The race to save Apollo 13

A little over 10 minutes earlier, Sy Liebergot, a controller at the Electrical, Environmental, and Consumables Management (EECOM) desk, had made the routine request that the crew “stir up” the Odyssey’s oxygen tanks. Stored in a cold ‘cryogenic’ state, oxygen and hydrogen flowed into three fuel cells where they were catalysed by electrodes to produce the lifeblood of the Apollo spacecraft: water, oxygen and electricity.

Stirring the tanks was supposed to ensure an accurate reading of how much of the strange substance (not quite liquid, not quite gas) remained. This time, however, failed switches inside the tank created a short circuit, igniting the Teflon insulation. The spacecraft shook and shuddered. Exchanging frightened glances with his crew, Lovell noticed that one of the craft’s two main power distribution panels was offline. “Hey, we’ve got a problem here!” shouted Swigert. Jack Lousma, the astronaut serving as CapCom (the sole official charged with communicating with the crew) asked the astronauts to repeat, prompting Lovell’s iconic phrase: “Houston, we’ve had a problem.”

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The rookie astronaut

Apollo 13’s crew found themselves assigned to the mission through the vagaries of Nasa’s crew selection process, a complex system predicated on merit, horse-trading and chance. James A Lovell Jr was a former naval aviator and veteran spacefarer who had flown into space on three previous missions, including the trailblazing Apollo 8 mission that had circumnavigated the moon in December 1968. Fred W Haise Jr was a rookie astronaut and former fighter pilot who had been selected for Nasa’s fifth class of astronauts in 1966. Lovell and Haise had both been part of the backup crew for Apollo 13 but were promoted to the prime crew after the original commander, Alan Shepard (the first American in space), was grounded to recover from an ear operation. The back-up’s back-up, Jack Swigert, was assigned to the crew after astronaut Ken Mattingly had been exposed to rubella. As the astronaut corps’ sole bachelor, the media was fascinated by Swigert, dubbing him a “swinger” with a “girl in every airport”.

Apollo 13’s mission profile reflected the ambitions of a space agency with two crewed lunar landings under its belt. July 1969’s Apollo 11 and November 1969’s Apollo 12 had both landed on lunar maria, dark patches on the near side of the moon named by ancient astronomers for their resemblance to earthly seas. These vast and dusty volcanic plains provided comparatively easy landing sites but from a geologist’s perspective they could not compare to the mysteries of the Lunar Highlands. Apollo 13’s landing site was near the mountain-like rim of the Fra Mauro crater. Named after a 15th-century Venetian cartographer, Fra Mauro’s topography presented a challenging landing as reflected sunlight would dissolve the shadows of its boulders and hills.

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For all their speechmaking and flag planting, the Apollo astronauts had work to do. In the cumulative three and a half days that they spent on the moon’s surface outside of their lunar modules, the crews of the entire Apollo programme collected and returned 382 kilograms of lunar rock and soil, obtained more than 6,000 images of the lunar surface and deployed 2,100 kilograms of scientific equipment. Apollo 13’s mission was to investigate whether material scattered by the impact that had formed the crater might shed light on the early geological history of the Earth and the moon. Haise and Lovell would drill 10 feet into the lunar surface as well as deploying equipment to measure lunar seismic activity, solar-wind particles and a Lunar Atmosphere Detector.

This busy schedule was, of course, contingent on the astronauts making it to the moon in the first place. Keeping three fragile human bodies alive in the pitiless void of outer space was an absurdly complicated task. Setting the wrong course at critical junctures during the mission might see the craft slam into the Earth or the moon or, grimmer still, stranded in orbit indefinitely. Cabin pressure had to be maintained, along with a supply of oxygen. If the craft depressurised then the crew faced the unimaginable agony of their blood boiling in their veins. Problems with their oxygen supply could lead to the crew rapidly asphyxiating or being gradually poisoned by the carbon dioxide in their own breath. The astronauts would feel drowsy before dizziness and confusion set in. Sweating and trembling with ragged breath, their vision would dim as they succumbed to unconsciousness.

Keeping three fragile human bodies alive in the pitiless void of outer space was an absurdly complicated task

All too aware that an addled astronaut – affected by deviations in temperature – might make a fatal error, Nasa set the command module cabin temperature of its Apollo spacecraft at the goldilocks temperature of 70oF (21oC).

Most frightening of all was the prospect of a fire. In the oxygen-rich atmosphere of a Nasa spacecraft, a small spark would blossom into an inferno. On 27 January 1967, Apollo 1 astronauts Gus Grissom, Roger Chaffee and Ed White were killed when an electrical spark ignited their command module during a pre-launch test. Nasa’s investigation ruled that, perhaps mercifully, they were asphyxiated by fumes before the flames could claim them.

Mid-course correction

Now, 55 hours and 55 minutes into the Apollo 13 mission, Nasa found itself confronted with a nightmare scenario once again. Apollo 13’s oxygen tank had ignited during what was supposed to be a comparatively uneventful stretch of space travel. After lift-off on the 11th, the command and service module Odyssey (the mission’s mother ship) had already retrieved its lunar excursion module Aquarius, the lunar lander and its ascent apparatus, from the discarded third stage of the Saturn rocket. The following day, the Aquarius-Odyssey assemblage had performed a mid-course correction burst of its engines to leave the so-called ‘free return’ trajectory that would have eventually seen the craft drift back to Earth. But then, on the 13th, disaster struck. Watching oxygen vent from the stricken spacecraft and reading indications that two of the craft’s three fuel cells had failed, the astronauts realised that a lunar landing was out of the question. Apollo 13’s mission was now one of survival.

