Category How Apollo Flew to the Moon

Rendezvous and docking

Getting off the Moon and returning to the relative safety of the command module was a feat that literally defined the mission plan. NASA even named it lunar orbit rendezvous (LOR) in view of the important benefits the technique promised in overall weight savings, including that of the launch vehicle. Yet, to many in NASA in the early 1960s, it seemed suicidal for one tiny spacecraft to launch and attempt to pull up alongside another tiny spacecraft, each whizzing along at some 5,800 kilometres per hour, around another world nearly half a million kilometres away. At that time, no one had even attempted rendezvous in the relative safety of Earth orbit in spacecraft that could at least return to the ground if things went awry. Space navigation techniques were rudimentry at best. There were no GPS satellites around Earth and even spaceborne radar techniques were merely theoretical. It was a measure of the managers’ faith in their engineers and scientists that they felt confident to march ahead with an apparently hare-brained scheme which, if it were to go wrong, would doom two men to certain death in lunar orbit.

Once LOR had been chosen as the preferred mission mode, NASA needed to practise the techniques of rendezvous around Earth. Through 1965 and 1966, the ten missions of the Gemini programme turned rendezvous from a frightening unknown manoeuvre into a routine operation. Appropriate procedures were learned through successive flights beginning with simple tasks:

• Could the manoeuvrable Gemini spacecraft station-keep with its spent upper rocket stage?

• Could two independently launched spacecraft rendezvous and station-keep?

• Could a spacecraft rendezvous and then dock with an unmanned target?

• Could it achieve the same feat within a single orbit?

All these lessons built NASA’s confidence in its procedures, and were directly applicable to Apollo’s need to rendezvous and dock around the Moon. The Gemini programme is often overlooked by writers eager to tell the story of how NASA prepared to venture to the Moon. But without it, Apollo could never have succeeded within President Kennedy’s deadline. Years later, David Scott, Gemini 8 pilot and veteran of Apollos 9 and 15, reflected: "You go away back, it was a big mystery

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

DOI 10.1007/978-1-4419-7179-1 13. © Springer Science+Business Media. LLC 2011
doing a rendezvous. Magic mysterious stuff! Now it’s just straight off – choof, bang.”

Heatshield: sacrificial surface

Heatshield designs for Apollo originated in the re-entry vehicles that were developed in the 1950s for nuclear warheads. These weapons were launched on ballistic arcs out into space by large rockets to increase their speed and minimise delivery times. However, their elaborate mechanisms had to negotiate the great temperatures generated by re-entry and so they were protected inside a vehicle whose outer wall included some form of heatshield. Initially heat sinks were used, but development of this Cold War technology led to the use of ablative materials for w’arheads and this technique wns used for many spacecraft heatshield designs, including Apollo, until the introduction of advanced ceramics such as those used in the Space Shuttle and the planetary probes of the 1990s and beyond. NASA’s return to the Apollo style of spacecraft in the early 21 st century, known as Orion, also saw a return to the same ablative material for its heatshield.

The ablative heatshield works by allowing itself to succumb to the enormous heat of re-entry. As it does so, it slowly chars and peels away, or ablates from the shield, taking heat with it and revealing a fresh surface to continue the ablative process. As long as the thickness of the shield is greater than the depth of erosion caused by re­entry, the heatshield will function properly.

The command module heatshield wfas made from shaped sections of steel honeycomb sandwich, which provided a substructure onto which a fibreglass honeycomb was bonded. There were over a third of a million cells in a complete CM heatshield. and each was carefully filled by hand with a reinforced epoxy resin using a specially designed squirt-gun. After curing and inspection, any imperfectly filled cells were carefully drilled out and refilled. The heatshield came in three sections: the aft shield was up to seven centimetres thick and Look the brunt of the re-entry heat; the centre shield tapered between four and two centimetres and covered most of the conical surface; the forward shield or apex cover completed the taper and was wrapped around the upper cone of the hull where the parachutes were stored. Each w’as shaped on large lathes to the correct thickness and rcchccked before being affixed around the internal structure of the command module.

AOS

Apollo ll’s troubles began as they came around the Moon’s eastern limb. There had been a major change to the configuration of the lunar module since Apollo 10 had rehearsed the descent orbit. Plume deflectors had been added around the descent stage to protect it from the blast of hot gas from the RCS thrusters and these were now interfering with the radiation pattern of the steerable high-gain antenna. Worse, Armstrong was flying with the windows facing the Moon to gain timings relating to his orbit. This meant that the steerable antenna had to peer past the LM structure. The diagrams that indicated the resultant restrictions and which angles the steerable antenna could use were in error. At acquisition of signal after Eagle had entered the descent orbit, mission control found that not only did this interference make voice communication with the crew difficult, it interrupted the engineering telemetry with which flight controllers would soon make a decision on whether to proceed with the landing.

