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

Chapter 9. INTO THE DARKNESS

Piercing sunlight flared through each of the command module's five windows as the spacecraft slowly rolled on its axis at the start of the fourth day. The crew experienced a gentle sense of momentum as the sunshine meandered through the cabin, slowly drifting across the glass on the instrument gauges and bouncing off the transparent breakfast bags. Sunlight and the Earth were largely all the men had seen through the windows since day two. They had been able to identify specific stars when working on the P52 computer program but familiar constellations had been obliterated by sunshine. Today would be different. While they ate, a cold gloom shrouded the spacecraft, and the sun's rays receded before being snuffed out altogether. The crew had coasted so close to their destination that, silently and without warning, they passed into the shadow of the Moon and perpetual day was exchanged for night. 'I feel that all of us are aware that the honeymoon is over,' wrote Collins. 'We are about to lay our little pink bodies on the line.'1 In a few hours Michael would climb into the left-hand couch, and once they reached the far side of the Moon he would fly them into lunar orbit. He hadn't slept particularly well and feared that the pressure of the work ahead was threatening to overtake them.2

Blocking the Sun's glare, the hostile surface of the Moon loomed towards them, filling their windows with an alien landscape that stretched for hundreds of miles. Much of the surface lay hidden in shadow, the darkness merging with the black sky above. 'We are able to see stars again and recognise constellations for the first time,' Armstrong told Houston. Away from the filtering effects of Earth's atmosphere, the stars didn't twinkle but stood out as static pinpricks of light. Whereas previous manned missions had been confined to Earth orbit, Neil was commanding the first flight to a specific destination – and now, suddenly, here it was, a little more than 11,000 miles away. As Earth's oceans reflected sunshine back out into space, pools of cool blue light were cast upon the lunar surface, illuminating it as if it were an empty stage lit for a sinister night scene. Earthshine is three times brighter than moonshine, and to Michael it revealed the 'most awesome sphere I have ever seen'.3 When the crew switched off the interior lamps to photograph the stunning view outside they found the light was bright enough to read by.

By putting the Moon between themselves and the Sun, the men had arranged their own solar eclipse. Although the Sun itself lay hidden from view, its atmosphere of hot gases could be seen streaming away from the edges of the lunar surface. Beyond the swathes of shadow, the Moon's entire circumference was crowned by a spectacular reddish-golden light. The ring of fiery colours was impossible to see from Earth with such clarity. Backlit by the Sun, the Moon took on a distinctly three-dimensional appearance. The crew could clearly see that it was no longer the romantic disc they had known since childhood but had become a giant rocky sphere, foreboding and unwelcoming, and apparently not much into romance after all. Lifeless plains lay at the foot of arid mountain chains. Here and there channels cut through great seas of dust, and everywhere craters of all sizes indicated an ancient landscape that had been bombarded by meteoroids for years beyond imagining.

Aldrin: 'It's quite an eerie sight. There is a very marked three-dimensional aspect of having the Sun's corona coming from behind the Moon the way it is.'

Houston: 'Roger.'

Aldrin: 'And it looks as though – I guess what's giving it that three-dimensional effect is the Earthshine. I can see Tycho fairly clearly – at least if I'm right side up, I believe it's Tycho – in Earthshine. And, of course, I can see the sky is lit all the way around the Moon, even on the limb of it where there's no Earthshine or sunshine.'

Now that they had travelled so close to the Moon, spectacular features such as the crater Tycho were particularly impressive. The Moon too had come quite a way, travelling nearly 200,000 miles since the mission began. While orbiting its bigger partner, the Moon simultaneously rotates so that it permanently presents the same side to Earth. While the near side has been studied by astronomers over many centuries, the far side has barely been examined at all. (Although it's sometimes erroneously described as the dark side, the truth is the Moon does not have a permanent 'dark side' any more than the Earth does.) Flying through darkness, Apollo 11 was being pulled towards the unmapped regions of the far side that were awaiting them 'over the hill'.

