The Science Behind the Apollo 13 Oxygen Tank Explosion

The Apollo 13 mission is perhaps best known for the famous phrase, “Houston, we’ve had a problem.” This problem was a catastrophic explosion in one of the spacecraft’s oxygen tanks, a moment that could have spelled disaster for the crew. In this article, we’ll delve into the science behind the Apollo 13 oxygen tank explosion, exploring the causes and the incredible problem-solving that saved the astronauts.

Understanding the Oxygen Tanks

The Apollo spacecraft carried two types of oxygen tanks: the cryogenic oxygen tanks and the environmental control system (ECS) oxygen tanks. The ECS oxygen tanks were responsible for providing breathable air to the astronauts. The explosion that occurred was in one of the two cryogenic oxygen tanks, and it was a critical component for the operation of the Service Module (SM).

Cryogenic Oxygen Tanks

The cryogenic oxygen tanks were unique because they stored oxygen in a supercooled, liquid state. Liquid oxygen was used to maintain a controlled cabin pressure, generate electricity, and provide drinking water for the crew. These tanks were incredibly cold, with temperatures around -297 degrees Fahrenheit (-183 degrees Celsius).

The Root Cause

The oxygen tank explosion was caused by a combination of factors, primarily related to the tank’s design and a series of events leading up to the explosion:

1. Design Flaw

The primary issue was a design flaw in the tank’s heating element thermostat. The tank’s interior had been exposed to a surge of voltage during pre-launch testing, causing significant damage to the thermostat’s insulation. This damage was not adequately identified or addressed before launch.

2. Cryogenic Conditions

The extreme cold of space and the supercooled oxygen caused the damaged thermostat to become brittle and prone to failure. This thermostat was responsible for maintaining the temperature of the liquid oxygen and preventing it from dangerously over-pressurizing.

3. Tank Stirring

During the mission, the tank’s fans were turned on to stir the liquid oxygen, which was intended to ensure even distribution. However, this stirring had an unintended consequence. It exposed the damaged thermostat to the supercooled oxygen, causing it to shatter and igniting the tank’s insulation.

The Explosive Result

As the thermostat insulation ignited, it created a rapid and uncontrolled release of oxygen, causing a violent explosion. The explosion resulted in the loss of the SM’s electrical power and significant damage to the spacecraft’s propulsion system. The mission’s lunar landing had to be aborted, and the focus shifted to safely returning the crew to Earth.

Ingenious Problem-Solving

The crew and ground control faced an unprecedented challenge, but their scientific and engineering knowledge, along with their determination to overcome adversity, ultimately saved the day. They had to find ways to conserve power, adapt the spacecraft’s course, and ensure the astronauts’ survival with limited resources.