Apollo 11 mission: no margin for error

  • Image credit: Apollo Archives
  • Astronauts Neil Armstrong, Michael Collins and Buzz Aldrin (left to right) inside the Mobile Quarantine Facility on the USS Hornet. 'I did not consider our work done until we were safely aboard the aircraft carrier,' Armstrong says. Image credit: Apollo archives
  • Armstrong's IV gloves, worn only for pressurised operations inside the spacecraft. Image credit: Jim Remar, Kansas Cosmosphere
  • The gloves worn by Neil Armstrong during his extravehicular excursion. The left glove features a duties checklist sewn on to the cuff. Image credit: Christopher Griffin
  • Armstrong took this picture of lunar module pilot Edwin Aldrin during their extravehicular excursion. The first man on the Moon and part of the lunar module can be seen in the reflection in Aldrin's visor. Barring a chance meteorite impact, those bootprints on the Moon's powdery surface will remain intact for millions of years.
  • Neil Armstrong's A7L helmet on the Apollo 11 mission, photographed by Christopher Griffith exclusively for PM.
  • Apollo 11 astronauts Buzz Aldrin and Neil Armstrong photograph each other in the lunar lander before (Aldrin) and after (Armstrong) their moonwalk. Image credit: Apollo archives
  • Apollo 11 astronauts Buzz Aldrin and Neil Armstrong photograph each other in the lunar lander before (Aldrin) and after (Armstrong) their moonwalk. Image credit: Apollo archives
  • Flight directors Gene Kranz, Glynn Lunney and Cliff Charlesworth (left to right) watch as the crew begins to explore the Moon. 'We were all engineers,' Lunney says. 'Because we were so busy thinking through what we were doing, and doing it, we didn't have much time to get emotional about it.' Image credit: Kennedy Space Centre
  • Astronauts Charlie Duke, James Lovell and Fred Haise in Mission Control. Only astronauts on the ground communicated with those in the craft. 'The thought was that a crewman in Mission Control would have a better understanding of what the crew was experiencing,' Duke says. Image credit: Kennedy Space Centre
  • Launch Control Centre personnel rise to watch through a window as Apollo 11 lifts off from the pad, 5,6 km away. About 450 people work in the firing room during countdown, including instrumentation controller JoAnn Morgan (third row of consoles, fifth from left). 'It's extremely intense work,' Morgan says. 'When you're going through the countdown and the launch, you're very focused. Everything is pre-planned - it's like a script in a play.' Image credit: Kennedy Space Centre
Date:30 June 2009 Tags:, , , , ,

The untold story of Apollo 11 – in the words of those who were there

It was the most famous step in human history. When Neil Armstrong’s boot first touched lunar soil on 20 July 1969, the event was celebrated worldwide as a triumph for humankind. And yet the hazy television images broadcast from space failed to convey the true audacity – the enormous risks, the technological complexity, the intricate teamwork – of the mission that put two Americans on the Moon.

To mark the 40th anniversary of Apollo 11, Popular Mechanics set out to document the full and unvarnished story. We interviewed more than three dozen flight controllers, engineers, scientists and astronauts, who described their roles from lift-off to splashdown.

PM’s reporting team included Jennifer Bogo, Davin Coburn, Adam Hadhazy, Joe Hasler, Erika Check Hayden, Clara Moskowitz, David Noland and Elizabeth Svoboda.

July 16, 1969 – Launch day
JoAnn Morgan, instrumentation controller, Apollo Launch Control, Kennedy Space Centre: “The pad at night was just glorious to see, with the whole vehicle bathed in these giant xenon lights. Because I got there before 3 am, it was near the very end of the propellant loading; there was a little venting of the liquid oxygen. It was just an enchanting sight to see, and I had the most positive feeling that this launch was going to be successful from the minute I parked my car and walked up to the firing room.”

Jay Barbree, correspondent, NBC News: “I’d been feeding radio spots until about midnight, so I never went home – I slept out there on a cot at Press Site 39.”

William Lucas, director of programme development, Marshall Space Flight Centre: “I was very uptight. We knew that there were thousands of parts that had to work or else we’d be in real trouble. And we knew that once we gave the ignition signal, there was nothing more we could do. It had to go.”

