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

Chapter 12. THE EAGLE HAS WINGS

Groggy after a difficult night's sleep, Michael Collins wondered whether the insistent voice in his ear could possibly be talking to him.

Mission Control: 'Apollo 11, Apollo 11. Good morning from the black team.'

Collins: 'You guys wake up early.'

On the morning of Sunday 20 July, Collins was woken 93 hours and 32 minutes into the mission, at 6.04am. The fifth day of the flight promised to be the most demanding, and none of the crew had slept well. 'The pressure was beginning to build at this point,'¹ Neil later said. After preparing the LM, the two spacecraft would undock. Neil and Buzz would then make the first of two burns, putting them in an elliptical orbit with a lowest point above the Moon of 8.3 miles. At this point, the crew would begin a second burn that would carry them down to the surface. For the moment, the men were just about to begin their tenth orbit around the Moon, and there were just two minutes to go before radio contact was lost.

Mission Control: '11, Houston. Looks like the command module's in good shape. Black team has been watching it real closely for you.'

Collins: 'We sure appreciate that. Because I sure haven't.'

As they passed around the far side Buzz entered the lower equipment bay and began to prepare for the landing that would take place in nine hours' time. He and Neil would remain in their pressure-suits throughout their time aboard Eagle, which meant that once again they would have to put on the urine and fecal collection devices. After doing this, Buzz pulled on a set of long johns that contained hundreds of thin plastic tubes. These allowed the underwear to be cooled by water during the arduous work on the surface. He then floated into the LM, making room for Neil to begin the same process, while Mike prepared breakfast.

In Houston, Mission Control's black team were coming to the end of their shift, and nearly two hours after they had woken the crew they began handing over to the white team of Gene Kranz. Carrying a plastic bag, Kranz walked into the Mission Operations Control Room and greeted his controllers as he slowly threaded his way towards his seat. By his own admission he was the most emotional of all the flight directors, and was keenly aware of the historical significance of what he and his men were hoping to do.² He hadn't slept well either. Leaving his bag at the flight director's console, Kranz headed out of the MOCR to pass the time of day with the engineers and contractors in the spacecraft analysis room. After chatting to Grumman's Tom Kelly and the president of North American Rockwell, by 8am he had returned to his console. From his bag, Kranz retrieved his white and silver waistcoat. Once he'd slipped it on he was ready to take over.

Aboard Columbia, breakfast was taking longer than usual. Tired, busy and preoccupied by the events ahead of them, the men fell out of their mealtime routine. Normally they helped each other prepare the many breakfast bags and packages, but with bits and pieces of their bulky spacesuits taking up precious room it had become difficult to move about. 'The rhythm got slightly out of whack,' Buzz remembered, 'and once we finally got it going properly we all three bemoaned the fact that the simple act of eating was something there was no training for.'³ After the meal, Buzz - still only wearing his long johns - returned to the LM to begin preparing Eagle for flight, a five-hour process. While Aldrin worked through his checklist, Michael helped Neil into his pressure-suit, doing up the inaccessible crotch-to-shoulder zip and checking everything was as it should be. Meanwhile, Mission Control read them the day's news.

Among the large headlines concerning Apollo this morning, there's one asking that you watch for a lovely girl with a big rabbit. An ancient legend says a beautiful Chinese girl called Chang-o has been living there for 4,000 years. It seems she was banished to the Moon because she stole the pill of immortality from her husband. You might also look for her companion, a large Chinese rabbit, who is easy to spot since he is always standing on his hind feet in the shade of a cinnamon tree. The name of the rabbit is not reported.

'Jesus Christ,' Collins thought to himself. While trying to make coffee and stay on top of the confusion around him he couldn't quite believe he was listening to Houston's thoughts on large Chinese rabbits.⁴ 'OK. We'll keep a close eye out for the bunny girl,' he told the ground.

Since the two vehicles would later be undocking, all three men would have to put on their suits, in case either spacecraft suddenly lost pressure, though Michael wouldn't be walking on the Moon and therefore wouldn't need the so-called 'liquidcooled garment' the others were wearing. After helping Collins into his suit, Armstrong entered the lunar module. Sunlight, streaming through the windows, bounced off the white beta-cloth locker covers, while in front of him the grey instrument panels had come alive in the orange glow emanating from the gauges.

After powering up the inertial platform that fed the primary computer, Neil and Buzz tested communications with Houston. They were about half an hour ahead of the flight-plan. While Collins gave Armstrong details of their position, to be entered into Eagle's guidance system, Buzz returned to Columbia to put on his pressure-suit. Once Aldrin floated back into the LM he shut the hatch and for the first time he and Neil were sealed inside the cramped spacecraft that would be their home for the next 30 hours. Michael then installed the probe and drogue docking assembly and secured Columbia's hatch. Now that Eagle was powered up and operational, he could open a valve that would allow the tunnel connecting the two spacecraft to empty of oxygen.

Collins: 'OK, I'm ready to go to LM tunnel vent.'