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It remained an uncertain journey. Lunar gravity includes mysterious pockets of energy which are strong enough to affect the orbit of unmanned probes. It was known that these patches of super gravity were associated with the flat lunar 'seas', where the interior rock was more dense than surrounding areas.4 These concentrations of mass (known as 'mascons') posed risks that were hard to calculate. Apollo 8 had investigated their impact on an orbiting spacecraft, but without a lunar module the crew had been forced to leave many questions unanswered.5 Would the LM be pulled off course at a critical moment during the landing? What effect would the mascons have on the rendezvous with the command module? Apollo 9 had proved the LM worked well in the benign conditions above the Earth. But it was hoped that by flying the spacecraft above the Moon, Apollo 10 would discover how it would react to lunar gravity. Accurate information was essential to those planning a future landing, among them Armstrong – who wanted to know as much about mascons as possible.6

McDivitt had encountered minor problems with his LM, as was to be expected with any prototype spacecraft. Modifications, and not an inconsiderable amount of faith, were adopted before the lander was permitted to venture into the potential dangers of lunar gravity. By the time Apollo 10 was ready to fly, there were just seven months left before Kennedy's deadline. In taking the complete Apollo system to the Moon for the first time, commander Tom Stafford, command module pilot John Young and lunar module pilot Gene Cernan were to put the 'tissuepaper' vehicle through a demanding series of tests, nearly a quarter of a million miles away from Earth. 'What do you tell your six-year-old daughter?' Cernan later asked. 'I don't know, I just tried to find a way that wouldn't disappoint her if I didn't come home.'

After launching on 18 May 1969, the Apollo 10 crew became the first astronauts to broadcast live, colour TV pictures from space. Later, inspecting the pressurised cabin of the lightweight LM, Young couldn't believe how far the hatch bowed out into the vacuum.7 On 22 May, Young remained aboard the command module (named Charlie Brown) while his crew-mates sealed themselves into the lander. Stafford and Cernan – who together had come close to disaster during the Gemini 9 EVA – then separated ('undocked', as NASA described it) from the command module at the start of their exploratory flight towards the probable landing ground. Within two hours Stafford and Cernan had flown the LM, call-sign Snoopy, down to a height of just 47,000 feet, or eight miles, above the surface.

In a viewing gallery overlooking the Mission Operations Control Room, senior NASA officials listened in as the LM made two low-level passes over the Sea of Tranquility. Flying almost precisely the same track across the lunar surface that Apollo 11 would take, Stafford and Cernan studied the proposed touchdown site, tested the landing radar and photographed distinctive landmarks.8 Soaring above cliffs 4,000 feet high, Cernan excitedly called, 'We is go and we is down among 'em.'9 Later he added, 'I almost felt like I had to pick up my feet, to keep them from dragging on the top of those mountain tops ... we really came in low and fast.'10 Both he and Stafford were amazed by the towering highlands and the spectacular craters. 'I've got Censorinus right here, bigger 'n shit!' exclaimed Stafford. In Mission Control, Chris Kraft cast a nervous eye back towards the viewing gallery. 'Son of a bitch...son of a bitch,' said Cernan as craters sped beneath them, each bigger than the last.11

Stafford and Cernan had been advised to keep the rendezvous radar on all the time in case they should quickly need to find the command module. It sent a continuous stream of data to the spacecraft's computer, and after completing their objectives the crew prepared to follow its lead back to Young. Suddenly Snoopy started bucking around the sky, wildly throwing itself about before rolling hard to the left. For eight long seconds the LM was out of control. 'Son of a bitch,' blurted Cernan over his open microphone, 'what the hell happened?' Stafford quickly jettisoned the descent stage and by reducing the weight of the spacecraft he found it easier to control the thrusters. Calming Snoopy's erratic behaviour, the crew fired the ascent engine before beginning their search for the command module. After completing the rendezvous, Stafford, Cernan and Young then headed for home. The problem with the LM was later traced to a checklist error in switch settings.12

Apollo 10 served as more than a simple rehearsal for the landing. Flight controllers helped to produce the first accurate flightplan for a lunar mission, viable navigation and tracking techniques were developed, and the procedures necessary for each phase of a flight towards the surface were proven in practice. By tracking the rendezvous, Mission Control was able to refine the model of the Moon's uneven gravitational field, thereby easing some of the concerns about mascons. Glitches encountered during the flight exposed weaknesses in the crew's checklists and hardware. These represented the final obstacles that could potentially delay preparations for Apollo 11. It was soon established that none was serious, and two weeks after the Apollo 10 mission ended it was confirmed that the landing was still on track.