To try and alleviate the problem, Charlie Duke in mission control passed on a recommendation from Pete Conrad, who was sitting close by, that they yaw the LM right by 10 degrees. Enough data did get through for the Go/no-Go decision to be made positively, though in the event, it had to be relayed via Mike Collins in the command module.

Science in the driving seat

Lunar exploration came of age with the J-class missions of Apollos 15, 16 and 17. Traverses on foot to single points of interest gave way to wide-ranging sorties that could visit multiple destinations. The crews were carefully coached on the skills of field geology and on the need for strict documented sampling of the rocks and soil. A powerful illustration of NASA’s move towards a science-based justification for the flights was the successful lobbying of the geology community to have a professional scientist included on the final Apollo mission.

To accommodate this expansion of Apollo’s science role, engineers made a series of improvements to both the Saturn V launch vehicle and the Apollo spacecraft. The payload of the launcher was increased by small improvements in the E-l engines and by the deletion of some of the ullage and retrorocket motors that pulled the first and second stages apart at staging. Minor improvements were made to the loading and utilisation of its propellants to ensure greater depletion at cut-off. Changes to the launch trajectory included using a more easterly launch azimuth to Lake maximum advantage of Earth’s rotation and a lower parking orbit because a rocket that did not have to lift so high could carry more weight.

Changes to the spacecraft included an extra hydrogen tank in the service module to supply more power and w’ater. Another oxygen tank had already been added in the light of the Apollo 13 incident. The LM was endowed with larger propellant tanks and additional tanks for water and oxygen along with an extra battery in the descent stage. This increased the time on the Moon from two to three days. The thrust of the LM’s descent engine was increased merely by extending the length of its nozzle to direct the expanding exhaust gases along the thrust axis before they are released to space. The limiting factor was the nozzle’s clearance from the lunar surface. The increased ability to take mass to the Moon was exploited to greatest effect by one additional piece of equipment housed in an empty bay of the descent stage; the lunar rover.

Wheels on the Moon

The extra mobility afforded by the lunar roving vehicle (LRV) had a profound effect on the scientific harvest that was gained from the Apollo J-missions and there were many reasons for this. It could take crews to diverse sites for study and sampling. It gave them a little physical rest as they drove between planned stops. It could carry a substantial load of tools, cameras and ultimately rock samples. And also by virtue of a remotely-controlled TV camera, each geology stop could be supported by the eyes and knowledge of the scientists and engineers on Earth.

The rover was an ingenious device that managed to fulfil a wide range of tasks within extremely narrow constraints. It had to be light in weight and foldable in order to be carried aboard the LM. It had to withstand the rigours of launch and the passage across cislunar space as well as being able to operate in the extremes of dust, vacuum and temperature on the Moon’s surface. Beyond the basic task of

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John Young works at Apollo 16’s rover. (NASA)

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David Scott works with engineers on a checkout of the deployment of Apollo 15’s rover from the side of LM Falcon. (NASA)

Motor controller

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Diagram of the layout of the lunar roving vehicle. (Redrawn from NASA source.)

transporting two crewmen and their tools across the Moon, the rover had to help them navigate while out of sight of the LM and it had to support a demanding suite of communications functions between the Moon and Earth, including live television. This unusual and highly successful contraption was designed, built and tested within 18 months of being given the go-ahead.

Л large square panel formed the central part of the chassis upon which were mounted simple foldable seats, an instrument panel and a T-shaped control stick. Two smaller chassis panels were attached at the ends, with hinges so the)’ could be folded against the central panel during flight. Each end panel held a pair of wheels which themselves were folded over the central chassis to allow the whole contraption to fit within one of the wedge-shaped bays of the descent stage. To deploy it. a crewman would pull on a lanyard to lower the rover from its bay. First the rear, then the forward chassis panels came free, both spring-loaded to fold out and engage in place. Likewise, the wheels w:ere spring-loaded to swing into their correct position and lock. Once the rover was on the ground, it was straightforward for the crewmen to lift it off its deployment hinge and begin to load it up with the tools, cameras and other equipment they would need for their traverses. The front chassis carried a pair of batteries that were installed in a fully charged state by technicians on the launch pad. In total, these could supply over eight kilowatt-hours of electrical power. Electronic packages were mounted nearby and these used the batteries as heatsinks. Engineers then arranged that when the rover came to a stop, the crew would lift dust covers to expose a series of radiators to deep space in order to release the accumulated heat.