Aldrin: 'You got it all vented now?'

Collins: 'Negative, it's a slow process. I'm on vent, but - it's just going to take a little while here.'

Aldrin: 'Roger. Just give us a call. We're pressing on with some other stuff.'

Now wearing their gloves and 'bubble' helmets, and connected to the life-support system, Neil and Buzz tested the suits' radio connections. They then fired the explosive bolts that unfolded the LM's four legs. Passing across the near side of the Moon on the twelfth orbit, Armstrong and Aldrin began checking the inertial platform and the primary computer. Houston needed to send information using the powerful S-band signal, which could only be done once the LM's most powerful transmitter/ receiver - the high-gain antenna - was directly facing Earth. Using controls in the cabin, Buzz tried to rotate it into the correct position but found its signal was blocked by the lunar module itself. For the moment they could only talk to the ground using less powerful omni-directional antennas. Once S-band communications became available, Houston sent navigation data to the abort guidance system (the AGS, serving as the LM's backup computer). After this, Armstrong and Aldrin tested their thrusters, the final major check they needed to perform. In Houston, Kranz had polled his controllers on whether they were happy to proceed with the undocking, and five minutes before the crew went 'over the hill' permission was given to separate.

Mission Control: 'Apollo 11, Houston. We're go for undocking. Over.'

Aldrin: 'Roger. Understand.'

Collins: 'Houston, Columbia.'

Mission Control: 'Go ahead, Columbia. Over.'

Collins: 'Roger. There will be no television of the undocking.

I have all available windows either full of heads or cameras, and I'm busy with other things.'

Before the mission Collins had admitted that 'I would be either a liar or a fool if I said that I think I have the best of the three seats on Apollo 11... but I'm an integral part of the operation and happy to be going in any capacity.'⁵ For the rest of the world, Neil Armstrong and Buzz Aldrin were just names in a newspaper - in Russia, Pravda had taken to calling Neil 'the Czar of the Ship' - but for Michael, Neil and Buzz were the only people who had shared everything he had been going through since Christmas. Now that the two of them were about to begin the key part of their mission, the time was fast approaching when he would have to bid them farewell. All that remained to be done was for the command module to be held still while Armstrong punched computer buttons as he finely tuned the AGS.

Collins: 'I have 5 minutes and 15 seconds since we started. Attitude is holding very well.'

Aldrin: 'Roger, Mike. Just hold it a little bit longer.'

Collins: 'No sweat, I can hold it all day. Take your sweet time. How's the czar over there? He's so quiet.'

Armstrong: 'Just hanging on - and punching.'

Collins: 'All I can say is, beware the revolution. You cats take it easy on the lunar surface. If I hear you huffing and puffing, I'm going to start bitching at you.

Aldrin: 'OK Mike.'

After Buzz finished setting up a 16mm film camera in his window, at 12.44pm Michael pushed a button releasing the latches holding the two spacecraft together. Excess oxygen immediately escaped from the tunnel, gently pushing the two spacecraft apart. From that moment Neil and Buzz were flying aboard a vehicle in which it would be impossible to come home.

Mission Control: 'Eagle, Houston. We see you on the steerable [antenna]. Over.'

Armstrong: 'Roger. Eagle is undocked.'

Mission Control: 'Roger. How does it look, Neil?'

Armstrong: 'The Eagle has wings.'

Mission Control: 'Roger.'

With the two spacecraft flying in formation, 60 feet apart, Collins took a careful look out of the small window directly in front of the left-hand couch.⁶ He had made a trip to the Grumman factory specifically to see what the lunar lander should look like once the legs were properly extended. Now, as Neil slowly rotated the LM, it seemed to Michael that with its legs locked in position Eagle was 'the weirdest-looking contraption ever to invade the sky'.⁷ A minute before he was due to move off to a greater distance, Collins embroidered the truth a little.

Collins: 'I think you've got a fine-looking flying machine there, Eagle, despite the fact you're upside-down.'

Armstrong: 'Somebody's upside-down.'

Armstrong: 'See you later.'

Collins: 'OK, Eagle. One minute until ignition. You guys take care.'

Firing his forward thrusters for eight seconds, Michael flew the command module away from the LM; at the same time Neil and Buzz tested the all-important rendezvous radar by locking on to Columbia's transponder. Once Columbia was a thousand feet away, Armstrong and Aldrin were ready to begin the first part of the descent to the surface, a manoeuvre known as descent orbit insertion (DOI). To put themselves on the correct approach route, the burn would have to be made while they were out of radio contact with Houston - like so many other key moments of the mission. In igniting their engine on the far side of the Moon, the spacecraft would enter an elliptical orbit. At its lowest point, this would bring Eagle down to just 50,000 feet (or 8.3 miles) above a spot 260 miles east of the landing site.⁸ One hour and six minutes after undocking, the ground gave permission for DOI, and ten minutes later the two spacecraft slipped out of contact, at the beginning of the fourteenth orbit.