Buzz Aldrin, lunar module pilot, Apollo 11: “I was the last one in, so I was let off the elevator at a landing one stop below while (Neil Armstrong and Michael Collins) were taken up to the capsule. I was standing on the edge of this swing arm looking out at this rocket, and the (ocean) waves coming in quite a bit lower, and the sun gradually coming up, and it was really a very lonely and yet private, peaceful moment before getting into that wondrous white machine that was going to propel us off into history – we hoped.”

Robert Sieck, spacecraft test and launch operations engineer, Kennedy Space Centre: “Since I was the backup engineer, I was not out at the Cape. I could watch the launch with my wife and my one-year-old daughter. The highway was absolute gridlock, and the cars and trucks weren’t trying to move. Everyone was there to watch history. The vendors were sold out of everything – no more T-shirts, caps, buttons or pins. People were pulling plugs of grass from the side of the road and stuffing them in zip-lock bags as souvenirs.”

Barbree: “We’re in the countdown, and I felt this little tap on my shoulder. I turned around and looked up and it was Jimmy Stewart and his wife, Gloria. And he said, ‘Is it all right if we watch from here?’ And I said, ‘Mr Stewart, you watch from wherever you want to’.”

Morgan: “It’s quite a physical experience, an Apollo launch, because it’s such a slow lift-off – and then the shock waves hit you. We could feel it happening in the firing room because we had these shutters and they would flap back and forth, rattle, and the consoles would vibrate.”

Lucas: “The stack of the Saturn V weighed a little over six million pounds (2,7 million kilograms), so we had about 7,5 million pounds of thrust at lift-off. When you see it lift off, it looks like it will never clear the tower. But as it burns away fuel, it gets faster – the weight at lift decreases, therefore it picks up speed. It ultimately gets up to about 24 000 mph (38 000 km/h) to get into the lunar trajectory.” Barbree: “As soon as they had translunar injection, we all ran like scared rabbits to the airport, where we had a jet chartered for the news media. We flew directly to Houston.”

Coasting to the Moon
Once the Saturn V cleared the tower, responsibility transferred from Launch Control at Cape Kennedy to Mission Control in Houston. After entering its second Earth orbit, the third stage reignited, sending Apollo 11 toward the Moon.

Jack Garman, group leader, programme support group, Apollo Guidance Software Section: “In the Mission Control Centre, they had kind of a congressional layout – the flight director was the president; then there were various positions in the main control room that handled different functions, and each of them had staff support in adjoining rooms.”

Gene Kranz, flight director (FLIGHT), White Team, Mission Control: “We always operated with four teams during the lunar missions. We did this to balance the training workload, and because shifts are pretty long so it gives ’em a break.”

Steve Bales, guidance officer (GUIDO), White Team, Mission Control: “We were all in the 25- to 28-year-old range, except for Gene, who was 35. People who were drawn to Nasa at the time were younger; it wasn’t as if anybody had done this particular job before. The crew, they were all 38, 39, 40 – seemed a lot older to us. Or at least to me, anyway.”

Neil Armstrong, commander, Apollo 11: “I was 24 when I joined NACA – later Nasa – and was given very challenging work both as a pilot and as an engineer in flight research. I was confident that men of that age could do the job. Additionally, this new Space Age required people who understood digital computers, and most of the people in that category were in their 20s.”

Garman: “Nobody knew much about computers in those days – and nobody knew much about flying spacecraft, either. If people thought, ‘Are a bunch of young kids gonna screw up this mission?’, we never heard it.”

Chris Kraft, director of flight operations, Mission Control: “On the way to the Moon, you might say, ‘Well, that could be a pretty boring time’. But that’s not true. There were times when you had to do things with the fuel cells, when you had to get rid of the water in the system. You’re making sure the thermal operation of the spacecraft is being done well. On Apollo it was called barbecue mode.”

Hugh Blair-Smith, software engineer for the Apollo guidance computer, MIT Instrumentation Laboratory: “For the long three days from the Earth to the Moon, they had to keep the spacecraft rotating just like a pig on a spit so the Sun wouldn’t be concentrated on any one side.”