For Armstrong, Apollo 10 was critical in providing first-hand experience of the LM's performance in lunar gravity, and he talked in detail to Stafford and Cernan.13 Also invaluable were the crew's observations of the surface. Stafford, Cernan and Young had laid a path to the Moon that stopped just a few miles short of the proposed landing site. They had 'painted a white line' in the sky, Cernan told the Apollo 11 crew during a post-flight briefing on 3 June.14 Stafford warned them that while parts of the landing zone looked smooth, other areas, particularly at the western end, were more dangerous than expected.15 Stafford had seen a large field of boulders in this region, and suggested that if Armstrong's approach were 'long' he might need to abort.16 The warning was taken only as informal advice; Apollo 11's designated landing site remained unchanged.

NASA's last three missions had been a triumphant success, and now that the Moon was in sight there was none of the hesitancy that had marked the preparations for Apollo 8. Neil, Buzz and Michael were thrust towards the centre of an enormous government organisation whose prime concern was the next manned mission. Now that their flight had been pushed into the spotlight, they found themselves at the head of the queue for the limited training resources.

For Neil, the LLTV continued to be a priority. After his ejection at Ellington Air Force Base in May the previous year, the vehicle had plummeted to the ground before bursting into flames beneath him as he dangled from his parachute. Landing a short distance from the wreckage, he escaped injury, beyond biting his tongue.17 Word quickly reached the nearby Manned Spacecraft Center, where an hour later Alan Bean overheard a group of fellow astronauts discussing the accident. 'That's bullshit!' Bean exclaimed. 'I just came out of [the] office and Neil's there at his desk ... shuffling some papers.' Running back to the office, Bean checked the story with Armstrong who to Bean's amazement coolly said that, yes, he'd been forced to bail out. 'I did go back to the office,' Neil later confirmed. 'I mean, what are you going to do? It's one of those days when you lose a machine.'18

Dangerous as the LLTV was, in Armstrong's opinion it provided the best preparation for flying something as unusual as the LM in the unfamiliar gravity field of the Moon. Bob Gilruth and Chris Kraft were nervous about their astronauts using such an unstable vehicle, but Armstrong and others fought their corner, insisting that the LLTV was the best facility they had for learning to land on the Moon.19 Since the final phase of the descent would be flown manually, the astronauts felt such practical training was essential. Ground-based simulators were useful up to a point, but at the heart of Neil's mission lay the challenge of a pioneering flight, and only the LLTV could help him properly prepare, both physically and mentally.

For Michael Collins, Apollo 11 presented a different set of challenges. In listing what he considered to be the 11 most dangerous elements of the flight, he found that two (launch and TLI) would be tackled by the whole crew. Another four (descent, landing, EVA and lift-off) would be carried out by Neil and Buzz - but the remaining five were largely down to him. The first was the separation of the command module from the third stage, leading to the docking with the LM. For Michael, perhaps the most daunting aspect of the docking involved the removal of the complicated probe and drogue assembly from the tunnel. The bulky components were awkward to handle, and during training the process was always a tricky manoeuvre. In space he would have to complete the procedure more than once, and if the docking mechanism failed to detach as planned Collins would have to dig out a tool kit and take the whole thing apart. 'I hated that probe,' he later admitted, 'and was half convinced it hated me.'20

The second item on Michael's list was lunar orbit insertion, the two-part manoeuvre that would carry them into orbit around the Moon. If he got this wrong he ran the risk of either banishing the crew into deep space or sending them crashing into the surface. The third item was the rendezvous, on which the lives of Armstrong and Aldrin depended. Fourth was the critical burn that would free them from lunar orbit and put them on the journey home. Finally, Collins would have to guide the command module back into the atmosphere at speeds approaching 25,000mph, to plunge into the ocean within reach of the rescue agencies.

