Apollo 13 was originally intended to become another Moon-landing mission, but the objective of the entire event soon funneled down into one goal: surviving. Aboard the Apollo Capsule were Astronauts Jim Lovell, Jack Swigert (backup), and Fred Haise. Around 56 hours into the flight, having traveled over 200,000 miles from Earth, the three reported an alarm that commenced while they had been stirring the cryogenic tanks, which not only contained the oxygen to breathe, but also the fuel cells to generate the main power source of the Command and Service Module (CSM). Within 3 hours, all of the electricity, power and water supply were out, and the temperature was close to freezing; luckily, the explosion that had been mysteriously concocted was in the CSM, while the astronauts were currently sheltered in the Lunar Module.
So how did this cataclysmic disaster occur? Before the launch of Apollo 13, NASA had transported one of the oxygen tanks that had previously been on Apollo 10. Many tests were done and while the Oxygen Tank No.1 worked completely fine, Oxygen Tank No.2, which had been from Apollo 10, was not functioning properly. One of the tests used on the tanks was to empty the tanks of liquid oxygen using gas oxygen; the second oxygen tank would not fully empty and was later hypothesized that damages to the tank during the transportation process were overlooked/missed. They decided to use an electric heater to clear off all the oxygen, yet it left horrible damage to the insulation and exposed dangerous wiring. Heaters and fans were also placed inside the oxygen tanks to increase the pressure to keep the oxygen flowing, and to allow stirring. Because the heater was not specifically designed for the tank, the controlled switches were damaged, allowing the oxygen tank to heat up to over 1000 degrees Fahrenheit during the flight. Furthermore, the gauges that measured the temperature were only set to 80 degrees, so the increase in heat was not noticed by the crew. The combination of all these problems soon turned to create calamity for the astronauts just days later.
Whilst the mission had been completely aborted, NASA and the crew still had to figure out a way to get the astronauts home safely, as improbable as it was at the time. The first course of action ordered was to reroute by orbiting around the moon, since landing would be impossible. In order to conserve the power supply, the temperature in the capsule was severely lowered, almost freezing. After tackling the power supply, the astronauts faced a more deadly problem surrounding the decreasing levels in oxygen and a rising in carbon dioxide. Additionally, the pipes and scrubbers from the CSM were not the same as those on the Lunar Module. Collectively, the crew and workers down at Houston worked out a way to create a Lithium Hydroxide Canister connector, which would be capable of sucking up CO2 (from the CSM). Using materials such as cardboard, duct tape, bags, and other spare materials, the team successfully created a device that could purify the air and ultimately keep the three astronauts alive. The final challenge the team faced was re-entering the Earth’s atmosphere, which would be one of the riskiest out of all the problems. As they approached descent, the astronauts were unsure whether the heat shields would hold, considering the rupture took out an entire panel around Sector 4 of the CSM, and the fall to Earth could easily burn up and destroy the LM. However, the heat shield held up and the crew of Apollo 13 had miraculously beaten all odds of survival with resilience and creative-engineering problem solving.