In their own words: the team behind Apollo 11 describe the 1969 mission to the Moon

This escalation of the American space programme required the expansion of Nasa and the recruitment and training of new scientists, flight controllers, computer programmers and astronauts.

John Aaron: I was fresh out of college, and walked into an environment [at Nasa] where everybody was standing around speaking a language I didn’t even understand. It was like I was in a foreign country. I never heard so many acronyms in all my life. I thought: “Wow – now what have I gotten myself into?”

Gerry Griffin: We had a lot of young people, some right out of college, and almost to a person they all excelled. I think because they were young they said: “We have got this task – heck, let’s see if we can make it happen.” It was the lack of fear. It wasn’t the lack of knowing that it was risky – they just weren’t afraid of it.

Margaret Hamilton: Most of us were fans of Kennedy: we all thought he was great. And if [his goal] had to do with exploring and discovering, how could we not? And how could we not do it by the time he wanted us to do it? Of course, it took a lot of nights and weekends, but we just had to fulfil that.

The Apollo 11 spacecraft comprised three sections: a command module named Columbia, incorporating a cabin for the astronauts, Neil Armstrong, Buzz Aldrin and Michael Collins; a service module, which provided propulsion, oxygen, water and electricity; and a lunar module, named Eagle, which would land on the moon and then carry the astronauts back into lunar orbit. The mission was overseen by the Mission Control Center in Houston, Texas.

GG: The Apollo 11 crew was made up of three really interesting guys. Neil was a great pilot. He was quiet, and didn’t really have a lot to say, but had a great sense of humour. He was a cool guy, really cool. He showed that when he had to eject out of the LLTV [lunar lander training vehicle] at Ellington [astronaut training centre]. He ejected, and then in the afternoon he was in his office. Most people would have been trying to figure out whether they were supposed to be in that business or not, but not Neil.

The crew was made up of three really interesting guys. Neil Armstrong was quiet, but had a great sense of humour

Mike, of the three, was by far the most fun guy. He had a loose way of doing things. He was a funny guy, a barrel of laughs to be around. He was the perfect guy to be the command module pilot because he had it all under control.

Buzz was a more complex personality. A brilliant guy, and from all accounts a good pilot. He was the more serious of the three – he didn’t fool around. He didn’t have that gregarious approach to people. He’s still that way, even in his later years; he never changed. If anything, he’s got a little more complex. But all three made a great crew because they figured out how to work together. And they pulled it off.

The descent

Apollo 11 launched from Kennedy Space Center, Florida at 13.32 UTC (Coordinated Universal Time) on 16 July 1969, entering Earth orbit 12 minutes later. After 1.5 orbits, boosters fired it on to a trajectory towards the moon. On 19 July, the craft passed behind the moon and fired its service propulsion engine to enter lunar orbit, from where it would begin the descent to the moon’s surface.

Steve Bales: We heard the command module first because they were at higher altitude, and they reported that things seemed to be going well. They had done a manoeuvre behind the moon to put them at a 50,000-foot altitude from which they would start their descent.

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Charlie Duke: At first, as we got AOS [acquisition of signal], Neil was pretty perceptive with his set of maps that he had, which showed the journey across the moon at certain times before PDI [powered descent initiation]. He said that things weren’t coming up right, according to these numbers. But we were confident, so we gave him a go for PDI.

SB: The high-gain antenna was not locking on. It would lock on and off, on and off. Don Puddy, the communications and environmental engineer, said to try a ‘yaw’, to try to move the vehicle a little bit, and it was enough. We had communications back and could see that things were going pretty well.

The engine hadn’t come on yet. We had about another ten minutes to decide whether to go or no go. And everything looked pretty good. And then there must not have been quite enough yaw, because we got noise like crazy. Data went in and data went out, came back, and we got close to the time when we had to start the engine. [Flight director] Gene [Kranz] asked us all if we were okay, and we said we were. So we started the engine.

CD: Once they started the engine, for some reason the communications got really, really lousy. I was using the call sign ‘Eagle’ for them and ‘Houston’ for us, of course. We had the comm guys, who had us reorientate several times to get better communications, because if you lost data for let’s say 30 seconds, then that was on the edge of an abort. Mission control had to know the status of the systems, had to know the trajectory. So we had to have basic, good reliable communications, and we had to manoeuvre a couple of times to get that.