With the Odyssey losing power, Mission Control had to quickly decide how to bring Apollo 13 home. The short way was a risky ‘direct abort’ trajectory, where the astronauts would jettison the lunar module and turn straight back using the Odyssey’s remaining power. The long way involved using the Aquarius, the cramped lunar module that had been designed for just two astronauts, as a lifeboat and using a free-return trajectory that would take the spacecraft around the far side of the moon before being pulled back to Earth. Kranz did not trust the astronauts’ chances in the dying command module. So, at 10:50pm Houston time, the crew abandoned the Odyssey and sought refuge in the Aquarius. At 2:43am the Aquarius’s engine fired, shifting the spacecraft back into the free-return trajectory.

With the astronauts safe in the Aquarius for the time being, Mission Control’s priority was to conserve power to leave Odyssey with just enough to make the necessary course correction manoeuvres for re-entry. Briefing the assembled controllers, Kranz declaimed: “Flight control will never lose an American in space. You’ve got to believe, your people have got to believe that this crew is coming home.”

As the drama unfolded in space, Nasa technicians scrambled to find a way to return the astronauts to Earth safely. In between working their way through “endless negotiations” and calculations, the technicians snatched what sleep they could in the break rooms or under their desks. Meanwhile, Ken Mattingly, the crew member Swigert had replaced, and other astronauts ran simulations to test what worked – and what did not.

Nixon’s nervous energy

Apollo 13’s problems had begun shortly after the crew concluded their first television broadcast. No major network had broadcast the footage live; having already achieved two moon landings, the Apollo formula had dulled with repetition. Once news of the crisis broke, however, Apollo 13 became the biggest news story of the day. Like many Americans, President Richard Nixon obsessively followed news of the mission; National Security Advisor Henry Kissinger recalled that the crisis “took a heavy toll on Nixon’s nervous energy”.

No sooner had one problem been solved than another presented itself. Conserving power meant sacrificing crew comfort as temperatures in the Aquarius plummeted. The breath of three astronauts in a module meant for two overwhelmed the Aquarius’s carbon dioxide scrubbers. Nasa’s engineers scrambled to come up with a way of adapting the square canisters from Odyssey to fit the cylindrical receptacles in Aquarius before the crew was poisoned. Joe Kerwin, a doctor-turned-astronaut who had taken over as capsule communicator, sent the crew on a frantic scavenger hunt to cobble together an improvised adaptor from a plastic bag, a cardboard flight plan cover, a sock and plenty of duct tape. Every procedure was checked and double checked, with EECOM controller John Aaron frequently demanding controllers start again from scratch if a proposed solution squandered water, power or oxygen.

The crew cobbled together an adaptor from a plastic bag, a cardboard flight plan cover, a sock and duct tape

Apollo 13’s trek home was punctuated by crises. On the afternoon of Wednesday 15 April, the tired, cold and dehydrated crew were shocked by another bang and a shudder. Aquarius’s Battery Two had exploded. Luckily this problem was survivable. Twice, in the early hours of Thursday and the morning of Friday, Mission Control had to instruct the crew to correct the Aquarius’s course.

As re-entry loomed, the crew prepared to jettison the Odyssey’s service module before moving from Aquarius back into the Odyssey’s command module for the ride down to Earth. Separating the service module offered the crew a sobering glimpse of the damage the first explosion had caused. “There’s one whole side of that spacecraft missing!” exclaimed Lovell as he peered through the Odyssey’s window. As they moved back from the Aquarius to the Odyssey, the crew brought scientific equipment to compensate for the lack of moon rocks that had been factored into the craft’s weight for re-entry calculations. At 10:43am Houston time, the crew jettisoned their trusty lifeboat. A little over an hour later re-entry began.

Re-entry took 14 minutes and for much of that time communication between the craft and the ground would be impossible. As the Odyssey hurtled through the atmosphere, its heat-shield wreathed in flame, a leaden silence descended over Mission Control as its controllers chain-smoked and prayed.

As the Odyssey hurtled through the atmosphere, a leaden silence descended over Mission Control

A minute and a half after the expected communications blackout time had ended, the controllers’ prayers were answered: a Nasa communications relay aircraft finally announced it had acquired a signal on Apollo 13. Cheers filled Mission Control, but there was one last hurdle: the systems used to warm the parachute systems had been powered down, raising the ominous prospect of a repeat of the April 1967 Soyuz 1 tragedy. Soviet cosmonaut Vladimir Komarov had been pulverised when his capsule’s parachute malfunctioned, smashing his spacecraft back into the Earth.

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Fortunately, Apollo 13’s parachute unfolded and communications were finally re-established with “Okay, Joe!” – Swigert’s crackling response to Joe Kerwin – as the Odyssey drifted towards the Pacific Ocean.

An estimated 40 million Americans watched the splashdown. Quoted in the New York Times, 49-year-old Thomas G McCarthy Jr of Pittsburgh spoke for many who had followed the story: “Thank God this thing is over; I got an ulcer worrying about it.”

Thomas Ellis teaches at the department of international history at LSE. The new BBC Sounds podcast, 13 Minutes to the Moon – Season 2, tells the story of the Apollo 13 mission. You’ll find it at bbc.co.uk/programmes/w13xttx2

Thomas Ellis will be discussing Apollo 13 on our podcast. You’ll be able to listen to that at historyextra.com/podcast

This article was first published in the April 2020 edition of BBC History Magazine