Apollo 13

• 1. Introduction

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  Apollo 13 launched from Kennedy Space Center on the 11th of April, 1970, carrying three astronauts toward what should have been humanity's third walk on the Moon. Two days into the journey, a routine switch flip triggered something the mission planners had not truly prepared for: a bang loud enough to shake the spacecraft, a loss of power, and oxygen bleeding silently into the void of space. The landing was over before it began. What followed was four days of improvisation, cold, thirst, and careful calculation, watched by tens of millions on Earth who had grown indifferent to space travel until it nearly ended in catastrophe. How did an oxygen tank turn a Moon mission into a survival story? Who made the decisions that brought three men home alive? And why, in the end, did the mission's commander call it a "successful failure"?

• 2. The Crew and the Crew Change

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  Jim Lovell, at 42, was the most experienced astronaut in the program at the time of Apollo 13. His 572 hours in space across three earlier missions, including Apollo 8, the first spacecraft to orbit the Moon, made him the natural choice as commander. At 38, Jack Swigert held a bachelor's degree in mechanical engineering and a master's in aerospace science; Fred Haise, 36, had served as a Marine Corps fighter pilot before becoming a civilian NASA research pilot.

  But Swigert was not supposed to be there. The original command module pilot was Ken Mattingly. Seven days before launch, Charles Duke, the backup crew's lunar module pilot, contracted rubella from a friend of his son. Duke had trained alongside the prime crew, and the exposure touched all five men. Of the five, only Mattingly lacked immunity through prior exposure. Mission rules would normally have grounded the entire prime crew and substituted the backup, but Duke's illness ruled that out too. Two days before launch, Mattingly alone was removed and Swigert took his seat. Mattingly never did develop rubella; he later flew on Apollo 16.

  The mission's insignia patch was untouched by the crew change. It was one of only two Apollo patches, the other being Apollo 11's, that carried no crew names, designed by artist Lumen Martin Winter, who based it on a mural he had painted for the St. Regis Hotel in New York City. Lovell chose the lunar module's call sign, Aquarius, for the bringer of water, and named the command module Odyssey partly in reference to Arthur C. Clarke's story adapted into the film 2001: A Space Odyssey.

• 3. The Tank That Was Already Broken

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  Oxygen Tank 2 had a history before it ever reached Apollo 13. Originally installed in the service module intended for Apollo 10, the tank's shelf was accidentally dropped at least 2 inches during removal at North American Rockwell's facility, because a retaining bolt had not been taken out first. A fill line assembly may have been loosened or damaged by the fall. The shelf was re-installed in the service module designated for Apollo 13 without a full re-test, and the spacecraft shipped to Kennedy Space Center in June 1969.

  The thermostatic switches inside the tank had a second vulnerability. The original 1962 specifications called for switches rated at 28 volts. Revised specifications issued in 1965 raised the required rating to 65 volts to allow for quicker pressurization at the launch site, but the Beech Aircraft Company of Boulder, Colorado, which manufactured the tank, never swapped the switches to match. During the Countdown Demonstration Test on the 27th of March, 1970, technicians could not empty the tank through the normal drain line. They turned on the heaters to boil off the oxygen. The switches were supposed to cut off the heaters before temperatures exceeded 80 degrees Fahrenheit, but they failed under the 65-volt supply. Temperatures on the heater tube may have reached 1,000 degrees Fahrenheit, almost certainly damaging the Teflon insulation on the wires inside. The temperature gauge was not built to read above 85 degrees, so the monitoring technician saw nothing alarming. That heating had been approved by Lovell and Mattingly and by NASA managers. Replacing the tank would have delayed the launch by at least a month.

• 4. The Bang and the Lifeboat

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  At 55 hours, 54 minutes, and 53 seconds into the mission, with Apollo 13 roughly 180,000 nautical miles from Earth, Jack Swigert activated the switches that stirred the oxygen tank fans. Ninety-five seconds later, a spark from the damaged wire insulation inside Oxygen Tank 2 ignited the Teflon. Pressure built until the tank dome failed. The resulting force blew out an aluminum panel from the exterior of the service module, snapping the high-gain antenna and cutting communication with Earth for 1.8 seconds. Swigert reported to Houston 26 seconds after the explosion: "Okay, Houston, we've had a problem here." Lovell repeated it: "Houston, we've had a problem. We've had a Main B Bus undervolt."

  The explosion had also slammed closed the oxygen valves on two of the three fuel cells, killing them instantly. Oxygen Tank 1 began losing its contents through a damaged line or valve. With the fuel cells dying, the command module had to be shut down to preserve its batteries for reentry, and the crew transferred to the lunar module Aquarius, built for two astronauts on the lunar surface for two days and now asked to support three men for four days.

  Flight Director Gene Kranz decided against a direct abort using the service module's engine, which could have been damaged in the explosion. Instead, the spacecraft would swing around the Moon, and the lunar module's descent engine would fire to push it back onto a free-return path toward Earth. At 61 hours, 29 minutes, and 43 seconds, a 34.23-second burn put Apollo 13 back on course. Kranz later said the crew's survival was partly due to their experience as test pilots, who knew how to act under life-threatening conditions.

• 5. Four Days of Improvisation

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  Carbon dioxide was the first quiet threat. The lunar module's stock of lithium hydroxide canisters, designed for two men over 45 hours, could not scrub the air for three men over four days. The command module had enough canisters, but they were a different shape and could not fit the lunar module's equipment. Engineers on the ground assembled a workaround from materials on the spacecraft: plastic covers from procedure manuals, duct tape, and other available items. NASA engineers called the improvised device "the mailbox." CAPCOM Joseph Kerwin read the procedure aloud over the course of an hour; Swigert and Haise built it, and carbon dioxide levels dropped immediately.