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On a steaming day in Houston, the crew's homes were crowded with visitors. Through the squawk boxes, everyone had overheard Neil and Buzz preparing the LM- but the technical jargon was sometimes hard to understand. 'Better than 90 per cent of what families could ever hope to hear on this party line was incomprehensible,' Jim Lovell later said.⁹ Joan was helped through some of the more complicated things by Apollo 9 veteran Rusty Schweickart. That morning she had attended the Presbyterian church where Buzz was an elder, taking with her their children Michael, Jan and Andy. Reporters had tried to capture a comment as she entered but Joan had waved them away before settling down to listen to a sermon about the 'epitome of the creative ability of man'.¹⁰ She was home by 11.30, and while she waited for the landing to get under way she watched the continuous TV coverage. Friends from church had brought lunch, including a cake with icing in the shape of an American flag beside the words 'we came in peace for all mankind'.¹¹ At her home in the suburb of El Lago, Janet was also watching the TV coverage, while Bill Anders, a member of the backup crew, tried to answer her questions about the landing. 'What can go wrong and they can still go?' she asked. 'It depends on what went wrong,' Anders told her.¹²

Since the launch, four days earlier, Janet, Joan and Pat had been keeping open house, with a steady stream of friends and relatives bringing them food and other gifts. Among those staying with Joan was Jeannie Bassett, who was helping to look after the children.¹³ Entering or leaving the crew's homes meant having to push through throngs of reporters camped outside. On the first day of the flight a photographer had sneaked over Joan's back fence, which had upset her.¹⁴ She very much wanted to give the right image to the press, but on her terms, and on the morning of the second day she made a point of raising the American flag on her front lawn to give them an early picture. Her duties done, she and the children sneaked out of the back of the house and into the car of a waiting friend who whisked them off to a shopping centre 12 miles away.¹⁵ Janet had spent much of the second day clearing leaves from the pool, before settling down to watch the TV broadcast in the evening. Joan also caught the broadcast, she and Jeannie helping the children to identify the voices as the crew described the Earth. 'You'd better watch yourselves, boys - you're going to run out of material,' she joked. 'Especially those three,' quipped somebody in the background. When Pat saw the broadcast she discovered Mike was growing a moustache.¹⁶

Despite attempts to remain light-hearted, by the third day the pressure was beginning to take its toll. Pat and Janet joined Joan for a pool party, the three of them giving a joint picture for the press. Reporters had managed to put questions to the children after Pat dropped them off at a day camp en route to the party. When six-year-old Michael was asked if his daddy was going to go down in history, he replied, 'Yeah,' but gave as good as he got when he asked, 'What is history?'¹⁷ When Pat went to get her hair done on the morning of the fourth day, three female reporters had managed to get appointments at the same time and at the same place. Later that day, listening to radios and squawk boxes, the wives waited for the men to safely come round from the far side of the Moon after LOI-1. Janet had been briefed by Apollo 10 commander Tom Stafford so that she would feel prepared ahead of the landing. That night, while her family and friends accepted a dinner invitation from next door, Janet stayed at home, preferring to eat alone.¹⁸

The following morning, Sunday 20 July, the Aldrin family attended the packed service at Webster Presbyterian Church. After the sermon, the Reverend Dean Woodruff broke the Communion bread and held it up for everyone to see, pointing out that a piece was missing. The implication was that it had gone with Buzz. He called on the Aldrin household later that afternoon, listening to the transmissions and sharing the tension during the radio silences.¹⁹ For 48 minutes in every two-hour orbit, the crew were out of contact with the Earth. During their fourteenth circuit of the Moon, Neil and Buzz would theoretically complete the DOI burn. No-one could know for sure until radio contact resumed. At that point, if all had gone to plan, the landing would begin less than 20 minutes later.

In TV studios around the world, anchormen and experts were preparing for what promised to be the most significant moment in television history. There was a sense that humanity was going somewhere radically new. Unlike historical voyages of discovery, this time, through the wonders of television, the explorers were bringing mankind with them. It was a tight squeeze. Diagrams and animations supplied by NASA revealed how the astronauts were standing up in the tiny cabin of the lunar module. After explaining to viewers that there wouldn't be any TV pictures from space until the moonwalk, the networks broadcast the radio messages sent to and from Mission Control.