The problem of surface navigation was solved by use of a directional gyro and by the measurement of distance based on pulses that marked the rotation of each wheel. The system’s logic was clever enough to select the third-fastest wheel so that slipping wheels would be ignored. By processing this information, the bearing and distance to an initialisation point could be displayed on the instrument panel. Normally, of course, this initialisation was done near the LM at the start of each day’s drive and it included an alignment of the gyro.

’’Okay, Bob, let me give you some numbers." said Gene Cernan to Robert Parker in Houston after he and. lack Schmitt had deployed their science station at Taurus – Littrow. They were ready to go on their first drive, but first Cernan had to initialise the rover’s nav system. He Look readings from a tilt meter that gave pitch and roll angles for the vehicle. The yaw angle could be worked out from a foldout sundial that indicated the angle of its centreline relative to the Sun.

"Sun shadow is zero. I am rolled right four degrees. I am pitch zero. I can’t be rolled right four degrees. That indicator can’t be right. I question that.’’ Perhaps the low’er gravity and the alien landscape were playing tricks with his sense of orientation. "I might be rolled left a couple of degrees. Are you happy with that. Bob? Roll indicator is indicating… Make it three degrees right.’’

"Okay, and I copy."

Almost instantly, a flight controller turned the attitude angles into a heading with respect to north w’hich Parker relayed to the Moon. "Okay, torque to 279." Cernan then slewed a heading indicator to show 279. The rover was aimed slightly north of due w’est. As they moved across the surface, the indicator would display their heading, and their route back would be shown by two numerical displays for bearing and distance.

Each wheel had its own 180-watt electric motor that was sealed into a pressurised unit along with gearing and a brake. A clever arrangement called a harmonic gear
stepped the motor’s rotation down by a ratio of 80:1 by having the motor turn an elliptical rotor inside a flexible cylinder. The cylinder had gear teeth on its outside which meshed with gear teeth on the inside of an outer ring, but only at the two ends of the ellipse. This arrangement meant that a complete turn on the inner rotor would move the cylinder by only a small number of teeth. The braking system was quite conven­tional, being operated by cable linkages which actuated drum brakes. All the control functions of the rover; steering, forward, reverse and braking; were brought into a centrally mounted T-handle that was accessible to both crewman though no LMP ever got to drive a rover on the Moon. Each wheel had a fender and these had pull-out extensions which were deployed to contain dust raised while driving. Seats, armrests and footrests were unfolded to their final positions, as was the console with its T-handle. At this point, the commander could get on, power it up and take it for the short drive to where their gear had been stored in the other stowage quads on the LM. The rubber tyres of the MET were discarded in favour of a mesh design made from piano wire that could withstand a large amount of deformation. An inner tyre of metal bands provided additional protection against hard impacts with rocks. The rover could clear a rock that protruded up to 30 centimetres. In planning a mission, there was usually some worry about whether the chosen site would be navigable to a rover. Pre-mission photography tended to lack the resolution to show small boulders that would reduce what NASA called ‘trafficability’; the rover’s ability to get about the site without being impeded by excessive numbers of rocks too large to drive over.

Pressure integrity

With the docking successfully completed, Worden pressurised the tunnel between Endeavour and Falcon, then removed the forward hatch and docking equipment to inspect the 12 docking latches. Meanwhile, Irwin copied down a P30 PAD from mission control for a burn that would eventually Lake the jettisoned LM out of lunar orbit to crash on the Moon.

Once the LM’s overhead hatch had been opened, Worden sent the vacuum cleaner through the tunnel to help the LM crew to deal with the dust on their spacesuits. Scott and Irwin then began to transfer all required items to the CSM, with a list in the flight plan indicating where each item should be stored. The list included film magazines, rock and soil samples, food, used urine and faecal bags and one of the oxygen purge system (OPS) packages from the surface. The OPS. w’hich had been mounted on top of one of the PLSSs during the moonw’alks. w’ould be needed by Worden during the coast home to Earth, for his spacewalk to retrieve film magazines from the cameras in the SIM bay. It contained high-pressure oxygen bottles that would provide emergency air to a suited crewman in case of a problem with their primary umbilical air supply.

