In Houston it was six minutes past nine at night on the fourteenth of April 1970. Fifty-six hours previously, the fifth mission to the Moon, the third with the objective of landing, had lifted off from Cape Kennedy. Just a few hours before, the crew had broadcast a seventy-two minute long TV show that was supposed to have gone out live to America, yet not one station aired it, the only people to see it live were those at Mission Control in Houston. The crew were now relaxed after having set up and tested the systems of the Lunar Module "Aquarius" for its upcoming mission to the Fra Mauro Highlands. Mission Commander James Lovell was busy stowing the camera that had just been used to show Mission Control the LM's interior, while Lunar Module Pilot Fred Haise was inside the docking tunnel, returning from the Lunar Module after closing down the ship. The Command Module Pilot, and a late replacement to the crew, Jack Swigert was sitting in the pilot's couch of the Command Module "Odyssey" when the call came from Houston for him to stir the cryogenic tanks. This was a fairly routine operation that would keep the liquid hydrogen and oxygen in the tanks mixed and their pressure up. They had already done this a number of times on this flight because a problem with one of the sensors in the number two oxygen tank meant that it was reading at a false level, above 100% full, and this time due to a master caution alarm, Mission Control wanted the stir to bring the pressure back up in one of the hydrogen tanks. Seconds later Missions Control would hear words that would bring a chill to their spines.

"Okay, Houston, we've had a problem here."

Hoax Claims: NASA achieved six perfect landings with nearly untested equipment. Nothing went wrong with any of the missions yet each craft was listed as having over 200 faults with it. This is impossible.

History Claims: None of the missions went without some sort of hitch. While Apollo 13 was the most dramatic of them, most of the missions suffered from something that, while it was unlikely to have endangered the crew, could have certainly prevented the landing for that mission had it not been for quick thinking and a number of inventive work-a-rounds.

A Troubled Start

In this section we are going to mostly focus on the Apollo 13 accident, but at the same time we will be briefly covering the accidents and incidents of all eleven missions, especially those incidents considered so serious that unresolved they would have endangered that mission's success.

Apollo 13's troubles seem to start a long time prior to the mission itself. Originally the crew was to have been Alan Shepard, Ed Mitchell and Stuart Roosa, but with concern about Shepard's ability to return to the space programme as quickly as Apollo 13, the decision was made to switch his crew to Apollo 14 and bring the crew of Apollo 14, James Lovell, Ken Mattingly, and Fred Haise, forward to Apollo 13. These problems continued when shortly before launch date it was discovered that the crew had been exposed to the German measles. Mattingly was the only one of the three who had never contracted the disease and after the trouble that occurred during Apollo 7, when all of the crew had developed head colds making them cranky and argumentative, along Russell "Rusty" Schweickart's space sickness, which nearly prevented the testing of the LM during Apollo 9, it was decided that there was no way that NASA could allow a crew member to become sick while in orbit about the moon, especially since he would have been alone in the CSM at the time. With this decision made, Mattingly was removed from the crew just three days before launch, his backup, Jack Swigert, replacing him.

After a period of hurried training to get Swigert up to speed and fitting seamlessly into the prime crew, things seemed like they might start going smoothly for a change, the weather being predicted to be good enough for the launch, though a stalled front over northern Florida did threaten to cause trouble if there were any delays. The previous launch, Apollo 12, had been done during a thunderstorm, ironically being the first flight to have its launch rules modified to allow such an action. As the rocket lifted off, it and the tower had been struck by twin bolts of lightning that knocked out the CSM's main power systems for several seconds. When it was restored, both the feed to Mission Control, and the information being displayed in the CSM itself was scrambled and incomplete meaning that there was no way to determine what, if any, damage had been done, and worse still, there was no way to actually fly the spacecraft without accurate information. Had it not been for the quick thinking of one of the ground crew, EECOM John Aaron, who analysed a correct problem and solution, Mission Commander Pete Conrad would have been forced to fire the escape tower rocket, aborting the entire mission. Instead Aaron determined that the problem was a malfunction in the launch vehicle's Signal Condition Equipment and was able to advise the crew to "try SCE to Aux," an act that would force the SCE to use its auxiliary power system and hopefully come back online, a rather obscure command that few in mission control even knew of. Al Bean, however, did recall the switch, because they had simulated a similar situation during training more than a year previously, and between Aaron's correct analysis of the situation and Bean's memory, the power and data feeds were restored correctly allowing the mission to continue.

