Category How Apollo Flew to the Moon

On the day after TEI. the J-mission command module pilots took centre stage. The SIM bay cameras used long lengths of photographic film stored in large cylindrical magazines. These were still in the service module and that would be discarded in a few days time to burn up and be destroyed in Earth s atmosphere. The film therefore had to be brought into the command module’s cabin, the only part of the spacecraft that would survive re-entry. To bring it in, the CMP had to perform a spacewalk.

Extravehicular activity (EVA) is the name NASA gave to what everyone else calls walking in space, or on the Moon. At the time of Apollo, it specifically referred to time spent in a spaccsuil when the air pressure outside the suit could no longer sustain life. It was another of those essential techniques for Apollo that NASA had learned during the Gemini programme.

Edward White, on Gemini 4, was the first NASA astronaut to leave his spacecraft. Part of his brief was political: America wanted their spacewalking astronaut to stay out longer than Alexei Leonov had done for the Soviets a few months earlier. White floated on the end of his umbilical and gingerly tried various techniques for moving around outside a spacecraft. Apart from some exertion while getting back into the cramped cockpit, White made EVA appear easy.

When Eugene Cernan attempted to don a jet-powered back pack on Gemini 9. he was the first to attempt to do substantial work during EVA. Cernan quickly found how difficult it w as to maintain control of body position in a completely Newtonian environment. The slightest twist, turn or push against the spacecraft would send his mass flailing away from where he wanted to go. Soon, the stress of his exertions began to take a toll on him, and because the suit could not cope with the heat he was generating, his visor began to fog up on the inside. When he was exhausted, he was called back by his commander, Tom Stafford. Almost unable to see through his visor, he drew7 himself hand over hand along his umbilical back to the hatch. Re­entering the cabin proved to be even more terrifying, as the two crewmen, their suits stiff with the air pressure within, battled to get Cernan far enough down into his seat to be able to shut the hatch over his head.

In the light of wrhat could have been a horrifying incident. NASA began to treat EVA very seriously indeed. During the final three flights of the Gemini programme. Mike Collins. Dick Gordon and Buzz Aldrin refined the techniques needed to work efficiently and safely outside a spacecraft. Handholds and foot restraints were added, a methodical approach was taken to all the movements needed for the EVA. and an underwater training facility was developed to simulate weightlessness.

Eor all the experience that was gained on Gemini, little actual EVA time was logged during the Apollo Moon programme in terms of a crewman floating outside the hatch of a weightless spacecraft. A lot of outside activity wxts logged on the Moon, but this was in a one-sixth g environment that the crews found very pleasant. During the Earth orbit operations on Apollo 9. David Scott and Rusty Schweickarl made tentative forays out of their CM and LM respectively: Scott just putting his head and shoulders out of the CM hatch while Schweickart egressed fully and placed his feet in so-called ‘golden slipper’ foot restraints on the LM’s porch for a test of the life-support back pack that the crews were to use on the Moon.

From Apollos 10 to 14 no crewman left the CM hatch for an EVA, although all crews trained for the possibility that, in the event of a docking problem, they might have to transfer from the LM to the CM via an EVA through the side hatches of both vehicles. When spacewalking finally returned to Apollo on the last three missions, it was something special. When Alfred Worden, Ken Mattingly and Ron Evans w-ent to retrieve film magazines from the SIM bay they became the only humans to have performed an interplanetary EVA.

Preparation for the EVA took a considerable amount of time because the spacecraft was packed with boxes of rock samples from the lunar surface. Also, three crewmen had to get suited up in the confined space of the CM, each methodically helping the other to check the integrity of his suit. Oxygen for all three men came from the spacecraft’s suit circuit with a particularly long umbilical being required to enable the CMP to get to the SIM bay. This made for a cluttered cabin with gloves and helmets floating among loops of hoses while three astronauts clambered into cumbersome spacesuits, two of which, after 20 hours of work in the dust and dirt of the lunar regolith. were extremely dirty.

The CM P carried an additional emergency supply of oxygen from a package his crewmates had brought back from the Moon. The oxygen purge system (OPS) normally sat at the Lop of a crew-man’s PLSS back pack when used on the lunar surface. Its function there was to act as a standby in case of a failure of the suit or the PLSS. If a hole were to open up in the suit or a problem were to occur with his oxygen supply, the OPS could supply oxygen from very high pressure tanks that would give the crewman extra minutes to deal with the situation. Although the back packs w ere jettisoned on the surface, the OPS were returned with the surface crew in case they had to support an EVA from the LM to the CSM. One of the OPS was transferred to the CSM to give their colleague an emergency supply during his EVA.

A television camera and a 16-mm movie camera were mounted on a pole which, once the hatch door was fully open, was inserted into a receptacle in the door so that the EVA could be filmed and Houston could watch a live view of its progress. The spacecraft’s attitude was changed so that the Sun shone obliquely across the SIM bay, but not directly into the cabin. All of the RCS thruster quads were then disabled, except for the one opposite the SIM bay so that minor rotational manoeuvres could still be carried out while the CMP was outside.

When all the crewmembers were safely sealed into their suits, the air in the cabin was expelled to space by opening a valve in the main hatch. Then, once the internal pressure in the cabin had dropped to a very low level, the hatch was opened, venting the last wisps of gas.

“Okay, Houston. The hatch is open." Cernan was now in command of his own mission, Apollo 17. and an EVA expert himself. He kept a close eye on his two rookie crewmen. Jack Schmitt and Ron Evans. Schmitt’s role on the EVA was to stand in the hatch and keep an eye on Evans, look after the umbilical and take the film magazines from him, passing them in to Cernan. Evans was going to manoeuvre himself along the side of the service module.

“Iley, there’s the Earth, right up ahead,” said Evans as he positioned himself in the hatch. “The crescent Earth.”

“Okay, Ron. You’ve got a Go for egress.” informed Cernan.

“Beautiful," replied Evans.

“Okay, and just take it slow," said Cernan. speaking from experience.

The door shielded the hatchway from the Sun. “Man. that Sun is bright," said Evans as he cleared the door. He was wearing a lunar extravehicular visor assembly (LEVA) that had been worn by one of his colleagues on the Moon and brought with them in the ascent stage.

“Pull down that visor, Ron. You’re going to need it,” advised Cernan.

“Yes.” " "

“You’re a long way from home. We don’t want to lose you.’’