Items not required by Endeavour for the remainder of its mission, such as used lithium hydroxide canisters, a second OPS and the now-useless docking probe and drogue, were left in the LM to be jettisoned with it. In the light of the Soyuz 11 incident, this jettison was to occur with the crew fully suited up. As Irwin w:as the last to leave Falcon’s cabin, he closed its overhead hatch behind him. Once everyone was inside the command module, the forward hatch was installed and the cabin checked for leaks. At this point. Scott had to deal with a slight pressure leak in his suit. “Okay, we are going to be a few minutes here. We’ve got to pul some LCG plugs in our suits and it’s going to take probably about 10 or 15 minutes to gel all that done.”

This communication was the start of a confused episode which involved checks of the suit and hatch for pressure integrity. Scott’s boss, Deke Slayton, came on to the communications loop, betraying management’s concern at the crew’s deviation from the flight plan. Scott’s use of the plugs in his liquid cooled garment (LCG) w:as a minor remedy for a leak that was probably brought on by the wear and tear from the tenacious and abrasive lunar dust.

“Hey, one quick question. How come you guys need plugs for those suits?’’ asked Slayton.

“Well, because, apparently, the LCG connection on the inside won’t hold an air seal,’’ replied Scott. “So we’re getting them taken care of with these extra little blue plugs we got that are airtight on the inside.”

“Roger. We thought those plugs only were required w’hen the LCG was not on. We’re trying to crack that one for you down here, Dave. There’s something screwy here.’’

“Okay. Well, we’ll put these plugs in and run another pressure integrity cheek and see how it works.’’

“Roger.”

Scott’s subsequent successful suit integrity cheek pul the crew slightly behind their timeline, but Slayton’s intervention displayed the start of jitteriness in mission control about the crew and their tiredness when a slightly abnormal situation arose. Then, with only a few minutes to go before LM jettison, another pressure integrity problem became evident when Worden reported the pressure difference between the cabin and the tunnel. “LM/CM dcha-P is 2.5… 2.0, excuse me.”

“Copy, 2.0,” confirmed Bob Parker at the Capcom console.

The crew had used the tunnel vent valve to bleed air out into space from between the two spacecraft. Had it been completely evacuated, this pressure reading, given in pounds per square inch (psi), would show between five and six psi because it indicated the pressure difference across the forward hatch. With a good vacuum in the tunnel, the reading would be essentially the absolute cabin pressure. Their procedures called for the reading to be at least three psi prior to jettison. The fact that it was only two psi, having earlier read three psi, strongly suggested that air was entering the tunnel through the hatch of one or other spacecraft. Compounding the jitters in the MOCR was the knowledge that, on the way to the Moon, there had been confusion between Scott and the MOCR about the settings of this valve, which could either vent the tunnel or allow the crew- to monitor the pressure but not do both.

“Okay, the LM/CM delta-P doesn’t look exactly right to us. What do you think?” asked Scott.

“We’d like to get another pound [per square inch of pressure] out of there.” replied Parker. “We’re showing about 3.5 in there.” But mission control were not reading this directly. They had deduced this figure by subtracting the reading they had been given from the measured cabin pressure (5.5-2.0 = 3.5).

“Okay.” said Scott, as he and his crew looked for answers. “We had a suspicion that possibly the LM overhead dump valve was open, and it might be.” That is, it was possible Irwin had inadvertently left it open a little when he left the LM. Scott tried venting the tunnel further. "It’s up to about 2.3 now,” he reported.

The flight controllers in the MOCR discussed the readings with Scott a bit longer, before reaching a conclusion that was an extreme rarity in the history of flight control a mistaken conclusion. Parker radioed up. “Dave, we think that the increase in the cabin pressure during the suit integrity check could have raised it from your side.” However, adding more air to the cabin by inflating the suits for Scott’s pressure test would have had the opposite effect, increasing the pressure difference across the hatch.

Then Parker let slip about how the ground and the spacecraft had got out of sync with each other. "Stand by. Dave; confusion reigns down here.” In the light of this, mission control decided to hold off on the jettison, back out of the situation they were in, and have the crew disarm the pyrotechnic devices that were about to cut loose the LM. If the crew’ were to remove the hatch to inspect its seal, an accidental detonation of the armed LM jettison explosives would be catastrophic.

