Moonshot: The Inside Story of Mankind's Greatest Adventure (34 page)

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.