Category How Apollo Flew to the Moon

"What’s the time?” asked Aldrin from Columbia’s right-hand couch. The crew of Apollo 11 had made their attitude checks prior to TEI. and were verifying that the engine bell was swivelling on its gimbal correctly in response to steering commands. Preparations were going smoothly and there was a light mood in the cabin as their incredible flight began to look as if it might actually come off.

“We have 12 minutes to go.” replied Collins, occupying the left couch.

Aldrin had been wondering what they should do once TEI w as completed: “You going to pitch up after the burn?”

“Sounds like a good idea,” agreed Collins. “Let’s look at the Moon after the burn. That’ll give us high-gain, right?”

“Cheek,” concurred Aldrin. Since they needed the spacecraft’s high-gain antenna to face Earth and it was positioned on the opposite side from their windows, it made sense to point the spacecraft down to have the high-gain in a favourable position for Earth and. meantime, watch the Moon recede.

“Okay, 10 minutes until Tig,” called Armstrong. ‘Tig’ was the ‘Time of ignition’ and everything they did worked towards it being on time and as flawless as possible. As they were over the far side of the Moon, where it also happened to be lunar night, neither the Sun nor Earth was shining across the landscape, and the only way to see the Moon’s position was by looking at a huge void where there were no stars. The spacecraft had to be travelling with its apex forward to enable the engine at the rear to accelerate them out of lunar orbit, and Collins was straining at the window for some kind of confirmation of this fact.

“I see a horizon,” he laughed. “It looks like we are going forward.”

“Shades of Gemini.” reminded Armstrong.

“It is most important that we be going forward,” stated Collins.

Aldrin began gently mocking his crewmate. “Let’s see. The motors point this way and the gases escape that way. therefore imparting a thrust that-a-way.” They all laughed.

This was a chance to pause and reflect during their preparations, and to look for the horizon that they were supposed to check in a few; minutes.

“Beautiful looking horizon." said Armstrong. “It’s hard to describe."

“God, it has an eerie look to it,” added Aldrin. “It’s not a horizon, it’s just a band.”

Collins and Aldrin could sec directly forward through their rendezvous windows

along the plus-.v axis and towards the sunrise. Armstrong’s view from the middle couch was limited to the hatch window just above his head.

‘’It was really eerie when it first came/’ said Armstrong as the Sun rose and the terminator came into view. "And the way the terminator is, you don’t see the whole Moon at all."

"I know.” said Collins. "I was looking at it upside down for a while.”

"Yes, and then that scares you,” added Armstrong, "because that says you’re going retrograde, right? Well, let’s see. if it’s upside down, you’re going backwards/’ Collins brought them back to their checklist. "Alright, we’re coming up on bus tie time; we’ve got a little over 6 [minutes] 50 [seconds] until fig.”

The crew returned to the protocol of challenge and response, with Armstrong reading out a line from the checklist and Collins repealing it once he had carried out the instruction. Once they had dealt with the internal configuration of the spacecraft it was time for another external check.

"Two minutes to get our horizon check at 10 degrees.’’ Armstrong had little option but to have his head in the checklist.

"Yes, and sneaking up on there, looks pretty darn good.” said Aldrin. "Looks like we’re darn near right.” The spacecraft was holding a steady attitude with respect to the stars so, in a sense, the Moon appeared like a great, rounded hill and they were in a helicopter approaching the summit, ‘fhe Moon’s horizon crept down Collins’s window towards the 10-degree mark. Aldrin’s window did not have that mark but he could infer it. "Okay, coming up on two minutes.” he eallcd, "and this damn horizon check is going to be. would you believe, perfect?”

"I hope so,” said Armstrong.

"fantastic,” enthused Aldrin. "First lime we ever got a perfect horizon check. Spent too many hours in the simulator looking for an unreal horizon. Alright, horizon check passes.”

"Beautiful,” agreed Collins, who armed one of the engine’s control banks then proceeded with Armstrong through the final lines of the checklist.

"Okay, stand by for 35 seconds,” announced Collins. "Mark it. DSK. Y blanks; EMS is in Normal.” The guidance system had begun to measure their acceleration. Aldrin came back, "Check.”

"Coming up on 15 seconds,” said Collins.

Armstrong readied himself at the computer keyboard for when the display w ould start flashing ’99’ at him, asking for permission to light the engine. "Okay. I’ll get the 99.” – – –

"Okay,” said Collins. "Stand by for ullage. Ullage.’’

"Cot the ullage,” reported Aldrin. Two rearward-facing thrusters lit up, gently pushing the spacecraft forward and bringing the weightless propellant to the bottom of the tanks as the crew counted down.

"Burn!” shouted Collins as the SPS engine lit. "A good one. Nice.”

"I got two balls,” called Aldrin.

As planned, only two of the four ball valves on the propellant feed lines had been opened by the computer.

"Okay, here comes ihc other two.” said Collins as he threw the switch to bring in the second control bank and bring the engine to its maximum thrust. “Man, that feels like g, doesn’t it?"

When they fired the SPS engine on arrival at the Moon, the tanks in the service module had been full and the LM was attached to their nose. Now the CSM was by itself and its tanks were only one-third full, giving the SPS the ability to accelerate the spacecraft towards 1 g.

Collins was closely monitoring the displays in front of him. "Pressures are good. Busy in steering, but it’s holding right in there.’’

“Hotv is it. Mike’.’" asked Aldrin from the right.

"It’s really busy in roll," replied Collins, "but it’s holding in its dead band. Looks like it’s holding instead of plus or minus five, more like plus or minus eight [degrees]. It’s possible that we have a roll-thruster problem, but if we have, it’s taking it out. No point in worrying about it. Okay, coming up on one minute. Mark it, one minute. Chamber pressure’s holding right on 100 psi."