Scott and his crew brought the tunnel back up to the same pressure as the cabin, then removed the hatch but found nothing untoward. In any case, it was perfectly possible that contamination to the seal, perhaps from lunar dust, could have been blown off as the hatch was removed. Now that they had an extra two hours before the next jettison attempt, because it had to occur at a specific point in the orbit, mission control decided to use the Lime to test the hatch seal thoroughly. The crew reduced the pressure in the tunnel low enough to give a reading of 3.5 psi and Parker asked them to hold it there throughout their next far-side pass to see whether it had changed when they reappeared 45 minutes later. Scott and his crew were thinking about food and wanted to take their helmets and gloves off to eat: "I guess in that case, we’ll probably break the suits down and then run another suit check before we see you around the corner.”

“Okay, we’ll buy that," replied Parker.

“It’s about time for dinner.’’ said Scott.

“I knew there was a reason.”

By this time, it was 18 hours since Scott and Irwin had suited up for their gruelling final day on the lunar surface. They had not eaten for eight hours, and had been fully suited for much of the time since before launch from the Moon 6 lA hours earlier. The problems with their suit and hatch integrity were compounding their tiredness and they were going to be a further two hours behind. They were keen to get settled down to a much-needed meal break.

“Okay, we’re about 3.2 [psi] now on the delta-P,” reported Scott. “We’ll leave LM [meaning tunnel] in Vent.”

“Roger.” replied Parker. “I understand; 3.2 and still venting.”

The confusion was being compounded. Mission control had asked for the tunnel pressure to be held around the far side, but SeoiL had understood that he was to leave it venting. Then the managers worried whether the crew’ should remove their helmets and gloves in order to eat. Breaking open their suits w’ould necessitate another check of their pressure integrity before LM jettison. Despite having earlier concurred with the request from the crew to do precisely this, the suit integrity check would pump air into the cabin and affect the reading on their pressure gauge, so Parker notified them of a compromise: "You are permitted to break the suits down, but do not do the suit integrity check until you come back around the other side; wfe can Lake another look at that tunnel.”

Once the crew’ reappeared from behind the Moon, Parker quizzed them. “How’ did the hatch integrity check go?’’

‘"Well, we’ve just had it in Tunnel Vent all the way around the back side as I think you suggested," replied Scott.

“Did you have a look at holding it in delta-P to see how it was holding on that?’’ queried Parker.

“No, we just left it in Tunnel Vent all the way around the back side,” reported Scott. “That’s what we’d thought you’d said to do. We can check it now.”

By now’, Glynn Lunney. the flight director on this shift, w’as becoming frustrated at the difficulty his team were having in getting this crew put to bed. Parker called up, “15, why don’t you bring it up to 3.5. and let us watch it for a w’hile. I think w’e garbled something there.’’ Lvcryone was keen that they jettison the LM only when the seal on the forward hatch w’as good.

LAST HOUR

As the mission entered its final hour, one chore for the astronaut in the right couch was to install a 16-millimetre movie camera in a bracket next to his rendezvous window. This would record the view from the window looking backwards along their glowing wake. The camera did not have a direct line of sight, but rather was mounted off to one side and used a small 45-degree mirror to see out.

In the meantime, a final few items were stowed away for the re-entry. These included the ORDbAL box, the COAS optical sight, the chlorine injector and gas separator of the water squirt gun. An important aspect of stowage for re-entry was to ensure that objects were not only well secured but that their weight, soon to rise more than six times their earthly weight, and their edges and points, did not strike a crew member or cause damage, especially to the aft hull. Additionally, items above the crew had to withstand the sudden shock of the spacecraft’s impact with the ocean’s surface.

With 50 minutes to go, tasks leading up to their meeting with entry interface were coming thick and fast. The heaters that were preheating the CM thrusters were switched off, and a check was made of the two batteries that would fire the pyrotechnic devices. These were separate from the spacecraft’s three main batteries.

If either battery indicated less than 35 volts, extra energy was taken from the main supply to ensure operation. The third of the CM’s other three batteries was connected across both of the main power busses. The batteries would become the spacecraft’s primary electricity supply after the fuel cells were cut adrift with the service module.

Л check was made to see that their backup attitude reference, the GDC. was not drifting excessively. If it was, then two instruments that were relying on its output had to be treated as suspect: the right-hand FDAI and the RSI, the latter being the instrument that showed the direction of their lift vector and therefore a key item on a manual re-entry.

THE JOYS OF LUNAR ORBIT

Whether they had entered the descent orbit or w’ere in the circular orbit that was a characteristic of the earlier expeditions, the crew had reached their quarry and. in most cases, could relax a little before the exertions of the next day: undocking, separation, descent and landing, along with, perhaps, a trip on the lunar surface. This was time to get out a meal, look after the housekeeping of the CSM and take photographs lots and lots of photographs.