The LEVA went over the crewman’s clear helmet to provide additional protection from the light and heat of the Sun. and as an extra shield against micrometeorites. It included two visors that could be pulled down if needed. The inner visor was clear for additional ultraviolet blocking. The outer visor was coated with an extremely thin layer of gold to reject both light and heat. This gold visor has become part of the astronaut’s iconography, being seen in all the most famous images showing a man on the Moon.

On Apollo 16. it was Ken Mattingly who made the EVA to the SIM bay. "Okay. How about if I get rid of the jett bag first?” One of the first tasks was to throw out the trash. All the disposable items they could find were packed into one bag that was jettisoned by gently pushing it into deep space, probably to enter Earth’s atmosphere and burn up a few days later.

“Bye-bye, bag. Okay. Okay, I’ll go out and get the TV.”

As Mattingly squinted in the Sun, he reminded Charlie Duke to bring down his visor too. “Ooh! Charlie, you’ll need the outer visor as soon as you get into the hatch.”

Mattingly manhandled the coils of his umbilical out of the hatch then put the camera pole into its receptacle in the door. He then worked his way along the handles, hand over hand, to the SIM bay, inspecting the side of the service module as he went. Training had shown that the best way to reach the bay was to move along the service module until hovering above the instruments, then use the handholds around the bay to get into the correct position to engage the feet in a restraint. Once there. Mattingly glanced towards where the spacecraf t was pointed and caught sight of the Moon with most of its disk illuminated by the Sun.

“Oh, man. Man, the old Moon’s out there. Okay, going after the pan camera. Okay, here comes the hard cover – gone.’’ He threw the outer metallic cover of the camera cassette away, then removed the soft, inner cover that was held on by Velcro and discarded this too. "Soft cover has gone. Okay. I’m going after the hook.’’ He attached a tether to the magazine as the Sun beat down from his right making him glad he was wearing Young’s LEVA. “Boy. that old visor of yours that outer visor on the glare shield really comes in handy.’’

Mattingly continued to remove the giant cassette. "The pip-pin is out, and I’m throwing it away. Okay, get my feet out. There’s one. There’s two. Okay.” As soon as his feet came free, he involuntarily rotated as if he were doing a handstand on the spacecraft and had to pull himself back in with his hands. With the magazine tethered to his wrist, he manoeuvred across the module towards Duke in the hatch and passed the heavy object across for Duke to send through to Young inside. Mattingly had another job to do while outside. He was to expose an array of test chambers containing microbes directly at the Sun for 10 minutes. This was an ultimately inconclusive experiment to determine the effect of the space environment on microbial growth.

As Mattingly sat astride the service module with his back to the hatch, Duke caught sight of Mattingly’s wedding ring tumbling in the strong sunlight. It had been lost earlier in the flight and they had been unable to find it among the cabin’s many nooks and crannies. By the time he thought to retrieve the ring, it had floated out of his reach and on into the void of space. Duke thought it a shame the ring would be lost forever but elected to say nothing of it to his crewmates because they had other things to concentrate on in this hostile environment. Yet of all the directions the ring could have taken away from the command module, Duke was astounded to see that it was headed directly for the back of Mattingly’s head. He then watched in fascination as it bounced off the LEVA and began a perfect Newtonian path back towards the hatch. Duke was not to be foiled a second time. As soon as the ring came within range, he carefully grasped it.

"Guess what I caught floating out the hatch?” said Duke, gleefully, if somewhat misleadingly.

"What’s that?” asked Mattingly.

“A ring.”

“Oh, is that right?”

“Yeah. I think it’s yours,” laughed Duke. “In fact, it had already gone out and hit you and was coming back when I caught it.”

“Boy, how’s that for luck?” laughed Mattingly

When Ron Evans got his opportunity to go outside his CSM America and retrieve the film cassettes, no one could have been happier about it than he was. Throughout his EVA, he hummed and chatted with a boyish delight. Working away outside the spacecraft, he waved at the camera.

“We see you waving,” informed Houston.

“Hey, this is great!” said Evans, his voice up an octave in the joy of being outside of the cramped cabin where he had been for over 10 days. “Talk about being a spaceman? This is it!”

Evans took a look at the damage that the SM skin had sustained during the flight. "Okay. Beautiful! Hey. the paint on here – it’s a silver paint and it’s just got little blisters on it. You just kind of peel it off with your fingers." Then he described his position between the two worlds. "I can see the Moon back behind me! Beautiful! The Moon is down there to the right – full Moon. And off to the left, just outside the hatch down here, is a crescent Earth." He noticed how the atmosphere scattered the sunlight towards the night side, extending the crescent. “But the crescent Earth is not like a crescent Moon. It’s got kind of like horns, and the horns go all the way around, and it makes almost three-quarters of a circle.”

Having manoeuvred into the correct position, he tried to settle into the golden slippers. “Okay, I’m having a little trouble, right now. just torquing down to get my foot in the foot restraint, for some reason. Okay, the right one s in. And the left one’s in. Hey, pretty stable right here. Let go of both hands? See?"

Happy as he could be. he went after the radio sounder’s cassette. “Okay, let’s try the old cassette. We’ll push down on it until it goes past centre. Ah-ha! I think that was more than [the expected] two pounds of force to come out. but it came out. And I’ve got the film.”

He brought the cassette to Schmitt and then returned for the panoramic camera’s film, all the time revelling in the experience.

“Houston, this is – Let’s see. when you’re EVA, they use your name, don’t they?” He wasn’t simply T7′ now.

“Ok ay, Ron,” humoured Houston. “Yes, sir, we’ll use it, Ron.”

“Houston, this is Ron. okay?” announced a gleeful Evans. “You hear me okay, I guess, huh?”

“Roger. Ron,” replied Houston. “Read you loud and clear.”

“Okay,” laughed Evans. “Oh. this is great. I’ll tell you!”

“Yes, we thought it was Mr. America.” With a pun on the name of the CSM, Houston was gently mocking him, but in his happiness he took it in good heart.

“Well, it is. Something like that. Oh, boy! Beautiful Moon! Full Moon down there. 1 can see the engine bell sitting back here. That’s a pretty good-si/ed thing, Loo. And, of course, the VHF antenna is still sticking out there.”

Evans held up the panoramic camera’s thermal cover for Houston to see. “Can you see that? The thing I’m holding up. It’s the cover that’s on the outside of the pan camera. It’s a thermal cover, see. that covers up the cassette.”

“Roger. Yes, we see it. Ron," confirmed Houston.