David Reed, flight dynamics officer (FIDO), Green Team, Mission Control: “There’s a lot of outgassing from the service module – venting stuff overboard. That will change the trajectory. If you’re going 238 000 miles out, and walk up to the side (of the craft) and even blow on it, that slight movement will be multiplied by a lever 238 000 miles long.”

Hal Loden, lunar module control officer (CONTROL), Black Team, Mission Control: “You don’t want to hit the Moon, but when you do miss it, you want to miss it at the right altitude and inclination so that you’ll go into orbit.”

Reed: “So we’ll track it for a while, notice the trajectory is changing, and make a mid-course correction.”

John Llewellyn, retrofire officer (RETRO), Green Team, Mission Control: “In those days, we didn’t have GPS and all that stuff. The crew didn’t have any of that, either. They had almost the same thing Columbus had – a sextant and a star field.”

Aldrin: “Because of the significance of the mission, we didn’t want to have any distractions in case we had other distractions that really required our attention. We had them take any extraneous experiments off the outbound leg, so we could concentrate on the midcourse corrections, the platform alignments, the reports, sleep and meals – things we really had to be doing.”

Doug Ward, Nasa public affairs officer: “In Mercury and Gemini nothing was released live – not even the air to ground. But once they got 10 or 20 thousand miles from Earth (on Apollo 8), they were in continuous contact. From that point on, all of the communication was live.”

Armstrong: “In all of science fiction – Jules Verne, HG Wells and others – no writer had ever envisaged that lunar explorers would be in communication with people on Earth or, even more surprisingly, be able to transmit still pictures or moving images back to Earth. So we understood that was an important component of our flight objectives.”

July 20, 1969 – landing day
A pair of lunar orbit insertion burns put Apollo 11 into orbit around the Moon. On the eleventh revolution, the White Team assumed the consoles in preparation for descent.

Kranz: “I remember very clearly when I left the house. I had my fresh haircut, and my wife had packed me a sack lunch that was enough for three shifts of people. As I arrived at my parking spot at (the Manned Space Flight Centre), I realised I didn’t remember driving through Clear Lake, or anything else. I was so preoccupied I was on autopilot.”

Bales: “When we came in that morning, the lunar module was dead. We had to power it up, get the thing aligned and checked out. In the simulations, that’s where we’d always had the biggest difficulty, really. We had never completed without some major problem – and I don’t know if we ever completed successfully in training – what we called a power-up and initialisation of everything, and then gone ahead and done a landing.”

Sy Liebergot, electrical, environmental and communications officer (EECOM), Black Team, Mission Control: “We had both the descent team and the ascent team in the Control Centre at the same time. If we had to abort and get off the lunar surface, the descent guys would move off the console and we ascent guys would move into position to perform the part of the mission we were specially trained for.”

Kranz: “I indicated that whatever decisions they’d make thatday, I’d stand behind them – that we came into the room as a team, and we’d leave as a team.”

Garman: “It got very, very real as (the spacecraft) went around the Moon and got ready to undock. In fact, I remember vividly them locking down the Control Centre. The guards were not to let anybody in or anybody out. Michael Collins in the command/service module performed a separation manoeuvre. Half a revolution later, Neil Armstrong and Buzz Aldrin, in the lunar module, executed a descent orbit insertion burn, which allowed gravity to begin to pull the vehicle toward the lunar surface.”

Aldrin: “At that point, we’re manoeuvring to go backwards, engine first and face-down, in the attitude where we’re going to start the powered descent.”

Joe Gavin, director, Lunar Module Programme, Grumman Aerospace Corporation: “The whole thing was tense, because we were basically aircraft designers. In the aircraft business, you always flight-tested something before you delivered it. In the case of the lunar module, you couldn’t flight-test it. Every launch was a brand-new vehicle.”

Ward: “All the way down, we kept losing communications and it would come back and we’d lose it again. I was right on the edge of my seat, thinking, ‘You know, we’re gonna abort for that’.”