How’ever, for the crew of Apollo 8 there was no time to relax. Once they had completed their LOI-2 burn, Frank Borman, Jim Lovell and Bill Anders had eight orbits and 16 hours remaining in the Moon’s vicinity. Their Lime was precious, and had been carefully rationed. Borman took care of actually flying the ship – not in the sense of sweeping over hills and dow:n valleys; orbital mechanics was the arbiter of their flight path. Instead, his job was to make sure that the spacecraft was aimed in

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Two era-defining craters seen from Apollo 17. Top. Copernicus, about 900 million years old, still sports a clear ray system. Below. Eratosthenes is similar to Copernicus in structure but is old enough, about three billion years, to have lost its rays.

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The view from orbit. Top left, Herodotus and Aristarchus among lava channels. Top right, Rimae Prinz and a lava-formed depression. Centre, Mons Riimker is a large, low volcanic mound. Bottom left, craters Stratton (foreground) and Keeler on the beat-up far side. Bottom right, central peak of Tsiolkovsky. (NASA)

whichever direction was required to satisfy the tasks of his colleagues. This became particularly important in view of their main windows having become fogged. To gain a clear view of the surface, they were left with only the two small forward-pointing rendezvous windows, whose narrow field of view was never intended to facilitate general photography.

Each orbital circuit was split into four by the geometry of the Sun and Earth with respect to the Moon, and this defined their tasks. Any task that involved working with mission control could only occur during a near-side pass. Anders’s prime responsibility was a programme of photographic reconnaissance of the Moon, and most of this work could only occur over the sunlit lunar hemisphere. Therefore, when they were over the night-time portion of the near side, he was free to check over the spacecraft’s systems and write down abort PADs from mission control. For about half an hour of each orbit, soon after AOS. the crew became especially busy as they approached Mare Tranquillitatis. As well as chatting to mission control, Lovell and Borman w orked together to view’ and photograph one of the planned landing sites, looking for visual cues that could be used by a landing crew’ and for obstacles that might pose a danger to a future lunar module.

Part of the reason for Apollo 8 going to the Moon, beyond the political act of getting one over on the Soviets, was to gain its much experience of lunar operations as possible before the landing missions were finalised. One of the techniques pioneered by this crew’ was the first use of the spacecraft’s guidance and navigation system, along with visual sightings of landmarks passing below-, to help to determine their orbit more accurately. Prior to the mission, a number of landmarks were selected for Lovell to view – through the spacecraft’s sextant. A mark was taken by pressing a button when a landmark was perfectly centred in the optics. From repeated marks and careful tracking from Earth, they were able to improve knowledge of the precise shape of the Moon, and also prove the techniques of lunar orbit navigation for future missions.

In addition to performing for the first time the unique tasks associated with flying next to another world, this crew continued to care for the spacecraft that was keeping them alive. Lovell occasionally took over the steering of the spacecraft while he looked for stars with which to realign the guidance platform. Anders looked after the environmental and propulsive systems, taking time out for a series of systems checks. All of their tasks were swapped around, allowing them, in turns, to gel some rest during this frenetic period as they tried to nurse their own exhausted metabolisms on a mission that, so far, had denied them adequate rest. Catching sleep when the other members of the crew were busy had proved impracticable on the way to the Moon. Trying to do so. as laid out in the flight plan, during the climax of humanity’s furthest adventure, proved even more difficult.

They had arrived tired and none of them could rest as they shared the excitement of seeing the Moon close up for the first time. By the seventh orbit. Borman began to notice that he was making mistakes. Worse, Lovell was having finger trouble with the computer. Aware that in a little over six hours they had to make a TEI burn to get themselves home, that they had a historic TV broadcast to make during the near-

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Landmark CP-1/8 next to a feature dubbed ‘Keyhole’ within a large far-side crater Korolev. (NASA)

side pass prior to that bum and that they had all been awake for at least 18 hours, Borman took control. “I’m going to scrub all the other experiments, the converging stereo or other photography. As we are a little bit tired, I want to use that last bit to really make sure we’re right for TEI.”

To make sure that mission control understood what he intended, he specifically referred to the CMP tasks: “I want to scrub these control point sightings on this next rev too, and let Jim take a rest.”

Despite the can-do spirit of his colleagues, Borman stuck to his guns. “You’re too tired,” he admonished. “You need some sleep, and I want everybody sharp for TEI; that’s just like a retro.”