“Whooooee!" laughed Evans as he tossed the cover past the camera’s field of view.

Houston noticed. “We just saw’ that cover.”

Humming away to himself, Evans attached the magazine to his wnist and pulled it free. "Out she comes. Nice and easy. This is a heavy son of a gun. Not heavy up here; it just has a lot of momentum to it. Once she starts pulling in one direction, it just takes a lot of force to stop it.”

As he hand-walked his way along the handholds, he noted how the heavy object moved. “Hey. it’s just kind of coming along with me. I’ll just let her do that. Hey, she’s just floating there. Thai’s good. Nice and slow, because you don’t want that
thing banging around too much up there, I don’t think. That’s the way it ought to be done, isn’t it?”

Evans passed the cassette to his colleagues and returned to the SIM bay for the mapping camera cassette. As he did, he found that he was becoming used to the mechanics of getting around in space, and decided to go back down to the SIM bay by aiming his feet directly for the restraint. "You know, I’ll just go backwards down there.” He hummed away to himself as he shimmied down the spacecraft.

"That’s an unorthodox way to enter the SIM bay, but it works. Once you get your feet in there, you almost feel like maybe they might come out, you know,” he laughed. "So I’m not sure you really trust them. The right foot’s in good and tight. Hello, Mom!”

"We see you, Ron. Looking great,” called Houston. The MOCR were enjoying the show too.

Evans then called to his children. "Hello, Jan. Hi, Jon. How are you doing? Hi, Jaime. Let’s see, I’m supposed to rest, though, aren’t I? What would you like to know about the SIM bay? Looks great.”

When compared to the light-hearted and longer EVAs by Mattingly and Evans on the later flights, A1 Worden’s foray to the SIM bay on Apollo 15 was a fast, efficient

affair where, although he enjoyed the experience, he wasted little time on the view. However, as he started to bring the mapping camera’s cassette towards the command module, he paused to look at Irwin standing in the hatch: "Jim, you look absolutely fantastic against that Moon back there. That is really a most unbelie­vable, remarkable thing.” Worden had no camera with him to record this unique interplanetary view, but after they returned to Earth, artist Pierre Mion carefully reproduced the scene in a painting.

When Worden had finished off by making an examination of the SIM bay on Houston’s behalf, he and Irwin got back into the cabin, took the camera pole with them and closed the hatch. As they waited for Endea­vour’s cabin to repressurise, Scott remarked how quickly Worden had undertaken the EVA. "You should have stayed longer.” Perhaps Scott Pierre Mion’s recreation of A1 Worden’s view was aware of how much time he had towards Jim Irwin and the Moon. spent outside on the Moon’s surface,
and here was his colleague’s chance to feel the exhilaration of spacewalking, yet he spent less than half an hour outside. Bui Worden, like so many crewmembers, brought an entirely businesslike attitude to his work. On one level, it would have been nice to have got the job done then spend a little time just enjoying the view’ and the experience. On the other hand, he w-as in a situation that had many possibilities for danger, where a technical problem could quickly develop into a lile-threatening scenario.

The cabin was repressurised from a rapid repressurisation system consisting of three small oxygen tanks that had been topped up prior to the EVA. These w’ere now’ emptied into the spacecraft. Also, the oxygen from the OPS tank was bled out to add to the pressure. The next time the door was opened, the command module would be silling on the waters of the Pacific Ocean.

After the horizon check, and a check of the VHF radio, the crew entered a code to tell P62 that they were about to shed the service module. The spacecraft was then yawed 45 degrees to the left. Since the CM’s thrusters could not impart translation motions, only rotations, it was the SM’s task to manoeuvre clear in order to minimise the risk of a collision.

Jettisoning the service module was an intricate task left almost entirely to automatic systems that not only severed the interface cables and pipes safely, they also ensured that the SM moved clear. However, the SM wns the primary source of power, oxygen and cooling, and inadvertently separating the two modules any earlier in the flight would have had disastrous consequences for the crew. Therefore, as with most other events that occurred only once yet demanded the highest reliability, the SHCS took care of disconnecting the umbilical lines between the two modules, cutting the ties that held them together and controlling the SM’s evasive manoeuvres, all of which occurred in just a few seconds.

The process began when the CMP applied power to the logic circuits of the SECS and armed the pyrotechnic system, connecting dedicated batteries to their control circuits. After the arming sequence was complete, the flip of a switch began the separation sequence. As w’ould be expected, this switch was guarded by a metal cover to avoid accidental operation. The SECS then assumed control. A command was sent to a controller box in the service module. This started a timer to trigger the RCS jets on the SM. ready to move the now unwanted hardware away from the CM after separation. Many systems on board the SM remained active to support the separation process. In particular. tw’O fuel cells continued to supply power for the jettison controller and the thrusters, and to fire the pyrotechnics that severed the steel lies holding the CM and SM together. First the eleetrieal connections across the umbilical w ere carefully disconnected by an arrangement of cams and levers in the CM, powered by a small explosive charge that literally unplugged the cables between the two modules and then another pyrotechnic charge drove a guillotine through all the cables and plumbing that ran between them. On command from the SM’s event controller, each of the three strong tension ties that ran through the heatshicld to hold the twro modules together w’as cut by two separate explosive charges in a manner that allowed springs beneath each of six support pads to push the modules apart.

As the service module came free, its controller fired its jets both to pull it away from the command module and to impart a spin that attempted to stabilise its

motion. On early missions those thrusters that were working to pull it away continued to fire until depletion or failure, but despite these efforts to take the SM well away from the CM the complex dynamics of the remaining propellant in the tanks caused it to turn around and approach the CM again.

During their debriefing, the Apollo 11 crew were asked if they saw their service module.

“Yes. It flew by us," said Mike Collins.

“It flew by to the right and a little above us, straight ahead," added Buzz Aldrin. "It was spinning up. It was first visible in window number four, then later in window number two, really spinning."

This problem w’as cured by shorter separation burns.

After the SM had gone, the crew quickly checked the pressures in their RCS tanks, safed the system that had fired the explosive devices, and checked that their batteries still had enough pow’er for the final leg of the mission. The CM w as yaw ed back 45 degrees in order to face backwards along their flight path and then pitched down to the correct attitude for atmospheric entry. At this point. Collins noted how the weak thrust from water vapour leaving the steam duct interfered with his attempts to yaw. The vapour came from the evaporator, now’ their only means of losing heat. “When I got a yaw’ rate started, the water boiler would fight me, the rate would reduce to near zero, and 1 would then have to make another input."