Kranz: “We gave ’em the go for the start of powered descent and, doggone it, right at the time the engines started, we lost data again. We picked it up momentarily thereafter, and very shortly after that a guidance officer indicated we had some trajectory perturbation. In fact, he said, ‘We’re halfway to our abort limit’. Well, that is sort of sporty before you even start down to the surface.”

Aldrin: “We’re about a minute, maybe two minutes, into powered descent, face-down, and Neil says to me, and the Earth, ‘I think we’re gonna be a little long’. I said to myself, how in the world can he really, at this point, tell that we’re gonna be a little long? But sure enough, we were.”

Armstrong: “Prior to igniting the lunar module’s descent engine to initiate the trajectory toward the lunar surface, I had been timing our angular rate over the craters on the surface below to calculate our altitude. I noted that, at ignition, we were somewhat west of our intended starting location. I inferred that our entire trajectory and landing point would be somewhat west of our landing spot.”

“I’ve learned that, whenever Neil says anything, you’d better pay attention because there’s good meaning to it.”

Bales: “The lunar module could do a lot of things independently, but it had to rely on people on the ground to tell the computer where it was starting on its landing position. On the back side of the Moon there had been some venting – some perturbations unknown to us. The time we gave them to light the engine was about four or five seconds late.”

Aldrin: “There comes a point in the checklist where we yaw around so that we’re face up, then pitch forward a bit before we throttle down. The purpose of doing that is to get the landing radar to lock on to the surface at about 30 000 feet (9 000 m).” Bales: “As soon as it locked on, the radar saw that we were going a little bit fast in radial velocity and corrected the computer. At the time, I thought our worst problem was over. It turned out our worst problem was just about to start.”

Aldrin: “We got the first 1202 alarm. So we look at each other, and we know it’s in the guidance and navigation dictionary, but rather than try and get it out while the module is making a powered descent, Neil asked them what’s the reading on the 1202 alarm. Then we got a 1201.” Charlie Duke, astronaut, capsule communicator (CAPCOM), White Team, Mission Control: “I was shocked. Actually, ‘stunned’ is a better word. I started reaching for my guidance and navigation checklist to see what a 1201 and a 1202 was. And, of course, Steve Bales knew immediately and didn’t hesitate very long to say, ‘We’re go on those alarms, flight’.”

Bales: “I barely heard him. If you listen to the (voice) loops, there’s a lot going on. And then finally the data comes in and we see the 1201, and Jack (Garman) is yelling – I mean, almost literally yelling, ‘It’s okay! It’s okay, as long as it doesn’t keep going on!’.”

Garman: “There was a team of flight controllers whose duty it was to come up with simulation profiles that train the flight controllers and astronauts together to survive and fix things. At one point, they had asked me to come up with a failure that was totally software-related. I did that months earlier, and they stuck that in during one of the simulations.”

Kranz: “Steve (Bales) had never seen this before. During the simulation, they had an abort, which was his call.”

Bales: “There’s a general rule in flight control: if you don’t know what to do, don’t do anything. The problem is, in the middle of a lunar landing, not doing anything is not an option.”

Garman: “Gene Kranz sat us all down and said, ‘I want you to figure out every possible alarm code that can happen in flight so that we’re prepared’. In those days, there was no such thing as desktop computers. So I wrote down all the alarm codes on a sheet of grid paper, with crib notes on what they meant and what our response should be. And I stuck it under the plexiglass of the console I was to sit at. And, lo and behold, one of them – well, a couple of them—popped up during the actual landing.”

Don Eyles, software engineer, lunar module guidance computer, MIT Instrumentation Laboratory: “What led to (the alarms) was an obscure mismatch deep in the electronics – two signals that should have been locked together in phase were only locked together in frequency. That hardware glitch involved the rendezvous radar, which really wasn’t needed during the descent to the Moon.”

Aldrin: “I left it on. That turned out to be the main cause, and maybe the cause, of the program alarms.” Eyles: “Based on a random-phase relationship between those two signals, the rendezvous radar electronics were sending pulses to the computer at a very high rate.”

Ward: “The computer was simply saying, ‘Hey, I’ve got more than I can handle but I’m gonna do the important things, so don’t worry about it’.”