He was comparing the TEI bum to the retro bum used to get out of Earth orbit and return to the ground. In many ways the two types of bum had similar dire implications if they were to fail, except that, lor the latter, there might be a remote possibility of a rescue mission around the Earth. Anders realised that his commander wasn’t fooling and suggested a way of getting more science done wBile they rested: "Hey. Frank, how about on this next pass you just point it down to the ground and turn the goddamn cameras on; let them run automatically?"

"Yes, we can do that."

Mission control were used to having things done as prescribed, but understood the crew’s need for rest. Still, Capcom Mike Collins had to relay a request for exactly what was being cancelled. "We would like to clarify whether you intend to scrub control points 1, 2 and 3 only, and do the pseudo-landing site; or whether you also intend to scrub the pseudo-landing site marks. Over."

Borman was uncompromising. Only the success of the mission was important to him. If he sensed that their reconnaissance task was jeopardising their chances of getting home, he had no hesitation in dropping it. "We’re scrubbing everything. I’ll stay up and point – keep the spacecraft vertical and take some automatic pictures, but I want Jim and Bill to get some rest."

Mission control relented. Anders, being a typical driven perfectionist, tried again to continue with his tasks: “I’m willing to try it," he offered.

"You try it. and then we’ll make another mistake, like "Entering’ instead of "Proceeding’ [on the computer] or screwing up somewhere like I did."

When Lovell spoke up. Borman stood his ground. “I want you to get your ass in bed! Right now! No, get to bed! Go to bed! Hurry up! I’m not kidding you, get to bed!"

Despite their tiredness, the crew completed their 10 orbits around the Moon over Christmas and fired their engine for a safe THI and return home.

Threading the peaks

Whereas the first three landings had been on open, if rugged sites, the approach taken by Falcon on Apollo 15 took the LM between a pair of mountains. This made the experience of landing somewhat different, especially during P64’s regime.

“Falcon, Houston,” said Ed Mitchell in mission control. “We expect you may be a little south of the site; 3,000 feet.” By that, he meant that their flight path, travelling

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Apollo 15’s flight path from the east threaded between two huge mountains on either side of the landing site. (NASA)

east to west, seemed to be taking them to a point one kilometre south of their intended target. When they started P64, Scott would have to steer to the right to get them back on track.

“Okay. Coming up on 8,000,” said Irwin as they passed 2,500 metres altitude. Even before P64, he had begun to concentrate on keeping his commander up to date. This was one of two events that biased Scott’s estimation of where they were going to land. The other concerned what he and Irwin saw out to the left prior to P64. “I looked out the window, and I could see Mount Hadley Delta. We seemed to be floating across Hadley Delta and my impression at the time was that we were way long because I could see the mountain out the window and we were still probably

10,0 to 11,000 feet high.” Scott then approached pitchover thinking he was going to land long and south, which was worrying because several kilometres to the west of the intended landing point was Hadley Rille, and he didn’t want to come down in its canyon. Actually, they were at about 2,750 metres, and the 3,350-metre mountain was towering 600 metres above them.

In later years, Irwin discussed the moment of pitchover. “We’re not looking down as we come over the mountains,” he chuckled. “We’re looking straight up until we get down to around 6,000 feet [1,800 metres] and we pitch forward about 30 degrees and, at that point, we could look forward and see where we were. We could see the mountains. 1 was startled because, out the window, 1 could see Mount Hadley Delta which towered about 6.000 or 7,000 feet above us. And we never had that type of presentation in the simulator." Landing simulations had used a small TV camera flying over a plaster model of the surface to present the crew with the view they would get out of their window’s. It included the impressive rille that would be in front of them, but not the mountains to either side of the approach track.

"When we pitched over." continued Irw’in, "I could see the mountain that tow’ered above us out Dave’s window. I’m sure it startled Dave, too, because we wanted to know, you know, were we coming in to the right place? Fortunately, the rille was there and it was such a beautiful landmark that we knew’ we were coming in to the right area. But we’d never had that side view in any of our simulations. It was just the front view, a level plain with the canyon. And it would have been very impressive to be able to look out as we were skimming over the mountains with about 6,000-foot terrain clearance. At that speed it would have been really spectacular, like a low-level pass as we came over the mountains down into the valley.’’

"7.000 feet. P64!" called Irwin as they passed 2.150 metres altitude.

"Okay." said Scott.

"We have LPD." said Irwin as an angle appeared on the DSKY.