At this point, in a heads-down attitude with the lift vector up and with everything verified, the CMP pressed ‘Proceed’ on the DSKY to give the autopilot control of their attitude. Its display showed their impact coordinates and a check of their heads – up, down status at wliich point ‘Proceed’ was again pressed to pass control of the re­entry profile fully into the computer’s hands.

Down the side of the PAD form was an area for comments that related to the burn, and in particular the set stars. As ever, the Apollo planners had looked for procedures and methodologies that would give the crews options to continue in the face of equipment failure. The set stars were to provide a backup attitude reference in ease the guidance platform failed to remain aligned to the desired RBBSMMAT.

Although it w’as something of an alphabet soup, the basic idea went like this. As well as the I M lJ with its gyro-stabilised platform, the spacecraft had two other sets of gyros: the body-mounted attitude gyros (BMAGs) and their associated electronics, the gyro display couplers (GDCs) that made sense of their output. Unlike the platform, which measured absolute attitude, the BMAGs really only measured changes in attitude. Therefore to determine absolute attitude, the GDCs had to work from a starting point and count the changes in attitude as measured by the BMAGs. It wasn’t as accurate as the IMU and was prone to drift but it would work for short periods. Normally, the GDCs got their starting point from the IMU merely by a press of the GDC Align button. But if the platform was lost, another way w’ould be needed to give the GDCs a valid starting point. Then, by processing the signals from the BMAGs. they could determine absolute attitude relative to the desired REFSMMAT. The aim of the set stars was to give the GDCs that starting point.

What mission control did was to give the crew two stars – in this Apollo 15 ease, Vega and Deneb – and a set of three attitude angles. To make the backup realignment work, the CMP needed to manoeuvre the spacecraft so that the stars were arranged in the scanning telescope in a predefined manner. This placed the spacecraft in a known attitude. In that attitude, the three given angles represented the spacecraft’s attitude with respect to the desired RBFSMMAT. enabling the

BMAGs and GDCs to work from that attitude as their starting point.

Fortunately, no IMU ever failed in flight and this procedure was never used.

The next comment in the PAD – No ullage – reminded the crew that because the SPS propellant tanks were full there was no need to settle their contents prior to the burn.

When there was a need, an ullage burn by the RCS thrusters forced propellant to the outlet end of the tanks to minimise the possibility of gas from the empty part of the tank being ingested into the engine.

After stating the mass of the lunar module, the comments went on to deal with the problems pertaining to Apollo 15’s faulty circuitry in the primary control bank of the SPS engine. If they could only use the good В bank, the slightly reduced thrust would increase the burn duration by 11 seconds to 6 minutes 52 seconds. It was decided, however, that the crew should let the burn begin under automatic control with the В bank, and then after several seconds manually engage the A bank. Shortly before the expected cut­off, they would disengage the A bank and let the automatic systems terminate the burn with the good bank, lest the short circuit in the A bank override the shutdown command.

The final point in this PAD was that should the В bank itself fail, the crew were to use the A bank manually to achieve the required delta-v and enter lunar orbit. In this case, they would have had to ensure shutdown by the simple expedient of removing power from the SPS which they would have achieved by pulling a circuit breaker.

This lengthy PAD demonstrates how, even on what was considered a ‘nominal’ flight, great lengths were taken by mission control and the crew to provide options to successfully pursue the mission in the face of a wide range of possible failures.

While the commander was Lending to the LM’s guidance needs, the LMP continued his checks with the activation of the communications system. Communications to the CSM were handled by two VHF antennae mounted fore and aft. Communica­tions to Earth, as well as the same ranging and tracking functions as found on the CSM, used either of two low-gain S-band antennae, also mounted fore and aft. For higher data rates, a steerable, high-gain dish was mounted high on the right-hand side of the ascent stage and it included systems to keep itself aimed towards Earth.

For the descent, the electrical power for the LM came from batteries mounted in the descent stage. Originally, the lunar module’s manufacturer, Grumman, had intended to power it with fuel cells, in a manner similar to the CSM and most of the Gemini spacecraft. Managerial and technical difficulties, mostly concerned with the interdependence of the power system with other systems in the already exotic LM, conspired with the race to get the spacecraft ready on time to force a switch to using batteries as the power source. Though heavy, batteries had the enormous advantage of simplicity, and since the LM was intended to be powered for only a few days, their weight penalty was no worse than the fuel cells. As part of the checkout of the LM, their health was closely studied, as were the extra set required for the ascent stage. The ascent stage carried a separate small set of batteries because it had to operate on its own for only a few hours for the trip from the surface of the Moon up to the CSM.

Another major item in the LMP’s checklist was the cooling system. Whereas the CSM used radiators and evaporators to lose heat from a water/glycol coolant, the LM relied on a sublimator to achieve the same task. These devices cooled by having ice directly sublimate to waiter vapour in a vacuum, in the process taking heat away from the coolant. The lunar spacesuits used the same cooling technique. Because the LM had no source of water available as a by-product of fuel cell operation, a large water tank was included in the descent stage, with a smaller supply in the ascent stage. The water/glycol coolant was pumped between the LM’s electronics and the sublimator by redundant sets of pumps. The pressures delivered by these pumps were checked before committing the LM to the surface.

Manoeuvring the LM was effected by a set of thrusters similar to the RCS jets mounted on the service module. Where each cluster of jets on the service module had independent propellant supplies, those on the lunar module had a common propellant system that, if the need arose, could be topped up from the propellant used by the ascent stage’s main rocket engine. As a further difference, the service module’s RCS quads w’ere mounted on the spacecraft axes, while those for the LM were set at the corners of a square around the spacecraft to keep the windows and hatchway clear. Before it could be used, the propellant system had to be pressurised. An explosively operated valve was opened to allow helium gas into the propellant tanks, at which point the crew and mission control could verify that the pressures within the system were as expected.

The spacecraft’s design had assumed that the windows would face forward during the final approach to give the crew a view of their landing site, and that it would pitch into this attitude from a windows-up attitude. If the window’s were facing up, and the landing radar had to face downwards, then its antenna had to be mounted on the base of the descent stage on the side opposite the windows.

“Intrepid, Houston,” called Carr to Conrad and Bean. "You’re looking good at three [minutes].’’

“Okay, Houston," replied Conrad. He w’as waiting for two indicator lights on the DSKY to go out, which would mean that the landing radar was producing valid measurements of their altitude and horizontal velocity. “I have an altitude light out; and I have a velocity light out.”

