Following the April 13 explosion that crippled the Odyssey command module, the crew of Apollo 13 sheltered in the lunar module 'Aquarius' as a lifeboat. On April 15, they performed a crucial engine burn behind the Moon to correct their trajectory and speed the return to Earth, buying time and fuel margins for a mission that had turned from moon landing to survival operation.
Mission Control's Gene Kranz had famously declared 'Failure is not an option' as engineers scrambled to solve problems no one had trained for: how to stretch power meant for two astronauts for two days across three astronauts for four days, and how to scrub rising carbon dioxide levels using a lunar module scrubber never designed to interface with the command module's square filter canisters. Engineers on the ground built a working fix out of plastic bags, cardboard, and duct tape, then radioed instructions up.
The April 15 burn, performed manually using the lunar module's engine with the crew sighting Earth's terminator through a window for alignment since the guidance computer had been shut down to save power, was one of several nerve-wracking maneuvers that determined whether the crew would survive reentry. Temperatures in the spacecraft dropped near freezing, and the astronauts lost significant weight from cold and dehydration. All three returned safely on April 17, in what NASA still calls a 'successful failure.'
Key people: James Lovell, Jack Swigert, Fred Haise, Gene Kranz