Astronauts Lovell, Haise and Swigert, lifted off aboard Apollo 13, on April 11, 1970. The target site for the spacecraft was a spot on the Moon called the Fra Mauro Formation. While in Earth's orbit over the Pacific Ocean, a rocket fired, sending the craft on its translunar path.
Less than two days later, on April 13, 205,000 miles from Earth, an oxygen tank exploded in the SM of the Apollo 13 spacecraft. Loss of oxygen and electrical power forced the crew of Apollo 13 to abort the planned lunar landing. The crew had to change its course, swing around the Moon, and head back to Earth. Accomplishing this feat was not as simple as it might sound. The crew had to overcome many obstacles before they would be out of danger.
Detecting key stars was the sole means of determining the spacecraft's position, or attitude. Shortly after the explosion, Lovell saw a mass of particles surrounding the spacecraft that looked like stars. Therefore, navigating the spacecraft was difficult for the astronauts.
The crew needed to align the Lunar Excursion Module's guidance system with that of the Command Module's, while it still had enough power.
To conserve power in the CM needed for reentry into the Earth's atmosphere, the crew shut down all unnecessary systems and moved into the LEM. Once inside the LEM, they had discovered that another problem needed their immediate attention.
The system for removing carbon dioxide from the LEM was not functioning properly. The LEM was progressively accumulating dangerous levels of carbon dioxide. Ground crews in Houston came up with a temporary air purifier that the crew could assemble, using materials aboard the Apollo 13 spacecraft.
Houston gave the astronauts detailed instructions for constructing the air purifier. The crew literally had to fit a square peg into a round hole. The air purifier worked, and the amount of carbon dioxide in the LEM, stayed below hazardous levels.
To reenter the Earth's atmosphere, the Apollo 13 spacecraft had to follow a definite course. To follow that course, the astronauts needed to find a focal point to use as a guide. The corridor for reentry into Earth's atmosphere was extremely narrow. Under normal circumstances, it would not have been a problem.
However, with conditions on the Apollo 13 spacecraft being what they were, moments that were more anxious lay ahead for the astronauts. If the craft came in too low, it would burn up in the atmosphere. If it came in too high, it would bounce off the Earth's atmosphere and be thrown back out into space.
As the world watched, prayed, and waited, the crew of Apollo 13 splashed down on April 17, 1970. The astronauts were seriously dehydrated and extremely weak, but they had made it back home.