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Apollo 13

Megaprojects are often designed to provide a sense of wonder. Colossal constructions, dazzling speeds and savagely impressive weaponry – but not this story. For one week in April 1970, the world held its breath as NASA attempted the seemingly impossible. What played out during those harrowing days was nothing short of extraordinary as the crippled Apollo 13 spacecraft was successfully brought home – after slingshotting around the moon.   

The story has of course been immortalised on the silver screen, with Tom Hanks uttering the now immortal words – “Houston, we have a problem”. Quick fact about that line before we move on. It wasn’t quite what was said – the sentence that was actually relayed from Apollo 13 was, “Houston, we’ve had a problem”. Minor semantics I know, but we do like to set the facts straight here on Megaprojects. Vocabulary aside, it was certainly one hell of a problem. 

If for some unbelievable reason you’ve never heard about this story, then you’re in for quite a treat. This is a real-life story that reads better than any Hollywood scriptwriter could possibly muster. A tale that has everything – failure, success, ingenuity and plenty of nail-biting drama.


It was a little over a year before Apollo 13’s launch that Neil Armstong took his giant leap for mankind. The success of Apollo 11 had been followed by Apollo 12 which had completed a precision landing on the moon. But with number 13, the focus wasn’t simply on making it to the moon and back, it would also carry out a much wider array of experiments on the moon’s surface than on the two previous missions. The mission’s motto was a nod to this – Ex luna, Scientia (From the Moon, knowledge)

Onboard was a seismometer that would measure the impact of the lunar module on the moon. The crew would also carry out a heat flow experiment, which involved drilling three holes 3 metres (10 ft) deep and recording the temperature from within. A charged particle lunar environment experiment would measure protons and electrons, while a lunar atmospheric detector and a dust detector would analyse particles on the moon’s surface.  

The original crew of Apollo 13 consisted of Mission Commander Jim Lovell, Command module pilot Ken Mattingly and Lunar Module pilot Fred Haise. At the time, Lovell, a 42-year-old who had spent a whopping 572 hours in space spread over three missions, was NASA’s most experienced astronaut.  

Trouble began one week before the launch when one of the backup crew came down with rubella, which meant, both the prime and backup crew had potentially been exposed as the two often trained together. Of the five remaining astronauts, only Ken Mattingly had not had the disease at a younger age, and the decision was made to swap Mattingly with backup command module pilot Jack Swigert just two days before launch. Not only did Mattingly never develop rubella, he would go on to play a key role in the successful mission to bring Apollo 13 home – but more on that later. 

The prime crew had spent over 1,000 hours on mission-specific training, meaning for each hour of the planned ten-day mission, they had trained for 5 hours beforehand. Swapping a team member so close to launch was far from an ideal situation, but as you probably already know, that would be the least of their worries.  


Apollo 13 blasted into the sky at 2.13 pm on April 11th 1970, but almost immediately, the carefully planned mission began to go awry. The Saturn V rocket that accompanied Apollo 13 came with three burn stages; the first stage was scheduled to burn for 168 seconds before detaching and falling back to Earth, the second stage would burn for 360 seconds and the third would fire on two separate occasions, the first for 165 seconds and the second for 335 seconds.  

Everything seemed fairly normal until the second burn cut out roughly two minutes early because of pogo oscillations, which is a wonderfully descriptive phrase that basically means extreme vibrations. Thankfully, the third stage and the onboard engines were able to burn for longer to compensate and remarkably, Apollo 13 entered a parking orbit in space close to where it should have been. A post-flight analysis found that the second stage had been just one cycle away from catastrophic disaster – so I suppose strangely, they were a little lucky during the opening act of this epic tale. 

A thorough diagnostic check was carried out over the next two hours, as per normal, before Apollo 13 fired its third stage for the last time, putting the spacecraft on its trans-lunar injection (path to the moon). Shortly after the TLI, Swigert successfully carried out the transposition manoeuvre which involved the command service module (CSM-Odyssey) docking with the Lunar Module (LM-Aquarius) and the third stage of the Saturn V rocket detaching, after which it was directed towards the moon, where it later crashed landed. 

Despite the incident with the second stage during launch, Apollo 13 had successfully come through two of the most difficult stages of the entire mission. It was time for the astronauts to settle in for the three day trip to the moon.   

On the third day of the mission, the crew took part in a television broadcast in which viewers were shown around the confines of Apollo 13. They didn’t know it at the time, but none of the major channels back in the U.S had chosen to air the broadcast. Apollo 11’s historic journey had been just 9 months prior, but enthusiasm around trips to the moon was already waning. Ironically, the events that were about to take place would catapult these astronauts onto television sets around the world and grip the American consciousness more than Apollo 11 ever had.  