In the Mission Operations Control Room (MOCR), Kranz and his team were waiting for Eagle to resume contact. Kranz felt that the air had started to 'crackle' as anticipation of the coming events took hold of his young flight controllers.²⁰ Sitting to his left was Charles Lewis who, having survived his brush with the 'natives' on Zanzibar, was now serving as an assistant flight director. Further along the third row was communications officer Ed Fendell, supporting Michael in the command module. According to Kranz, Fendell liked to poke fun at his fellow controllers, but while some found him disruptive, Kranz respected his independence and reliability. Also supporting Columbia were John Aaron and Buck Willoughby (call-signs EECOM and GNC), who would be on hand to help Collins should he need to rescue the LM. Eagleitself was assisted by most of the rest of the controllers, including Dick Brown, who looked after communications and sat next to Fendell. In front of them, flight surgeon John Zieglschmid sat near to Deke Slayton and CapCom Charlie Duke, while across the aisle to the right were Bob Carlton and Don Puddy. The dry, laconic Carlton (call-sign Control) was monitoring Eagle's navigation, control and propulsion systems, while the quick-witted Puddy (known as TELMU) watched the electrical power and life-support equipment. In the front row sat Steve Bales, the diligent Guido officer, who was looking after the LM's radar and computers and who had requested the extra training sessions to study the alarms. To his left, watching the LM's trajectory, was flight dynamics officer Jay Greene, described by Kranz as a cocky 'pipe-smoking rabblerouser'. The final members of the slightly rebellious front row were Chuck Deiterich, who would help plot a route home in an emergency, and Gran Paules, who was supporting Bales. Assisted by their backroom colleagues, the white team were monitoring the 270 measurements continuously transmitted by the LM.²¹

Also sitting in the MOCR were astronauts Pete Conrad, Fred Haise, Jim Lovell and Bill Anders, while at the back, in 'management row', were Bob Gilruth, George Low, Chris Kraft and General Sam Phillips, Director of the Apollo Program. Behind the windows of the viewing gallery were more senior NASA figures from than had ever been gathered in one place before. They included administrator Tom Paine, the directors of four space centres (including Wernher von Braun), and astronauts Tom Stafford, Gene Cernan, Jim McDivitt and John Glenn. With them was John Houbolt, the man who had so energetically pushed for lunar orbit rendezvous.

When radio contact was lost prior to the DOI burn, Kranz suddenly became aware of the pressure his young team was under. Their average age was just 26, and some, like Puddy and Bales, had come straight from college. Instructing them to switch from the usual voice loops, he addressed them on a private internal circuit. Cornered in the viewing gallery, the brass were literally cut out of the loop. Later, Kranz remembered that he 'had to tell these kids how proud I was of the work that they had done'. In a stirring, off-the-cuff speech, he reminded them that by landing a man on the Moon they were about to write history. He finished by saying that whatever decisions they chose to make he would stand by them, for 'we came into this room as a team and we will leave as a team'.²²

The morning's tasks had occasionally felt like a simulation. When Kranz ordered the doors to be locked, no longer was there any doubt that this was the real thing. From now on no-one would be able to enter or leave Mission Control until the crew had either crashed, aborted or landed.²³

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Nearly eight minutes after losing contact with the ground, Neil and Buzz ignited the LM's engine for the first time. The DOI manoeuvre began in almost total darkness, only the thinnest rays of the Sun reaching beyond the curve of the Moon. Burning for nearly 30 seconds, the engine produced enough thrust for them to feel its force in their legs. Once the burn was complete, Eagle was flying faster and lower than Columbia, and descending all the time. By the time they were ready to resume contact with Houston, 40 minutes after DOI, Armstrong and Aldrin were already down to an altitude of 18 miles and coasting at nearly 3,700mph.²⁴ The LM was in a horizontal position with its engine facing the direction of travel, so that it might have been described as flying backwards. It was also flying windows down. Had they not been in weightlessness, Neil and Buzz would have considered themselves to be travelling feet first and face down. In this attitude they could look down at passing landmarks and use their engine as a brake. With the Sun on its back, Eagle's golden foil glittered brightly against the grey plains below as it swooped low and fast across the surface.

More than 40 miles above, Michael used his sextant to follow its progress. 'The LM is nearly invisible,' he later said, 'and looks like any one of a thousand tiny craters, except that it is moving.'²⁵ Although he was coasting behind the LM, his higher altitude meant that Columbia would peer over the edge of the Moon before Eagle, which in turn meant that Collins was the first to get through to Houston. Immediately, Charlie Duke wanted to know about the LM's burn.

Mission Control: 'Columbia, Houston. Over.'

Collins: 'Houston, Columbia. Reading you loud and clear. How me?'

Mission Control: 'Roger. Five-by, Mike. How did it go? Over.'

Collins: 'Listen, babe. Everything's going just swimmingly, beautiful.'

Mission Control: 'Great. We're standing by for Eagle.'

Collins: 'OK, he's coming along.'

At 2.48pm, a wave of energy ran through the MOCR as Houston resumed contact with Eagle. Just two minutes later, however, the all-important high-gain signal dropped out. While other mission rules dealt with clearly defined problems, the question of whether there was enough telemetry or not was down to Kranz's personal opinion. He felt that of all the rules in the book, 'this is the only one that really bothers me, because it's a pure judgment call'.²⁶ The link was re-established, but just four minutes later, with Eagle now down to around 12.5 miles altitude, the controllers' screens froze once again. In a little over 10 minutes' time, Neil and Buzz were due to begin the powered descent initiation (PDI), their second and final burn. But if the situation didn't improve soon Kranz knew he might have to send them around the Moon on another orbit. After that, if he still wasn't ready to allow the final burn, the LM's dwindling electrical supply would force him to scrub the mission.

