The purpose of stirring the cryogenic tanks containing the hydrogen and oxygen was to give more accurate readings of how much gas was left. But because of an electrical fault, one of the oxygen tanks exploded. Initially the crew thought a meteoroid had hit them, but it soon became apparent they were losing oxygen.
56 hours into the mission, at about 03:06 UT on 14 April 1970 (10:06 PM, April 13 EST), the power fans were turned on within the tank for the third "cryo-stir" of the mission, a procedure to stir the liquid oxygen inside the tank which would tend to stratify.
But when Swigert turned on the fans on the second oxygen tank for a routine “cryo stir” on the night of April 13, the damaged wiring caused a spark, starting a fire. At 9:08 pm, with its internal pressure mounting, the tank exploded.
To get around the problem, workers turned on heaters inside the tank to warm up the remaining liquid oxygen, turning it into gas that could then be vented to the outside. The thermostat inside the tank was supposed to prevent the temperature from exceeding 80 degrees Fahrenheit (25 degrees Centigrade).
In short: you stir oxygen to keep the cryogenic elements in the tanks from developing pockets where the temperature/density of the material varies.
A routine stir of an oxygen tank ignited damaged wire insulation inside it, causing an explosion that vented the contents of both of the SM's oxygen tanks to space. Without oxygen, needed for breathing and for generating electric power, the SM's propulsion and life support systems could not operate.
To answer the updated question of "Would replacing a damaged tank have prevented the Apollo 13 incident"? Absolutely yes. Bearing in mind that that tank was damaged in two completely separate, mostly unrelated ways. It had some damaged plumbing, preventing a testing drain for completing correctly.
During the Apollo 13 mission, the LM environmental control system provided a habitable environment for about 83 hours (57:45 to 141:05 GET). Cabin temperature remained low due to low electrical power levels. This caused crew discomfort during much of this period, with cabin temperatures ranging between 49°F and 55 °F.
The command module of Apollo 13 entered Earth's atmosphere and splashed down on target on April 17 at 1:07 PM Eastern Standard Time. The mission has been referred to as a successful failure, in that all the crew members survived a catastrophic accident.
Overall crew safety was estimated at 99.9 percent. But a 1965 assessment of these risks had found that, based upon the current plans and technology, the probability of mission success for each flight was only around 73 percent, while rated per-mission crew safety sat at 96 percent.
Mission Control waits with tension and dramatic music. The clock passes four minutes before they see the chutes open on the spacecraft. In real life, it took six minutes. Air & Space Magazine talked to Kranz about it.
Along the counter of the OMEGA Apollo 13, there's text that reads, “What could you do in 14 seconds?” The message is a reference to the critical window the crew had to burn the engines on the Apollo 13 mission.
Designed to house only two people, the craft quickly filled with dangerous levels of carbon dioxide. To save themselves, the astronauts had to somehow attach a square CO2 scrubber to the circular opening of the lunar module's filtration system.
The purpose of stirring the cryogenic tanks containing the hydrogen and oxygen was to give more accurate readings of how much gas was left.
All three astronauts were forced to pile into the lunar module (LM), which had enough oxygen to support the astronauts, but had been designed for only two. The carbon dioxide produced by all three astronauts exceeded the capacity of the onboard lithium hydroxide filters.
HOUSTON, Texas -- It was April 13, 1970 that the now famous words were spoken from Apollo 13, "Houston, we've had a problem." Apollo 13 had just experienced an explosion and astronaut Jim Lovell called mission control in Houston to report the problem.
Apollo 13's Forgotten Hero. If you've never heard of Glynn Lunney, it's only because he did an exacting job exactly right. Glynn Lunney, seated at left, consulting with Apollo 13 flight controllers.
Four of America's moonwalkers are still alive: Aldrin (Apollo 11), David Scott (Apollo 15), Charles Duke (Apollo 16), and Harrison Schmitt (Apollo 17). In all, 24 American astronauts made the trip from Earth to the Moon between 1968 and 1972.
The TLI placed Apollo on a "free-return trajectory" - often illustrated as a figure of eight shape. This course would have harnessed the power of the Moon's gravity to propel the spacecraft back to Earth without the need for more rocket fuel.
3.5 Apollo 13
During the second period, the Commander, Command Module Pilot, and Lunar Module Pilot slept 5, 6, and 9 hours, respectively. The third sleep period was scheduled for 61 hours, but the orygen tank incident at 56 hours precluded sleep by any of the crew until approximately 80 hours.
Mattingly had been scheduled to fly on the Apollo 13 mission, but three days prior to launch, he was held back and replaced by Jack Swigert due to exposure to German measles (which Mattingly did not contract).
On April 15, 1970, Apollo 13 was 254 km (158 miles) from the lunar surface on the far side of the moon—and 400,171 km (248,655 miles) above the Earth's surface, meaning the crew of Apollo 13 set a Guinness World Record for the farthest distance from Earth reached by humans.
Discussions between the Apollo 13 crew
According to Jim Lovell, there were no discussions or fights, as portrayed in the movie. The most important thing for the crew at that point was to focus on their greatest goal: to return home.
Apollo 13 was NASA's third moon-landing mission, but the astronauts never made it to the lunar surface. During the mission's dramatic series of events, an oxygen tank explosion almost 56 hours into the flight forced the crew to abandon all thoughts of reaching the moon.
Instead of lead, which is very dense and therefore resistant to motion, different materials--Aluminum, Titanium and Teflon, specifically--were the primary materials used in space suits to protect astronauts against radiation . But Aluminum cannot provide effective shielding against Gamma or neutron rays [5].