Shortly after Lovell wished those back on Earth a pleasant evening and shut off the camera, mission control asked Swigert to stir the fans within the fuel tanks in response to an earlier malfunctioning sensor. This is a perfectly normal procedure and is typically done once a day, but on this particular day, it led to disaster.


95 seconds after the switch to stir the tanks had been activated, an explosion rocked Apollo 13. Power and communication momentarily went out, before Swigert uttered those famous words for the first time, which were then relaid to mission control by Lovell – “Houston, we’ve had a problem. We’ve had a Main B Bus undervolt” – meaning the voltage being produced by the fuel cells was insufficient.   

Oxygen levels began falling as warning lights flashed manically across the CSM’s control panel. It was Lovell who was the first to notice “a gas of some sort venting into space”. It was quickly becoming clear that the most serious incident in space NASA had ever experienced was now underway.

Now, remember there were two modules still in operation at this point. Odyssey, the command service module, which was designed to carry the astronauts to and from the moon and also needed to be used for re-entry and Aquarius, the Lunar Module, which was small, cramped and really only designed to land on the moon and take off from it. 

The explosion had occurred within the fuel tanks of the Odyssey but as far as everybody involved knew, the Aquarius was still functioning properly. The decision was made to power down the Odyssey in the hope of retaining enough oxygen and power to successfully re-enter the Earth’s atmosphere. At the same time, they would power up the Aquarius then move across into the Lunar Module.

The process of powering up the Aquarius took some time even under normal conditions but Lovell and Haise worked quickly and just under three hours after the explosion the Aquarius was ready. While they did this Swigert powered down the Odyssey and shortly before midnight back on the U.S East Coast, the three astronauts moved down into Aquarius, which had suddenly become their lifeboat. 

To the Moon     

The immediate danger had passed but the challenges facing the three men were enormous. There was the question of whether the spacecraft should be immediately turned around, a process known as a direct abort, or try to slingshot around the moon and return to Earth that way. Did they have enough oxygen? Could they get rid of carbon dioxide? Could the small Aquarius that had been designed to be used for just two to three days be used for four or five? There was little the astronauts could do at this point, but back at mission control, calls were going out to bring every available person in to help. The original mission objective had been scrapped. The only goal now was to bring the limping spacecraft and its three occupants home safely.   

The decision was made to slingshot around the moon. A direct abort would have required the use of the service propulsion system (SPS) on the Odyssey, a system that nobody could be sure had not been damaged during the accident. It was a risk that they couldn’t take and the astronauts were informed that they needed to transfer the guidance system’s orientation information from the Odyssey to the Aquarius. 

61 hours and 29 minutes after takeoff, the descent propulsion system onboard the Aquarius was fired for 34.23 seconds which took Apollo 13 back onto a return trajectory with an expected splashdown in the Indian Ocean four days later. It was the first of many difficult steps to come.  

As morning broke in the United States news of Apollo 13’s perilous situation was played out on TV and in newspapers across the country. At 6.21 pm EST on 14th April, Apollo 13 disappeared behind the dark side of the moon and communication with mission control was temporarily lost. We can only imagine how the astronauts must have felt staring down at the lunar surface as they passed over their planned landing site, Fra Mauro. But if there was a smidge of a silver lining, it was that Apollo 13 claimed the record for the furthest distance from Earth for a manned space mission at 400,171 kilometres (248,655 mi) – a record that still stands to this day.

The Burn

The decision had been taken at mission control to fire the DPS on the Aquarius after re-emerging from the moon’s shadow. This was a process known as the PC+2 procedure and would not only shorten the flight time back to Earth by 12 hours but would also provide a splashdown in the Pacific, where the majority of rescue teams currently were. This type of manoeuvre normally comes with a host of navigational tools to ensure accuracy, but for those on board Apollo 13, the best they had was good old fashioned eyesight. 

In this kind of situation, astronauts are trained to be able to navigate using the stars, but with light bouncing off the debris still coming from the Odyssey, it would have been impossible. Instead, Swigert aimed at the only large object that they could trust – the sun. 

At this point, it’s probably worth reminding you that the man behind the controls of the Lunar Module, 38-year-old John Swigert wasn’t even supposed to be on board Apollo 13. The last-minute rubella case had dramatically altered his role in the mission and the pressure on him as the crew prepared to fire DPS must have been unimaginable. If Apollo 13 veered too far off course, it might struggle to ever get home. 

But the burn was nearly flawless. 79 hours and 27 minutes after take-off, the DPS on the Aquarius – an engine primarily designed to get the astronauts down to the surface of the moon then back up, was fired for 4 minutes and 23 seconds. The result was less than 0.3 meters (1 ft) per second off the desired course, considering the circumstances, it was as close to perfect as you were likely to get. 

Now that Apollo 13 was on a correct course for Earth, the crew shut down almost everything inside the Lunar Module to conserve power. Things were about to get very cold, but as it turned out, the temperature would not be their biggest dilemma. 