"Looks good," agreed Aldrin.

Collins continued with his commentary. "Gimbals look good: total attitude looks good. Rates are damped out. Still a little busy."

There was no problem with the roll thruster, but the sloshing propellant could have a significant effect on the spacecraft’s attitude which was corrected by the thrusters and the engine gimbals.

"Two minutes. Mark it," continued Collins. "When it hits the end of that roll dead band, it really comes crisply back." Collins was describing how well the computer was able to deal with the CSM’s tendency to drift off in attitude.

“Okay, chamber pressure’s falling off a little bit." Collins had one eye on the gauge that showed the pressure within the combustion chamber. "Now it’s going back up; chamber pressure’s oscillating just a tad."

Armstrong called out. “Ten seconds left.”

"We don’t care about the chamber pressure," said Collins. "Brace yourself. Standing by for engine off."

The 2 minutes 28 seconds that mission control had predicted for the burn came and went, but the engine was still firing.

“It should be shut down now’," said Armstrong.

Collins queried him, "Okay?"

“Shutdown," called out Armstrong.

Collins stopped the engine at the same time as the computer. It had burned for 3.4 seconds longer than predicted because its thrust during the LOI burn had been slightly high and mission control had used that data when planning TEI. In the event, a slight change in mixture ratio lowered the thrust and so it burned a little longer to achieve the same change in velocity.

"Let’s look at what we got," said Collins as they brought up the residual velocity components. "Beautiful," he commented, “,v and r, 0.2." A burn that had changed their velocity by 1,000 metres per second was showing an error of only six centimetres per second. "SPS, I love you," he exulted. "You are a jewel! Whoosh!"

As with the LOI burn, no one knew anything of this in the MOCR or anywhere else on planet Earth. Any communication with Columbia was blocked by a 3.476- kilometre ball of rock. What they did know in mission control, down to the second, were the limes when the CSM would come back into view if the burn had worked, and if it had not. The increase in velocity would dramatically shorten how long it was out of sight.

The first operational step in preparation for re-entry occurred a few hours out, when the crew stopped the spacecraft from slowly spinning on its long axis in the so-called
barbecue mode for the final time. The time remaining in space no longer warranted the protection provided by thisywM’.vive thermal control rotation. Once he had control of the spacecraft’s attitude, the CMP had a final chance to practise his techniques of navigation, partly in case communications were lost and the spacecraft had to make its approach without assistance from Harth. but mostly to provide yet another data point for engineers about the crew’s ability to fly autonomously. Prior to his exercise, he carried out his penultimate platform realignment.

On those later advanced missions that carried a SIM bay in the service module, the crew powered it down for the last time before the final correction burn opportunity. As the film canisters had long since been extracted from the cameras, only a few instruments were still operating and. even then, they were only looking at deep space. Those mounted on the end of 7-metre-long booms were retracted except during the Apollo 15 mission when the booms were jettisoned – probably as an engineering test of that capability on their first outing.

It was around this point in the descent that the last Apollo command module to enter space ran into problems. During their return from the first international link­up in Earth orbit, the Apollo-Soyuz Test Project, the crew failed to switch on the Earth landing system at the right time. This episode illustrates how quickly an otherwise nominal mission can be derailed by a small operational error. Vance Brand was flying in the left couch with ‘l orn Stafford in command occupying the centre couch and working through the checklist with him. Somehow, they missed the step where the Earth landing system should have been powered and. all too quickly, they realised that the apex cover was still attached when it should have already departed. Brand punched the button to manually jettison it, and did the same for the drogue chutes. Unfortunately, in the rush, the RCS jets were not disabled, and when the drogue deployment caused the spacecraft to sway, the RCS jets began to lire to damp out these motions. By this Lime, the cabin pressure relief valve had begun to admit air from outside and, as it did so. exhaust from the jets, including a fraction of unburnt propellant, entered the cabin where the highly noxious chemical irritated the skin and eyes of the crew and caused them to cough. After struggling through the remainder of the descent and a hard landing that left the spacecraft upside-down. Stafford found Brand to be hanging in his straps unconscious. He struggled to get oxygen masks on his crewmates and gain control of the ship.

If a 24-sccond burn made around the Moon’s far side could lower the spacecraft’s near-side altitude from 300 kilometres down to only about 15 kilometres, it is easy to appreciate that an overburn of only a few seconds would so reduce the altitude that an impact with the surface could become a real possibility. The resultant precautions involved in the DOI burn are especially understandable in view of the fact that there was considerable uncertainty about the Moon’s precise shape, especially with regard to the more northerly regions that would later be overllown by two of the J-missions. Apollos 15 and 17, where some of the mountains reach four or five kilometres above the surrounding terrain.

As with all burns, the amount of delta-v was monitored by the crew via the DSKY. For a DOI burn, the typical delta-v was 210 feet per second (64 metres per second), which was the amount by which their velocity along the. v axis had to drop. One second of burn accounted for about 10 feet per second. As the burn progressed, they would see this value decrease towards zero. If the computer did not shut the engine down at the expected time, the crew had to promptly terminate the burn manually. They would then consult the DSKY to see if there was any overburn. The rules were that if they had slowed a mere 2.2 feet per second (0.67 metre per second) more than planned, they should immediately use their RCS thrusters to regain this speed. If they had overshot by as much as 10 feet per second (three metres per second), they were to turn the spacecraft around 180 degrees and regain the lost speed by firing a burp of the SPS.

