The Story of Apollo 13

Apollo 13 was the seventh manned mission in the American Apollo space program and the third intended to land on the Moon.

The craft was launched on April 11, 1970, but the lunar landing was aborted after an oxygen tank exploded two days later, crippling the Service Module upon which the Command Module depended.

Despite great hardship caused by limited power, loss of cabin heat, shortage of potable water, and the critical need to jury-rig the carbon dioxide removal system, the crew returned safely to Earth on April 17.

Seven days before launch, the Backup Lunar Module Pilot, Charlie Duke, contracted rubella from one of his children. This exposed both the prime and backup crews, who trained together.

Mattingly was found to be the only one of the other five who had not had rubella as a child and thus was not immune. Three days before launch, at the insistence of the Flight Surgeon, Swigert was moved to the prime crew.

Kranz’s team was on duty when part of the Apollo 13 service module exploded and they dealt with the initial hours of the unfolding accident.

His “White Team”, dubbed the “Tiger Team” by the press, set the constraints for the consumption of spacecraft consumables (oxygen, electricity, and water) and controlled the three course-correction burns during the trans-Earth trajectory, as well as the power-up procedures that allowed the astronauts to land safely back on Earth in the command module.

He and his team, as well as the astronauts, received the Presidential Medal of Freedom for their roles.

The Apollo 13 mission was to explore the Fra Mauro formation, or Fra Mauro highlands, named after the 80-kilometer-diameter Fra Mauro crater located within it. It is a widespread, hilly selenological area thought to be composed of ejecta from the impact that formed Mare Imbrium.

Approaching 56 hours into the mission, Apollo 13 was approximately 330,000 km (205,052 miles) from Earth en route to the Moon. Approximately six and a half minutes after the end of a live TV broadcast from the spacecraft, Haise was in the process of powering down the LM, while Lovell was stowing the TV camera, and Houston flight controllers asked Swigert to turn on the hydrogen and oxygen tank stirring fans in the Service Module, which were designed to destratify the cryogenic contents and increase the accuracy of their quantity readings.

Almost two minutes later, the astronauts heard a “loud bang” accompanied by fluctuations in electrical power and firing of the attitude control thrusters. The crew initially thought that a meteoroid might have struck the Lunar Module.

The number-2 oxygen tank, one of two in the Service Module, had exploded. Damaged Teflon insulation on the wires to the stirring fan inside oxygen tank 2 allowed the wires to short-circuit and ignite this insulation. The resulting fire rapidly increased pressure beyond its 6.9 MPa limit and the tank dome failed, filling the fuel cell bay with rapidly expanding gaseous oxygen and combustion products. It is also possible some combustion occurred of the Mylar/Kapton thermal insulation material used to line the oxygen shelf compartment in this bay.

The damage to the Service Module made safe return from a lunar landing impossible, so Lead Flight Director Gene Kranz ordered an abort of the mission.

The existing abort plans, first drawn up in 1966, were evaluated; the quickest was a Direct Abort trajectory, which required using the Service Module Propulsion System engine to achieve a 1,853 m/s delta-v.

Although a successful SPS firing at 60 hours ground elapsed time would land the crew one day earlier, the large delta-v was possible only if the LM were jettisoned first, and since crew survival depended on the LM’s presence during the coast back to Earth, that option was “out of the question.”

Kranz chose the alternative circumlunar option, using the Moon’s gravity to return the ship to Earth. Apollo 13 had left its initial free-return trajectory earlier in the mission, as required for the lunar landing at Fra Mauro. Therefore, the first order of business was to re-establish the free-return trajectory with a 30.7-second burn of the DPS.

The descent engine was used again two hours after pericynthion, the closest approach to the Moon (“PC+2 burn”), to speed the return to Earth by 10 hours and move the landing spot from the Indian Ocean to the Pacific Ocean.

A more aggressive burn could have been performed at PC+2 by first jettisoning the Service Module, returning the crew in about the same amount of time as a direct abort, but this was deemed unnecessary given the rates at which consumables were being used.

The 4-minute, 24-second burn was so accurate that only two more small course corrections were subsequently needed.

Availability of lithium hydroxide (LiOH) for removing carbon dioxide presented a serious problem. The LM’s internal stock of LiOH canisters was not sufficient to support the crew until return, and the remainder was stored in the descent stage, out of reach. The CM had an adequate supply of canisters, but these were incompatible with the LM.

Engineers on the ground improvised a way to join the cube-shaped CM canisters to the LM’s cylindrical canister-sockets by drawing air through them with a suit return hose. The astronauts called the jury-rigged device “the mailbox.”

As Apollo 13 neared Earth, the crew first jettisoned the Service Module, using the LM’s reaction control system to pull themselves a safe distance from it, instead of the normal procedure which used automatic firing of the SM’s RCS.

They photographed it for later analysis of the accident’s cause. It was then that the crew were surprised to see for the first time that the entire Sector 4 panel had been blown off.

According to the analysts, these pictures also showed the antenna damage and possibly an upward tilt to the fuel cell shelf above the oxygen tank compartment.

With the lunar module jettisoned, the command module Odyssey began its lone re-entry through the atmosphere.

Odyssey regained radio contact and splashed down safely in the South Pacific Ocean, southeast of American Samoa and 6.5 km (3.5 nmi) from the recovery ship, USS Iwo Jima.

The crew was in good condition except for Haise, who was suffering from a serious urinary tract infection because of insufficient water intake. To avoid altering the trajectory of the spacecraft, the crew had been instructed to temporarily stop urine dumps. A misunderstanding prompted the crew to store all urine for the rest of the flight.