Moonshot: The Inside Story of Mankind's Greatest Adventure - Dan Parry (2009)

Chapter 10. PUSHED TO THE LIMIT

The final say on whether Apollo 11 would launch on schedule was down to the crew as much as anyone, and determined to make the deadline they pushed themselves through their training regime. For six months, Armstrong, Collins and Aldrin regularly spent 14 hours a day, six days a week, preparing to fly to the Moon.1 With evenings and weekends often devoted to studying, this was the most demanding period of their lives. While Michael got to grips with the computer and the rendezvous procedures, Neil and Buzz worked in the lunar module simulators, particularly Grumman's elaborate replica at the Cape. Like its command module counterpart, the cabin of the LM simulator mirrored the real thing. Hooked up to external computers, the instruments indicated apparent changes in the flight-path as the crew perfected engine burns and other manoeuvres. Initially the practice flights were straightforward and free of problems – 'nominal' in NASA-speak. But like Michael, as their skills developed, Neil and Buzz began to be tested by their instructors.

Shortly after the mission rules were issued on 16 May, the flight controllers were due to begin their own training for the descent to the surface. In a spacecraft, as in an aeroplane, the commander has the final say and the controllers knew that in certain situations Neil might overrule them. To discuss this possibility, Gene Kranz held a meeting with the crew.2 They were joined by Charlie Duke, an astronaut who had been selected in 1966. Duke, who had yet to fly in space, had served as a CapCom on Apollo 10, doing the job with such a degree of reliability and easy confidence that Armstrong requested he serve as CapCom for the descent. An air force pilot from North Carolina, Duke successfully supported both the flight controllers and the astronauts. To the controllers he represented the accessible side of an overstretched and rapidly tiring crew, who spent much of their time at the Cape. At the same time, he defended the crew's opinions among a tight team of people who had little personal experience of the demands facing the astronauts. Sometimes occupying a precarious position, Duke did a smooth job in extending understanding on both sides.3

In his meeting with the crew, Kranz said that if difficulties developed early in the descent Houston would halt the mission and start the rendezvous procedure. Such problems were potentially easier to deal with than emergencies that might occur during the middle of the flight. If the mission needed to be aborted, the descent stage could be jettisoned and an attempt made to return to orbit. But the lunar module had been tested in just two manned missions and both had ditched the descent stage under calm conditions at high altitude. Armstrong considered aborts to be 'not very well understood'. The theory called for the descent engine to be closed, pyrotechnic bolts to be ignited, the descent stage to be jettisoned and the ascent engine to be fired. 'Doing all of that in close proximity to the lunar surface was not something in which I had a great deal of confidence,' he later said.4 For Kranz, a late abort was like a parachute – only to be used as a last resort after all other options had been tried.5 Both he and Armstrong believed that if a problem should strike just as the LM was about to land, actually settling down on the surface would be better than attempting a last-minute abort. At least this would provide a full set of technical data that could improve the chances of the next mission.

In the last few hundred feet of the descent, only the crew would know whether it was safe to land. But just how far would they push their luck? Kranz knew that on this issue Armstrong had his own thoughts, 'I just wanted to know what they were'.6 Neil kept his opinions to himself, and since he was less than forthcoming, Kranz was left to guess what he might do if it were possible but risky to reach the surface. He suspected Armstrong would press on, 'accepting any risk as long as there was even a remote chance to land'.7 Neil later admitted that he would have been willing to use what he called his 'commander's prerogative' to disregard a mission rule, if he felt that was 'the safest route'.8 He said that while he would not have continued if there were only a 'remote chance' of landing, he would have pushed on if there were a 'good chance' of settling down safely.9 Unsure what Armstrong might do in the event of difficulty, Kranz decided he would let the descent continue as long as there was a chance of success.

Such gaps in communication were to be addressed during a formal series of joint simulations involving Neil, Buzz and the flight controllers. These sessions, focusing on the landing, could not begin until late May because of delays in developing software for the LM simulators.10 Since the final phase of the descent would last just 12 minutes, a number of training 'runs' could be carried out in a single day, under the supervision of the Mission Control Center's Simulation Branch. A handful of simulation supervisors (shortened to 'Sim Supe') took responsibility for various phases of the mission, and between them they trained the prime and backup crews for Apollo 11, as well as four teams of flight controllers. To accommodate everyone, the simulators were run 16 hours a day. With the computers stretched to the limit they frequently broke down – leading to varying degrees of abuse being directed at the technicians.