Whatever the result of the DOI manoeuvre, once the crew were happy with it, they began to prepare for a possible bail-out burn. This was in case some other sign, in particular radio tracking from Earth, were to suggest they were at risk of impacting the ground. If so. they had at most an hour before the unthinkable would occur, and because they were over the far side at the time of the DOI burn, they would have no confirmation one way or the other for half of that time. The exquisite accuracy of radio tracking could only be brought to bear after AOS. with less than half an hour remaining to any theoretical impact. Therefore, w? hile the tracking stations measured their trajectory, the crew waited for a call from mission control to confirm that their orbit wasn’t going to spray them across some near-side mountain at over 5,000 kilometres per hour. This never became a real threat, and the crew’s and mission control felt confident enough with their hardware and procedures to view the bail-out burn as little more than a formality, but, in the NASA way, they were prepared for it.

In all instances, the two spacecraft were allowed to separate once the LM was well into the checkout of its systems and no problems were being encountered. For the later missions, Apollo 14 onwards, mission control read up a PAD with which the CMP could make his circularisation burn. In truth, the orbit that resulted from this burn was not really circular but was made deliberately elliptical. This reflected the fact that FIDO was compensating for the perturbation of the CSM’s trajectory by the Moon’s mascons, and although the effect of these gravitational irregularities was not well understood by the flight dynamics team, they hoped that by the time the LM was due to return, the orbit would have tended towards circular.

The descent orbit that the LM had been left in had its perilune over the near side, 500 km short of the landing site. Therefore, the eireularisaiion manoeuvre required a short burn of the SPS engine – lasting only about four seconds – to be carried out around the Moon’s far side which would lift the CSM’s perilune up to about 110 kilometres. For all SPS burns, an elaborate series of procedures had to be carried out to prepare and check the engine and its control systems. One of these checks was to verify that the gimbal-mounted engine could be aimed before and during the burn, and it was in making this check that a problem occurred that nearly cost Apollo 16 its landing on the Moon.

As Mattingly made his checks. Young joked to Duke at how things had begun to stack up against them; meaning the problems they were having with the steerable antenna and RCS pressures. "Charlie, this is fun, by golly,” he laughed. "It’s really the worse sim I’ve ever been in."

"It’s really bad, isn’t it.” agreed Duke.

The crews had become used to dealing with difficult scenarios during the many and varied simulations that comprised their training. But by the time they went on their flights, they were often struck by how calm things were because, for most of the time, things worked. The simulator supervisors w’ere no longer throwing obtuse scenarios at them to test how – they and mission control would respond. But to Young, this LM checkout w-as starting to feel like a particularly nasty simulation. Just then, Mattingly called across their VIIF link. "Iley, Orion."’

"You speak?” said Young. "Go ahead, Ken.”

"I have an unstable yaw’ gimbal number 2. It oscillates in yaw any time it gets excited.”

"Oh, boy,” said Young. Things were already bad but they had just got a lot worse. The SPS included a system called thrust vector control (TVC) that steered the engine during a burn. Mattingly had discovered that its backup mechanism was shaking wildly every time he tested it. They needed that engine to get home and this sounded like a show’-stopper.

"You got any quick ideas?” asked Mattingly.

"No, I sure don’t.” said Young.

Their mission rules said that the main and backup actuators for both the engine’s pitch and yaw gimbals had to check out as fully functional, or the crew – had to return home forthwith which would mean cancelling the lunar landing.

"I’m sure sorry about this,” said Mattingly, "but that number two servo is just oscillating like a wild man. It could be a switch here somew-here, but I sw’ear, I’ve checked them all I can. I guess I’ll power them dowm.”

"Yep, and tell the ground when you go around.” said Young.

"Okay,” replied Mattingly. "Brother, w’hat a way to start the day. huh?”

As they were still around the far side, Houston had no inkling of the problem until CSM Casper reappeared around the eastern limb. Meanwhile, Young brought Orion back tow’ards Casper to await Houston’s decision.

"Houston. This is Caspercalled Mattingly as soon as he had established communication with Earth. "We did not do Circ. and I’d like to talk about the TVC servo loops.”

“Understand. No circ." confirmed Jim Irwin.

Immediately, teams of engineers in Houston began to work the problems that had been reported for the two spacecraft, calling on support teams at the manufacturers in California and Long Island.

Young had psyched himself up for the landing and now it did not look like it was going to happen. “Man, I’m ready. he told Duke. “I’m ready to go down and land. 1 think thal’d really be neat.’’

Duke was not optimistic. "I bet we dock and come home in about three hours."

After four hours, when both spacecraft had gone behind the Moon for a second time since reporting the problem, managers decided that it was safe to proceed with the landing. Their rationale was that if the main actuators controlling the SPS engine were to fail, the backup system would kiek in. That is. they thought that its wobble did not threaten its primary function, that of bringing the crew home. Six hours later than planned, and about as long a delay as could have been accommodated. Young and Duke landed safely at Descartes. Although the extra hours spent in orbit had eroded the LM’s overall pow’er supply and the surface time had to be trimmed to suit, they completed an essentially full mission.

In the LPD, the engineers had devised a simple but powerful and ingenious way to tell the commander where P64 was taking them. It was as basic a device as you could hope to find in a high-tech spacecraft, though its operation depended on what was then one of the world’s most sophisticated small computers. It consisted of nothing more than vertical lines carefully scribed onto the inner and outer panes of the commander’s forward-facing w indow.

The lines calibrated the commander’s line of sight, as measured from a line directly forwards from his eye, downwards in degrees. To use it properly, he merely positioned himself in such a way that the two sets of lines were perfectly superimposed, which meant that he was in the proper position and their sight lines were valid. As the computer flew’ the LM to a landing, it displayed an angle on the DSKY that represented the line of sight to the expected landing site. The commander looked past the markings towards the surface and noted the terrain in front of him that coincided with the stated angle. That, at least, defined a downrange coordinate. Simultaneously, the computer would yaw the LM left or right so the line itself defined a lateral coordinate. The combination of the two pointed to the designated landing site. This lightweight but elegant solution also allowed him to redesignate the landing site by nudging his hand controller left, right, back or forward, and P64 would then aim the LM for the new target.

