The mission that proved human resilience
“Houston we’ve had a problem”
These words spoken by Commander James A Lovell Jr. would become some of the most famous in spaceflight history (1). Even before launch, Apollo 13 seemed surrounded by bad luck. The number thirteen itself carried superstition, and concerns only grew when the original command module pilot, Ken Mattingly, caught German measles and was replaced just days before launch by Jack Swigert. Few could have predicted just how close this mission would come to disaster (2).
On April 11, 1970, the Saturn V rocket lifted off from the Kennedy Space Center, carrying astronauts Jim Lovell, Fred Haise and Jack Swigert. Apollo 13 was meant to be the third lunar landing mission, following the successes of Apollo 11 and 12. Those earlier missions had created the impression that moon landings were becoming routine. Apollo 13 would prove just how wrong that assumption was (2).
Shortly after launch, the Saturn V experienced an early shutdown of one of the second-stage J-2 engines. To compensate, the remaining engines burned 34 seconds longer, and Mission Control confirmed the spacecraft appeared to be in good condition. Everything seemed fine, until it wasn’t (2).
Just minutes later, an explosion tore through oxygen tank number two in the service module. The blast also damaged oxygen tank number one, threatening the loss of electrical power, breathable oxygen, and drinking water. Within eight seconds, pressure in one tank dropped to zero. These oxygen tankers fed the spacecraft’s fuel cells, which generated electricity and water. This meant that the crew’s survival systems were failing (2).
That was the moment Lovell radioed Mission Control:
“Houston, we’ve had a problem. We’ve had a main B bus undervolt.” (1)
The lunar landing was immediately canceled. Apollo 13’s mission was now about survival.
With the command module, Odyssey, losing power, the astronauts were forced to retreat into the lunar module, Aquarius, using it as a lifeboat. The problem? Aquarius was designed to support two astronauts for two days, not three astronauts for four days. Resources were stretched to the limit. Each astronaut survived on only six ounces of water per day. Cabin temperatures dropped below 40 Fahrenheit (4 Celsius degrees), leaving the crew cold, exhausted, and unable to sleep. Even more dangerous was the rising level of carbon dioxide (3). Lithium hydroxide canisters were meant to remove CO2 from the air, but the square canisters from the command module did not fit the round opening in the lunar module. Without a solution, the crew would suffocate. Engineers on the ground devised an improvised fix using plastic bags, cardstock duct tape, and a spacesuit hose. This ingenuity saved the crew’s lives (4).
The new mission plan required Apollo 13 to swing around the Moon on a free-return trajectory, using lunar gravity to slingshot the spacecraft back toward Earth. Navigation relied on the sun as an alignment star since many instruments powered down. The crew used Aquarius’s engines to perform three trajectory correction burns, including a critical burn that added 941 km/h (585 mph) to their velocity and cut 10 hours off the return trip. Power consumption was reduced by 80% to conserve energy for reentry. One final challenge remained: powering up the command module. The crew had to do a process that normally takes three months in just three days, risking electrical failure and dangerous condensation. Odyssey was the only part of the spacecraft capable of withstanding Earth’s atmosphere and Aquarius had to be discarded (1).
On April 15, Apollo 13 entered Earth’s gravitational influence at a distance of 348,064 km. The service was jettisoned. The astronauts transferred back into Odyssey and powered up its life-support systems. On April 17, 1970, Apollo 13 splashed down safely in the Pacific Ocean at 1:07PM EST, 142 hours, 54 minutes, and 41 seconds after launch (1).
An investigation later revealed the cause: the oxygen tank heaters had been changed from 28 volts to 65 volts, but the thermostatic switches were never updated to handle the higher voltage (3). The switches failed, allowing the heater to overheat, damaging insulation and causing a short circuit that ignited the tank and blew off a side panel of the service module. As a result of Apollo 13, NASA implemented major safety improvements, including additional oxygen tanks and back up power sources, ensuring future crews would be protected (1).
Apollo 13 never landed on the moon and still became known as NASA’s “successful failure”. It proved that teamwork and calm decision making could overcome even the most catastrophic failures.
Sources:
- Britannica Editors. (2009, August 11). Apollo 13 | Mission, History, & Facts. Encyclopedia Britannica. https://www.britannica.com/topic/Apollo-13-mission
- Apollo 13 – NASA. (2023, March 15). NASA. https://www.nasa.gov/mission/apollo-13/
- Lunar – Missions – Apollo 13 Mission. (2026). Lunar and Planetary Institute (LPI). https://www.lpi.usra.edu/lunar/missions/apollo/apollo_13/
- Apollo 13. (2021, August 17). Si.edu. https://airandspace.si.edu/explore/stories/apollo-missions/apollo-13
Images and Links:
DIY lithium hydroxide filters built by Apollo 13 crew. https://airandspace.si.edu/explore/stories/apollo-missions/apollo-13
Apollo 13 crew from left to right: Fred Haise, Jim Lovell, Jack Swigert. https://www.biography.com/history-culture/a65639778/onscreen-history-behind-apollo-13
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