On April 11th, 1970, at thirteen minutes past two in the afternoon, the Saturn V carrying the Apollo 13 mission, lifted off into cloudy, but calm skies. Things seemed to be going well, until late in the second stage burn. With two minutes of burn to go, the rocket began to experience dangerous pogo actions that threaten to tear the rocket apart, just as was to happen two years later with the fourth launch of the Soviet N-1 rocket. Unlike the N-1, the Saturn Rocket was able to detect the oscillations and as a result it shutdown the central rocket on the second stage, an action that stopped the pogo, though it meant that the other engines had to fire for longer to achieve that orbit required. Aboard the Command Module the wry comment, "Hopefully that will be this mission's glitch," was made.

Coasting to the Moon

Earth Orbit was made nearly exactly on profile, even with the second stage burn trouble. The crew stayed in Earth Orbit for just under two and a half hours, completing one and a half orbits before the Saturn IVB Booster was fired and they were on their way to the moon. Thirty minutes later the CSM undocked with the booster. Explosive bolts were fired to separate the SLA panels from between the CSM and the Booster, revealing the Lander inside. On Apollo 7 these panels simply folded outwards, like a flower opening, but one had stuck at a 25° angle, something that would have made it impossible to dock with a LM Target inside had they been meant to do so. The simple solution of removing the SLA panels from the booster after they had folded back prevented a repeat problem of a panel getting stuck and interfering with any docking on later missions.

Still even with the panels removed, it would take nerves of steel to manoeuvre the CSM about and close in onto the LM to dock the two craft together. It didn't always go perfectly either. With Apollo 10 the central stack rotated 3.5° leading to a fear later in the mission that when the LM separated in Lunar Orbit, it might shear off important clamps resulting in the inability to re-dock with the CSM. Ground control was able to allay these fears though when after checking with the manufacturer it was found that the stack could handle a 6° twist before problems occurred. The later mission also had their problems in this area. The next mission to fly, Apollo 14, was nearly aborted when it took six attempts to get the docking probe to engage. Without a lot of persistence and patience on the part of the crew, it is possible that they would have lost the LM and never been able to land. Apollo 17 found that even when the docking probe did engage, it still didn't mean that everything would work, and while running inspections, the crew discovered that one of the four locking clamps had failed to engage, a problem that could have compromised the tunnel causing both spacecraft to decompress. They were forced to engage the clamp manually.

With the LM docked to the CSM, the Saturn IVB Booster's engines fired for eighty seconds to move the rocket away from the Stack and later a further burn would place it on a collision course with the moon, the impact read by seismic experiments left behind by Apollo 11 and 12. Meanwhile the Apollo 13 CSM/LM continued coasting on its way to the Moon, the crew applying a rotation to the craft to once more face along their line of travel so they would be in position for a later burn. Thirty Hours into the mission, the SPS was fired to do a mid course correction, the event televised in their third transmission of the mission, the first two being a short test in Earth orbit and a seventy-two minute long transmission during the LM docking. Things continued to go well until forty-six hours into the mission. The crew did a routine stir on the oxygen tanks. During this stir, the readout on tank two spiked and set itself to an "off scale high" reading of over 100%. Despite a few attempts to reset this reading it refused to change and it was determined that the trouble was caused by a fault in the wire or the gauge itself. Either way the crew and mission control were reasonably unconcerned with the trouble. Further fears were allayed an hour later when the tanks were once more stirred without incident, and again four hours after that. Apart from the anomalous reading, all appeared to be working fine.

After a rest period, Haise and Lovell entered the LM and powered it up, checking the systems and readying it for the lunar mission. This was broadcast back to NASA on the TV, and once finished, while Fred Haise closed down the LM once more, Lovell made his way down into the CM storage compartment to stow the camera away. Swigert meanwhile was dealing with a caution alarm that was noting that the cryogenic hydrogen tank 1 was low on pressure. About thirty seconds after the alarm he received a message from Mission Control to stir all the tanks and turn on their heaters to get the pressures back up. Swigert responded and ninety seconds later all hell broke loose on the spacecraft. Mission Control lost all telemetry from the craft for nearly two seconds, and when it was restored, the numbers were all over the place. Seconds later they would hear the words that confirmed what the readouts were telling them.

"Okay, Houston, we've had a problem here."