Immediately Conrad had his angle, he looked out his window to see w here it was aimed. “Hey, there it is!” he called excitedly as he recognised an arc of craters and, just before them, the Snowman. “There it is! Son-of-a-Gun! Right dow n the middle of the road!”

“Outstanding!” said Bean who then began feeding LPD angles to his commander. "42 degrees, Pete.”

“Hey, it’s targeted right for the centre of the crater!” enthused Conrad. “I can’t believe it!”

“Amazing!” agreed Bean. “Fantastic! 42 degrees, babe.”

After the mission, Conrad talked about this moment when their plans for an accurate landing came good. “For the first couple of seconds, I had no recognition of where we were, although the visibility was excellent. It was almost like a black-and – white painting. The shadows were extremely black, illustrating the craters; and, all of a sudden, when I oriented myself down about the 40-degree line in the LPD, our five – crater chain and the Snowman stood out like a sore thumb.”

With the departure of his two erewmates to the lunar surface, the CMP had a bigger space in which to move around so life on board the Apollo command module became somewhat more comfortable. Michael Collins elaborated on this extra space in his autobiography.

‘T have removed the centre couch and stored it underneath the left one, and this gives the place an entirely different aspect. It opens up a central aisle between the main instrument panel and the lower equipment bay. a pathway which allows me to zip from upper hatch window to lower sextant and return.” One reason that Collins created this extra room in the cabin was in ease his erewmates returned and found they could not get through the tunnel for whatever reason. All three men would be in their space suits and the two surface explorers would enter through the main hatch, clutching boxes full of rocks. Collins appreciated the extra room now afforded him: "In addition to providing more room, these preparations give me the feeling of being a proprietor of a small resort hotel, about to receive the onrush of skiers coming in out of the cold. Everything is prepared for them; it is a happy place, and I couldn’t make them more welcome unless I had a fireplace.”

Collins had a relatively short time alone in the command module, and much of it was spent on housekeeping duties or looking through the sextant in vain to find his colleagues on the surface. He also found that there was very little time available to speak with mission control. Only one communication channel was available between the Moon and Earth through a single Capcom and this was being dominated by the large amount of chit-chat from the guys on the surface as they talked to mission control and to each other. This became somewhat problematic as the needs of the orbiting CSM and its sole occupant vied for Lime on a link that was already busy with the important task of keeping two men alive and working on the surface of an airless world.

Richard Gordon on Apollo 12 had a similar experience, except that he had no problem finding the LM. given Pete Conrad’s pinpoint landing. Towards the end of Gordon’s Lime alone in the CSM, he did get to push the science possibilities of the orbiting spacecraft a little when he operated a cluster of four Hasselblad film cameras mounted on a ring, each loaded with black-and-white film and each shooting through a different filter. This cluster was attached to the hatch window and allowed him to photograph the surface in red, green, blue and infrared light. The idea was to detect subtle hue variations across the surface that would relate to the composition of the soil. Telescopic studies had shown that some mare surfaces had a slight reddish tinge while others were bluish. A similar experiment had been attempted on Apollo 8 when Bill Anders photographed the maria through red and blue filters. However, excessively fatigued. Anders had inadvertently installed a magazine of colour film on the camera instead of the black-and-white magazine required by the experiment.

After Apollo 12. NASA decided that the increasing complexity of the missions required there to be two Capcoms, one for each spacecraft. This was readily achieved since the MOCR was already partially divided between the LM and CSM monitoring functions and there were separate consoles for the LM systems (Control, who looked after the LM’s guidance systems and engines, and TELCOM, later TELMIJ. who oversaw its electrical and environmental systems, much as НЕСОМ did for the CSM).

As their crewmates laboured on the surface dealing with suits and geology in the Moon’s dust pit, the CMPs handled an incessant programme of data collection and observation, while they simultaneously cared for the spacecraft. In addition to their planned tasks, it was not unusual for the CMP to deal with requests from geologists for yet another observation, or for a flight controller to seek clarification of a nuance of the CSM’s operation. This could create a steady chatter over the airwaves during each pass across the near side.

“It turned out that my favourite experiment in orbital science was the bistatic radar," said Ken Mattingly after his Apollo 16 flight. T his experiment used the spacecraft’s communication antenna to beam radio energy at the Moon as the spacecraft passed across the near side while radio telescopes on Earth received the echoes. To work, the signal from the antenna transmitted only a carrier wave and therefore could not carry information. “That meant the ground couldn’t talk to me for an hour and a half. I had a chance then to go to the bathroom, eat dinner, and get an exercise period or look at the flight plan. I think you really need those kind of periods every now and then throughout the day.”

Occasionally the CMPs got Lime to enjoy the view and the experience of coasting across the Moon alone. Owing to the easterly position of the Apollo 17 landing site, most of the near side track was in lunar night, but it was a night time lit by an Earth that was much larger and far brighter than the Moon appears to us. “Boy.“ reported Ron Evans, “you talk about night flying, this is the kind of night flying you want to do, by the full’ Earth.”

“Is that right?” said Mattingly, now’ in the Capcom role in the MOCR.

“Beautiful out there,” said Evans as he watched the ancient landscape of the Moon drift by, illuminated by the soft blue-white glow of his home planet.

As America coasted over to the western limb, Mattingly warned that when Evans eamc back around he would read up a lengthy scries of updates to the flight plan to satisfy the geologists’ desire for further photographic coverage. lie then asked for a stir of the spacecraft’s hydrogen tanks. It was December 1972. midwinter on Earth’s northern hemisphere.

"You’re lucky you’re up there tonight. Ron. We’re having really ratty weather down here. Low clouds and rain and drizzle and cold.” said Mattingly.

"Oh, really?" replied Evans as he approached the edge of Mare Orientale. a spectacular impact basin barely visible from Earth and unrecognised until the 1960s.