“Roger.’’

Conrad then looked at the DSKY’s display for a number. "I’m showing minus 918. Minus 1.000. Looks good. How’’s it look to you, Houston?"

The number, called ‘dcita-H’ was telling him that their height, as measured by the landing radar was 1.000 feet or 300 metres lower than the computer’s estimation based on its knowledge of their orbit.

“Roger; it looks good. Recommend you incorporate it,” said Carr as the flight controllers passed on their wisdom.

“No sooner said than done. Let me know witen it converges. I’m going back to my normal displays.” With this declaration that the radar’s height measurement was reasonable, Conrad commanded the computer to accept the radar data, compare it to its current estimation of their height and rate of descent, then attempt to lly a compromise between the two. Having done so. il then revised their trajectory to high gate and repeated the cycle until its estimation of their height converged with the data coming from the radar. This gradually folded the new’ data into the flight path without causing a sudden transient. The delta-H figure on Apollo 12 was small – radar and computer were almost in agreement. Had the radar shown them to be 10.000 feet or 3.000 metres higher than the computer believed them to be. an abort would have been called for because they would have run out of fuel before reaching high gate.

When Armstrong and Aldrin arrived at Tranquillity Base, their flight plan gave them a rest period before they were to embark on their historic moonwalk. NASA’s operational conservatism had not wanted to load them up with too much in one day. But many believed that the crew would be too keyed up to rest at that point and there were tentative plans to bring their EVA forward. One hour after landing. Armstrong announced his decision. “Our recommendation at this point is planning an EVA, with your concurrence, starting about eight o’clock this evening. Houston time. That is about three hours from now. We will give you some lime to think about that."

Charlie Duke promptly gave Houston’s reply. “We thought about it; wre will support it. We’re Go at that time.’’

Aflcr the mission, Armstrong explained their thinking. “There were two factors that we thought might influence that decision. One was the spacecraft systems and any abnormalities that we might have that we’d want to work on; and the second was our adaptation to one-sixth g and whether we thought more time in one-sixth g before starting the EVA would be advantageous or disadvantageous at that point. Basically, my personal feeling was that the adaptation to one-sixth g was very rapid and [it] was very pleasant, easy to work in. and I thought at the time that we were ready to go right ahead into the surface work and [so I] recommended that."

For the most part, crews had their first surface EVA on the day of landing. Apollo 16 was one exception. The 6-hour delay in its landing had changed mission control’s view. “You probably gathered that we want y’all to sleep first," said Jim Irwin in Houston.

“That suits us," said Duke, not entirely honestly. “Jim. I feel exactly like I thought I was [going to feel], I really want to get out, hut I think that discretion is the better part of the valour here.’’

Decades later. Duke regretted the decision. “As a hindsight observation, it wasn’t a good idea. I think we should have gotten out first. I had a tough time getting to sleep. My mind wras just racing and I wanted to get out. I was thinking about all that was coming up; and the excitement had just passed; and. you know, my mind was just whirling. 1 think wn had so much adrenaline pumping we could have gone, probably two days – forty-eight hours – without any problem. So, looking back, I think we made a mistake. But it’s done."

The other exception to EVA on landing day was Apollo 15. They had a SEVA!

SEVA

David Scott’s flight was the first J-mission, the first to have a rover and the first where science defined the mission. Back in 1964, when geology training began for the prospective lunar explorers, Scott’s teachers spotted that, more than the other jet – jockeys that passed through their hands, he possessed a mind that was receptive to scientific enquiry. When his Moon mission came up. his enthusiasm and excitement for Apollo’s scientific quest easily transferred to the other members of his crew, and to those subsequent members of the J-mission crews who, like him, came from a test – pilot background. Don Wilhelms, who played a major part in transforming Apollo into a hunt for geological answers, described Scott, Jim Irwin and Л1 Worden as "the geologic crew”.

Scott had been impressed by the teachings of geologists like Caltech professor Lee Silver and USGS staffer Gordon Swann who had been brought in to give the crews training in field geology, as distinct from the previous classroom instruction. When approaching a new’ geological site, one of Silver’s techniques was to find a high spot, even the vehicle that had brought them there if needs be, to gain an overview of the site before digging into the detail of stones and bedrock. This site survey gave the bigger picture; what the major rock exposures were, what type of rocks they held and at w’hat angle the layers of rock dipped. Scott decided that since there were no plans for an EVA on the day of their landing, he w’ould make a stand-up extravehicular activity (SEVA) instead.

The arguments to convince managers that a SEVA was worthwhile included a need to maintain the crew’s circadian rhythm. At the time, it was felt that a full 7- hour EVA after landing would have meant an excessively long day. Yet. to sleep so soon after arrival would lead to a shorter than normal day. The SEVA would fill the gap and help to release the excitement they would naturally feel at having landed on the Moon. Also, Apollo 15 s northerly site had not been well mapped by the Lunar Orbiter probes whose high-resolution imagery had been expended near the equator. In particular, no one really knew w’hether Iladley provided a suitable surface for the rover, and if significant problems became visible from up top then his descriptions would be useful in revising the planned drives.

From Scott’s point of view, the best reason for the SEVA was the science, as he later recalled. "To be able to stand there and just look at all that stuff. I mean, that was just a mindblower to be able to just stand up there and gaze around and report what you saw% knowing full w’ell that Lee Silver and Gordon Sw’ann and the guys in the Backroom are listening to every word.”

As well as the SEVA, Scott and the geologists wanted to take a telephoto lens. "We spent a lot of time and energy justifying the 500-mm lens,” remembered Scott. "And the final trade-off was in abort propellant. They reduced the amount of abort propellant on the landing by witatever the mass of the telephoto lens w’as. There was a lot of scepticism on whether it would be useful at all. But, gosh, you go out in the field with a bunch of geologists and you can’t get to the mountain and it becomes obvious that a telephoto picture is a lot better than nothing.”

Once he had got his head out of the overhead hatch. Scott began to photograph the virgin site using a 60-mrn lens to take an all-round panorama and then his telephoto lens to capture features of special interest. With that out of the way, he began what, according to Wilhelms, ranked as "the best geological description by an astronaut on the Moon.”

"All of the features around here are very smooth,” reported Scott. "The tops of the mountains are rounded off. There are no sharp jagged peaks or no large boulders apparent anywhere.”

