Apollo 13 was planned to be the third manned trip to the moon, after the famous 1969 mission of Apollo 11 and the subsequent Apollo 12 mission in the same year. The crew was made up of Fred Haise, James Lovell and John Swigert, who replaced Ken Mattingly shortly before launch after he was exposed to German measles. The mission was to conduct experiments on the surface of the moon and photography. Apollo 13 was made of two separate spacecraft; orbiter Odyssey where the crew would live on the journey and lander Aquarius. At 2:13pm EST, April 11, 1970, Apollo 13 was launched.
2 days after launch, a warning signal appeared on a hydrogen tank on Odyssey. It could have meant that the gas in the tank needed to be resettled by fanning and heating in a procedure known as a “cryo stir,” which was designed to stop the gas settling in layers. Swigert flicked the switch for what was supposed to be a routine procedure. The spacecraft shuddered as oxygen pressure dropped and power was lost. Swigert contacted Mission Control on the ground, uttering the famous words “Houston, we’ve had a problem.” At this time, oxygen tank 2 was signalling that it was empty as oxygen tank 1 slowly emptied over the next 2 hours. 2 of the 3 fuel cells, that used oxygen from the tanks to run, shut down immediately and the third stopped once the oxygen from tank 2 had depleted. It was later discovered an exposed wire in oxygen tank 2 had sparked and caused a fire.
Despite the fire on Odyssey, the landing module Aquarius remained undamaged. The crew moved into the module that was only designed to be used until it was close to the moon. All systems on Odyssey were shut down to preserve power from a reserve electronic power source on board for re-entry. Aquarius was only designed to run for a total of 45 hours. The focus of the mission was now to get the crew home safely and to do that, the plan was to carry on towards the moon under the power of the landing module, orbit around it and shoot back down to Earth.
In order to save power on Aquarius, power consumption was cut to 20%. This led to temperatures to drop close to freezing and some of the food became inedible. Liquid for the astronauts was also rationed to save water to cool down hardware. Each of the crew consumed only 20% of their regular water intake. Another major problem was removing carbon dioxide. A day and a half after the fire, carbon dioxide had grown to harmful levels. However, Mission Control devised a way to attach lithium hydroxide cannisters designed for Odyssey, which were used to remove carbon dioxide, to the module, by using plastic bags, tape, hoses, and cardboard. The device known as the mailbox, undoubtedly saved the life of the crew.
As Apollo 13 was approaching Earth, Odyssey had to be powered, which it was never designed to do whilst in flight. Temperatures had dropped to be cold enough for water to condense on surfaces, which could have caused a shorting of the electrics on board. With advice from Mission Control and the grounded pilot Mattingly, Odyssey was powered successfully.
Just prior to re-entry, Apollo 13 faced yet another problem. How to get Odyssey and Aquarius to separate to a safe distance. A team of engineers were given a single day to come up with a plan. They agreed to pressurize the tunnel between the two spacecraft to produce enough force to separate safely. They had just 6 hours to compute the pressure required. It worked successfully, and the crew safely re-entered the atmosphere in the landing module and landed in the Pacific Ocean. All three crew survived the ordeal and Lovell and Swigert arrived back to Earth in relatively good health. Haise was suffering from a kidney infection caused by a lack of water intake although eventually recovered. Despite failing in its original mission, the story of Apollo 13 is remembered for the crew arriving back on Earth after overcoming numerous obstacles and showed how NASA could solve life-threatening situations in space.