Apollo 13 Houston, we’ve had a problem On the 40th anniversary of the explosion on board the Apollo 13 spacecraft as it headed to the moon, Richard Corfield reports on the cause and how teamwork returned the three astronauts to Earth safely Three, two, one, lift off! On 11 April Fra Mauro 1970, Apollo 13 blasted off from In short highlands, a Nasa’s base in Cape Kennedy, 40 years ago Apollo 13, hilly region Florida, US, and headed to the carrying Jim Lovell, Fred near the Mare moon. The mission: to learn more Haise and Jack Swigert, Imbrium – the about the science of Earth’s moon. headed to the moon to second largest But it never made it that far. Within discover more about crater on the three days of leaving Earth – and lunar science moon. ‘The Fra about 200 000 miles from home Three days into the Maura formation was – the three men on board were mission there was an believed to have been fighting for their lives. explosion on board, exposed by the large impact Fantastic teamwork brought the caused by an electrical that created the Imbrium rocket’s astronauts – Jim Lovell, problem basin,’ says Apollo geologist Fred Haise and Jack Swigert – back Strong teamwork Farouk El-Baz. This basin, thought down to Earth alive, and the flight meant Nasa could to have formed millions of years ago, of Apollo 13 has passed into the lore overcome numerous with its hills and undulating valleys of space exploration as one of the hurdles, including power was a challenging place to land. But greatest challenges that Nasa ever shortage, to get their the chance of bringing back rocks faced. three astronauts home that would date the Imbrium impact unharmed was too tempting to resist, according Scientific quest to El-Baz. The Apollo 11 and 12 missions had But it wasn’t to be. On the morning already shown that it was possible of 13 April 1970, Swigert performed to land on the moon, and Apollo 13 a routine stir of the tanks of liquid had a different assignment. ‘The oxygen and hydrogen (contained in first two flights to the moon were the spacecraft’s service module) that basically to prove that we could supplied the command (re-entry) put a man on the moon and get module’s electricity-producing him back safely,’ explains Apollo fuel cells. Immediately there was a 13 commander Lovell. ‘But after bang, and a tremor ran through the that, the whole purpose of the lunar spacecraft. For a second there was a flights was for science – to learn stunned silence on board and then more about the moon itself.’ Swigert spoke the words that have NASA Apollo 13 was heading for the gone down in history. ‘Hey, Houston. 58 | Chemistry World | March 2010 www.chemistryworld.org We’ve had a problem here.’ ‘The severity the command and service modules Initially, Jack Lousma – the orbited the moon). capsule communicator Swigert was of our situation talking to at Nasa’s mission control dawned on us Relocating in a hurry in Houston, Texas – was at a loss. The team needed to quickly move ‘Say again please,’ he requested. when I saw the orientation data from the This time it was Lovell who replied, oxygen was navigation system of the command ‘Houston, we’ve had a problem. module into the lunar module. Lovell We’ve had a main B bus undervolt.’ escaping from says, ‘that was really the critical One of the oxygen tanks had both the tanks’ part, because we were not able to exploded. do any of our own [navigational] John Aaron, a flight controller alignments in the lunar module due based at mission control at the to the millions of pieces of mylar time of the incident, explains the which were travelling with us due to seriousness of the situation: ‘the the explosion.’ The mylar insulating shock and damage of the explosion material was reflective, and was caused the fuel supply of oxygen moving along in tandem with the and hydrogen to the fuel cells to be spacecraft preventing the crew cut-off and thus no power could be from identifying the stars that they generated, causing the voltage on routinely used as navigational aids. main bus B [one of the spacecraft’s So in the 15 minutes or so before two electricity supplies] to drop the command module lost power, below proper operating range.’ the three astronauts transferred ‘The spacecraft was designed to the information, copying figures by safely operate on one bus, however hand and doing the mathematical some system redundancy would be corrections in their heads while staff compromised in such a condition,’ at Houston checked them using slide he adds. rules. Lovell continues: ‘we were Then movement caught Lovell’s able to transfer the guidance system eye. ‘The severity of our situation and then to do the programming dawned on us when I looked out using the lunar module system.’ the window and saw our oxygen But there was another problem escaping not only from the tank brewing. In Houston, Aaron realised that had exploded but also from the that the power situation on the second [and last] tank,’ he says. spacecraft would soon become By this time mission control was critical. ‘My first thoughts upon registering what flight director entering mission control that night Gene Kranz described as a cascading was one of influencing the team to failure onboard Apollo 13. One quickly terminate trouble shooting failure was propagating into many of the “failure” and instead power failures, and such an event was down the command module in order considered so unlikely that the to save precious emergency battery simulator specialists had never tried power to support re-entry back at to simulate it, he explains. Earth,’ he says. This module would With the oxygen tanks venting have to be powered back up again, to into space, Houston gave the be used by the astronauts to re-enter order for the crew to leave the the Earth’s atmosphere – as it was command module and move into the only section of the spacecraft the lunar module (the section of the Apollo 13’s service with parachutes and the heat shield spacecraft intended to make the module was badly needed to survive the extreme heat trip to the moon’s surface – while damaged by the explosion of re-entry. As the astronauts settled into the lunar module, the mission controllers on the ground were busy identifying yet another imminent problem – the carbon dioxide concentration in the lunar module was rising. Carbon dioxide was removed from the atmosphere of both the command and lunar modules using lithium hydroxide filters. In theory it should have been a simple matter to use the extra filters from the command module but there was one major problem; those in the command module were square while the ones in the lunar module were round. ’Looking back on it now it was an NASA www.chemistryworld.org Chemistry World | March 2010 | 59 Apollo 13 mission control radioed up the NASA welcome news that they were back in the re-entry corridor. It was almost time for the crew to start the command module’s power-up procedures for re-entry. On the ground Ken Mattingly – an astronaut who had pulled out of the Apollo 13 mission at the last minute due to health concerns – was streamlining the command module’s power-up procedures to save vital amps. Jack Clemons, an Apollo 13 systems engineer based at mission control says, ‘it was fortuitous that they had Mattingly. Here was a guy that had been intimately involved with all spacecraft’s systems and mission planning until just a few days before launch. He knew what the astronauts would be doing at every point in the flight and was able to effectively beta test the new and innovative procedures that were being made up before they were transmitted to the spacecraft.’ All over the US, Nasa contractors were equally busy. ‘The command module’s navigation systems had never been designed to be put into cold storage for several days in space and then switched on again,’ explains Chris Riley, author of the book Haynes Apollo 11 owner’s engineering goof obviously,’ says normal circumstances, controlled The DIY adapter meant workshop manual and co-producer Lovell. ‘We didn’t have enough the duration and intensity of the square cartridges fitted of In the shadow of the moon (a film lunar module canisters, and the engine firing. The burn would into the lunar module’s about the Apollo missions). ‘So the lunar module was only designed have to be done manually by the round CO2 filters guys at the Massachusetts Institute to support two people for two days astronauts. Fortuitously Lovell had of Technology who had designed not three people for four days,’ – the been a member of the Apollo 8 crew the inertial guidance system got a time it would take to get back to which had experimented with using refrigerated meat wagon and they Earth. But Kranz points out there the terminator – the line which stuck the powered-down flight was an engineering reason for divides night from day on the face spare in there for several days and the different shapes of the filters, of the Earth – as a fixed celestial then restarted it. It came back on ‘the lunar module was weight and reference point in the event of a without any problems and in doing volume critical, so a round scrubber computer failure and knew that it so gave an estimate for how long that fitted better into the available space.’ could be done successfully.