"Yes. You walk outside, you just about can’t see the top of building 2.”

"Gee whiz! Guess I picked a good time to be gone.” said Evans.

“Thai’s for sure.”

Evans was enjoying the view when he spotted a flash on the surface, probably a meteor strike. "Hey! You know, you’ll never believe it. I’m right over the edge of Orientale. I just looked down and saw a light-flash myself.” Jack Schmitt had seen a similar flash just after they had entered lunar orbit.

"Roger. Understand,” replied Mattingly.

"Right at the end of the rille that’s on the east of Orientale.”

On Apollo 15. A1 Worden figured that since he was going to be reappearing from around the Moon’s far side every two hours, it would be a fitting gesture to greet the planet in a variety of languages to make explicit that he was greeting the whole Earth and its inhabitants, not just its English speakers. With help from his geology teacher. Farouk El-Baz, he wrote down the words, "Hello Earth. Greetings from Endeavour." phonetically in a selection of longues. Then, as he re-established communication with Earth, assuming that the pressure of work had relented enough, he would choose one of these languages as his way of greeting the world.

Worden found his time alone in the CSM to be busy but not unpleasant. When asked about how hard mission control would drive him after his rest break, he said, "It was not generally difficult to begin work in the morning, because I was usually awake by the time they called. Also. I spent roughly half [of my] time on the back side of the Moon, and so 1 had about an hour each revolution when 1 could not talk to Houston in any event. I was up and going before talking to Houston because I did not sleep that much during the orbital phase."

Another time, he recalled, "My impression of the operations of the spacecraft was one of complete confidence in the equipment on board. Things worked very smoothly, and 1 didn’t have to keep an eye on all the gauges all the Lime. The rest of the spacecraft ran just beautifully the whole time. The fuel cells ran without a problem. In fact, everything ran just beautifully, and I really had no concern for the operation of the spacecraft during the lunar orbit operations.”

Just being human

Everyone involved in Apollo’s exploration of the Moon was acutely aware that time on the lunar surface, or in lunar orbit for that matter. w:as gained at extraordinary expense, was extremely precious and had to be carefully rationed to gain maximum scientific return. Nonetheless, the human dimension, the sense of the occasion or our innate tendency to lighten things up a bit often managed to shine through. Every crew left objects behind, perhaps for future visitors to find or maybe just in the knowledge that something meaningful had been left behind on that extraordinary world. Like Worden’s greetings, Evans’ joy at flying in Earthlight or an impromptu ballet display that Jack Schmitt indulged in on the lunar surface, there would be moments of humanity that w ould turn these periods of relentless data gathering into something to which a wider audience could relate.

As would be expected, Apollo 1 l’s brief EVA was crammed with activity. Armstrong and Aldrin had to hustle to get everything done but time was set aside for a conversation between the crew and President Richard Nixon who spoke from the While House. Then, after they had conveyed their gear and samples up to the LM, Armstrong remembered one other item. “How about that package out of your sleeve? Get that?” He was still on the surface and Aldrin was in the cabin receiving the gear.

“No.”

“Okay, I’ll get it when I gel up there.”

“Want it now?” asked Aldrin.

“Guess so.”

Aldrin removed the package from one of his sleeve pockets and tossed it down to the surface where Armstrong positioned it with his foot.

“Okay?”

“Okay,” replied Aldrin, both men happy with its placement. The pouch contained patches and medals to honour space travellers – Russian and American alike – who had died, a gold olive branch to represent Apollo ll’s peaceful goals and a small silicon disk etched with messages from world leaders.

The seriousness of Apollo 11 gave way to the exuberant fun of Conrad and Bean just four months later. Their big idea was to smuggle a timer on board that would have operated their Hassclblad camera with a time delay. This would have allowed both crewmen to pose in front of the Surveyor 3 probe. They took great care to ensure the timer got to the Moon but when it came time for their surreptitious photograph, they could not locate it in the bag where it lay. By this lime, the bag was full of rocks and copious quantities of the tenacious dust that covered everything. Later, as they dumped the contents of the bag into a rock box next to the LM. the timer appeared. “That was when we should have done it,” recalled Bean years later. "We’d have had the LM in the background. We could have shook hands in front of the LM. It’d be the end of the HVAs. Been a great picture.”

On Apollo 14. A1 Shepard’s passion for golf inspired his stunt. Facing the TV camera at the end of his final EVA, he launched into his demonstration. “You might recognize what I have in my hand as the handle for the contingency sample return; it just so happens to have a genuine six iron on the bottom of it. In my left hand. I have a little while pellet that’s familiar to millions of Americans.”

Shepard dropped the smuggled golf ball and prepared to take a shot. The constraints of the suit forced him to swing his improvised golf club with one hand and on his first attempt he merely buried the ball in the dust.

“You got more dirt than ball that time,” observed Ed Mitchell.

“Got more dirt than ball.” agreed Shepard. “Here we go again.”

His second shot connected to move the ball about a metre, though in the wrong direction.

"That looked like a slice to me, Al,” said Fred Haise in Houston.

"Here we go,” said Shepard. “Straight as a die; one more.”

He was successful at the third attempt and also gave a second ball a clean hit, sending them both soaring into the distance.

"Miles and miles and miles,” he said as the second ball flew off.

"Very good, Al,” said Haise.

Mitchell also tried a little sporting activity during their final moments when he threw the support for the solar wind experiment, javelin style, as far as he could. Both the javelin and one of Shepard’s golf balls ended up in a small crater about 25 metres away.