Garman: “The problem is that those program alarms set off what is called the ‘master caution and warning’, which is red lights and very large klaxon sounds – if you’ve seen submarine movies, kind of like the klaxon that goes off when they say, ‘Dive! Dive’. And as I gathered from after-flight readings, the heart rates for Neil Armstrong and Buzz Aldrin went up just a bit.”

Armstrong: “The powered descent was the most challenging segment of the flight. The systems were heavily loaded, the margins were slim, and this would be the first time that the entire descent strategy would be fully tested. A decade earlier, while I was flying in the X-15 programme, we learned, surprisingly, that all the pilots, while flying the X-15, had heart rates between 145 and 185. It reflected the mental intensity appropriate for a challenging situation. The Apollo data seemed to correlate well with our prior experience.”

Duke: “I didn’t notice anything panicky, any tension at all in them. We just kept feeding them the information, trying to be as professional about it as possible. I don’t think I was relaying any anxiousness in my voice – I tried not to, anyway – but tension was building.”

Aldrin: “As long as you’ve got communication, Houston knows what (the problem) is, and they have more information, so they’re going to be the ones that call the shots.”

Liebergot: “We weren’t exhaling, but very businesslike. And that’s not to say the job was just ho-hum; it was not. It’s that we, with hearts racing, did our job.”

Eyles: “The final landing phase was the point where the astronauts took over semi-manually to manoeuvre the spacecraft like a helicopter. When I say semi-manually, I mean that the automatic system was controlling the throttle to maintain a commanded descent rate while the astronaut commanded the attitude of the spacecraft in order to scoot along the surface in whatever direction he needed to go.”

Bruce McCandless, astronaut (CAPCOM), Green Team, Mission Control: “Neil was flying, looking for a boulder-free spot. It’s fair to say people were holding their breath. But Neil had a considerable amount of experience in the lunarmodule simulator and in the lunar-landing research training vehicle.”

Armstrong: “Every flying machine has its own unique characteristics, some good, some not so good. Pilots naturally fly the craft in such a manner as to take advantage of its good characteristics and avoid the areas where it is not so good. In the case of the lunar module, surprisingly, it flew much more smoothly than I had expected based on all the simulator work we had done. It was a welcome surprise.”

Bales: “There wasn’t a lot being said, but we had a lot of data. I was thinking, ‘What in the bloody heck is going on?’. Normally, in the simulations, once (Armstrong) got on a path to come down, he killed all the velocities but altitude rate and pretty much just came straight down. But hewasn’t. He had a forward velocity of 20 feet per second. And, of course, that was eating up fuel.”

Kranz: “We got what we call ‘low level’ in the propellant tank. Once we got that indication, we knew we’d have roughly 120 seconds of propellant remaining at a hover throttle setting.”

Bob Carlton, lunar module control officer (CONTROL), White Team, Mission Control: “We had never seen that light, never expected to see it. In all of the sims, we had so much margin, that wasn’t normally a factor.”

Garman: “At that point there was nothing the ground could do except watch. It became a spectator activity. The tension went up noticeably. Very noticeably.”

Duke: “Everybody was glued to his monitor.”

Carlton: “I had a stopwatch. I’m looking at it, and at the same time I’m looking at the altitude, and I can see it’s still a long way down. I didn’t know it, but the guys were flying over a crater. We call up 30 seconds. I’m thinking there’s no way we’re going to make it.”

Kranz: “I’m a Catholic, and in the flight director business, you want all the help you can get.”

Carlton: “When the engine shut down, I had 18 seconds to the point where we would have aborted.”

McCandless: “I was in the control centre as a spectator, sitting right next to Charlie Duke, who was the capcom. Once Neil came back with his transmission, ‘Tranquillity Base here. The Eagle has landed’, in spite of the earlier admonitions to maintain decorum, we burst into spontaneous cheers and applause.”

Duke: “As you can hear in the transcript, I was so excited, “tranquillity” came out, “twank”. I caught myself before I finished the word, “Twank – I mean, Tranquillity. Roger, Tranquillity, we copy you down’.”