Aboard the spacecraft the crew were trying to figure out what was going on. They had heard a loud bang and the spacecraft had shuddered quite badly. They had several alarms going off, the main one being a low DC main bus B voltage. This continued a few seconds, the level indicator on the number 2 oxygen tank fluctuating as well until it returned to above the 100% position. The next information seemed to take things from bad to worse. Lovell radioed through that they appeared to be venting something, and shortly after the levels in the number 1 oxygen tank started to fall rapidly, along with the power from fuel cell 1 and 3. Attempts to switch over systems to Tank 2 proved fruitless, and as the situation became increasingly desperate, the decision was made to shut down the remaining number 2 fuel cell and prepare the LM as a lifeboat.

A little over two hours after the accident the crew was inside the LM, the CSM had been shutdown with only the reserve oxygen in the surge tank, a system used to re-pressurize the cabin after dumping the atmosphere, and the only power available being from the batteries designed for re-entry left to keep it alive when needed. The crew was going to have to survive the trip in the LM, there would be no landing at Fra Mauro, there might not even been a way to get home. Getting into the LM itself hadn't been easy for the crew. Due to all the interdependent systems onboard there was a very specific procedure to bring up the LM's systems, and the very first step was a bigger problem right then. To activate the LM's systems they needed power, but that power come through an umbilical to Odyssey and with no power coming from the crippled CSM, the LM was dead was well. On the ground the LM Team frantically rewrote the manual, coming up with workarounds and new procedures almost on the fly. While the Descent Module batteries were isolated and unusable without power to the "on" switch, the Ascent Module's batteries weren't. In just thirty minutes, they had a sequence of switches and circuit breakers designed to get power from the Ascent Module's batteries to the LM systems so that they could begin the power up of Aquarius.

On the ground Mission Control was working out various options to get the crew home in one piece. It soon became apparent that whatever solution they used would not be involving the SPS. This powerful rocket would have been the best to use, but due to its unknown condition, and the huge power cost of powering up the CSM to use it, the idea was abandoned quickly. Later missions come to find that SPS trouble could be potentially disastrous as well. The first two J-missions both suffered problems. In Apollo 15's case the trouble started when its SPS's Bank A valves stuck open, telling the computer that the engine was firing when it wasn't. Not only was this disastrous to the navigation systems, but it lead to a real possibility of the SPS firing erroneously, meaning the ship could be sent into an incorrect and dangerous orbit wasting precious fuel and perhaps even requiring the use of the LM main engine to recover, a result that would have caused an abandonment of the mission. With a work around program, which ignored the open bank switch, sent up to the crew to enter into the computer, and the ability to open and close the valves manually tested, the mission was able to proceed without disaster.

Apollo 16 found they had trouble with their system as well. Shortly after the LM separation in Lunar Orbit, an oscillation problem with the secondary gyroscopes, required for determining the exact direction the SPS was pointing, was discovered. Without the system it was possible that not only would there be little chance of catching the LM if something went wrong with the Ascent stage, but that the CSM might not be able to even break lunar orbit at all, leaving the crew trapped there. So it was that both the LM and CSM stayed close together while the problem was deal with and Ken Mattingly got the gyroscopes to read correctly, only once he'd showed that this was done the "Go To Land" being given to Duke and Young rather than aborting the mission and returning to Earth.

With the only choice left being to use the LM descent engine to return the Stack onto a free return trajectory and then to speed them up for the return home trip, Mission Control needed to make sure that there would indeed be enough thrust required to achieve it, and that, with the mass of the CSM attached to the top of the LM, the force of the engine wasn't going to just crush the delicate lifeboat. What was known was that it was indeed possible for the LM to act as the propulsion main engine. In fact this had even been tested on the very first manned LM trial back on Apollo 9. The main trouble was that the LM's navigation computer was made for landing on the moon, not travelling between Earth and Moon, and so could not be used to control the burns. The first, a short burst of thirty-four seconds to return the craft to a free return trajectory, was to be done before reaching the moon. For the second, however, the crew were going to have to fire the Descent Engine for far longer, over two hundred and sixty seconds, and this was to be after the twenty-five minutes the crew were on the far side of moon and out of radio contact with NASA. If anything else failed during that time, the crew wouldn't be able to call for help. Even once they were around the moon, they would have to fire the descent engine without a navigational system. While timing the burn with the mission clock they would have to fly the ship manually, just using visual markers to keep them on course, in this case attempting to keep a small part of the sun in the centre of the top window. It was a difficult option, but it was their only one, and there was plenty that could have gone wrong.