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SB: We lost the data and everything else for, I think, about a minute. It came back solid; I was looking at my displays, and I was in big trouble because that vehicle was going toward the moon at 20 feet per second faster than it should be, and didn’t know it. The ground radar did – I had that information as well as the computer. I was comparing them, and I said: “Oh, my gosh – if it grows by another 15 feet per second, I’ve got to abort.”

Here was some 26-year-old kid, sitting at a console, who could stop the lunar mission.

JA: Jay Greene [the flight controller] was worried about landing long [because they knew by then that the lunar module was moving faster than they expected it to]. The fuel guy, Bob Carlton, did start working it right away, but as things got tighter and tighter he started getting worried about fuel.

SB: It [the rate of acceleration] did not grow. I was sitting there praying, because at some point the landing radar would come on. Sure enough, at 35,000 feet the landing radar came on and said: hey, you’re going too fast. So we told the computer that the radar was right. At that point, I thought my problems were over for the day – but my problems were just starting.

The alarms

CD: Then we started having computer overloads. That was the shocker for me – when crew said 1201 alarm, 1202 alarm. I thought: “That’s it – we’re not going to land.”

SB: We got this 1202 [program alarm]. I thought: “What? 1202?” The crew saw it four seconds before we did, because we were running about four seconds behind. 1202. I was frantically trying to remember what the ‘blank’ it was.

GG: Thank god the descent team had simulated just before [the mission]. They aborted a simulation run, in fact, and it made them tune up what the computer could and couldn’t do.

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SB: The last simulation we ran before the Apollo 11 mission, we were in the control centre, cruising the vehicle. Halfway down through the descent, we got a similar type of alarm, called a 1210, which meant that two things were trying to talk to the computer at once. I called an abort. At the debriefing we had after every simulation, we got in a big technical argument with the simulation supervisor, [who said] “I don’t think you should have called that abort.” I said: “Well, you’re not right.” Gene came up to me and said, “Steve, I want you to have a new mission rule set that covers all these unexpected alarms.”

So I assigned my backroom guy, [computer engineer] Jack [Garman], who was an expert in software, and he came back about a week later and said: “Steve, here are the rules.” I went through them with him one by one and I signed them off. If we hadn’t have done that, I don’t know what would have happened. We might have gone on, we might have not, but boy, was it helpful. It was the last thing in the world I thought we would have had.

Jack, after about ten seconds, who had been frantically looking through his notes, says: “Steve, it’s one of those – if it doesn’t happen too much, we’re go.” I looked up at my other displays, which said we were at the right altitude. We now knew how fast we were going toward the moon, and I said: “Flight, we’re go on that alarm.” We caught it just in time, because it took us 15 or 16 seconds from the time it happened. That’s an eternity.

CD: Those alarms kept coming up. We had seen a few of these alarms in training, but nothing as repetitious as it was on Apollo 11. But I never got a sense of panic from the crew. Neil said very little on the descent; mostly it was Buzz Aldrin. We had hot mikes in the cockpit, and every word uttered was transmitted to earth. Buzz was reading out, like I was, all of the information, and Neil was receiving that information, and occasionally would transmit.

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Mission control determined that these ‘executive overflow’ alarms, indicating that the guidance computer could not complete all of its assigned tasks in real time, did not indicate that it was unsafe to continue the descent. At the time, the cause was diagnosed as the rendezvous radar switch being in the wrong position; a 2005 paper suggested that it may have been caused by a hardware design fault.

The landing

CD: So now we’d had two problems: the communications problems and the computer problems. And now, as they pitched over to see the moon for the first time, Neil said: “We can’t land here – there’s a big area of rocks.” So he levelled off and flew over this unsuitable area, then pitched up to slow down and start on his descent. Well, that gave us a fuel problem: we hadn’t budgeted for that kind of trajectory, so we were getting very, very short, [close] to minimum fuel.

Jim Lovell: The landing was kind of hairy, because they were sort of running out of gas. Neil kept changing his landing area, going on forward and forward because he was overflying a large crater of some sort.