Ward: “Kranz immediately got on the loop and said, ‘Everybody settle down. Settle down. We’ve got some critical calls to make, and we’ve got to focus on what’s coming up here’. But in the meantime, we could hear this roar from the viewing room behind us. All of the politicians and top managers and astronaut families and so on were back there behind the glass.”

Aldrin: “It was certainly momentous, but there were no trumpets blowing or cymbals crashing. We’re there, we’re two guys, and we’re not the yippee type. We see something, absorb it, think about it and that’s it, accept the way it is.”

Lunar exploration
After checking the spacecraft’s systems, Mission Control confirmed it was safe to stay on the lunar surface. The Black Team moved into position until the crew was ready to exit the craft – when the Green Team would take over.

McCandless: “After they were given the ‘stay’ call and shut down lunar-module systems, I headed for home, which was about 10 minutes away, to get a bite of dinner.”

Ward: “The original plan was that they weren’t going to get out of the lunar module until the next day. They were going to get eight hours of sleep and the next quote-unquote morning go do the first extravehicular activity.”

McCandless: “But when I was pulling into the driveway, my wife came running out waving her arms. ‘They can’t sleep! Go back!’ So I turned around.”

Milt Windler, flight director (FLIGHT), Black Team, Mission Control: “It was a pretty easy decision. You probably can’t stop them, so why not go ahead and do it? Plus, we were all ready to get on the Moon, too.”

Don Beattie, programme manager, Apollo Lunar Surface Experiments: “One scientist had projected that when the lunar module landed, it would disappear into levitated dust. Even though we landed the Surveyor spacecraft successfully, that was a real concern. Another was that the dust would be pyrophoric – that when they opened the cabin of the lunar module, oxygen would react with dust and explode. There was no way we could be sure until the guys opened up the door and the oxygen flowed out.”

McCandless: “They depressurised the lunar module, opened the hatch and Neil came down the ladder. There was a crude black-and-white TV camera, which transmitted images along the lines of a white blob going down some sort of inclined structure. I remarked, ‘Okay, Neil, we see you now, we’ve got you on TV’.”

Ward: “I was very conscious of the fact that what the crew said was extremely important historically. The commentator stepped on a foot switch that interrupted the air to ground, so anytime we talked it obliterated whatever the crew was saying.”

Barbree: “He gets to the bottom of the stairs, takes a step on the Moon to make sure he can, steps back up and says, ‘That’s one small step for (a) man, one giant leap for mankind’.” *

McCandless: “The first order of business was collecting a contingency sample. Neil was supposed to scoop up whatever was near his feet, the first thing that was handy, so that in the event of an emergency they would have at least something to show for having been there.”

Beattie: “The bulk sample had a different purpose – to make sure that we got a very wide variety of material.”

Chuck Berry, chief flight surgeon, Nasa: “We were concerned about the metabolic cost of working in the bulky suit. The best way to monitor them on the lunar surface turned out to be the change in water temperature in the water-cooled undergarments. We had sensors to measure that, and we could then sort of gauge how far they could go.”

Armstrong: “On the lunar surface, we had both the 16 mm movie camera and the television camera in fixed positions so our surface activities would not be slowed by camera position and setting requirements.”

Harrison Schmitt, astronaut, mission scientist for Apollo 11: “Once an extravehicular activity starts, the crew is going tomove along the timeline and get as much done as they possibly can. Buzz Aldrin was talking about a lot of things that he was checking, like mobility.”

Aldrin: “After the flag was up, I made a point of being in front of the camera just demonstrating different means of moving around.”

Schmitt: “While he was doing that we were all wondering what Neil was doing. Well, Neil was deploying a small set of experiments as well as collecting this very fine and diverse group of rocks and soil. Not only did he get a very wide distribution, but he also thought the box looked a little empty, so at the last minute he filled it with just the dirt, so to speak – what we call the lunar regolith. That sample turned out to be the best, most comprehensive sample of the lunar regolith that was ever taken on any of the Apollo missions.”