During Apollo 9 the LMDE had developed a marked stutter when it was at 20% power. During a landing this could have been quite a problem, but it had been fixed by the time Apollo 10's LM, Snoopy, flew. Apollo 14 was to suffer from an abort problem when what is believed to have been a ball of solder lodged in the abort switch forcing it on. By tapping on the panel the crew were able to loosen it, but they still had to wait on a solution, as if the switch activated while they were landing, it would have fired the ascent engine and aborted their landing. A program to ignore the abort switch during certain events was devised and added manually. After that their landing became even more complicated when the landing radar switched to an incorrect band, a situation that would have resulted in forcing them to attempt an abort, faulty switch and all, had cycling the switches through manually not restored it. Even Apollo 11 had problems with flying their LM. Because of the tunnel still being slightly pressurised, the LM was given an extra push that resulted in them coming in a little long, right into a field of boulders. Neil Armstrong had to take control and fly the LM to locate a safe place to land. During this time a number of 1201 and 1202 alarms sounded indicating that the computer was overloaded and was dropping information. It turned out that radar tracking to the CSM was still on and this overburdened the computer. Armstrong landed the craft with just forty-five seconds of fuel left for the descent engine.

Hoax Claims: NASA claims that the Apollo 13 craft got cold in space, but since it was in direct sunlight it should have heated up.

Science Claims: The ways to heat and cool the Apollo spacecraft were mostly passive. That is they worked without intervention, and in most cases of the cooling, power. The main form of thermal control was by isolating the outer layers with the inner layers preventing the transfer of heat through the skin of the craft. Reflective materials added to this by reflecting much of the IR light from the ship and helping to keep its skin temperature down. Heat inside the ship was provided for the most part by the electronics systems, and a series of radiators were used to draw excess heat from these and radiate it into space, keeping the cabin from overheating. When Apollo 13 had its accident, to conserve power the crew was running only the minimal amount of electronics, hardly enough to heat the cabin. When they blocked out the sunlight so they could sleep, this was enough to overbalance the thermal control to the advantage of the radiators that were drawing heat from the interior if the LM and CSM. Without an additional heat source, the cabins could do nothing but cool down and freeze.

It's Cold in Space

Twenty-four minutes and thirty-five seconds after Loss of Signal, Mission Control got the message they had been longed to hear. The crew were still safe and now the Apollo 13, having been slingshot about the Moon, was on its way home. Two hours later the long burn went as planned, with only a slight deviation required later. Still even with that news, things still weren't going to be easy. Carbon Dioxide was building up in the cabin of the LM because of there being three people inside instead of two. Add to this was the fact that the only spare Lithium Hydroxide canisters belonged to the CM and, having a different manufacturer, were a different shape to what the LM required. Technicians on the ground managed to solve this problem, having the crew construct a makeshift system that attached onto the LM's air intake. Using parts of the spacesuits, the bags that held their Liquid Cooled Garments and a lot of tape, they connected hoses to the CM LiOH canister, forcing the LM system to draw air in through the filter and in doing so, scrub the dangerous levels of CO₂.

Further troubles occurred when the crew blocked out the sunlight to allow themselves some darkness to sleep. With the electronics shutdown to conserve consumables in the LM, and no sunlight let in to help heat the craft, the passive heat exchangers carried on doing their job, radiating the heat out into space. The effect was to dramatically cool the LM, causing Haise to develop a cold and worse, a lack of drinking water, due to the loss of the CM fuel cells and depleting LM supplies, added to his woes with him also developing a bladder infection.

As the Apollo craft approached Earth, the crew were going to have to power up the CM again and prepare it for the re-entry. Along with a large team of experts, Ken Mattingly had been called back in to help, and they spent much of the time during the mission dealing with a way to power up the CSM with their limited supplies of battery power. In the end it was determined that the crew were going to need to use the LM batteries to recharge the CM batteries and that they could reverse a system that would usually be used to supply power to the LM from the CSM fuel cells. This still left two serious worries. It was unknown how damaged the craft was, and if the heat shield had been affected. Should it have been damaged, the heat of re-entry would have destroyed the capsule. Even if they survived that, there were still two unknown factors, would there be enough power to fire the chutes, and would they actually open. Either scenario would have the potential to have killed the crew if at least two of the chutes failed. If only one failed then the craft would land safely, and in fact later on the return of Apollo 15, this did occur when one chute collapsed and refused to open. Since the system was designed to operate with just two, the third being a backup, Apollo 15 landed safely, but for Apollo 13 this was still a major unknown.