That was good news. They would have little difficulty driving the rover across the landscape as planned. Scott worked his way around the view, describing everything he saw while giving clock-face references with respect to the LM’s west-facing aspect. "As I look on down to my seven o’clock, I guess I see Index Crater here [in] the near field. But, back up on Hadley Delta, to the east [at Silver Spur], why, again I can see a smooth surface. However, I can see lineaments. I’ll take a picture for you.”

The Moon’s immense antiquity drapes almost all its bedrock with a thick blanket of beat-up, pulverised rock. Since bedrock is what geologists like the most, by virtue of it being in situ, any sign of it on the lunar surface gets their attention, especially when they see layering. Scott’s lineaments, on the feature they had happily named Silver Spur for their geological mentor, appeared to be such layering.

"There appear to be lineaments or lineations dipping to the northeast, parallel [to each other]. And they appear to be, maybe, three per cent to four per cent of the total elevation of the mountain, almost uniform [spacing]. I can’t tell whether it’s structure or internal stratigraphy or what. But there are definite linear features there, dipping to the northeast, at about, oh, I’d say 30 degrees.”

Silver Spur was too far away to visit, but with his telephoto lens Scott was able to gain clear images of the structures for the geologists.

For the two later missions, the justifications for a SEVA lessened and it was dropped. Scott would be the only commander to look out of the top of his LM in what Jim Irwin likened to Desert Fox in his Panzer.

SUITING UP

If a crew intended to leave the lunar module soon after landing, their preparations were reduced by virtue of being already suited. In fact, for the first three landings, suits were never removed while on the Moon. Their task primarily involved changing over from the LM’s oxygen and coolant water to that supplied from their back pack, the portable life support system (PLSS, pronounced ‘plies’). Once they had put their helmets and gloves back on, there were a large number of checks to be made.

The LM provided very little room for two crewmen wearing suits with PLSSs attached, so one of the first tasks was to lay out all the items they would need at positions where they could get to them without undue difficulty. They checked their zippers, the double locks that would hold their gloves and helmets in place, then positioned themselves to put their back packs on. The sequence of steps in the process was very carefully choreographed. Among all the unstowing of cameras, boots and other paraphernalia was one important task; to deploy a VHF antenna on the outside of the LM by turning a crank. One of the crew had to manoeuvre to the back of the cabin to get at it. When crews had eight hours or more hard work outside while sealed inside a suit, some food was welcome while an occasional drink was essential, so for the later missions, bags of water and a food bar would be installed within the neckring. Then coatings of anti-fog treatment would be applied to the inside of their helmets.

Before they added their oxygen purge system (OPS) to the top of the back packs, a check was made of the pressure in the oxygen tanks within. Each OPS had two spherical tanks with the gas inside stored at an extremely high pressure. A small gauge was provided to check its value. Depending on how a crewman’s PLSS or suit had failed, the OPS would provide at least 30 minutes of emergency oxygen and cooling by the regulated discharge of the contents of its tanks. In fact, the OPS carried more than three times as much oxygen as did the PLSS itself but the latter was merely recycling the gas in a loop and topping it up as necessary as it was consumed.

As the Apollo 14 crew worked through their suiting up procedures, they reached the point where they had to don the PLSS. Mission control had them call out where in the checklist they were. “Okay, Houston,” called Ed Mitchell. “We’re at that point where we hand the real PLSS out and get the lightweight one.”

Once again, the crews could not help but compare their amazing experience on the surface of the Moon with the endless rehearsals they had put in before the flight. During their training exercises or when they had checked out Ant ares itself, they had used a real PLSS up to the point of donning it, but the back packs were uncomfortably heavy in Earth’s gravity and unwieldy in the tight space of the LM cabin. To avoid damaging flight hardware, the real PLSS would be exchanged for a lightweight mock-up. Ron Blevins was an instructor who would typically make the exchange.

“Roger,” laughed Capcom Bruce McCandless. “I’ll have Ron come on up the ladder.”

Crews did find the LM cabin to be a much more pleasant environment when the one-sixth-g of the Moon ruled the physics of their work. “The only time I found the lunar module really confining was when we started moving the PLSSs around,” remembered Charlie Duke. “We move one of the PLSSs on the floor between us, and we pick it up and put it somewhere else. We’d done that in training and John just struggled to get that thing up, because it was heavy! You know, 155 pounds [70 kg]. They had a lightweight mock-up which 1 think was a little bit lighter. But up there, in that one-sixth g, boy, he just picked it up with one hand. It was just tremendous. It made you feel like Superman.”

With the OPS attached to the top of the PLSS, connections were made between the two, including a feed to the antenna on top through which the crew would keep in touch with each other and Earth. Then they would don the PLSS. “Getting the PLSSs on was very difficult,” recalled Gene Cernan. “It was a two-man operation. The PLSSs were strapped to the side walls, at working height, and you had to back up against yours and the other guy would then unhook it from the wall and help you get it strapped to your back. The LM was so small that it was a very difficult operation, even in soft (unpressurised) suits.”

To control and monitor most of the functions of the suit, a remote control unit (RCU) was attached to the chest. It had a quantity gauge for oxygen; switches that controlled their water pump and fan assembly, and their communications; and there were flags that indicated the status of the back pack. These gave warnings for oxygen, water and carbon dioxide as well as for the suit’s pressure. On the front was a bracket upon which a crewman could attach his Hasselblad camera. Once the suit’s systems had been connected up, it was time for checks of the communications

between each other and with mission control. That’s when Conrad and Bean came unstuck.

The checklists the crews used were very thorough. Every connection and every switch position was detailed for the men to check, and the procedures were practised repeatedly before the mission. The problem for the Apollo 12 crew was that they had done this so many times that they thought they knew it. More importantly, they were used to their training hardware. A1 Bean explained: ‘’The gear used down at the Cape [for training] have the comm switches on them but you don’t have to use them at all for comm.” Hence they did not have to actually operate the switch during training, as Conrad pointed out, “fn training, we always just read it in the checklist and kept on going.”

“Here’s an example of the gear we’re using [on the Moon] not being configured precisely like the gear we use in practice; and that cost us,” recalled Bean. In fact it cost them nearly 20 minutes in a machine whose operational lifetime was measured in hours. Differences between training and flight hardware would bite them again when their TV camera was damaged by being inadvertently aimed at the Sun. The crew had only ever practised with an inert mock-up and had no appreciation of the flight unit’s susceptibility to direct sunlight.