Given that there was a chance Neil and Buzz might not return from the Moon, Collins had to know how to accomplish the final tasks on his own. He never gave odds on the possibility of coming home alone, and the subject was barely discussed beyond estimates about how long he could wait in lunar orbit before running low on consumables. The command module could afford to remain in position for two days longer than scheduled, by which time no-one would be in any doubt about the fate of Armstrong and Aldrin since the LM's oxygen and power would last only 24 hours.21 Neil's personal opinion was that 'on a risk-gain ratio this project would look very favourable compared to those projects that I've been used to in the past 20 years'.22 Fretting over moral arguments, what-ifs or the implications for the future was not the 'right stuff'. Nevertheless, there was no escaping the reality of the situation. As far as Collins was concerned, 'they know and I know, and Mission Control knows, that there are certain categories of malfunction where I just simply light the motor and come home without them'.23

Journalist and speechwriter William Safire was asked to prepare a statement for Nixon that could be used in the event of a disaster. Calling him on behalf of the White House, Frank Borman told Safire, 'You want to be thinking of some alternative posture for the president in the event of mishaps ... like what to do for the widows.' Safire duly wrote a speech in which Nixon would say, 'Fate has ordained that the men who went to the Moon to explore in peace will stay to rest in peace.' Safire also drafted proposals on protocol that might be followed, including the thought that after Nixon had contacted the families, a clergyman should adopt the same procedure as a burial at sea.24

Beyond some of the trickiest moments of the trip, Michael was also responsible for keeping the spacecraft on track throughout the flight. This involved learning the intricacies of the guidance and navigation system, particularly the computer. Permanently cosseted and frequently tetchy, the computer nestled at the centre of the system like a giant queen bee, its 'operator error' warning light frequently stinging Collins as he struggled with the complexity buzzing at his fingertips. Only by spending hours in the simulator did he begin to master it. Of the three command module simulators available, the machine in Houston was mostly used for research and Michael principally used the two at the Cape. But from the moment his training began in January he had trouble getting access to any of them. Until March, priority went to the Apollo 9 crew and their backups, with the Apollo 10 prime and backup crews next in line. Collins was part of the fifth flight in the queue. He, Neil and Buzz were only given top priority once Apollo 10 was ready to fly, by which time there were just two months until they themselves were due to launch.

To enter the simulator, Michael climbed a carpeted staircase up to a hatch 15 feet above the ground. Built by North American, inside it closely replicated the command module, complete with images of constellations, the Moon and the Earth visible through the windows.25 Technical equipment and machinery were housed in more than a dozen odd-shaped boxes mounted on the shell of the simulator, each the size of a washing machine. From the outside it looked such a jumble of parts that when John Young first saw it he dubbed it the Great Train Wreck.26 The instrument displays were driven by a mainframe computer, controlled by a team of instructors whose task it was to prepare Collins for any eventuality. As virtual lunar and command modules attempted to rendezvous beside a virtual Moon, the computer kept track of Michael's progress. If the LM failed to reach the surface, or if it got there early or late, or was delayed in its journey back to the command module, the rendezvous would shift from a textbook manoeuvre into one of a number of emergency procedures. Sometimes the command module would need to remain in a high, slow orbit to meet its errant partner while in other situations it would have to fly low and fast. Nevertheless, Collins could only go so far in mounting a rescue attempt. There would be no point in retrieving Neil and Buzz only to find there wasn't enough fuel to get home.27 Collins practised 18 different options, and at the end of each session the instructors told him whether the rendezvous had succeeded before he had run out of time, fuel or both.28

The crew had to complete many mandatory simulations involving Mission Control before they could be said to be ready. With the flight fast approaching, the mission managers began to fear they might not make it.29 The 16 July launch date had been dictated by the need for the Sun to be in the best position to provide ideal lighting conditions during the landing. If necessary, lift-off could be pushed back a month as similar conditions would return in mid-August. But no-one wanted to ask for a delay, and to Deke's occasional questions about progress Michael gave reassuring answers. Privately, however, when they became the next crew to fly Collins felt that they still had a year's work ahead of them.30

Now with free access to the simulator, Michael anxiously sought to get to grips with his rendezvous procedures, entering notes, diagrams and instructions in the 'Solo Book' he would rely on once Neil and Buzz had departed. For each rendezvous option, a checklist had to be written detailing the sequence to be followed when pushing switches and using the computer. In focusing on the most likely scenarios, Michael struggled to find the time to master some of the more obscure alternatives, and as May slipped into June he stayed at the Cape for days at a time, working in the simulator. After each session he would wander over to the instructors and check the 'Collins looks good' light they had fitted to their huge bank of consoles. Usually it was glowing cheerfully. If not, he would switch it on himself.31 The instructors' computer, updated after the McDivitt and Stafford missions, had the final say over everything – until it broke down and stranded everyone in a bout of frustration while an army of technicians battled away at the problem. Sometimes Michael would spend hours going through the early orbital procedures only for the rendezvous itself to be suddenly scrubbed by the computer 'bombing out'.32