Armstrong’s famous words have been the subject of much speculation. Lunar surface communications were voice-activated and subject to interference, so a vowel could easily have been dropped. Armstrong confirmed to PM that he did articulate the “a”

Blasting off the surface
After a 22-hour stay on the Moon, Aldrin and Armstrong prepared to fire the ascent stage of the lunar module to launch back into lunar orbit.

Reed: “My job was to come in prior to ascent, find out where they landed, and use that information to compute their launch time. Then we’d upload that to the crew. When I called the tracking people, the guy at the other end of the line said, ‘Dave, take your pick. I’ve got five different landing sites’. He said we know where the lunar module thinks it landed, where the backup guidance system thinks it landed, where the radars on the ground tracked them, where we targeted them, and now we’ve got the geologists saying a different location.”

McCandless: “In the meantime, Mike Collins in the command module orbiting overhead was tasked to use a telescope to try to locate the lunar module. Poor guy never really got any sleep for trying to find it.”

Reed: “I took my headset off, which is what you do if you don’t want anybody to hear what you are about to say, and told Gene (Kranz), ‘We have a problem – we do not know where the hell they are’.” There was only one way to figure that out. The capcom woke Buzz Aldrin one rev early to do a rendezvous radar check. Because I knew where the command module was and I had the vectors that allowed me to translate back down to the surface, I could find out where the lunar module was. They were off another five miles from anything that we had.”

Gavin: “In my mind, the riskiest unknown in the whole mission was the take-off. When the astronaut pressed the button, a whole bunch of things had to happen. The explosive bolts connecting the two stages had to fire. And then the ascent engine had to be ignited to lift the ascent stage off. And somehow as it left the descent stage, the exhaust from the ascent engine had to go somewhere.”

Owen Garriott, astronaut (CAPCOM), Maroon Team, Mission Control: “The engine on the lunar module has one chance, which must be perfect. People had spent a lot of time back at Grumman doing the design, preparation and testing for it.”

Aldrin: “As I got down on the floor to sleep (the night before), I could see the broken head of a circuit breaker. It was the engine-arm circuit breaker – the one that’s got to be in to get electricity to turn the ascent engine on. Since it was on my side, obviously I would have to take the blame for my backpack knocking against things clumsily and breaking it off.”

Loden: “That circuit breaker allowed the lunar guidance system to start the engine automatically – but there was another way to start the engine. We had redundancy. They would have had to hit a pushbutton manually at T minus zero.”

Aldrin: “It looked as though there was enough left to push (the breaker) in. When the time came, I just said I was going to push it in with a pen.”

Glynn Lunney, flight director (FLIGHT), Black Team, Mission Control: “Once the ascent stage is lit, the vehicle really jumps off the Moon.”

Aldrin: “It was not a gradual lift-off. It was a sudden departure – but without any of the forces that go along with rapid acceleration. Looking out the window, everything was getting smaller so fast that (we didn’t really notice) the craft going through a gradual pitch forward. In order to dock with the command/service module, the lunar module executed a series of burns, bringing the two craft together.”

Blair-Smith: “The lunar orbit rendezvous wasn’t that different from what the Geminis did in Earth orbit. But it was more nerve-wracking because if it didn’t work, where everybody would be left was not going to be very good for them.”

Gavin: “It was an emotional worry that people had. But those of us who were directly involved with the details were always very confident – otherwise we wouldn’t have said we were ready to go.”

The return trip
Two hours after the vehicles docked, the command/service module jettisoned the lunar module. The main engine then fired to send Apollo 11 on a trajectory for Earth.

McCandless: “Lunar orbit insertion was critical to a mission’s success, but it was less critical to the survival of the crew than the trans-Earth injection burn. If you couldn’t get out of lunar orbit, you had a real problem.”

Alan Kehlet, Apollo chief project engineer, North American Rockwell: “Some guy ran an analysis of all the critical events that had to take place and came to the conclusion we didn’t have enough reliability, that it would never work. But we discarded it.”

McCandless: “It pretty well boiled down to the SPS – service propulsion system – engine; that had redundant valves, circuits, actuators, switches. Everything was singlefold redundant.”