After Shepard’s indulgent golf swing, David Scott focused on science in his earnest demonstration of high-school physics. He and Joe Allen, his Capcom during his surface exploration came up with the idea of dropping a hammer and feather simultaneously to show viewers that, as predicted by well established theory, both masses would fall at the same speed. Scott was worried that static electricity might ruin the experiment and had brought two feathers, one to rehearse with and one for the TV. In the event, he did not have time for the trial run and hoped it would work first time, which it did. Allen was subsequently responsible for a chapter in Apollo 15’s Preliminary Science Report that summarised the scientific results of the mission. Among the more obscure descriptions of the various experiments and investigations was this paragraph, written with perhaps a hint of tongue-in-cheek humour:

"During the final minutes of the third extravehicular activity, a short

demonstration experiment was conducted. A heavy object (a 1.32-kg aluminum

geological hammer) and a light object (a 0.03-kg falcon feather) were released

simultaneously from approximately the same height (approximately 1.6 m) and were allowed to fall to the surface. Within the accuracy of the simultaneous release, the objects were observed to undergo the same acceleration and strike the lunar surface simultaneously, which was a result predicted by well – established theory, hut a result nonetheless reassuring considering both the number of viewers that witnessed the experiment and the fact that the homeward journey was based critically on the validity of the particular theory being tested.’’

Flaying with gravity was the theme of John Young’s signature stunt on Apollo 16. During their first EVA, when he and Charlie Duke were working around the LM, they took time out for the almost obligatory tourist shot of each crewman saluting next to the Stars and Stripes.

‘ Iley. John, this is perfect.” said Duke gleefully, ‘with the LM and the rover and you and Stone Mountain. And the old flag. Come on out here and give me a salute. Big Navy salute.”

“Look at this," said Young.

lie worked his arm so the suit’s cables would permit a salute then promptly launched himself nearly half a metre off the ground. Young’s total mass was about 170 kilograms including his suit and FLSS. But on the Moon it felt more like 30 kg and with barely a twitch of his legs and feet, he jumped a second time. Duke took a photograph at just the right moment to show Young apparently floating above the lunar surface.

As they wrapped up their final EVA. Young and Duke decided to Lake lunar athletics a stage further. Using the rover to steady himself. Young began to jump, getting higher each time until he reached a height of 70 centimetres. “We were gonna do a bunch of exercises that we had made up as the Lunar Olympics to show you what a guy could do on the Moon with a back pack on, but they threw that out.” “For a 380-pound guy, that’s pretty good,” said Tony England, their Capcom. Having seen his commander go ahead with some simple athletics, Duke decided to join in with a leap of his own. "Wow!” he exclaimed as he saw how high he could rise but as he descended, he realised that he had imparted a little backwards rotation. In his slow-motion fall, and with a moment of fear and panic welling up inside, he realised that he was going to fall onto his PLSS.

“Charlie!” called Young. The FLSS was not designed to Lake a fall like this. “That ain’t any fun, is it?" said Duke sheepishly as he lay on his PLSS facing upwards.

“Thai ain’t very smart,” pointed out his commander.

“That ain’t very smart,” agreed Duke trying unsuccessfully to turn over. “Well, I’m sorry about that.”

Young saw how much dust he was going to have to brush off Duke’s suit. “Right. Now we do have some work to do.”

“Agh! How about a hand. John?”

All the crews took a childish delight at throwing things in the weak lunar gravity. They were especially impressed at how bulky but light items like sheets of plastic foil would sail off in perfect ballistic trajectories undamped by air resistance. At the end
of the final EVA on the Moon’s surface, Gene Cernan saw a chance for a really good throw. He and Jack Schmitt shared a geology hammer and there was now no further use for it. ‘‘You ready to go on up?” he asked of Schmitt.

“Well, I don’t know,” replied Schmitt who then rattled off a list of further tasks remaining.

“Well, watch this real quick.”

When Schmitt saw what Cernan was about to do with their one geology hammer, his own boyish instinct kicked in. “Oh, the poor little… Let me throw the hammer.” After all, he was the geologist, ft only seemed correct that he should get to throw the geology hammer.

Cernan acceded. “It’s all yours. You deserve it. A hammer thrower. You’re a geologist. You ought to be able to throw it.”

Schmitt took the hammer away from the spacecraft and prepared to throw it. “You ready?”

“Go ahead,” said Cernan.

“You ready for this?” repeated Schmitt, building up to the great moment. “Ready for this?”

“Yeah,” said Cernan, then added a warning. “Don’t hit the LM. Or the ALSEP.”

Schmitt brought his arm back and swung with his whole body to launch the hammer in front of the LM.

“Look at that!” cried Cernan as the hammer arced out over the land­ing site, over their footprints and their wheeltracks and over all the discarded gear they were about to leave behind, perhaps for eternity. “Look at that! Look at that!”

After a flight lasting seven sec­onds, long enough for Cernan to take a series of pictures of its coast, it landed halfway to the ALSEP site in a plume of dust, where it still lies. “Beautiful,” said Schmitt. “Looked like it was going a million miles,” said Cernan, “but it really didn’t.”

“Didn’t it?

One of the most ubiquitous activities carried out on the lunar surface was geological sampling. Each successive mission returned more rock mass than the previous and in total, the amount of rock and soil brought to Earth by the Apollo missions was 382 kilograms well over a third of a tonne. But of greater importance than the sheer mass of material is the fact that the majority of it was carefully selected by trained human eye and brain and then painstakingly documented as it was sampled, especially during the J-missions. Those samples are now among the most highly prized pieces of material on Earth.

There are actually other sources of lunar rock available to scientists. Three Soviet spacecraft successfully gathered 0.326 kg of soil from various sites including a core

sample from below the surface. In more recent years, a class of meteorite has been shown to have originated from the Moon, blasted into space by an impact event to eventually pass through Earth’s atmosphere and reach the surface. None of these secondary sources have the provenance of Apollo’s documented samples.