With many of the mandatory training exercises still to be completed, Collins yearned to tuck himself away in the simulator every day. But managers, memos and phone messages persistently demanded his attention. NASA's Langley centre – home of the Lunar Landing Research Facility, dangling from its A-frame – invited Collins to fly a full-size replica of the command module that was suspended from wires. Time also needed to be set aside for the centrifuge at the Manned Spacecraft Center (MSC), and for fitting the pressure-suits in Delaware. Publicity photos had to be taken, meetings had to be attended (in various corners of the country), long-lost relatives chasing tickets to the launch had to be answered, and the family in Houston couldn't be ignored. With the training regime pushing ahead at full steam, the only lingering doubt was whether everyone would be ready. In the first weeks of June, Deke asked Neil, Buzz and Mike whether another month would be necessary but each of them stuck to the launch date.

On 17 June, Sam Phillips, the director of the Apollo programme, led a nine-hour flight readiness review at the MSC. Among other things, this focused on whether an attempt to land should continue if communications with Earth were disrupted. The exchange of information was essential. Mission Control managers, led by Chris Kraft, knew that in the event of a crash they would need to have enough data to be able to reconstruct what went wrong. At the end of the meeting, Phillips announced that the preparations were on target and he permitted Apollo 11 to proceed as planned. Collins was elated. Technicians at the Cape could now begin loading the spacecraft with hypergolic fuels. These were so corrosive that if the launch were delayed to August, any last-minute hardware failures could lead to serious problems. The fuel tanks would have to be drained and parts of the vehicle would have to be sent away to be repaired, and no-one knew how long this process might take.33

The debate about aborting the landing if communications were seriously interrupted rumbled on for weeks. Flight director Gene Kranz was asked to write down agreements on the subject, to be added to the rest of the rules for the mission. Writing mission rules was one of the first jobs Kranz had performed while working on the Mercury programme. In meetings held before each flight, Chris Kraft had tried to identify areas of uncertainty so that solutions could be agreed, which were then written down by an assistant. The assistant – Kranz – produced lists of all the agreed decisions, a task he was appointed to two weeks after joining NASA. Looking him in the eye, Kraft had muttered, 'Everyone else is tied up. You're all I've got.'34 At other times, on the instructions of his indomitable boss, Kranz ignored the agreed decision and wrote down what Kraft told him to.35 He put everything in an easily digested format, listing potential problems alongside the appropriate action to be taken.

The list of rules used during the Mercury programme was 30 pages long. By Apollo 11 it was up to 330.36 The first complete version was published on 16 May, and while some rules were virtually written in blood ('if data from the landing radar is not available before the LM descends to 10,000 feet, the landing must be aborted'), others gave the crew room for manoeuvre.37 Each flight controller would only allow a critical phase of the mission to begin if he were sure that the vehicle was measuring up to the rules. If everything was satisfactory, he would say so to the flight director. With a lot of information to be passed to one man by many controllers in a short time, the only way to do this quickly was to offer a simple yes or no – which in NASA jargon became 'go' or 'no go'. Even this could be confusing. After landing on the Moon, did 'go' mean 'OK' or did it mean 'leave'? To prevent the spacecraft launching unnecessarily just seconds after touching down, go/no go would become stay/no stay. The mission rules were supplemented by the flight-plan and associated checklists which together detailed everything that would or could happen throughout the trip. Individual controllers also prepared their own personal books. Kranz was so worried about losing his that he made them instantly recognisable by plastering them with pictures of women from the swimsuit edition of Sports Illustrated.38

Following lessons learned during training, new rules were added every week based on agreements between flight controllers, engineers, managers and astronauts. Kranz found that Buzz, who reminded him of an eccentric teacher, 'generally dominat[ed] the crew side of the conversations'.39 He admired Aldrin's intricate grasp of rendezvous trajectories as he gave his forthright opinions to the 'trench', the front-row controllers whom Kranz knew to be a pretty forthright bunch themselves. Neil was more the quiet observer, 'but when you looked at his eyes,' Kranz later said, 'you knew that he was the commander and had all the pieces assembled in his mind.' According to Kranz, the astronaut who spent the most time getting to know the key people in the Mission Operations Control Room was Mike Collins, whom Kranz regarded as 'steady, dependable' with 'a reputation as being extremely competent in his judgement'.40 Working alone throughout much of his training, Mike knew that during the mission the flight controllers would be looking over his shoulder, and he was grateful for their support.