Kehlet: “(Apollo 11’s command module) had the bestperforming engine and equipment. We didn’t have a lot to spare, mainly because of cost, so the idea was that you robbed the next vehicle to go to the Cape for equipment you needed. I made sure that 107, the spacecraft on mission Apollo 11, got separated from all that.”

Loden: “Of course, the lunar module stayed in orbit around the Moon and we watched it die. It was like losing a good friend. But it performed its job tremendously well, and we configured certain systems in ways that, after jettison, would give us insight as to how long it could last.”

Carlton: “The name of the game for us flight controllers was to try to learn the outer limits of all of our equipment. Some people called it playing with it, but it was serious business. We wrung that thing out.”

Gavin: “And then the rest of the mission was a matter of waiting until orbital mechanics brought everybody back to Earth.”

24 July 1969 – splashdown
After a three-day coast toward home, the command module separated from the service module and entered Earth’s atmosphere.

Reed: “Coming back from the Moon, you’re coming in a lot hotter than ever before – at 36 000 feet per second. In Earth orbit, it’s 25 000.”

Kraft: “Because the velocity is so high, if you tried to come in directly, the heat-shield requirements would be too great. So what we did was get them into the atmosphere, skip it out to kill off some of the velocity, and then bring it back in again. That made the total heat pulse on the heat shield of the spacecraft considerably lower.”

Windler: “It was (still) so hot that the heat shield was abrading and there was a big ionisation shield all around them. It prevents communication until (the command module) slows down enough for that to stop.”

Clancy Hatleberg, pararescue-man, underwater demolition team 11, US Navy: “The USS Hornet had steamed all night long with the helicopters, the two recovery teams and myself. The sea states were the highest we had ever encountered in any of the simulated exercises that we had performed in preparation.”

Aldrin: “There’s a big solidness to the force as you’re coming into the atmosphere, and it’s gradually decelerating the spacecraft. You could sense a g before it really showed up on the indicator, and by then it’s pretty firm. It’s pushing you toward the back of the couch and down.”

Hatleberg: “I was in helicopter 66. I remember looking out of the cockpit, and I could see we were on the outskirts of a storm: the Sun was rising up above the clouds, but it was dark down below. It was sort of like being caught between night and day. Then all of a sudden I saw this streak coming through the upper atmosphere. It looked like a meteor. And then three chutes opened up.”

Aldrin: “It was a moderate jolt. Then there’s a bit of a sway once you’re hanging there. When you’re actually on the water, there’s a firmness that didn’t exist before; there’s an intellectual knowledge of being supported by something.”

Hatleberg: “Once everything was in place, I jumped into the raft and they lowered the decontamination bottles and the (biological isolation garments) and the mitt that I used to wash down the command module and the astronauts. I gave a thumbs-up to the helicopter when the decontamination was complete and 66 came into position and lowered a net.”

Liebergot: “We didn’t consider them recovered until we saw the astronauts removed from the command module in the ocean by helicopter and step out on the deck of the aircraft carrier. Only then did we celebrate. We were steely-eyed missilemen. That was our deal.”

McCandless: “The whole mission was about as close to perfect as you can get with three human beings onboard and an unexplored terrain.”

George Mueller, associate administrator for manned spaceflight, Nasa: “Looking back, it was really a whole lot of people working on the same problem, making sure the piece that they had would do what it was supposed to do when it was supposed to do it – 10 million pieces and 400 000 people. And every one of those people was very, very dedicated.”

Liebergot: “We were young and we were fearless and, after all, nobody had ever told us young engineers that we couldn’t successfully land humans on another planet. So we did it.”

Along with Nasa historians and archivists, PM would like to thank the following Apollo 11 veterans, whose perspectives were invaluable to our research: Aaron Cohen, Chuck Deiterich, Paul Donnelly, Charlie Dumis, Jackie Smith and Tom Sylvester.

Related material:
* Apollo 11 video: launch, landing and return
* Restored Apollo 11 moonwalk video: see the first steps taken on the Moon as people on Earth saw them on TV.
* Video of the Eagle landing on the Moon.
* Information about the newly restored video from the 20 July 1969 live television broadcast of the Apollo 11 moonwalk.
* Apollo 11 conversations Earth didn’t hear now online.