Scott finally saw’ wiiere he was going. Ilis impression of landing long had been wrong, but mission control’s southerly estimation was correct. "LPD. Coming right," he said as he began a series of redesignations to move the computer’s targeting north to where they had planned to touch down.

To deal with ihc mountainous terrain around the Hadley landing site, planners had made a change to the approach phase of the descent. Instead of making a shallow approach of only about a 12-dcgree angle to the ground as the previous missions had done. Falcon came in on a much steeper 25-degree approach path.

"Four-zero." called Irwin as he began feeding Scott with constant updates of the LPD angle on the window and their altitude.

"5.000 feet. 39. 39. 38. 39."

"4.000 feet. 40. 41. 45. 47. 52."

"3.000 feet. 52. 52. 51. 50. 47. 47."

"2.000 feet. 42."

"Okay. 1 got a good spot." said Scott once he had decided where he was going to set it down.

SCIENCE STATION IN LUNAR ORBIT

Apollo 13 saw a serious push to use the CSM as an orbiting science platform from which to reconnoitre the lunar surface. The primary tool for this was the Hycon lunar topographic camera: a monster instrument modified from an aerial reconnaissance camera, whose 467-millimetre-focal-length lens peered out through the round hatch window and exposed square 114-millimetre negatives. The Hycon had an unhappy career in Apollo. It lay unused on board the Apollo 13 command module while the crew struggled to reach home after their mission was aborted. It was sent once more on Apollo 14. Once alone in his domain, and having made the circularisation burn to take the Apollo 14 CSM Kitty Hawk into a 110-kilometre orbit, Stu Roosa began a photographic pass that was to have included the Descartes region where scientists were considering sending a future mission. After about 200 exposures, the camera failed, never to work again despite the best troubleshooting efforts of Roosa and mission control.

The SI. VI bay

Lunar science from orbit really got into its stride with the J-missions. just as surface exploration had. In particular, one of the six sectors in the cylindrical service module which had been largely empty on previous missions, gained a bay of instruments and cameras that could be trained on the lunar surface for the five or so days that the CSM spent in orbit. This scientific instrument module, or SIM bay, was operated by the CMP from the time the spacecraft entered orbit until the service module was jettisoned shortly before re-entry.

Each example of the SIM bay that flew carried two cameras: a mapping camera and a panoramic camera, both of which were heavily derived from aerial and space reconnaissance cameras that were classified at the time. Each bay also included a suite of sensors, some of which were deployed out on the ends of retractable booms. These could divine the mineral composition of the lunar soil by sampling its various emissions. On Apollos 15 and 16. a tiny satellite was ejected just before the crew left to come home. It monitored the particles and fields mound the Moon for up to a year.

Подпись: Mapping camera Configuration of the major instruments in the Apollo 15 SIM bay. (NASA)

The full capabilities of the SIM bay were never brought to bear on the whole lunar surface, largely because the CSM’s orbit was defined by the position of the landing site. This limited the reach of the cameras and sensors to a narrow swathe near the equator. At one time, planners had envisioned an I-mission that would have placed a CSM in a polar orbit for a full month, from which its cameras could have imaged the entire surface at a consistent lighting angle, and its remote-sensing instruments could similarly have sampled the entire Moon. With Apollo in its declining years, funds for such a mission were not forthcoming and the scientists had to wait a generation for comprehensive coverage from advanced probes sent by a number of interested nations.

THE LONG FALL TO EARTH

The coast back from the Moon could be something of an anticlimax, particularly during the early Moon flights. The main purpose of the mission had been achieved, most of the danger had been successfully negotiated, and if the crew and mission control could keep the CSM working well, a safe return was likely. This was a chance for the crew to rest a little, and an opportunity to reflect on their successes and, perhaps, some of the problems they had encountered. There would often be a TV show or two beamed to the masses, and an interplanetary press conference for the world’s journalists. But everyone involved knew that danger could lie in the unguarded moment and at no time did the flight controllers drop their attention, even as the crew slept.

ft would be a mistake to think that nothing happened on the way home, although duties were certainly much lighter. There was no lunar module to take up the surface crew‘s time and some of the housekeeping duties around the command module could be shared among all three crewmembers. Some flights were lucky enough to witness interesting astronomical events during their return; others had various small science and technology experiments that made use of the very rare and expensive time during which NASA had people in space. The J-missions. in particular, had a heavier workload during their coast home because they had a bay full of science instruments in the service module, and while there was no Moon nearby for them to sense and sniff, they could be used for a little pathfinding astronomy.