Once a desirable rock or maybe an interesting patch of soil had been identified, the two crewmen began a practised sequence of tasks to properly gain the sample along with as much contextual information as was possible in the brief time available. The normal procedure began with a gnomon being placed on the opposite side of the sample from the Sun – in the down-Sun position. The gnomon was a small tripod arrangement with a central staff that maintained true vertical, as explained by Jack Schmitt: “The gnomon gave you the local vertical, a 40-centimetre scale, a shadow which gave you azimuth, and also had a greyscale and three international colour references for photometric calibration.”

Next, a crewman took two photographs of the sample prior to it being moved. These were taken with Sun shining across the sample so that its shape stood out and were therefore called cross-Sun images. Because he took a step to one side between exposures, they constituted a stereo pair which would allow the sample’s topography to be determined back on Earth. At about the same time, the second crewman took a down-Sun image towards the gnomon which recorded the intrinsic colour and tone of the sample in the same frame as the calibration card. At some point in the sequence, another shot was taken with some notable feature in the background. “We would take a ‘locator’ back to something like the rover,” explained Schmitt years

later, "just so that there was something in the picture that could be used to work back to where the sample had been taken. We’d just turn around and take a picture of the rover or of the horizon. Originally it had to do with the LM being in the picture as a ‘locator’ because, from the geometry of the lunar module and knowing how it had landed, you could work back along a ray to where you were and, as well, get a distance based on the size of the lunar module.”

For photography, NASA’s crews came to favour the Hasselblad camera after Wally Schirra took one with him on his Mercury flight in 1962. For use on the lunar surface, NASA worked with the Hasselblad Company to produce a specialised version of their professional SLR camera. This took square images on 70-mm-wide thin-base film designed to maximise the capacity of the film magazines. A battery – powered autowinder was added and the normally black finish on these cameras was changed to a reflective silver to minimise the absorption and emission of heat as it was moved in and out of the Sun’s rays. Crews could hold the camera with a special handle or chest mount it on the front of their RCU.

Researchers were keen to extract as much scientific information as possible from the resulting images so changes were made for the purposes of photogrammetry, the measurement of objects using photographs. A 60-mm lens, mildly wide-angle for the format, was specially designed to give accurate image geometry. Flight lenses were individually calibrated so that their image geometry was well understood. And since the plastic base of photographic film is prone to thermal expansion and contraction, the cameras included a means of marking a known geometry within the image at the moment of every exposure. A glass screen called a Reseau plate, upon which were inscribed a series of crosses at 1-centimetre spacing, was added directly in front of the film. When a picture was taken, the crosses left their imprint in the image for a future researcher to use when measuring angles. These crosses now adorn some of the 20th century’s most iconic images and perhaps the greater imprint they leave is in the eyes of graphic designers who use them as a motif to represent space travel and science. To mitigate the build up of static electricity and resultant sparks that might affect the image, the Rescau plate had an extremely thin layer of gold applied, thin enough to pass light.

With initial photography out of the way, the sampling itself could begin. The crews carried a selection of tools to take samples, particularly a scoop and a pair of tongs. While one crewman lifted the sample, the other took a numbered bag from a dispenser, often attached to their camera, and held it in position to allow the rock or soil to be dropped in. ЛИ the while, there wfas a verbal description which ended with the bag number being called out so a geologist in the science baek room could cross­reference it on return to Earth.

Two-man sampling w’as found to be much more productive than one crewman trying to work single-handedly but on occasion, perhaps when one crewman was occupied by another task, the second could usefully spend his time w orking alone. Schmitt often found himself in this position: "With two of us working together, bagging samples was fairly easy, but it was a lot harder solo. You had to hold the bag in one hand, and somehow or another get your scoop out over it so that you could dump something in it. And it was not easy, because you’re moving your arms against the pressure in the suit while gripping both the bag and the scoop."

After three days, Schmitt became quite adept at solo sampling, but not before he came a cropper at a small crater halfway through their second EVA. As Cernan worked to obtain a core sample. Schmitt Look samples at the crater’s edge, gathering soil and rock fragments in a scoop and. with some difficulty, pouring them into sample bags. When he finished with the scoop, he would rest it against his legs while using his two hands to manipulate the bag. Often the scoop would fall to the ground which forced him to bend one knee and lean down to retrieve it. Each sample bag went into a large sample collection bag that he sat on the ground beside him. As he turned at the end of this effort, he inadvertently knocked the bag over and spilled the smaller sample bags across the surface.

"Aaaah!” he cried, dropping to the surface on his hands and knees to gather his samples. "You don’t mind a little dirt here and there, do you, gang?’’

"No," replied Bob Parker in mission control.

Schmitt’s next problem was getting back up from his position kneeling on the outer slope of the crater. He brought his torso upright then straightened his legs. As he successfully got to his feet, the bag slipped from his grasp and impulsively, he leaned over to retrieve it. only to bring his centre of mass too far forward. Gravity took control and pulled him face-down into the dust once again as his legs Hailed uselessly off the surface. It Look him a while to return to a kneeling position from which he could regain his feet.

Mission control watched Schmitt’s pirouettes and spills with a mixture and bemusement and concern. "Hey, Gene, would you go over and help Twinkletoes, please?"

Cernan looked across. "Want some help. Jack? I’ll be there.’’

“No! I don’t need any help.” said Schmitt, annoyed at his display in front of the TV camera. “I just need belter bags.”

Schmitt checked his camera lens was clean and finished up at the crater. As they prepared to drive off. Parker had one further message for him. “Be advised that the switchboard here has been lit up by calls from the Houston Ballet Foundation requesting your services for next season."

“I should hope so,” replied Schmitt at which point he adopted a mock ballet pose, hopping on one leg with the other stretched out behind him. After two hops, he promptly fell on his face again. "How’s that?"