The Sim Supe for the descent phase was Dick Koos, who – according to Kranz – 'was a thin guy, wore wire-rimmed glasses, expressed himself in incomplete sentences, and seemed unsure of what he was trying to say'.11 Beyond his understated demeanour lay a talent for dragging astronauts and flight controllers through sweat-drenched training sessions that Kranz said took him and his team to a 'place beyond exhaustion'.12 Frank Borman later remembered that while his crew were preparing for Apollo 8, 'we were killed more times in simulation than you can shake a stick at'.13 Armstrong believed 'these were the most extensive simulations I had ever encountered'.14

The first few formal sessions were designed primarily to develop everyone's understanding of the landing sequence. At the same time, they also identified points of no-return. At these moments, each controller was required to give a curt 'go' or 'no go' depending on whether he felt confident in letting the mission continue. These early exercises also helped prepare everyone for the fact that the distance between the Moon and the Earth would delay communications. Travelling at the speed of light, radio messages from the Moon take 1.5 seconds to reach Earth, adding at least a three-second delay to any response urgently required from the ground.

As the training progressed, the procedures improved, and new mission rules were agreed before the next round of simulations began. Focusing on aborts, these threatened to take everyone on a steep learning curve. In each simulation, Armstrong and Aldrin worked closely with the controllers on the latest challenge Koos had thrown at everyone. Nobody beyond Koos and his team knew what the next problem would be. In some cases the crew would act quickly without advice from the ground, at other times they urgently needed support. Working in this way the two flight teams became familiar with each other, and all the while Koos continually tried to expose the fault lines between them. Sometimes Collins would be involved, for example when the LM crew and the ground controllers practised the rendezvous procedure. Everybody knew what was at stake. The simulations consequently became as realistic and as demanding as possible, with Koos raising the tension in every successive session. Trajectory problems, electrical failures, emergency launches, master alarms and data dropouts – anything was possible. 'Nothing is sacred; no quarter is given and none asked,' Kranz later wrote.15

After each round of simulations, Neil and Buzz spent time on their own, refining their procedures and leaving the flight controllers to do the same. The mission rules would then be updated, and the next series of exercises would begin. Once again Koos would scatter catastrophes about, daring the crew and controllers to take on his mischievous team of instructors. After particularly difficult sessions, the flight controllers would conduct a soul-searching inquisition into what had gone wrong. Especially challenging was the 'dead-man's box', the region between the surface and a few hundred feet above. At this height, the complex relationship between speed, altitude and time made a safe abort impossible.16 This wasn't lost on Armstrong. With Kranz and his team sitting on a planet far removed from them, Neil knew the final decisions would be down to him. Chris Kraft, the director of flight operations who saw his flight directors as 'God', wondered whether Armstrong would be prepared to accept a higher degree of risk than he was ready to allow.17

In mid-June, Kraft brought Neil into Mission Control to go over the rules that had been agreed so far. As far as Kraft was concerned, Houston was running the show and an independent decision by the crew 'wasn't something we encouraged'.18 Yet Armstrong made no secret of the fact that he would be the man on the spot. Neil, who was first and foremost a test pilot, knew that instruments could sometimes give faulty readings, needlessly causing concern. Unless the spacecraft was actually out of control, what was there to worry about? But inaccurate telemetry sent from space could prompt a controller to mistakenly order a safe flight to be aborted. Neil's opinion on the issue 'led to some heated discussions', Kraft wrote. '"I'm going to be in a better position to know what's happening than the people back in Houston," he said over and over,' Kraft later remembered. 'And I'm not going to tolerate any unnecessary risks,' Kraft retorted, 'that's why we have mission rules.' In the final weeks before the launch, Kraft suspected Armstrong still privately harboured doubts about some of the rules. 'I wondered then if he'd overrule all of us in lunar orbit,' he said.19

In addition to his work in the LM simulator, Neil spent a further 34 hours practising descent trajectories, both at the research facility at Langley and in the Lunar Landing Training Vehicle.20 He continued to believe that the LLTV provided the best training despite his accident in May 1968, which prompted modifications to the machine's control system. But after Houston's chief test pilot Joe Algranti was forced to eject from the improved version in December, Chris Kraft and MSC director Bob Gilruth were ready to bar anyone else from flying it.21 Once again the astronauts fought back, Armstrong as keen as anyone to fly it. As the next commander to go into space, and the first to attempt a lunar landing, his opinion could not be overlooked. After further modifications, by June 1969 a new LLTV was ready, and Neil was among the first to fly it.22

Kraft asked him to justify his use of such a hazardous vehicle.