Carbon Dioxide 

The three major calculations taken into consideration in the rescue of Apollo 13 were, fuel, power and oxygen and fortunately for those onboard, all three were in good shape as they headed for home. But another calculation had been missed – the accumulation of carbon dioxide. 

Both the Aquarius and the Odyssey came with canisters of lithium hydroxide pellets which absorbed carbon dioxide. However, the canisters on the Aquarius were only designed to support two astronauts for 45 hours during the planned moon landing phase and not three men for four days. The Odyssey came with its own canisters, but inexplicably, they were different sizes. As carbon dioxide levels continued to climb rapidly, it was clear that even if Apollo 13 made it safely back to Earth, the three astronauts would die of carbon dioxide poisoning long before that hatch could be opened. 

Personally, this is one of my favourite parts of the whole story and a truly spine-tingling moment in the film. A group of engineers at mission control assembled a selection of items that the astronauts had on board, including flight manuals, duct tape, pipes, wiring – you name it – and successfully created a filtration device. The procedure was then relayed to the crew of Apollo 13 and quickly built. Once it had been finished, all eyes settled once again on the carbon dioxide gage. It seemed to level off, then started falling. The device – now known as the mailbox – had just saved their lives. 


As Apollo 13 neared Earth, conditions inside the Aquarius were deteriorating rapidly. Water levels were running dangerously with the crew down to a daily ration of just 0.2 litres (6.8 fl oz) of water (daily recommendations for men is 3.7 litres -125 fl oz) The three astronauts lost a combined 14 kilograms (31 lb) throughout the mission, while Haise developed a painful urinary tract infection. The temperature inside the Aquarius fell to as low as 3 °C (38 °F) with condensation accumulating throughout the module.

Now, remember when I said Ken Mattingly, the pilot who had been taken off the flight at the last minute still had a role to play in this story, well, here it is. The next major problem facing the Apollo 13 crew was how to power up the Odyssey using the least amount of power possible. To make this even more complicated, this was a procedure that had never been done before in space. 

Mattingly, as well as other engineers on the ground, had been working tirelessly to produce a set of steps to restore power to the mangled Odyssey, which the crew carried out without any significant problems. Two further course corrections were needed and done so by simply aiming Apollo 13 at the night/day line creeping across the Earth. Once this was done, the crew made their way back into the Odyssey, strapped in – and prepared. One hour before reentry, the Aquarius was disengaged and broke up as it entered the atmosphere. 

As the Odyssey hurtled towards Earth’s atmosphere, there were absolutely no guarantees. If the heat shield had been compromised during the accident, all their efforts would count for nothing. The typical communication blackout for a command module re-entering was four minutes. Much longer than that and it was likely the heat shield had failed.  

Despite this being an American mission, this was now a global event as millions around the world watched live on television. Numerous nations had already pledged their assistance should the craft go off course. Pope Paul IV led 10,000 people in prayer at the Vatican, while an estimated 100,000 gathered for a religious festival in India offered their prayers to bring the astronauts safely home. During an age of increasing partisanship around the world, this was an event that everybody was well behind.   

As Apollo 13 entered the Earth’s atmosphere, communication with mission control was lost, leaving only radio static. Helicopters began circling the projected splashdown area.  

The four minutes came – and went. 

TV cameras searched the sky for any sign of a parachute. The five-minute mark passed with many in mission control now assuming the heat shield had failed. Six minutes passed. Hope was fading.  

Suddenly, a red and white parachute was spotted. Jim Lovell’s voice was finally heard over the radio. Celebrations erupted in mission control, across America and around the world. As the battered remains of Apollo 13 drifted down from the sky, the unthinkable had been achieved. 

The Successful Failure

The cause of the explosion was later found to be down to a change in voltage on board that had occurred years before. The initial 28 volts had been increased to 65 but unfortunately, not everybody got that memo. The manufacturer of the thermostat located inside the oxygen tanks had not been informed of the change. To compound this, the tank itself had been dropped two years prior and damaged, a fact that didn’t become clear until much later. During a pre-flight test, the temperature inside the tank had caused the thermostats to weld shut, which again was missed.   

Once the tanks were stirred the temperature reached over 500C (1000F) and ignited the insulation inside, causing the fuel cell bay to quickly fill with gaseous oxygen and combustion products, leading to the explosion. 

It had been a harrowing, terrifying, yet glorious tale. From the resilience of those onboard to the incredible ingenuity of the engineers on the ground, the story of Apollo 13 is one of those captivating dramas that holds you transfixed until the very end.  

The successful return of Apollo 13 after such a series of unfortunate events was always made for Hollywood. The rejoicing seen around the world eclipsed other major events, including the landing of Apollo 11. Jack Gould of The New York Times said famously, that Apollo 13’s flight “which came so close to tragic disaster, in all probability, united the world in mutual concern more fully than another successful landing on the Moon would have”.

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