With time ticking by, Duke asked for help from Collins.

Mission Control: 'Columbia, Houston. We've lost Eagle again. Have him try the high gain. Over.'

While Neil checked their position relative to objects on the surface, Aldrin monitored the primary and backup computers, and did what he could to maintain communications. He adjusted the position of the high-gain antenna, Eagle's strongest transmitter- receiver, but once again it was trying to send its signal through the body of the spacecraft. With the LMquickly approaching the critical low point in its orbit, all that Buzz picked up was static.

Collins: 'Eagle, this is Columbia. Houston lost you again. They're requesting another try at the high gain.'

Mission Control: 'Eagle, Houston. We have you now. Do you read? Over?'

Aldrin: 'Loud and clear. I don't know what the problem was there. It [the steerable high-gain antenna] just started oscillating around in yaw. According to the needle, we're picking up a little oscillation right now, as a matter of fact.'

With less than six minutes until the burn, Armstrong was advised to yaw ten degrees right to make communications easier. But again there was no response from Eagle. With time running out, Kranz had to decide whether he could let the descent begin. He needed to poll his team on the landing, but waited 40 seconds longer than scheduled before asking them for a judgement based on the most recent information. As he rapidly went through the call-signs, Kranz received a curt 'go' from each man - then Steve Bales reported, 'We're out on our radial velocity, we're halfway to our abort limits.' The spacecraft's rate of descent showed a discrepancy Bales couldn't explain. Jay Greene also noticed that the LM was lower than expected. Despite the references to 'abort' before the burn had even begun, Kranz told Duke, 'CapCom, we're go for powered descent.'

Duke passed on the instruction, but again there was no response. Unable to talk directly to Buzz, Charlie again asked for help from Michael, who was now 120 miles behind Eagle.

Mission Control: 'Columbia, Houston. We've lost them on the high gain again. We recommend they yaw right 10 degrees and reacquire.'

Collins: 'Eagle, this is Columbia. You're go for PDI and they recommend you yaw right 10 degrees and try the high gain again.'

Collins: 'Eagle, you read Columbia?'

Aldrin: 'Roger. We read you.'

Collins: 'OK.'

Mission Control: 'Eagle, Houston. We read you now. You're go for PDI. Over.'

Aldrin: 'Roger. Understand.'

Coasting over the surface towards the shadows looming up at them from the west, Buzz switched on the 16mm camera in his window, recording their panoramic view of the brightly lit ground passing below. While Michael moved freely around the spacious command module, looking through the sextant and monitoring the flight-plan, Neil and Buzz were held in position by their cables as they checked their position. If they were much higher than 51,000 feet at PDI, they risked running out of fuel.²⁷ The Manned Space Flight Network was able to give a rough estimate of their altitude but could be up to 10,000 feet off. Neil had to supplement its information with his own calculations.²⁸ While waiting for ignition, Armstrong noted the speed at which objects on the ground passed along a scale etched on his window. By combining this information with the LM's velocity and orbital period, he was able to do some quick arithmetic to gauge Eagle's altitude.

Satisfied with his calculations, he and Buzz waited for the computer to complete its countdown to ignition - and at 3.05pm Armstrong permitted Aldrin to instruct it to fire the engine. Five seconds later, Neil called 'ignition', simultaneously telling Houston and millions of TV viewers around the world that the final leg of Apollo 11's historic journey had begun.²⁹

Up to this point, the fuel in Eagle's tanks had been floating in weightlessness. When the thrust from the engine caused it to settle, Houston had a chance to assess the quantity consumed during the previous burn. But again the telemetry dropped out, and Bob Carlton was left to guess how much fuel they had left. He could do little more than say that the crew had roughly 12 minutes to reach the landing site. While Kranz and Duke each wondered whether they were doing the right thing in pushing forward despite the communication problems, Neil and Buzz were preoccupied with their own concerns.³⁰ Up to PDI, everything they had done had been tested on previous missions. Now, as their altitude dropped to 47,000 feet, they were descending into the unknown. In case of an emergency the crew chose to leave their rendezvous radar on, allowing it to send regular updates to the computer.

Buzz noticed an electrical meter was fluctuating, but Neil suddenly discovered they had a bigger problem. Eagle's landing radar wouldn't begin operating until they descended to between 40,000 and 35,000 feet. Until then he needed to compare the time they arrived above familiar hills and craters with estimates that had been worked out previously. In doing this, Neil discovered that they were ahead of where they should be.

Armstrong: 'OK, we went by the 3-minute point early. A little off.'

Aldrin: 'Rate of descent looks real good. Altitude - right about on.'

Armstrong: 'Our position checks downrange show us to be a little long.'

Mission Control: 'Roger. Copy.'

The unexpected increase in speed Bales had noticed had now become apparent to Neil as he realised they were around three seconds further along the flight-path than they should have been. As each second equated to one mile, this meant they would be touching down at the far tip of the landing ground. They were heading towards the region Stafford had said was littered with rocks. Unknown to the crew or Houston, when the LM had undocked, oxygen escaping from the tunnel had given Eagle a slight shove. Neil had tried to cancel any residual rates of motion, but the tunnel vent and other manoeuvres had put him slightly ahead.