'It's absolutely essential,' Armstrong told him, 'by far the best training for landing on the Moon.'

'It's dangerous, damn it,' snapped Kraft.

'Yes, it is,' Neil replied. 'I know you're worried, but I have to support it. It's just darned good training.'

Kraft received the same response from other astronauts, so 'with our fingers crossed, we let them keep it', but a compromise was reached in that only the commanders of lunar missions were to fly it.23 Neil flew the machine a total of 27 times, more than any other astronaut.24 Buzz never got the chance.

After the flight readiness review of 17 June, Neil, Buzz and Michael transferred to the Cape where they could work at maximum capacity with minimum interference. Having been cleared for launch, Collins moved to Florida 'with my bottle of gin and my bottle of vermouth, and a heavy load removed from either shoulder'.25 Hidden away on the fourth floor of the Manned Spacecraft Operations Building, the crew were given small, windowless bedrooms that were joined to a shared living room, exercise room, sauna, dining room, kitchen and briefing room. After a hurried breakfast, each morning they would go to the simulators awaiting them in a nearby building and work until lunchtime, when they would attend to piles of sandwiches and phone messages. In returning his calls Michael found that many of the conversations followed a similar theme: '"Oh really, Mrs —, you haven't received an invitation to the launch? Why, I can't understand that, anyone as dedicated to the space program as you have been!" Who the hell is in charge of this anyway,' he would ask himself, 'and why is this broad calling me?'26 His brief lunch over, Collins would climb back into the couch for the next rendezvous workout, knowing that no matter how rickety the simulator computers were, Neil and Buzz probably had it worse.

Difficulties with the LM simulator, and its connections to Houston, began to put Armstrong and Aldrin behind in their tight training schedule. 'The amount of work seemed endless,' Buzz later wrote, 'and, at times, practically insurmountable.'27 There was more talk of delaying the launch to August but neither man openly supported the idea. Yet nor did they seem eager to commit to July. Collins wondered whether they needed time simply to complete minor things or whether they were genuinely unprepared. With several mandatory simulations yet to be completed, it was hard to escape a growing sense of pressure as they tried to get everything done. When the hardware was working satisfactorily, Armstrong tried to wring as much as he could from each training session. He had been involved in the design of simulators since his days at Edwards, and knew that by actively encouraging problems there were useful lessons to be learned.28 Neil wanted to use the LM simulator to do something more than just 'win', as others did. 'They tried to operate perfectly all the time and avoid simulator problems,' he said. 'I did the opposite.'29 Armstrong knew that the occasional 'crash' would reveal useful information about difficult parts of the trajectory. For Buzz, however, a crash wasn't the kind of thing he felt they should be striving to achieve. Aldrin believed they should be mastering not the simulator but the mission.30

Collins recalled that, late one night, Buzz angrily told him they had been replicating a landing when a thruster had stuck open and they had been ordered to abort. Neil did not react immediately, and by the time he tried to take action the computer showed that the LM had already fatally crashed. Michael remembered that Buzz was incensed and, accompanied by a bottle of Scotch, 'kept me up far past my bedtime complaining about it'. Suddenly Neil emerged from his bedroom and entered the debate, at which point Michael crept off to bed, grateful for the fact that in the command module it was just him and the computer, 'and if that son-of-a-bitch mouthed off, I would turn off its power supply'.31 Buzz found that what he referred to as Armstrong's 'communication reticence' was compounded by his own inability to penetrate it.32At breakfast the following morning, Michael noticed that neither of his crew-mates appeared ruffled after what he assumed to have been a 'frank and beneficial discussion, as they say in the State Department'.33

Occasionally the three of them would train as a team on the elements of the mission they would perform together, such as the launch. By the end of the training schedule, Neil had accumulated 383 hours in the LM simulator, and a further 164 hours in the command module. Aldrin's figures were even higher, at 411 and 182 respectively. As was to be expected, Collins focused almost exclusively on the command module, spending three times as long as Armstrong in studying as many aspects of the spacecraft as he could.34