With the final oxygen connections made from the OPS to the PLSS, each crewman took a last long drink from the LM’s water supply before they sealed themselves off by donning their helmets and gloves. Care was taken to ensure their microphones were properly positioned as there would be no opportunity to reposition them once outside. They then transferred the suit’s oxygen and cooling water hoses from the LM to the PLSS and put on their hard-wearing outer gloves. Because they would get no cooling from the PLSS until they were in a vacuum, crews from Apollo 12 onwards made sure to give themselves an extra shot of cooling water from the LM through their liquid-cooled garment before this changeover.

The next step was to make sure the leakage from their suits was acceptable. Rather than build suits that were completely airtight, engineers accepted a slight leak rate in the knowledge that the PLSS supply would be adequate to make up for the loss across the duration of the EVA. This ‘pressure integrity’ check required the suits to be inflated above cabin pressure until the gauges on their cuffs indicated 3.7
to four psi. The oxygen supply was then turned off and the gauge watched for a minute. Their check­list stipulated that they should not observe a drop greater than 0.3 psi, some of which was merely due to them breathing the oxygen or the gas getting into all the nooks and cran­nies within the suit.

Lost air

Once everyone was happy, it came time to let the air out of the cabin, or depressurise, to use the parlance. There were two valves the crew could use to achieve this; one on the forward hatch that led out to the ladder, and the other on the overhead hatch that would lead to the tunnel and the CSM once they redocked. The handles for these dump valves had three positions; open, closed and an intermediate position called ‘automatic’ which was its normal setting in which the valve acted to protect the spacecraft against excessive internal pressure. It remained closed until the cabin’s pressure reached a threshold of about one third of nonnal Earth atmospheric pressure with respect to the outside. It then opened to vent air until the pressure dropped below the threshold.

The procedure for depressurisation was to set the dump valve in its open position and drop the cabin pressure from its normal reading of about five psi until it indicated 3.5 psi and then stop. They then monitored their suits to ensure that they were also dropping to maintain the correct relative pressure. If all was well, the dump valve was returned to the open position until the cabin was evacuated enough that the forward hatch could be opened. When sensors indicated less than 3.5 psi, the EVA was deemed to have begun and Houston would begin to time the crew’s progress.

On Apollo 11, the depressurisation proved to be a lengthy procedure. Unlike subsequent missions, Eagle’s forward dump valve had been fitted with a bacterial filter which halved the rate at which air could depart the cabin. As the amount of air within the LM decreased, so did the pressure that was pushing it through the depress valve and thus the rate of evacuation tailed off. It took about three minutes for the cabin pressure to indicate only 0.2 psi but even this was too high for a crewman to directly open the hatch. It had to get nearer to 0.1 psi. Yet at such low pressures, the cabin began to be replenished by internal sources that further slowed the depressurisation, as Armstrong explained after the flight. “It took a very long time to depressurise the LM through the bacteria filter with the PLSS adding gases to the cockpit environment or something adding some cabin pressure. The second was that

we weren’t familiar with how long it would take to start a sublimator in this condition. It seemed to take a very long time to get through this sequence of getting the cabin pressure down to the point where we could open the hatch, getting the water turned on in the PLSS, getting the ice cake to form in the sublimator, and getting the water alarm flag to clear so that we could continue. It seemed like it took us about a half hour to get through this depressurisation sequence.” To speed up the process on subsequent flights, not only was the filter dropped, crews took to grabbing the corner of the hatch and peeling it open.

The sublimator that Armstrong was referring to was the central element of the PLSS’s cooling system. Water was fed directly to the vacuum where its evaporation and eventual sublimation from ice to a gas cooled a separate water circuit that cooled the crewman. This emission of vapour was the reason that later crews pre­cooled themselves before disconnecting their water from the LM. It was better not to start the sublimators until the hatch was open and a vacuum had been established in the LM.

Once the hatch was fully open, the commander manoeuvred himself onto the floor, kneeling with his feet towards the open hatch. Guided by his LMP, he crawled backwards through the hatch onto the porch, a small platform between the hatchway and the top of the ladder. When Neil Armstrong got onto the porch, he reached to his left and pulled a nearby D-ring which allowed one of the side panels of the descent stage to hinge open. A small TV camera was mounted upside down on the panel and strategically aimed to document his descent into the history books. On

Earth, TV converters at the ground stations had circuitry to flip the image the right way up.

In the expectation that a descending LM was likely to deform the crushable interior of the landing legs and compress them, the lowest step of the ladder was set the best part of a metre above the footpad. However, on all missions, there was little appreciable compression of the gear, necessitating a gentle leap from the bottom step to the footpad in the low lunar gravity. Only then could a boot print be made in the lunar surface.

One particular problem with the rover became a serious nuisance for the Apollo 16 and 17 crews. The commanders on those two missions had a habit of storing their geological hammers in pockets sewn onto the shins of their suit legs. Though they could reach down and grab the hammers when needed, they had difficulty seeing them, given that the chest-mounted RCU blocked their view. Unfortunately, as they worked around the rover, both John Young and Gene Cernan caught the right-rear fender extension with the hammer and broke it off.

Young broke his fender partway through their second day and after that, anytime they drove, they and everything on the rover were showered with dust. Unlike the rubber wheels on the MET which tamped down the soil into smooth ruts, the open framework tyres of the rover lilted dust and threw it into rooster tails. Engineers began to worry when the blackened covers began to warm up the batteries and the dust made the radiators less efficient.

Then Cernan did the same thing on his first EVA. He initially tried to use sticky tape to reattach the fender but dust affected the adhesive and it proved to be less than successful. That night, mission control came up with a repair which Young tested in a suit before he passed the details on to Cernan in the morning. In the LM, Cernan took four maps from a book and taped the stiff cards into one large sheet. He took these outside along with two clamps that were normally used to mount little

utility lights onto the protective frame of their alignment telescope. At the rover, the clamps held the card onto the existing fender’s support structure to fashion what was a very successful repair.

The Apollo programme left behind an archive of data and over a third of a tonne of samples, which, to repeat the publicist’s mantra, really did keep scientists "busy for years” and they have formed the bedrock on which theories of planetary formation and evolution have been built. Prior to the space age, planetary science was in the doldrums, with only blurred photographic evidence to feed scientific curiosity. With Apollo’s scientific harvest, planetary science entered an age in which ground truth – actual rocks gathered in situ could inform new theories and help to sort the wheat from the chaff.