Being required to stay attached to the LM for keeping their batteries charged from its power, the crew detached from the SM and for the first time could see the severe damage done to it by the explosion. One side of the module was entirely blown out, the high gain antenna damaged, and the fuel cells broken. All sorts of debris hung from what was a gaping hole in the side of the craft. The biggest fear now was that the heat shield had been damaged, and with the hole in the side of the SM extending all the way to the top where the CM's heat shield was, this was a decided possibility. However with little they could do even if it was, the crew prepared for LM jettison and CM re-entry. Keeping pressure in the tunnel, to push the two craft apart, they released Odyssey seventy minutes before re-entry with the words, "Farewell Aquarius, and we thank you."

One hundred and forty two hours, forty minutes past the launch, Odyssey re-entered Earth's atmosphere and went into blackout. No one but the crew would know her fate for eight long minutes until S-Band was re-established, a moment that was greeted with cheers and tears. Odyssey landed just one mile from its touchdown point with a better landing than that of Apollo 12's, which had been a 15g landing into rough seas, an event that caused the Data Acquisition Camera the LMP had forgotten to stow, to come lose and hit Alan Bean in the head, knocking him out temporarily. Within forty-five minutes, the crew of Apollo 13 had been rescued and were aboard the U.S.S Iwo Jima. It was only after their return to Ellington AF Base that they became aware of the media interest in their flight. For a mission that had received so little attention that its main broadcast had been dropped from live television, once the accident had occurred, the media couldn't get enough of the story.

In the words of Richard Nixon, Apollo 13 was a "Successful Failure." Mission Control Director Gene Kranz termed it as "Our Finest Hour." Either way it was to signal the end for the Apollo Missions. With a number of senators already looking for an excuse to redistribute the money that Apollo was taking up, the accident, accompanied with the falling interest of the American people in the project, meant that there was little opposition to the cancellation of the programme. Four more Apollo missions would fly, but that was it. No politician wanted dead astronauts to be part of his re-election portfolio and so with the President pushing for a new Space Shuttle programme, Apollo was ended.

The Accident

Like many of Apollo 13's troubles, the cause of the main accident started long before the actual event. There was no one cause to this accident, there generally isn't to any accident, but rather a chain of events that all meet at the wrong time to produce the explosion. The oxygen tank had been dropped which resulted in minor damage to the filler tube. This wasn't serious, but it did mean that when tested it couldn't be detanked properly, some liquid oxygen remaining in the bottom. It was decided to remove this by leaving the heater on overnight, thus heating and driving the LOX away. This would likely not have caused any problems, except the thermostat switches that would have to turn off the heater had not been changed with a redesign of the tank electrical system. This meant that they were not designed to handle the 65V that was being used during the tank pressurisation and testing, but rather the older specifications of just 28V, which was used in the Block II CSM. Because of the voltage being over twice the thermostats specification, they sparked when they attempted to open to turn off the heater during the detanking, resulting in the switches actually welding themselves together in the on position instead. Unable to turn off, the heaters caused the interior of the tank to heat up to around 540°C in some parts, enough to severely damage the Teflon insulation coating on the stirrer fan wires. With damaged insulation it was possible for the wires to short out, which they did fifty-six hours into the mission causing the insulation to ignite and the tank to rupture damaging the other oxygen tank, the fuel cells and various other parts of the craft. In a ironic phase of luck, had the damaged sensors not shorted out, then Mission Control would not have ordered the stirring of the tanks as often and the fatal stirring would likely have occurred while Lovell and Haise were on the Lunar Surface. Without the power of the LM's Descent Engine, there is no way that Apollo 13 could have broken from Lunar Orbit, and even had they been able too, the LM's limited Ascent Module resources could not have supported them long enough to get them home. This first problem probably saved the crew's lives.

As can be seen, most missions had something go wrong, from the seriousness of Apollo 13's ruptured tank and Apollo 14's LM abort and radar problems, to the more mundane complications of Apollo 15's LRV losing its front wheel steering and power and all three LRVs having their rear fenders broken off. Even John Young's breaking of the Apollo 16 Heat Flow experiment wasn't a major event, but it certainly was an event that made their mission less than perfect. Of all the missions, Apollo 8 (with the Commander getting sick) and Apollo 17 (a problem with Nitrogen mixing in the Oxygen Tanks, and a docking clamp not locking) were the ones with the least incidents. The simple thing that History shows us though is that those that claim the missions occurred perfectly are totally wrong. Not one of the eleven manned missions went perfectly, but rather through the skill and teamwork, a huge amount of training and simulation coupled with the ability to think and act on that training and even a little bit of good luck, the crews in the craft and people on the ground managed to beat the odds and pull through regardless of what happened to try and stop them. It was against these adversities and challenges that NASA indeed had their finest hour.