The final simulation, late on the afternoon of Saturday 5 July, was expected to be a simple confidence-boost for the controllers. Armstrong and Aldrin did not take part and the Mission Control team trained instead with the Apollo 12 backup crew, Dave Scott and Jim Irwin. According to Kranz, things were going smoothly when three minutes into the landing Dick Koos triggered a series of computer alarms that had never been seen before. Steve Bales, the 26-year-old guidance officer, suddenly discovered the LM's computer was reporting a 1201 alarm code. A glossary of the LM software showed that 1201 meant 'executive overflow, no vacant areas' – and Bales realised the computer was overloaded. He had no mission rules on how to react to a 1201 alarm, and as more warnings appeared he called his software expert Jack Garman, who was in one of the backroom offices. Both knew the computer was unable to complete some of its tasks, but Bales couldn't tell which of them were being neglected and he urgently advised Kranz to abandon the landing. Kranz quickly agreed. 'If there was one word guaranteed to get your attention in Mission Control,' he wrote, 'it is the word abort.'35

Kranz believed he had given the correct order, but Koos knew otherwise. Whatever the computer's difficulties were, everything else had been working properly. 'This was not an abort. You should have continued the landing,' he told Kranz's team during a subsequent debriefing. Bales was devastated: on the last simulation before launch he had needlessly halted the mission. At first Kranz was angry that they had ended on a failure but he knew the lesson had been necessary.36 That night Bales investigated the problem, and the following morning he worked with various alarm codes in hastily arranged simulations. He added a new entry to the mission rules book, listing a dozen alarms that could prompt an abort. They did not include 1201. The changes were included in the final edition of the book, which was published just five days before the launch. While the crew were familiar with its key points, no-one could be expected to memorise the whole book, and since they were not required to commit the many alarm codes to memory they were not told about the new rule.37

With the training schedule now largely complete, Chris Kraft asked Neil, 'Is there anything we've missed?'

'No, Chris,' Armstrong replied, 'we're ready. It's all done except the countdown.'38

Lingering in the back of Kraft's mind, he later wrote, were memories of the conversation about who would have the final say, the astronauts or Mission Control. But by then he knew there was nothing left to be said. 'We had come at last to this point,' he recalled, 'and for a moment I felt my legs shake.'39

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Armstrong: 'Burning; we're looking good.'

Collins: 'Pitch trim is up at 1.5 degrees, cycling about that, which is a little bit off the simulation value. Yaw trim is cycling about zero. Chamber pressure is 95.'

The lunar orbit insertion (LOI) burn began precisely on time. With the service module's engine silently ejecting a bright streak of flame, the spacecraft began to slow and the crew found themselves pushed against their seats as a reassuring sense of gravity briefly replaced weightlessness. When the pressure in the combustion chamber began to rise above its predicted level of 95lb per square inch, the crew realised that the engine was working harder than expected. This meant it would operate for less than the predicted time of six minutes and two seconds, and would be shut down early by the computer. While keeping an eye on the chamber pressure, Collins was also watching the two flight director attitude indicators. Each featured a ball display that allowed the crew to monitor the vehicle's attitude in space.

Collins: 'OK, she's steering like a champ; chamber pressure sneaking up to 100.'

Armstrong: 'We're now predicting 5 seconds early, 05:57.'

Collins: 'Ball number 1 and ball number 2 both right on value. Roll zero, pitch 225, roughly, and yaw 348; and hold.'

Armstrong: '10 seconds.'

Collins: 'OK, 9, 8, 7, 6, 5, 4, 3—'

Armstrong: 'Shutdown.'

The engine cut their speed from 5,600mph to 3,700mph, allowing them to be captured by the Moon's gravity.40 They had now entered an elliptical orbit, taking them around the Moon on a great oval-shaped path that at its highest point carried them nearly 170 miles above the surface and at its lowest brought them down to 60. During the burn, the computer monitored how far they had drifted in the roll, pitch and yaw axes. They could have easily wandered off course. But the computer had successfully kept them on the straight and narrow, and they had strayed by only one tenth of a foot per second in each axis – something that impressed them all.

Collins: 'Minus 1, minus 1, plus 1. Jesus! I take back any bad things I ever said about MIT – which I never have.'

Armstrong: 'That was a beautiful burn.'

Collins: 'Well, I don't know if we're 60 miles or not, but at least we haven't hit that mother.'

Aldrin: 'Look at that! Look at that, 169.6 by 60.9.'

Collins: 'Beautiful, beautiful, beautiful, beautiful!'

Aldrin: 'What – what'd it say ... 60.2.'