For the moment, however, he had other concerns. After passing over the crater Maskelyne-W he began to roll the spacecraft over by 180 degrees so that they would no longer face down but directly up. Initially this took much longer than expected, but once Neil adjusted the hand controller they began turning more quickly until they were looking straight up into space. They were now less than 40,000 feet above the Moon, low enough for the landing radar to begin sending information to the computer. In trying to estimate their height, the guidance system disagreed with the figures supplied by the radar, differing by 2,900 feet. Focusing on the instruments, Buzz reported the difference to Neil.

Aldrin: 'Delta-H is minus 2900. [D, or delta, stood for difference, and H for height.] We got the Earth right out our front window.'

Mission Control: 'Roger. We copy.'

Aldrin: 'Got the Earth right out our front window.'

Armstrong [to Aldrin]: 'Sure enough.'

While Buzz had set his microphone to 'vox', transmitting everything he said, Neil's was on 'push-to-talk', so that Houston only heard his words when he wanted them to. At one point during training, Neil's reluctance to share everything with the world had led him to mutter a comment to Buzz about 'that damned open mic of yours'.³¹ Pushing the transmit button on his hand controller, Armstrong asked Houston to assess the difference in their altitude estimates. While managing a stream of data from the rendezvous radar, the computer was now also accepting updates from the landing radar. Neil and Buzz had the option of telling the computer to ignore the rendezvous updates, but they didn't choose to do this following advice received in training. However, the training had been devised for Apollo 10. With no intention of landing, Stafford knew he would rendezvous after a relatively short flight. He had no desire to switch the radar off and never got low enough for the landing radar to pose any problems. Eagle's computer was now receiving data from both radar systems at once. When Buzz gave it the additional task of looking at the difference between the two altitude estimates, it began to perform a combination of tasks that had not been tried before. In checking the spacecraft's current position, firing thrusters and setting the forward trajectory, the computer was running out of spare capacity, and at five minutes into the burn it triggered a yellow warning light along with an intermittent alarm.

Armstrong [to Houston]: 'Program alarm.'

Mission Control: 'It's looking good to us. Over.'

Armstrong [to Houston]: 'It's a 1202.'

Aldrin: '1202.'

Armstrong [to Aldrin]: 'What is it?'

On the ground, Bales - who had been preoccupied with the navigation error - now needed to work out how much trouble the computer was in. He quickly talked over the internal radio loop to Jack Garman, his backroom specialist, who told him that 1202 was a reference to 'executive overflow'. The computer was struggling to complete some of its tasks, just as had happened prior to the 1201 alarm during training. To Neil and Buzz, however, the alarm code was unfamiliar, and Armstrong was forced to break his concentration and pay close attention to the spacecraft's systems. Without knowing what the problem was it was impossible to know how much danger they were in.

This time, unlike the training session, Bales looked at whether there were any actual problems with the guidance and navigation data. The telemetry suggested that everything seemed to be working well. Since the computer hadn't crashed altogether but had simply returned to the top of its list of tasks, Bales decided the alarm could be ignored. The computer could still function - as long as it wasn't pushed any further. If it began to trigger successive alarms he knew they would have to abort. Armstrong didn't know if they were at that point already, and Buzz later said that 'hearts shot up into throats while we waited to learn what would happen'.³²

Bales told Kranz that the mission could continue, and Kranz instructed Duke to give the go-ahead to the crew.

Mission Control: 'Roger. We're go on that alarm.'

With Eagle now down to 27,000 feet, less than 30 seconds later the alarm rang out again. This time Buzz realised it sounded whenever he asked the computer how far they were from the landing site.

Aldrin: 'Same alarm, and it appears to come up when we have a 16-68 up.'

Mission Control: 'Roger. Copy.'

Armstrong [to Aldrin]: 'Were we - were - was it [their delta- H] coming down?'

Aldrin: 'Yes, it is coming down beautifully.'

Mission Control: 'Eagle, Houston. We'll monitor your delta-H.'

The spacecraft was flying at 800mph, at an altitude of three and a half miles. Now that Houston was easing its workload, the computer was free to begin the next phase of the landing sequence. At six minutes and 25 seconds into the burn the digital autopilot slowed the engine. Still flying horizontally, feet first, Neil would soon have to slowly pitch up so that Eagle assumed more of an upright position.

At home in Houston, Janet Armstrong and 12-year-old Ricky sat on the floor listening to the television while studying lunar maps and diagrams. Thinking of Neil standing up like a trolleybus driver as he flew towards the surface, Janet excitedly called out, 'Come on, come on, trolley!'³³

In Mission Control, Jay Greene - his quickfire Brooklyn accent cutting across the radio loop - told Kranz that the trajectory looked good. At 5,000 feet above the ground Neil got ready to take over from the digital autopilot, and with less than four minutes remaining he briefly tested the hand controller. Satisfied with its response, he focused on the view ahead. The surface was filling more and more of his window as Eagle approached a vertical position, the Sun now directly behind them. At 4,000 feet Kranz polled the controllers ahead of the landing.