Communication between Collins and the ground, like most components of manned space-flight, relied on procedures developed during Mercury. At launch, messages sent to the crew were transmitted directly from the Cape. But since radio signals travel in a straight line, communications would stop the moment the rocket went over the horizon, less than ten minutes after lift-off. There would be no telemetry from the booster, nor from the spacecraft it was carrying, and Houston would not know whether it was safe to let the crew head towards the Moon. During Mercury an additional transmitter was built on Bermuda, in British territory. But since a rocket travelled round the Earth in an hour and a half it would not be within reach of a single transmitter for very long. A chain of tracking stations was needed around the world.

In seeking to build transmitters at sites across three continents, Kraft and his colleagues suddenly found themselves embroiled in international politics. Dealing with the Brits was one thing, but installing tracking stations with space age telemetry facilities in remote corners of Africa was something else. Seven sites involved the State Department in 'serious diplomatic discussion', as Kraft put it, while two others were in the middle of oceans, and for these NASA needed help from the navy.41 Some of the locations were so remote Kraft felt that 'the word primitive was the accurate description'.42 According to Gene Kranz, late one night in 1962 flight controller Charles 'Skinny' Lewis was driving the two members of his team back to their quarters on Zanzibar when he saw a roadblock made of burning oil drums 'manned by natives not in uniform'43. Lewis, a former tank commander who before joining NASA had never left America, accelerated towards the barrier and escaped by smashing his way through the blazing obstacles.

By the late 1960s, the tracking stations had been substantially developed and brought within the control of NASA's Manned Space Flight Network. The MSFN permitted a permanent link between Houston and Apollo 11 through a worldwide chain of 17 ground stations, supported by four specially adapted ships and up to eight aircraft. Eight of the ground stations were equipped with 30-foot antennas, capable of tracking the spacecraft in Earth orbit and for some distance beyond. Once the crew had reached an altitude of 10,000 miles, communications would be provided by the more powerful 85-foot antennas installed at Madrid, Canberra in Australia and Goldstone in California. These used a system known as S-band, a single signal capable of simultaneously carrying tracking data, telemetry, voice and television. The spacecraft responded by bouncing the signal back, which helped the ground keep track of its position. As the Earth spun on its axis, at least one of the three powerful antennas would be in sight of the Moon throughout the mission, with each station handing control to the next to maintain a continuous connection.

Voice signals, tracking data and telemetry were passed to Houston via NASA's Communications Network, which linked the ground stations and other facilities through two million miles of landlines and undersea cables. Relying on six intermediate switching centres around the world, and two communications satellites, the network included redundant signal routes to increase reliability. Some remote switching points were triggered automatically whenever the CapCom began to speak. Each time he pressed his microphone button, it emitted a short beep known as a Quindar tone. This prompted the remote site to begin operating, and gave a distinctive sound to transmissions from Mission Control.

All communications were routed through NASA's Goddard Space Flight Center in Maryland. From there, radio signals were relayed to and from Mission Control, where secure rooms on the ground floor housed the Real Time Computer Complex. Houston's powerful computers monitored launch operations as well as the continuous supply of tracking and telemetry data. The data was recorded, processed and sent upstairs to the Mission Operations Control Room (MOCR), where it was displayed on the controllers' consoles. The flight surgeon might look at Neil's heart-rate while the CapCom talked to Buzz, at the same time a flight controller could follow the spacecraft's position displayed on a wall-sized map, while the man next to him monitored the performance of Columbia's thrusters. Once the LM separated from Columbiaat the start of the descent, the MSFN would have to supply this information for two spacecraft simultaneously. Reliability was critical since mission rules could lead to an abort if the signal from space failed at key moments during the landing.