Collins: 'You want to write that down or something? Write it down just for the hell of it, 170 by 60, like gangbusters.'

Aldrin: 'We only missed [the predicted highest orbital point] by a couple of tenths of a mile.'

Collins: 'Hello, Moon; how's the old back side?'

With the burn complete, they were free to look out of the windows at the alien landscape below. In the great void of space here was land – like home. Although baked by the Sun, the barren ground appeared coldly foreboding and anything less like home was hard to imagine. A 'withered, sun-seared peach pit' Michael called it. 'There is no comfort to it...its invitation is monotonous and meant for geologists only.'41Even its colour was hard to judge. Apollo 8 reported the surface to be black-grey-white, while Apollo 10 described it as black-brown-tan-white.42 Armstrong, Aldrin and Collins had been asked to settle the issue, and to them there appeared to be truth on both sides. The colours varied according to the angle of the Sun. Immediately either side of the region of shadow the ground appeared to be a shade of grey, but once lit by bright sunlight it was more tan, fading to brown and then grey as it shrank into the darkness once more.

Coasting around the remainder of the far side, Neil, Buzz and Michael were still out of radio contact, and for a moment it felt as if the grown-ups had left the building. Free to enjoy the view, the crew looked in amazement at the enormous craters passing beneath them. Their excitement led to unguarded comments that they knew would not be broadcast to the nation – but which were captured by a tape recorder.

Armstrong: 'What a spectacular view!'

Collins: 'God, look at that Moon! Fantastic. Look back there behind us, sure looks like a gigantic crater; look at the mountains going around it. My gosh, they're monsters.'

Armstrong: 'See that real big-'

Collins: 'Yes, there's a moose down here you just wouldn't believe. There's the biggest one yet. God, it's huge! It is enormous! It's so big I can't even get it in the window. You want to look at that? That's the biggest one you ever seen in your life. Neil? God, look at this central mountain peak.'

Armstrong: 'That's kind of a foggy window.'

Collins: 'That's a horrible window. It's too bad we have to shoot through this one, but – oh, boy, you could spend a lifetime just geologising that one crater alone, you know that?'

Armstrong: 'You could.'

Collins: 'That's not how I'd like to spend my lifetime, but – picture that. Beautiful!'

Aldrin: 'Yes, there's a big mother over here, too.'

Collins: 'Come on now, Buzz, don't refer to them as big mothers; give them some scientific name.'

Aldrin: 'It sure looks like a lot of them have slumped down.' [The tops of the craters had collapsed into the pit below.]

Collins: 'A slumping big mother. Well, you see those every once in a while.'

Aldrin: 'Most of them are slumping. The bigger they are, the more they slump – that's a truism, isn't it? That is, the older they get.'

Radio contact with Mission Control was imminent, and not wanting their initial public exchange with Houston to begin with a conversation about ageing mothers, slumped or otherwise, Armstrong changed the subject: 'Well, we're at 180 degrees, and now we're going to want to stop that and start a slow pitch-down.'

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The far side of the Moon had eluded man's curiosity until October 1959 when the first eye-opening pictures were sent home by a Russian probe. Astronomers were taken aback by the far side's heavily cratered landscapes, devoid of seas and strewn with what Collins later described as an 'uninterrupted jumble of tortured hills'.43 Anxious to demonstrate prowess in the emerging space-race, in December 1959 NASA commissioned its own series of probes, named Ranger. Rangers 1 and 2, however, never got beyond short-lived low-Earth orbits, and Ranger 3 missed in its attempt to reach the Moon. Ranger 4 suffered electrical failure, 5 also missed, and for good measure also suffered electrical failure, and 6 was disabled at launch; but Ranger 7 proved, five years later, that NASA could also snap pictures of the Moon. Deliberately plunging towards the lunar surface, before it was destroyed on impact Ranger 7 briefly transmitted TV images that were a thousand times sharper than anything that had been seen through a telescope.44 They revealed not the jagged mountains that appeared in the speculative paintings by Chesley Bonestell, but rolling hills and open spaces. Since boulders littered the ground, it appeared the surface was capable of supporting a spacecraft.