Mission Control: 'Eagle, Houston. You're go for landing. Over.'

Aldrin: 'Roger. Understand. Go for landing; 3,000 feet.'

Mission Control: 'Copy.'

Aldrin: 'Program alarm - 1201.'

Alarms sounded a total of five times during the descent. They did not recur frequently enough to prompt an abort but they were a major distraction for Neil. The computer was bringing them down on a specific trajectory and would not swerve from its course despite the fact it couldn't tell whether it was taking them towards rocks or a crater. Neil needed to keep an eye on where they were heading. Yet as much as he wanted to monitor their descent, each time an alarm went off he was forced to look down at the instruments to see if everything was all right. As a result he missed many of the landmarks he had memorised. 'I just didn't get a chance to look out the window,' Armstrong later said.³⁴

Armstrong [to Houston]: '1201.'

Mission Control: 'Roger, 1201 alarm. We're go. Same type. We're go.'

Aldrin: '2,000 feet; 2,000 feet.'

Armstrong [to Aldrin]: 'Give me an LPD.'

After interrogating the computer, Aldrin obtained a landing point designator angle of 47 degrees. By looking at this angle on the scale etched on his window Neil could see where the computer was leading them. As they came down to just a thousand feet above the surface, again there was a program alarm and again Neil was forced to shut it out of his mind as he focused on the landing. With the fuel decreasing all the time he couldn't afford to spend time on a problem that wasn't critical. The computer was bringing them down just short of a crater that was the size of a football field and surrounded by boulders, most of them as big as cars. The LM would survive a landing on sloping ground but rocks could damage its legs or tear open its fragile skin.

At around 600 feet Armstrong activated the hand controller and, following the pilot's maxim of 'when in doubt, land long', cut his rate of descent and tipped Eagle forward slightly. Flying the spacecraft like a helicopter, Neil allowed the main engine to carry them across the dangers below, at a speed of 40mph. Now entering the dead-man's box, if the engine failed there was little he could do about it. Come what may, in less than three minutes the limited amount of fuel would force him down. Yet looking at the ground ahead Neil still didn't like what he saw.

Armstrong [to Aldrin]: 'Pretty rocky area.'

Ignoring the difficulties below, Buzz continued to support Neil with a constant account of their progress, his life now in Armstrong's hands.

Aldrin: '600 feet, down at 19 [feet per second].'

Aldrin: '540 feet, down at 15.'

Aldrin: 'OK, 400 feet, down at 9; 58 [feet per second] forward.'

Armstrong [to Aldrin]: 'No problem.'

Aldrin: '350 feet, down at 4 ... 330, 3½ down. OK, you're pegged on horizontal velocity.'

Uncertain where he was and running low on fuel, Neil finally spotted a suitable area, sandwiched between more craters and another boulder field. By now 'quite concerned' about the fuel level, he still had some distance to cover to reach safety.³⁵ 'I was being absolutely adamant,' Armstrong later said, 'about my right to be wishy-washy about where I was going to land.'³⁶

In Houston, Janet put her arm round Ricky's shoulder as she sat with a hand over her mouth. To most TV viewers there was barely any indication of just how much pressure the men were under.

As he cleared an 80-foot crater, Armstrong was still covering a greater distance horizontally than vertically. At less than 100 feet, with dust being blown aside and obscuring his visibility, he faced a multitude of competing demands. He needed to be edging forward at the moment of landing in order to stay clear of the dust kicked up by the rocket exhaust. The rate of velocity must not be fast enough to risk damaging the legs, and he would have to avoid a slope of more than 15 degrees. He could not land while drifting sideways, and he must avoid craters. At the same time he must remain aware of their abort options, his position relative to the Sun, and the fuel rate called out by Buzz. Above all he had to come down soon.

In Houston, the controllers could see the LM's odd trajectory and could not understand what was happening. Why wasn't he landing? Bob Carlton's figures showed there was just 5 per cent fuel remaining. In his relaxed southern drawl he called 60 seconds, Duke passing on the message. Later, Charlie Duke said the atmosphere was so tense you could have cut a chunk out of it. Anxious to do what he could to help the crew, at one point he was jabbed in the ribs by Deke who muttered, 'Shut up, Charlie, let 'em land!'³⁷

Leaning against a doorframe in her living room, Joan Aldrin dabbed her eyes with a tissue.³⁸ In homes around the world millions of people listened to the sound of one of the spacemen calmly reading out some numbers, everything apparently going smoothly.

Aldrin: '40 feet, down 2½. Picking up some dust.'

There was no mistaking that comment by anybody: the Moon was real, and at last so was the chance of landing on it.

Aldrin: '30 feet, 2½ down. Faint shadow.'

Aldrin: '4 forward, 4 forward. Drifting to the right a little. OK. Down a half.'