JA: It was quite a drama and it wasn’t fake – this was the real drama. We were holding our breath. At the terminal phase [flight controller] Bob Carlton was calling out the fuel reads: “60 seconds, flight.” The crew was calling out numbers, the lunar module was reporting that they could see the manoeuvring system, and Neil was a-hold of the throttle, skating across the landscape. We were about to turn blue. But it did sound like we might not make it.

CD: [I gave the instruction that] he had 60 seconds to land. Then I called 30 seconds, and they still weren’t all the way down, but they were close. According to my stopwatch, 13 seconds later I heard ‘contact engines stop’. We knew they were on the ground, but the tension in mission control was through the roof. I had never felt that tension before in mission control. Everybody was dead silent, glued to their consoles, listening intently.

They were going to land. The abort call is not that you’re out of gas; you’ve still got about 4% left in the descent tanks, and that was to be used to throttle up to 100%, to get a positive rate of climb away from the moon. That 4% could be used to land from 30 feet, and they were 20, 30 feet off the moon, so they were going to land.

Jerry Bostick: In my mind, I thought: okay, Neil, you’re going to have to take over and do this. I was convinced that, even if we had called an abort, Neil’s response would have been: “Say again, Houston?” and by that time he would have been on the ground. I asked him [whether that was accurate] years later, and he said “You’re right”.

He could fly anything. If he had run out of fuel from the main engine, somehow or other he would have figured out how to get it on the ground, without question. He was absolutely the right person for that job. The Apollo 11 crew were the best that you could have chosen. I had less experience working with Mike Collins but he was also Mr Cool. He was in the same camp as Neil. We had great confidence in the crew.

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JL: Armstrong was very calm. He was an engineer, and you could tell that he always thought about something before he said it. He didn’t mince too many words.

GG: I’ll never forget when Neil and Buzz were coming down that final phase. I still get chills [when I think about it]. Buzz was reading out altitude and descent rates to Neil, and between a couple of reads he said “we’re picking up some dust”. I thought, good god, we’re there – we had an engine that was blowing dust off the moon.

That still sends chills up my back. We’re going to make it, and we’ve done it in this decade, just like President Kennedy said we would.

CD: When we got to touchdown it was a great sigh of relief. I quickly said “copy, you’re down” but there was no response right away. And then Neil came back in the coolest, calmest voice you could possibly imagine, and said: “Houston, Tranquility Base here – the Eagle has landed.” I was so excited. If you listen to the transcript, I say: “You’ve got a bunch of guys who are about to turn blue, but we’re breathing again.”

There were only three of us [in the mission] who knew that when Neil landed on the moon he was going to change his callsign from ‘Eagle’ to ‘Tranquility’: Buzz, Neil and me. It was so exciting.

The legacy

When Eagle landed at 20.17 UTC on 20 July, Neil Armstrong announced that its name had been changed to Tranquility Base. Armstrong then became the first man to walk on the moon – an event broadcast to more than 600 million people around the world. After 21 hours on the moon’s surface, Eagle returned to rejoin the Columbia in lunar orbit. The Apollo 11 crew returned successfully to Earth on 24 July, effectively signalling the start of the end of the Space Race.

Michael Collins: The subject of nationalism comes up frequently today, and it is sometimes applied to the Apollo programme. I think that is way wrong. Harking back to the trip that the crew of Apollo 11 took around the world after the flight, before the trip I thought that the overall reaction would be: “Well, you Americans finally did it, didn’t you?” Instead of that, everywhere we went, there was a unanimous: “We did it! We did it!”. That is the part of Apollo I think is really wonderful: no matter what your country or religion, the reception we got was unanimous. We – humanity, we human beings – we did this wonderful thing.

GG: I can remember thinking that what we were doing was important, but I never thought at the time – it took me a while, and then I recognised it – that what we were doing was making history, and such a strong statement of history. I didn’t put it in those terms. I was probably a little young to think through that. Also, it was our job, and we had been assigned to do that.

I felt a lot of pride for the country and for everybody around the world. The world audience was pulling for us (except maybe for a few countries). 1968 had been such a terrible year for assassinations and campus unrest and an unpopular war going on, and I’ve always thought that the Apollo 11 flights stopped that clock for a second and gave people something positive to think about. There was a little bit of hope that maybe things that were hard and difficult and stressful could get done.

This content first appeared in issue 16 of BBC World Histories magazine