Following Kennedy's challenge to land on the Moon, NASA commissioned the Surveyor series of probes. Designed to carefully examine the nature of the surface, the information they would send home was urgently needed by Tom Kelly's team working on the lunar module. In May 1966, Surveyor 1 gently landed in the Ocean of Storms; equipped with a television camera, it sent back images of a flat area pockmarked by rocks and craters. Surveyor 2 was lost en route to the Moon, but in April 1967 the third Surveyor also successfully landed in the Ocean of Storms. Fitted with a mechanical arm, it managed to dig into the surface, unearthing details about the material below. Surveyor 4 was also lost, but the fifth probe reached the Sea of Tranquility where it investigated the chemical properties of the lunar dust, work that was later extended by Surveyor 6 in the Meridian Bay.

As well as discovering general details about the surface, NASA also needed to identify places that might serve as landing sites for manned missions. The ideal spot would be within easy reach of a spacecraft that was travelling on a free-return trajectory and had little fuel to spare. In practice, this meant finding an area within a narrow band stretching horizontally across much of the middle of the near side of the Moon. The site would have to be away from high hills and deep craters, which might send misleading altitude signals to the landing radar. It would have to be largely smooth and predominantly flat, and would have to receive a consistent level of sunlight in case the launch were delayed. A lunar day lasts two weeks, and during the Moon's lingering dawn the long shadows cast by the Sun made it easier to spot rocks and craters when looking from above. All of this meant that ideally the landing would be attempted just after local sunrise at a suitable site near the eastern half of the equator. This way, as the Sun moved further west, areas in the western region of the equator would become available once the shadows began to shorten at the first location.

Using telescopes, the Apollo Site Selection Board initially produced a list of 30 potential landing grounds. These were to be photographed from a height of 35 miles by the Lunar Orbiter missions, NASA's third series of probes. In August 1966 Lunar Orbiter 1 sent home medium-resolution pictures of nine of the targets. These included an area in the Sea of Tranquility, later labelled Apollo Landing Site 2 (ALS-2). Lunar Orbiter 2 later photographed a further 11 sites, and also sent back high-resolution images of some of the places inspected by its predecessor, among them ALS-2.45 Some of the pictures were given to the press, and a spectacular image of the crater Copernicus appeared on front pages around the world. Released from the flat pictures taken with telescopes, for the first time the Moon was exposed as a three-dimensional place where towering mountains overshadowed haunting valleys, and empty stretches of wilderness extended for miles in all directions. The photograph gave millions of people a chance to see for themselves what it might be like to study the surface from a pilot's perspective.

Landmarks on routes approaching the most promising landing sites were photographed by Lunar Orbiter 3, and pictures from all three Orbiter missions helped the selection board whittle down the options to five areas. In looking for a flat plain in the east near the equator, the Sea of Tranquility stood out as an obvious candidate, and here two sites were chosen, ALS-1 and ALS-2. The first was inspected by Apollo 8, and Apollo 10 flew over the second, both bringing back pictures that helped the crew of Apollo 11 prepare for their own mission.46 It was decided that Armstrong and Aldrin would attempt to land at ALS-2, in the south-western part of the Sea of Tranquility. If the flight were delayed, secondary sites further west were located in the Sinus Medii (almost in the centre of the visible face of the Moon) and in the Ocean of Storms.

Meanwhile, having taken the first pictures of the far side of the Moon, the Russians continued to develop their Luna series of probes. In many cases their unmanned spacecraft outperformed America's just as decisively as their manned missions beat NASA's in achieving key objectives. Luna 9 landed on the Moon in January 1966, four months ahead of Surveyor 1. Although cosmonauts were unlikely to reach the surface, some in NASA feared that a Russian probe might still try to retrieve the first samples of lunar rocks. Three days before the launch of Apollo 11, on Sunday 13 July 1969, the Soviet Union announced that Luna 15 had been launched on a mission to the Moon. Amid US fears that Armstrong's crew would have to contend with a chunk of Russian metalwork in their vicinity, there were suggestions that Luna 15 might scoop up some dust and bring it home while Neil and Buzz were still strapping on their boots.

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Thirty-four minutes after Mission Control lost contact with the crew, the powerful antenna in Madrid picked up their signal as the spacecraft came within sight of the Earth. It was Houston's first indication that the initial LOI burn had been successful. Many of the features on the desolate far side were unnamed, but now that Apollo 11 was coasting across the near side the crew were passing over more familiar ground. For months, Neil and Buzz had been studying photos of distinctive landmarks they would look out for during critical phases of the descent. Features of the Moon were identified, in Latin, according to rules set out by the International Astronomical Union in 1961. The plains, traditionally described as oceans and seas, were named after states of mind, such as the Sea of Tranquility and the Sea of Crisis. The highlands were named after mountain ranges on Earth, and craters recalled eminent scientists, while some of the smaller features were informally named by the two previous Apollo missions.47

Armstrong: 'Apollo 11 is getting its first view of the landing approach. This time we are going over the Taruntius crater, and the pictures and maps brought back by Apollo 8 and 10 have given us a very good preview of what to look at here. It looks very much like the pictures, but like the difference between watching a real football game and watching it on TV. There's no substitute for actually being here.'