Aldrin: '20 feet, down a half; drifting forward just a little bit. Good. OK.'

In Houston, Carlton counted down the seconds as the fuel supply reached a critical level. To Kranz he sounded completely unperturbed, as if 'out picking cotton'.³⁹ Other than Carlton, the MOCR was silent, the rest of the controllers almost not daring to breathe as they helplessly waited for Eagle to land. Carlton reported there were just 45 seconds remaining. No-one reacted. Kranz knew the crew must now either abandon it or come down immediately. He didn't know how high they were when they'd started picking up dust, but since they must be within reach of the surface he had to accept that the final decision was Armstrong's.

Fifteen seconds later, Carlton spoke again, and again Duke passed on the warning.

Mission Control: '30 seconds.'

Armstrong [to Aldrin]: 'Forward drift?'

Armstrong was struggling to see the ground through the clouds of dirt rising up from the surface. He was a little confused, he said later, about Eagle's sideways motion and he tried to focus on anything that appeared to be static. 'I could see rocks and craters through this blowing dust,' he recalled.⁴⁰

Aldrin: 'OK.'

Suddenly a blue light on Armstrong's instrument panel lit up as one of the six-foot probes beneath Eagle's landing pads made contact.

Aldrin: 'Contact light.'

Armstrong [to Aldrin]: 'Shutdown.'

The right and forward landing pads reached the ground simultaneously as Neil brought Eagle smoothly down to the surface. He had intended to let the LM fall the last three feet but he didn't have time to switch the engine off early, as planned.⁴¹ 'It just settled down like a helicopter on the ground and landed,' Armstrong later said.⁴²

Aldrin: 'OK. Engine stop. ACA out of detent [the hand controller needed to be put in the correct position].'

Armstrong: 'Out of detent. Auto.'

Aldrin: 'Mode control, both auto. Descent engine command override, off. Engine arm, off; 413 is in [a reference to an AGS program].'

Armstrong [to Aldrin]: 'Engine arm is off.'

Neil, the soft-spoken auditor's son from small-town America, had landed on the Moon. It was later established that he had more fuel than he thought (which wasn't registered due to sloshing in the tanks). Nevertheless Armstrong had enough for only another 25 seconds of flight. Now, his immediate task was to confirm the landing for the benefit of everyone listening in. Reluctant to say 'Houston, Eagle, Eagle has landed', he had decided in advance what he was going to say and had warned Charlie Duke.

Duke: 'We copy you down, Eagle.'

Armstrong: 'Houston, Tranquility Base here. The Eagle has landed.'

Still wearing their helmets and gloves, Armstrong and Aldrin smiled at each other and warmly shook hands. Buzz later said, 'I had known what he was going to say, but he had never told me when he was going to say it.'⁴³

While Buzz's emotional reaction to the landing was 'quickly suppressed', in Joan Aldrin's front room everyone burst into applause - everyone other than Joan, who left them to it and walked into Buzz's study in search of privacy.⁴⁴ In the Armstrong household, Janet and Ricky hugged each other in delight.⁴⁵

In New York, an announcement was made at Yankee Stadium, where 16,000 people cheered and sang 'The Star-Spangled Banner'. In Moscow, cosmonauts - including Alexei Leonov, who had performed the world's first EVA - heard the landing on television and applauded their rivals' achievement. In Britain, TV viewers were glued to the country's first all-night broadcast, including coverage of jubilant scenes in Trafalgar Square. In Japan, Emperor Hirohito also followed the landing on television, and later cancelled his plans in order to watch the moonwalk. It was 3.17pm in Houston, where cheering and applause in Mission Control's viewing gallery took the controllers by surprise. 'There's nothing in training that prepares you for that second,' Kranz remembered.⁴⁶ John Houbolt, hoping the world would freeze at that moment, was congratulated by Wernher von Braun amid a frenzy of flag-waving and back-slapping. The euphoria threatened to catch on in the MOCR, but between them Slayton and Kranz brought the noise back to an acceptable level so that the team could establish whether Eagle was in any immediate danger.

Duke: 'Roger, Tranquility. We copy you on the ground. You got a bunch of guys about to turn blue. We're breathing again. Thanks a lot.'

Duke slumped back in his chair and grinned at Slayton.⁴⁷

Armstrong: 'Thank you.'

Duke: 'You're looking good here.'

Armstrong [to Aldrin]: 'OK. Let's get on with it. [To Houston] OK. We're going to be busy for a minute.'

They needed to quickly check that the LM was safe. If an emergency rendezvous were needed Eagle would have to launch within the next 12 minutes, before Columbia flew out of reach. Prior to the mission, it had been agreed to make two successive decisions at this point as to whether it was safe to stay. Less than two minutes after the landing, the flight controllers quickly checked the LM's systems before announcing all was well. They confirmed their decision seven minutes later, after a more detailed study of the telemetry. Once Michael passed out of range he would not return for another two hours, so for a little while yet at least Neil and Buzz had the Moon to themselves.