM dropped to around 38 degrees F and the crew stopped using it for their sleep breaks. Instead, they jury-rigged beds in the warmer LM, though warmer is a relative term. The cold kept the crew from resting well and Mission Control became concerned that the resulting fatigue could keep them from functioning properly.
Another concern was their oxygen supply. As the crew breathed normally, they would exhale carbon dioxide. Normally, oxygen-scrubbing apparatus would cleanse the air, but the system in Aquarius wasn’t designed for this load, there was an insufficient number of filters for the system. To make it worse, the filters for the system in Odyssey were of a different design and not interchangeable. The experts at NASA, employees and contractors, engineered a makeshift adapter from materials the astronauts had on hand to allow them to be used, thus lowering the CO2 levels to acceptable limits.
Finally, Apollo 13 rounded the Moon and began its journey home to Earth. However, the crew’s troubles were not over.
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