Soaring 127 miles above the surface, the feature Neil particularly wanted to see was the landing ground. Eleven miles long and three wide, it was still officially identified as ALS-2, but the astronauts had come to refer to it using the baseball term 'home plate'. Half the Moon was bathed in sunshine, but for the moment the landing site lay just beyond the terminator, the line dividing sunlight and darkness. Dawn would not reveal it until the following day. Until then Armstrong would have to content himself with studying the approach route, including the hill Jim Lovell had named after his wife.

Aldrin: 'We're going over Mount Marilyn at the present time, and its ignition point.'

Mission Control: 'Roger. Thank you. And our preliminary tracking data for the first few minutes shows you in a 61.6 by 169.5 orbit. Over.'

Aldrin: 'Roger.'

Mission Control: 'And Jim is smiling.'

Armstrong: 'Currently going over Maskelyne. And Boot Hill, Duke Island, Sidewinder, looking at Maskelyne-W, that's the yaw round checkpoint. Just coming into the terminator.'

And with that, the crew flew back into the Moon's shadow, knowing that somewhere down in the darkness ALS-2 was awaiting them.

While coasting through dark skies, at around 1.50pm they tried to answer questions about the surface until Neil reminded Mission Control that they were tucking into lunch. He wanted to focus on the next major task on the flight-plan, the second lunar orbit insertion burn, but he knew Houston had other ideas.

Mission Control: 'We'd like to know if you're still planning to have the TV up with the beginning of the next pass. Over.'

Armstrong: 'Roger, Houston. We'll try to have it ready.'

Mission Control: 'This is Houston. We are inquiring if it is your plan to. Over.'

Armstrong: 'It never was our plan to; but it's in the flightplan, so I guess we'll do it.'

Mission Control: 'Houston. Roger. Out.'

While passing behind the far side for the second time, the astronauts set up what Neil once referred to as the 'camera claptrap'. There hadn't been time on the ground to practise using it. 'Neil and Buzz didn't even know how to turn it on or focus it,' Collins recalled, 'and my knowledge of it was pretty sketchy.' Having had a chance to play around with the equipment on the way to the Moon, they were now a little better prepared to start filming the surface. Nevertheless, Michael was mindful of advice he had been given, reminding him that there would be a billion people watching, 'so don't screw it up'.48

By the time they swung back into radio contact they were already broadcasting TV pictures. For the first time during the mission, the lunar surface – which for so long had been preoccupying so many minds – suddenly became clearly visible to those on the ground. Impressed by the quality of the images, Bruce McCandless told the crew that Houston was receiving a beautiful colour picture of the Moon's horizon, capped by the empty blackness of space.

Now 92 miles above the hills of Smyth's Sea, Neil, Buzz and Michael once again looked for the approach to the landing site. Collins had noticed that the LM (still docked with the command module) had a tendency to sink down towards the surface and he put this down to the effect of the mysterious mascons. While Buzz described the craters passing beneath them, Mike asked the flight controllers to watch the telemetry so that they could see the effect for themselves.

Travelling east to west, nearly 26 minutes after resuming contact with the ground the spacecraft passed over the triangular shape of Mount Marilyn for the second time. Apollo 11's elliptical orbit meant its altitude was changing all the time, and as they continued towards the landing site the crew were now around 150 miles above the surface.

Aldrin: 'The largest of the craters near the centre of the picture right now is Maskelyne-W. This is a position check during descent at about 3 minutes and 39 seconds, and it's our downrange position check and cross-range position check prior to yawing over face-up to acquire the landing radar. Past this point, we would be unable to see the surface below us until getting very near the landing area.'

Mission Control: 'Roger. I imagine you'll get a real good look at that tomorrow afternoon.'

Then once more the crew plunged back into darkness, the Sun setting in the east behind them.

