The dark expanse of space is illuminated by a cloud of fire surrounding the command module of the spacecraft. The warning lights have woken the crew as they hurtle through the hallways while avoiding the deadly explosion. This was the horrifying reality that the crew members aboard Apollo 13 faced on April 13, 1970.
The Apollo 13 spacecraft launched on April 11, 1970, in Cape Kennedy, Florida, and was deemed a “successful failure” by NASA. While en route to the moon, one of the oxygen tanks exploded and damaged multiple fuel cells on the spacecraft, threatening to destroy systems that were vital to the survival of the crew.
The crew was made up of three astronauts: Jim Lovell, the Commander; Jack Swigert, the Command Module Pilot; and Fred Haise, the Lunar Module Pilot. Apollo 13 was both Swigert and Haise’s first mission into space, whereas Lovell had previously been a part of Gemini VII and XII flight programs, as well as Apollo 8, the first human spacecraft to reach the moon.
Apollo 13 was conducted to collect data in the Fra Mauro region, a heavily eroded crater on the moon, to gain insights into the moon’s geology
The plan was for the spacecraft to launch in early April and orbit the moon, landing in the Fra Mauro region. The crew would then conduct two moonwalks in the area, collect rock samples, and deploy scientific instruments to gather data before rendezvousing with the command module. It was vital that the launch occurred during appropriate conditions —one important factor being the sun’s angle with Fra Mauro —to achieve a successful landing.
Crew preparation began on Aug. 1, 1969, when Lovell, Swigert, and Haise started their training as backup crew for the Apollo 11 mission. The groundwork involved classes on the Apollo spacecraft and its operation, refining their star sighting abilities to determine position and velocity in the spacecraft and photography equipment training for the various cameras used to document the flight. Over 1,000 hours of training was required for the crew participating in the Apollo 13 mission.
To ensure the safety of the crew, numerous ground tests and modifications took place prior to the launch of Apollo 13. Among these modifications was the installment of the No. 2 oxygen tank, previously installed in the Apollo 10 service module. During preparation for the Apollo 10 mission, the oxygen tank was damaged, removed from the spacecraft and taken to the factory for repairs. Ultimately deemed safe, it was installed in the Apollo 13 spacecraft.
The Apollo 13 tests indicated that the tank was malfunctioning, as an attempt to empty it to 50 percent capacity to prevent safety hazards only brought it down to 92 percent capacity. Before the flight, the test director attempted to “boil off” the remaining oxygen by using the electrical heater within the tank. This caused the internal heating elements of the tank to be severely damaged by the eight-hour, continuous use of 65-volt direct current power.
The spacecraft carried two liquid hydrogen tanks and two liquid oxygen tanks–including the damaged tank from Apollo 10–on the flight. While performing maintenance after takeoff, the crew noticed that the flawed oxygen tank wasn’t correctly emptying itself, so they decided to heat the tank overnight in an attempt to burn the liquid oxygen off of the tank and prevent potential safety hazards.
Because of the damaged internal heating system in the No.2 oxygen tank, the shut-off switch on the tank heater failed, bringing the temperature of the tank to over 1000 F. This damaged the insulation of the wires inside the oxygen tank, essentially turning the tank into a time bomb.
On April 13, at 55 hours and 55 minutes, the No. 2 oxygen tank exploded, causing the No. 1 tank to fail as well–the subsequent investigation after splashdown indicated a rupturing line or a leaking valve in the first tank, caused by the explosion. The explosion also caused the command module’s electricity, light, and water supply to fail when the spacecraft was still 200,000 miles from Earth and had yet to complete its lunar landing. Two of the fuel cells, which supplied the spacecraft with its main source of electricity, had failed and the crew’s oxygen levels were rapidly depleting as the No. 1 tank’s oxygen began to escape and was vented out of the spacecraft.
“As soon as I looked out the window and saw our oxygen escaping and our fuel cells dead…[then] the apprehension turned into, boy, are we going to get back home again, or what’s happening, or what can we do?” Lovell recalled in a 2020 interview with Air and Space.
The crew attempted to close the hatch between the command and lunar modules to prevent the loss of additional oxygen, but it wouldn’t stay shut. The pressure in the No. 1 oxygen tank was steadily falling towards 200 pounds per square inch. If it reached 200, the spacecraft’s oxygen would be lost and its last fuel cell would die, leaving the crew stranded in space.
The three astronauts rushed to the lunar module lifeboat, which would provide them with a way back to Earth; however, the two-man lifeboat didn’t have all of the necessary systems to sustain three astronauts for 90 hours, double the time that it was built to withstand.
The lifeboat had multiple problems involving consumable resources: power, water, carbon removal, and temperature, which had decreased to 38 F as a result of the necessary electricity conservation. Since it was meant to run for only 45 hours, the ground crew had to devise a calculated path that would allow the lunar module to get back to Earth safely without running out of fuel.
To deal with the other problems with the lifeboat, the astronauts created makeshift devices which charged the command module’s batteries using the lunar module’s power to allow the lifeboat to get back to Earth. They also used plastic bags, cardboard, and tape to attach canisters from the command module to the lunar module system to remove carbon dioxide from the spacecraft for the crew’s safety, and conserved water and food to last the journey back to Earth.
At 11:53 a.m. on April 17, 1970–four days after the initial explosion and three hours after they shed the service module–Lovell, Swigert and Haise left the lunar module Aquarius and splashed down in the Pacific Ocean. The mission was deemed a “successful failure” because although the initial moon touchdown was abandoned, there were no casualties and the Apollo system was improved for following missions to avoid similar incidents.
Lovell later said of the splashdown, “My favorite memory of Apollo 13 is splashing down in the ocean…and [knowing] that we had successfully come home.”