  Power and water presented a second threat. The lunar module ran on silver-zinc batteries that, unlike the command module's fuel cells, produced no water as a byproduct. Swigert filled what drinking bags he could from the command module's water tap before it was shut down. Even rationing personal consumption to 200 milliliters per person per day, Haise initially calculated they would run short of cooling water about five hours before reentry. In the end the spacecraft landed with 28.2 pounds of water remaining, partly because Apollo 11's jettisoned lunar module had kept operating for seven to eight hours after its water was cut off, giving engineers confidence in the margin.

  The cabin temperature fell to 38 degrees Fahrenheit. Lovell considered ordering the crew into their spacesuits but judged that too warm. He and Haise wore their lunar EVA boots instead; Swigert had no lunar overshoes because he had not been assigned a moonwalk. He had also got his feet wet filling water bags and suffered most from the cold. The crew was told not to discharge urine to space to avoid disturbing the trajectory. The three men lost a combined 31 pounds before splashdown, and Haise developed a urinary tract infection, likely worsened by the restricted water intake.

• 6. Bringing Odyssey Back

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  At 133 hours into the flight, Mission Control allowed Lovell to fully power up the lunar module to warm the cabin before the command module restart, a procedure that had never been intended to occur in flight under those conditions. Flight controller John Aaron, along with Mattingly, who worked the problem from the ground, and a team of engineers devised the power-up sequence step by step. Lovell used the running lunar module computer to take a navigational sighting and calibrate the inertial measurement unit, then transferred that calibration in reverse to the command module's computer, shaving steps from the restart process.

  Separating the lunar module before reentry posed one final problem. The normal procedure, used after a Moon landing, called for the service module's thrusters to pull the command module away after the lunar module was released. The service module was already gone. Grumman, the lunar module's manufacturer, assigned a team of engineers from the University of Toronto, led by senior scientist Bernard Etkin, to calculate exactly how much air pressure to leave in the docking tunnel so it would push the two modules safely apart. The solution worked.

  Apollo 13's shallow reentry path lengthened the communications blackout from the expected four minutes to six minutes. Controllers feared the heat shield had failed. Odyssey regained contact and splashed down in the South Pacific Ocean, southeast of American Samoa and 6.5 kilometers from the recovery ship USS Iwo Jima. The lunar module Aquarius reentered and was destroyed, its remaining pieces falling in the deep ocean. The SNAP-27 plutonium cask settled 10 kilometers down in the Tonga Trench; later helicopter surveys found no radioactive leakage.

• 7. Aftermath and Accountability

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  NASA Administrator Thomas O. Paine and Deputy Administrator George Low appointed a review board the same week the crew returned. Chaired by Edgar M. Cortright, director of NASA Langley Research Center, and including Neil Armstrong among its members, the board sent its final report to Paine on the 15th of June. It traced the accident through the dropped tank shelf in 1968, the underrated thermostatic switches from 1962, the overheated Teflon insulation during the March 1970 test, and the fatal spark from Swigert's routine fan activation. The board praised what it called "outstanding performance on the part of the crew and the ground control team."

  For Apollo 14 and later missions, engineers removed the stirring fans and added a third oxygen tank placed in a separate bay with an isolation valve. All electrical wiring in the damaged bay was sheathed in stainless steel. An emergency water supply of 5 gallons was stored in the command module, and an emergency battery was added to the service module.

  None of the three Apollo 13 astronauts flew again. Lovell retired from NASA and the Navy in 1973 and entered the private sector; he died in 2025 at age 97. Swigert left NASA to enter politics, was elected to the House of Representatives in 1982, and died of cancer before he could be sworn in, aged 51. Haise flew the Space Shuttle Approach and Landing Tests before retiring from NASA in 1979. On the 5th of February, 1971, Apollo 14's lunar module Antares landed near Fra Mauro, the site Apollo 13 had aimed for; Haise served as CAPCOM during the descent.

• 8. Memory and Meaning

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  An estimated 40 million Americans watched Apollo 13's splashdown live on all three television networks. The rescue received more public attention than any spaceflight to that point other than the first Moon landing. Pope Paul VI led 10,000 people in prayer for the crew; four Soviet ships headed toward the landing area to assist. Jack Gould of The New York Times wrote that the mission had united the world in shared concern more fully than another successful landing would have.

  Yet the outpouring faded. Author Colin Burgess noted that once the crew was safely back, public apathy set in again. Some officials, including Manned Spaceflight Center director Robert R. Gilruth, drew the conclusion that continuing to send astronauts on Apollo missions made eventual deaths inevitable and called for ending the program quickly. Nixon's advisers recommended canceling the remaining lunar missions; budget cuts made the decision easier, and during the pause after Apollo 13, two missions were cut. The program ended with Apollo 17 in December 1972.

  The 1995 film directed by Ron Howard and starring Tom Hanks as Lovell introduced the phrase "Failure is not an option," spoken by Ed Harris as Gene Kranz, though Kranz himself never said it during the mission. The phrase became so tied to Kranz that he used it as the title of his 2000 autobiography. The mural that artist Lumen Martin Winter used as the basis for the mission patch was purchased by Tom Hanks after the film wrapped and now hangs in the Captain James A. Lovell Federal Health Care Center in Illinois, a final connection between the story told on screen and the man who lived it.