Switching off the camera, they were now able to focus on LOI-2 – the second lunar orbit insertion burn. This was designed to exchange Apollo 11's elliptical path around the Moon for a more circular orbit. The previous two lunar missions had tried to reach as circular an orbit as possible, only to find that the mascons later pulled them out of position. Apollo 11's burn would take the orbital wobbles into account, allowing them to pull the spacecraft gradually back into a precise orbital path.

After McCandless read up the data they would use to get home if the 17-second burn did not go to plan, Collins completed a P52 exercise to check their position. They then lost contact with Houston at the start of their third orbit. Collins put the spacecraft in the correct attitude to be able to begin the burn, which once again would take place on the far side, beyond assistance from Houston. Again the engine had to fire precisely on time, at 80 hours, 11 minutes and 36 seconds into the mission. It could not be allowed to continue for a second longer than scheduled or else 'we'd be on an impact course with the other side of the Moon', as Buzz put it.49 Once Michael was ready, at 4.43pm he allowed the burn to begin. The engine started smoothly and the manoeuvre successfully put the spacecraft in a near circular orbit roughly 60 miles above the Moon. Now travelling at a little over 3,600mph, it would complete one circuit every two hours. Michael would stay on this track for the remainder of his time in lunar orbit, and would not fire the engine again until he was ready to begin the journey home.

After making radio contact, the crew let Mission Control know that LOI-2 had gone to plan. In the hours before they went to bed their final task of the day was to prepare for the landing, due to take place the following afternoon. Equipment needed to be transferred into the lunar module which meant that once again they had to open the hatch and remove the docking mechanism. As Buzz began carrying supplies into the LM, he noticed that the terminator had crept back a fraction and that for the first time the landing site was softly emerging from the darkness. He found himself looking down on what he considered to be a beautiful landscape, and he urged Neil and Michael to look for themselves. The area was still streaked by long shadows, and privately Michael thought he couldn't see anywhere smooth enough 'to park a baby buggy, never mind a lunar module'.50 Even Buzz admitted the whole region looked eerie.

Following a suggestion by Michael, they agreed to stow the docking mechanism in the cabin, rather than secure it back in position. 'I'd rather sleep with the probe and drogue than have to dick with it in the morning,' he said. Replacing the command module hatch, he began to prepare dinner. Meanwhile, Buzz quietly ran through the many procedures they would be following in the morning, leaving Neil to his own thoughts. Procedures could be followed from checklists but some things were left to Armstrong's personal preference, including the first words he would say on the surface.

En route to the Moon, Michael and Buzz had asked Neil what he might say.51 They were not alone in their curiosity. In late June, George Low, the Apollo programme manager, had asked Armstrong whether he had thought about his choice of words. Neil had replied, 'Sure, George, I've been thinking about it. Tell everybody thanks from all of us. We know how hard everybody's been working.'52

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In Mission Control, Flight Director Cliff Charlesworth (centre) sits to the right of Gene Kranz.

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Soon after arriving in orbit, the crew's faces filled with blood until their bodies adjusted to weightlessness.

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Buzz Aldrin in the lunar module, photographed by Neil Armstrong during the long journey to the moon.

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The lunar module, Eagle, after undocking from the command module. The long rods under the landing pads are lunar surface sensing probes.

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The television image that millions around the world were waiting for on July 20th 1969. Armstrong steps off the ladder on to the lunar surface.

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Aldrin prepares to step on to the lunar surface.

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Buzz Aldrin, in Armstrong's iconic picture of man on the Moon.

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Aldrin beside the US flag. The footprints of the astronauts are clearly visible in the soil of the Moon.

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One small step ... Buzz Aldrin's bootprint.

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Buzz Aldrin and, to his right, the Solar Wind Composition experiment.

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A relieved Armstrong back in the LM after the moonwalk.

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Buzz's position on the right-hand side of the lunar module cabin. In the window is a 16mm film camera.

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Lt. Clancy Hatleberg closes the spacecraft hatch while the crew await rescue. Leaving Columbia Aldrin said he was struck by a 'peculiar sense of loss'.

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Officials join the flight controllers in celebrating the return of Apollo 11. Third from left (foreground) is Chris Kraft, fourth is George Low and fifth is Bob Gilruth.

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President Nixon welcomes the astronauts aboard the USS Hornet. The crew are already confined to the Mobile Quarantine Facility, MQF).

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Inside the quarantine facility.

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New York City welcomes the three astronauts, in a shower of ticker tape.