Although redundancy and reliability were built into the communication systems, Apollo 10 had still encountered many problems. Course corrections and PTC manoeuvres frequently left the spacecraft's antennas in a position where they were either pointing away from Earth or trying to send a signal through the body of the vehicle. Sometimes John Young in the command module had to ask Houston what the astronauts in the lunar module were trying to tell him. Prior to Apollo 11, these issues were addressed by better co-ordination of both the manoeuvres and the communications demands. To maintain the strongest signal, the crew were trained when and how to swiftly switch antennas.

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Armstrong: 'The view of the Moon that we've been having recently is really spectacular. It fills about three-quarters of the hatch window, and of course, we can see the entire circumference, even though part of it is in complete shadow and part of it's in Earthshine. It's a view worth the price of the trip.'

Mission Control: 'Well, there are a lot of us down here that would be willing to come along.'

Collins: 'I hope you get your turn, and soon.'

Armstrong: 'One of these days, we'll be able to bring the whole MOCR along, I hope. Save a lot of antenna switching.'

Mission Control: 'That's jolly.'

Drifting closer to an alien world that was itself moving towards them at more than 2,200mph, the crew were now caught up in a galactic game of chicken. Instead of hopping over the tracks in front of a speeding train, they had to put themselves in a position where the 'train' – here, the size of a small planet – effectively picked them up and carried them along with it. Getting into lunar orbit was fraught with danger. If they did nothing, they would be pulled around the far side and flung back into space towards the Earth on a free flight home, without having to use the big engine at the back of the service module. By burning the engine for precisely six minutes and two seconds they hoped to slow down enough to enter lunar orbit. If the engine failed to ignite, their 'free-return' trajectory gave them a hope of coming back. However, if the braking manoeuvre lasted longer than planned, it might cause the spacecraft to slow so much it would crash into the surface. If the engine stopped early, the crew would be sent off into space at an angle that could be impossible to recover from. Apollo 8 had reduced the risk by breaking the lunar orbit insertion (LOI) manoeuvre into two separate burns. Apollo 11 would do the same.

To successfully perform LOI-1 Michael would have to fire the engine at precisely 75 hours, 49 minutes and 49 seconds into the mission – while they were behind the far side. Radio signals could be sent to and from the spinning spherical Earth via the elaborate network of radio stations, but the spinning spherical Moon didn't have much beyond dust. Radio communications would be unable to curve round to reach the far side, so LOI-1 would have to be done without the support of Mission Control. If it were unsuccessful, Collins would need to urgently establish whether they would be able to get home, and if so how – something he had practised many times in the simulator.

Three hours before ignition, at 9.22am on the morning of Saturday 19 July, a long list of numbers was read up to the spacecraft, giving Michael navigation instructions and details on roll, pitch and yaw. The radio link would break at 12.13pm. A few minutes before losing contact flight director Cliff Charlesworth asked each of his controllers for a go/no go decision on LOI. The spacecraft was now 9,000 miles away from the Moon. With the two fast approaching each other, the distance between them would be covered in less than 12 minutes.

Mission Control: 'Apollo 11, this is Houston. Over.'

Aldrin: 'Roger. Go ahead Houston, Apollo 11.'

Mission Control: '11, this is Houston. You are go for LOI. Over.'

Aldrin: 'Roger. Go for LOI.'

Mission Control: 'Apollo 11, this is Houston. All your systems are looking good going around the corner, and we'll see you on the other side. Over.'

After a flight of nearly 240,000 miles, during which they had made just one course correction (a three-second burn on day two), Armstrong, Aldrin and Collins dodged the leading edge of the Moon by just 309 miles. Having halted PTC, the main engine faced the direction of travel as the spacecraft silently coasted through the darkness at 5,200mph. The crew were now less than eight minutes from LOI. Above them, the stars were beginning to fade as the first rays of sunshine reached over the curved horizon, stretching towards the approaching spacecraft. With two minutes to go they slipped from the gloom into glaring sunlight, and for the first time they could clearly see the heavily cratered landscape, more than 2,000 miles wide.

Collins: 'Yes, the Moon is there, boy – in all its splendour.'

Armstrong: 'Man, it's a—'

Collins: 'Plaster of Paris grey to me.'

Aldrin: 'Man, look at it.'

Armstrong: 'Don't look at it. Here we come up to ignition.'

Aldrin: '8 seconds.'

Collins: 'Stand by for ignition.'

Armstrong: 'Burning.'