Our current understanding of how the Moon was formed first gained acceptance at a eonferenee in Hawaii in 1984. This idea, chiefly proposed by William Hartmann and Alistair Cameron, has yet to be toppled. It is a story of birth rising out of incomprehensible violence.

Our solar system formed about 4,600 million years ago out of a coalescing cloud of dust and gas known as the solar nebula. Most material ended up in the Sun, but some formed a disk out of which the planets gradually grew, or accreted – a process whereby gravity causes loose material in space to gradually gather into ever larger bodies. The light pressure and solar wind from the new star tended to push lighter substances out to the further reaches of the system while heavier substances tended to remain in the Sun’s vicinity. This created predominantly rocky planets near the Sun. gaseous giants further out, and frozen worlds beyond the point at which even gases become liquid or solid.

About 40 million years after the solar system’s birth, two nascent planets were orbiting the new Sun at similar distances and it was only a matter of time before they met. The larger body, our proto-Earth, received an off-centre impact by a body half its diameter in a tremendous cataclysm. The iron cores of the two worlds merged and a large amount of mantle material was ejected to form a giant cloud of debris around what was now Earth.

In a relatively short Lime, some accounts suggest within only a year, this ejected material had itself coalesced to form a new, smaller world – the Moon. As it did so, the huge energy of its fast accretion melted its outer layer to form an ocean of molten rock, or magma, that lasted long enough to fractionate – like a salad dressing that has been left in a cupboard for too long. As the lighter components rose to the Lop. they cooled and crystallised to form a solid crust. They were typically light-coloured and rich in aluminium. Below the crust, in the mantle, the rocks were heavier and richer in iron. The regions that were last to solidify gathered up those elements that had difficulty fitting into the crystal lattice, leading to them being described as KREEPy.

The solar system was still a mass of debris for the first 800 million years of its existence and large impacts were commonplace on all the planets. The Moon retains the scars of this bombardment in the form of large craters, often overlapping one another, all over its lighter-toned surface. During this time, it sustained a particularly large collision when an object gouged out the South Pole-Aitken Basin, a 2.500- kilometre depression on the Moon’s far side. About four billion years ago, the

impact of large objects seems to have peaked before tailing off suddenly. The dark patches wc now see on the Moon’s near side were mostly formed within huge circular basins that were formed by the largest of these impact events. Of particular interest to the lunar science community was the Imbrium Basin, which was dated to 3.91 billion years ago from Apollo samples. Scars from its formation can be traced across much of the near side and therefore its age provides an important benchmark for the relative ages of other superimposed features. As noted, the formation of this basin excavated rock from deep within the Moon that had KREEPy characteristics.

About half a billion years later, prodigious quantities of lava, rich in iron and magnesium, were erupted through the fractured crust. It filled the basins and other low-lying areas to form enormous smooth basalt plains to which we applied romantic names like Mare 1 ranquilliiatis, Mare Serenitatis and Oeeanus Proccllar – um. The last gasps of this activity probably died out ‘only’ about a billion years ago but its peak was around 3.3 billion years ago. Since then, little has changed on the Moon. The material from the bottom of the Apollo 15 deep core had lain undisturbed for 500 million years. Every few tens of millions of years, there is a very large impact that produces a spectacular fresh crater and sprays the landscape with a new layer of rubble and dust. Apart from that, the occasional large object and a slow but incessant barrage of hypervelocity grains of dust sandblasts the top layer of the surface. Across the eons, the topography becomes rounded off and the landscape is draped with a thickening blanket of ground-up rock, the lunar regolith.

This is the kind of profound knowledge produced by careful, focused exploration. As later generations of probes extended our reach into the depths of the solar system, their new data has elaborated on the story of planetary genesis gleaned by men who explored a new w orld in person and applied the power of human intelligence.

MISSION ACCOMPLISHED… NEARLY

With their exploration to the lunar surface finished, their rock samples stowed and the orbital science programme completed, it was time to return to the home planet. At this point, the Apollo spacecraft consisted of just the CSM, the LM ascent stage having been jettisoned and, in some cases, made to crash on the Moon for the benefit of the seismometers emplaced by the crews.

Return to Earth was achieved by the last major firing of the SPS engine. This burn had terrified managers for years, and amply fed the hunger of newspaper and television journalists for riveting speculation about doomed astronauts marooned in their cocoon of failed technology around a forbidding, desolate planet while waiting for a time when their own exhalations would begin to asphyxiate them even as they heroically struggled to repair their flawed ship. The terror and hyperbole was driven by the knowledge that, while a failure to enter lunar orbit would have resulted in a return to Earth, failure of the burn to leave lunar orbit would, by all analyses, have led to the deaths of the crew. As no fail-safe system existed, the SPS had to be totally reliable.

A FIERY RETURN

Arguably the most audacious feature of an Apollo flight was to have the crew re­enter Earth’s atmosphere in the manner that they did. In the final minutes of a mission, a lump of metal and plastic, three crewmen and a few dozen kilograms of moonrock, altogether weighing nearly six tonnes, came barrelling in from outer space at speeds approaching 11 kilometres per second as Earth’s gravity hauled them in. As it entered, the air in front of the blunt end of the command module was brutally compressed in a shock wave that generated temperatures approaching 3,000°C. All that stood in the way of the crew being incinerated by this extraordinary heat was a coating of resin and fibreglass that NASA’s engineers reckoned could withstand the punishment.

In truth, the heatshield that surrounded the Apollo command module was very conservatively engineered for two main reasons. When the spacecraft’s design was frozen, engineers still had a poor knowledge of how the superheated air of re-entry would flow around the upper walls of the spacecraft. Although this surface did not bear the brunt of the heat, they decided to cover almost all of the hull with the heatshield material. Additionally, the original specifications had required that the shield should tolerate a much longer passage through the atmosphere, 6,500 kilometres, than ever proved necessary. The command modules that returned from the Moon typically flew for only about 2,200 kilometres through the atmosphere, which nearly halved the overall amount of heat the shield had to endure. In practice, although the heatshield took a lot of punishment across its curved aft section, much of its conical surface was barely singed by re-entry. Even the reflective Kapton tape that had been glued to the spacecraft’s exterior for thermal control in space was usually found to be still adhering to much of the hull. On recovery, pieces of Kapton were occasionally peeled off by those in attendance and kept as souvenirs.

W. D. Woods, How Apollo Flew to the Moon, Springer Praxis Books,

DOI 10.1007/978-1-4419-7179-1 15. © Springer Science+Business Media. LLC 2011