Two days into what should have been a mission to the Moon, disaster struck Apollo 13. A new film explores the drama – and astronaut Jim Lovell recounts the incredible efforts to bring the crew back.

14 April 1970, the crew of Apollo 13 – Jim Lovell, Jack Swigert and Fred Haise – are two days into their mission and well on their way to the Moon. Earlier in the day at mission control in Houston, capsule communicator (Capcom) Joe Kerwin had reported that the spacecraft was “in real good shape”, and joked to the crew “we’re bored to tears down here.”

In fact, Nasa’s third Moon landing had completely failed to capture the public imagination. “People were getting bored,” Lovell (now 89 but sounding 20 years younger) tells BBC Future. “The publicity for Apollo 13 you could find on the weather page of the newspaper, that was it.”

At 55 hours and 46 minutes into the flight, the crew finished their live TV message to Earth. They had taken viewers on a tour of their command module and lunar lander. None of the major TV networks carried the broadcast.

“The media didn’t have anyone at the control centre,” says Sy Liebergot, who was sitting at his position behind the Electrical Environmental and Communications (Eecom) console. “They figured the public wasn’t interested in us going and landing on the Moon.”

Only recently out of college, Liebergot was among the dozens of young men – most in their 20s at the time of the Moon landings – recruited into mission control. Responsible for the health of the critical life support systems on the Apollo spacecraft, he features in a new documentary movie, Mission Control: The Unsung Heroes of Apollo.

The data went crazy, there was a lot of commotion in the room. We didn’t know what we were seeing – Sy Liebergot, mission controller  

The philosophy of overseeing manned space flights from a single room, with a clear chain of command, had been developed by Chris Kraft, who had honed his ideas in aviation testing. Kraft likened mission control to an orchestra, with separate sections co-ordinated by a conductor or, in this case, Flight Director.

All commands went through ‘Flight’ and were communicated to the astronauts via a single Capcom – usually an astronaut. “We on the ground knew more about the spacecraft and its operation than the crew,” says Liebergot. “Work the problem – that was the mantra. It’s not the training kicking in, it’s the training to become disciplined.”

Everything possible had been done to eliminate confusion or muddled decision making. In fact, drama was the last thing anyone wanted.

“Thirteen,” says Capcom Jack Lousma, before the crew were due to settle down for the night. “We’re got one more item for you when you get a chance, we’d like you to stir up your cryo tanks.”

These tanks, in the spacecraft service module, were Liebergot’s responsibility. They held oxygen and hydrogen, which was converted to electricity and water in three fuel cells – powering the capsule and providing the astronauts with drinking water. The routine instruction to turn on stirring fans was to make sure the liquid in the fuel vessels was properly mixed, to ensure the gauges gave accurate readings.

Swigert flicks the switches for the fans. Two minutes later, there is a bang and the master alarm sounds.

When the explosion first occurred, we didn’t know what had happened – Jim Lovell  

On the ground, Liebergot is beginning the last hour of his eight-hour shift and is the first to see something has gone wrong. “The data went crazy, there was a lot of commotion in the room,” he says. “We didn’t know what we were seeing.”

That eight-hour shift would eventually end three days later.

“Houston, we’ve had a problem here,” Lovell tells mission control. “It looks to me, looking out the hatch, that we are venting something. We are venting something out into space.”

It was becoming clear that this was no telemetry error.

“When the explosion first occurred, we didn’t know what had happened,” says Lovell. “It wasn’t until I saw the oxygen escaping and saw on the instrument panel that we’d completely lost oxygen out of one tank, and it was rapidly disappearing out of the second, that I realised we were in deep trouble.”

With the TV stations scrambling for information, interrupting programmes to cut to mission control, Flight director, Gene Kranz, had his team “work the problem”. Everyone in the room was instructed to talk only on their headsets, call in their support staff and establish what was wrong.

“It never occurred to us that we wouldn’t bring the crew back alive,” says Liebergot. “That was not the attitude of flight controllers.”

But 200,000 miles (322,000 kilometres) away and still heading away from Earth, Lovell was not as certain. “We didn’t have any solutions about how to get back or exactly what to do,” he says. “That was perhaps the low point in the flight as regards the odds of whether we would get back to Earth or not.”

With responsibility for the failed systems, Liebergot’s role now was to attempt to save as much oxygen and, therefore, power on the damaged spacecraft as possible. His strategy, using an emergency procedure drawn up in the event of a fuel cell failure, was to begin powering down the spacecraft – reducing the demand on the one remaining operational fuel cell.

“The job was to keep the fuel cell in the command module going long enough for the astronauts to get into the lunar lander and get those systems working,” he says. “And that’s what we did in a very orderly, trouble-shooting procedure to keep the fuel cells going.”

Up in space, the crew weren’t floating around waiting for instructions. They had already begun moving across to the fully intact lunar lander, although Lovell soon realised it was not going to be comfortable.

“The lunar module is very fragile,” he says. “It was only designed to support two people over two days and as I counted the crew there were three of us and we figured it would take four days to get back.”

“We finally got to the point where we realised we weren’t going to be able to land on the Moon, the mission was gone,” says Liebergot. “The decision was made to loop around the Moon to intercept the Earth.”

Over the coming days, mission controllers worked around the clock – grabbing a few minutes of sleep under their desks when they could – to get the Apollo 13 crew home. There were plenty of problems to “work”. They planned thruster burns to stay on course and figured out how to keep the astronauts alive – using a plastic cover, an old sock and duct tape to fit the square carbon dioxide scrubbers from the command module into the round scrubber holes in the lander.

“It was a collaboration, a tale of two groups,” says Lovell, who makes it clear in our interview that neither group was having an easy time. “One in a comfortable control room with hot coffee and cigarettes – that had to come up with the ideas to get us back… and the second group in a cold, damp spacecraft to correctly execute those decisions.”

Even when Liebergot’s Eecom team managed to power-up the capsule again for the safe return to Earth, there was no guarantee the crew would survive. In their efforts to save energy, mission control had been forced to sacrifice the electrical power used to keep the parachute systems warm.

“If the pyrotechnics that fired the parachutes failed,” says Lovell, “we would have been on course but going too fast to survive a water landing.”

It was only, on 17 April, when TV viewers around the world watched the Apollo 13 capsule descend through the clouds on its three parachutes to splash down in the Pacific that mission controllers knew they had been successful. The crew became international heroes. After celebratory cigars were handed round in the control room, Liebergot and his Eecom team headed home to sleep. A few days later, they were back at work, planning the next mission.

Today you are as likely to see women as men behind the consoles of mission control but the principles, originally set out by Chris Kraft in the 1960s, are still in place. Each mission is a team effort. Behind every astronaut there are hundreds of people doing their best to ensure the crew makes it back to Earth alive.

And, says Lovell, the Apollo 13 mission remains one of its finest hours. “In retrospect after years of thinking about it,” he says, “the explosion of Apollo 13 was probably the best thing that could have happened to the space programme.”

Mission Control: The Unsung Heroes of Apollo was released worldwide on 14 April. It is selected as one of BBC Culture’s Nine Films to Watch in April and you can hear a full interview with Liebergot and extracts from the film in the Space Boffins Podcast.

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