The little crater where Jack Schmitt fell, frolicked and performed his little dancing stunt will forever be known to researchers as Ballet Crater.

The obvious way to rendezvous was to launch off the Moon on a trajectory that directly intercepted the CSM using a single burn of the ascent engine. This was discarded for many reasons. The timing of the launch would have had to have been extremely accurate for the LM to intercept a spacecraft passing by at 1.6 kilometres per second. Even with such split-second accuracy, engineers knew’ that the expected variations in the thrust from the ascent engine would cause the EM to miss the CSM by gross margins. Additionally, the short duration of the approach gave little time to

calculate and correct the trajectory. Furthermore, the closing speed would have been higher than the RCS thrusters could be expected to overcome and if the approach was missed, the LM would find itself in an orbit whose perilune was likely to be below the lunar surface – that is, it would climb, arc back and crash onto the Moon. Direct ascent rendezvous was dangerous in many ways, and on top of all that it would be very difficult for the CSM to rescue a stricken LM.

fn addressing these problems, engineers settled on a more elaborate technique that took a step-by-step approach to incrementally bring the LM towards the CSM in a manner that could be analysed and controlled.

Ed Mitchell, LMP on Apollo 14, once wrote. "Preparing for a burn is a serious business, and before each one. Slu [Roosa] would announce, ‘It s sweaty palms lime again, gentlemen."’ The TEI burn tvas the one where mission control sweated more than usual, and that of Apollo 8 on Christmas Eve of 1968 was viewed with greater apprehension than any other, simply because it was the first. Its CSM was only the second Block II Apollo spacecraft to have flown in space, and they had sent it and its living human cargo all the way around ihc Moon. While ihc engineers had complete confidence in the reliability of the SPS engine, there was always a deep fear that, somewhere in ihc system, human frailly would cause a problem. In the MOCR, a clock counted down to the moment w’hen, if the burn had gone well, the spacecraft should come around the limb. The Earth station at Honeysuckle Creek in Australia was mosi favoured and its 26-mcirc anienna listened carefully.

The time for acquisition of signal (AOS) arrived, and almost immediately, engineers ai Honeysuckle reported a Unified S-band radio signal coming from the spacecraft.

"Apollo 8, Houston," Capcom Ken Mattingly called out to the crew as the engineers in Australia worked to lock ihc great dish’s receivers and transmitters onto the spacecraft.

"Apollo 8. Houston. Apollo 8, Houston,” continued Mattingly.

"Apollo 8. Houston. Apollo 8, Houston.”

"Houston, Apollo 8. Over.” called Jim Lovell from the speeding spacecraft.

"Hello. Apollo 8. Loud and clear.” replied Mattingly, speaking on behalf of all at mission control, all of them relieved that they had pulled off the most daring part of the flight.

"Roger.” said Lovell. Then, with the holiday period in mind. "Please be informed, there is a Santa Claus.”

"Thai’s affirmative,” agreed Mattingly. "You are the best ones to know.”

Soon after CSM Charlie Brown appeared on its way home after TEI on Apollo 10, commander Tom Stafford, wiio tvas an enthusiastic proponent of television from Apollo, turned the spacecraft around to aim their colour TV camera at the receding Moon. One of his impressions when seeing the entire ball of the Moon in one view’ was: "It’s a good thing we came in backwards at night lime where we couldn’t see it, because if we came in from this angle, you’d really have to shut your eyes.”

When Columbia similarly reappeared on time after Apollo ll’s TEI burn. Duke was ready to quiz the crew.

"Hello Apollo 11. Houston. How did it go? Over.”

Collins cheerily replied, "Time to open up the LRL doors. Charlie.” The crew

were now officially in quarantine and were destined to spend most of the next three weeks isolated in the Lunar Receiving Laboratory in Houston.

"Roger,” said Duke. "We got you coming home. It’s well stocked.” Armstrong provided the details of the bum and then praised their trusty SPS engine. "That was a beautiful bum. They don’t come any finer.”

David Scott concurred with how well the SPS worked on Apollo 15: "What a smooth bum that one was. Just can’t beat these rocket engines for travelling.” On his mission, and all the J-missions, it was customary to adjust the spacecraft’s attitude so that the mapping camera could photograph the retreating Moon, and perhaps image more of the polar regions which had been relatively poorly covered by the Lunar Orbiters. Each succeeding exposure showed the Moon receding further and further into the darkness of space.

Apollo 16’s view of the receding Moon taken by its mapping camera. At first, only the far side was visible, but gradually, the eastern mare came into view. (NASA)

As Alan Bean watched the stark lunar globe move away from Yankee Clipper on Apollo 12, he and his crewmates were struck by the unreality of their situation. "This Moon is just this white ball right out in the middle of a big black void, and there just doesn’t seem to be any rhyme or reason why we are here, or why it’s sitting out there. All the time we were in lunar orbit we were discussing this thing – how unreal it looked. And it is amazing to us to fly around it as it is. When you just think about going to the Moon, it is very, very unreal to be there. It’s really getting small in a hurry. It’s just sort of unreal to look outside. It is almost like a photograph moving away from you. It doesn’t seem possible it can be a whole sphere that you were orbiting a couple of hours ago.”

When the CSM left Earth, the service module’s tanks were loaded with 18.5 tonnes of propellant. By the time it was on its way back, the majority of this had

been consumed. What remained had been kept aside as a contingency in case the CSM had to make manoeuvres to rcseue a stricken LM in lunar orbit. For the Apollo 8 flight, with no LM to transport to lunar orbit, the tanks were still a quarter full after TEI. while for Apollo 11, which did have a heavy LM. only an eighth remained. Not all of this remaining propellant was usable. By Apollo 17, the planners had become more knowledgeable about the spacecraft and its capabilities and felt confident to plan the mission such that, after TEI, only four per cent of usable propellant remained in its tanks.