Apollo 13

Apollo 13 was the seventh crewed mission in the Apollo space program and the third intended to land on the Moon, but it is best known for the critical in-flight emergency that forced the crew to abort the lunar landing and return safely to Earth. Launched on April 11, 1970, the mission experienced a catastrophic failure two days into the flight when an oxygen tank exploded, crippling the Service Module. Through the ingenuity of the crew and Mission Control, the astronauts survived the ordeal and splashed down in the Pacific Ocean on April 17, 1970.

Mission Overview

The Apollo 13 mission was commanded by James A. Lovell, with John L. "Jack" Swigert as the Command Module Pilot and Fred W. Haise as the Lunar Module Pilot. Swigert was a late replacement for Ken Mattingly, who was grounded by the flight surgeon after exposure to rubella. The mission launched from Kennedy Space Center in Florida aboard a Saturn V rocket. The primary objective was to explore the Fra Mauro formation on the Moon, a hilly geological area believed to contain ejecta from the impact that formed the Mare Imbrium. The crew successfully entered a translunar trajectory and was approximately 200,000 miles (320,000 kilometers) from Earth when the incident occurred.

The In-Flight Emergency

On April 13, 1970, at 55 hours and 54 minutes into the mission, Mission Control requested that the crew stir the cryogenic oxygen tanks to prevent the supercold fluid from stratifying. When Swigert flipped the switch, a spark ignited damaged wire insulation inside Oxygen Tank 2, causing it to explode. The explosion blew off an exterior panel of the Service Module and damaged Oxygen Tank 1, leading to a rapid loss of electrical power, water, and breathable oxygen.

Following the explosion, Swigert radioed the now-famous words, "Okay, Houston, we've had a problem here," which Lovell subsequently repeated as, "Houston, we've had a problem." Realizing that the Command Module (CM), Odyssey, was losing its life-support capabilities, Mission Control directed the crew to power it down and use the Lunar Module (LM), Aquarius, as a "lifeboat."

Return to Earth

The Lunar Module was designed to support two astronauts for two days on the lunar surface, not three astronauts for four days in deep space. To survive the journey back to Earth, the crew and Mission Control had to improvise solutions to severe shortages of power, cooling water, and carbon dioxide removal. The crew built a makeshift adapter using plastic bags, cardboard, and duct tape to fit the square carbon dioxide scrubbers from the Command Module into the round openings of the Lunar Module's system.

To conserve power for the critical reentry phase, the crew powered down almost all non-essential systems in the LM, enduring near-freezing temperatures and limited water rations. Mission Control calculated a series of crucial trajectory correction burns using the LM's descent engine, including a critical burn to place the spacecraft on a free-return trajectory around the Moon. Hours before reentry, the crew powered up the Command Module, jettisoned the damaged Service Module and the Lunar Module, and successfully reentered Earth's atmosphere. Apollo 13 splashed down safely in the South Pacific Ocean on April 17, 1970, and the crew was recovered by the USS Iwo Jima.

Investigation and Cause

Following the mission, NASA convened an accident review board to determine the cause of the explosion. The investigation revealed that the failure was the result of a combination of factors, including damaged pre-flight wiring and a flawed thermostat design. Oxygen Tank 2 had been dropped during pre-launch testing, causing slight internal damage. Furthermore, the tank had been subjected to high-voltage direct current during a ground test, which melted the Teflon insulation on the internal wires because the thermostatic switches were incompatible with the voltage being used. When the tank was stirred in space, the exposed wires short-circuited, igniting the insulation in the pure oxygen environment.

Legacy and Cultural Impact

Apollo 13 is often referred to by NASA as a "successful failure" because, despite the mission's primary objective being aborted, the safe return of the crew demonstrated the agency's ability to handle deep-space emergencies. The incident led to significant redesigns of the Apollo spacecraft, including the addition of a third oxygen tank isolated from the other two, upgraded wiring, and the removal of the stirring fans, which were deemed unnecessary. These modifications were implemented for Apollo 14 and subsequent missions.

The mission has left a lasting mark on popular culture. The phrase "Houston, we have a problem" (a slight misquotation of the actual transmission) has become a widely used idiom to informally declare an unexpected problem. The events of the mission were dramatized in the 1994 book Lost Moon by Jim Lovell and Jeffrey Kluger, which was adapted into the highly acclaimed 1995 film Apollo 13, directed by Ron Howard and starring Tom Hanks as Lovell. The Apollo 13 crew was awarded the Presidential Medal of Freedom, the highest civilian honor in the United States, by President Richard Nixon.