Things get harder when the debate moves to alleged technological absurdities or anomalies regarding the Apollo missions: many objections can’t be debunked without in-depth technical and historical knowledge.
7.1 Why did nobody ever go to the Moon again?IN A NUTSHELL: Because going to the Moon is very difficult, very expensive and very dangerous, and today nobody wants to go there, since there’s no longer a political imperative that justifies risking lives and devoting massive manpower and resources to the challenge. The Cold War is essentially over; the Soviet Union, once the rival to beat in the space race, no longer exists. Also, we’ve already been to the Moon and we’ve found no viable reason to go back with crewed missions. That doesn’t mean that we can’t, couldn’t or didn’t.
THE DETAILS: If we really were able to go to the Moon with 1960s technology, why don’t we go again? Some conspiracy theorists suggest, with this question, that we don’t go back because if we did it would become evident that we never went with Apollo. Others claim that even today it would be technically impossible and therefore it was equally impossible in the 1960s. But there are also honest doubters who simply ask themselves why we don’t repeat the fantastic voyage with today’s far more modern technology.
The answer is disarmingly simple: putting astronauts on the Moon is very difficult, hugely expensive (at least for NASA’s rather measly budget) and extremely dangerous, and today there’s no political motivation for spending massive amounts of public money and for risking human lives in the world’s spotlight in this way. The disasters of Apollo 1, Soyuz 1 and 11, and of Shuttles Challenger and Columbia have shown all too clearly that the loss of a spacecraft crew is seen as a national tragedy and can be justified only if the stakes are tremendously high.
At the time of the Apollo flights, it was a national imperative to beat the Soviet regime and to rebuild the political and technological prestige of the United States. There’s no such imperative today; there’s no totalitarian enemy to beat. In the 1960s, politicians funded the Moon landings with approximately 170 billion dollars (in current terms) and the lives of the astronauts were considered expendable for the sake of the nation. Thus many technical compromises were made which increased the chances of failure.
For example, Apollo 12 was launched during a storm and was struck twice by lightning, almost killing the crew (Figure 7-1).
Figure 7-1. Lightning strikes the Apollo 12 launch pad at liftoff. NASA photo S69-60068.
The lunar module had a single descent engine and a single engine for return from the Moon; likewise, the command and service module had to rely on a single engine. If any of these failed, the astronauts would die.
Crucial and delicate rendezvous maneuvers had to be performed in orbit around the Moon, instead of close to Earth, to reduce the weight of the spacecraft. In this way, if the lunar module failed to meet the command module after landing on the Moon, no rescue was possible.
Every mission had its share of malfunctions and near failures. Apollo 13 even suffered a crippling oxygen tank explosion that forced to abort its lunar landing. If the explosion had occurred during return from the Moon instead of on the way out, when onboard reserves were still high and the lunar module was still available as a lifeboat, the outcome would have been fatal.
Today, NASA’s budget is almost halved compared to the Apollo era,* the safety requirements are far more stringent and the loss of a crew is politically far less acceptable.
* In 2010 dollars, the total sum of NASA budgets in the period from 1963 to 1969 was 209.2 billion; from 2003 to 2009 it was 113.1 billion.
The race to beat the Soviets ended four decades ago, so space missions are carried out for science rather than for national pride, taking lower risks and using uncrewed spacecraft, which have achieved amazing scientific successes throughout the Solar System; crewed spaceflights have been confined to Earth orbit, for example to assemble and visit the International Space Station.
Right now there is no political, technical or scientific reason that justifies the cost and risk of a crewed return to the Moon. Moreover, for the United States it would be a repeat.
It may seem absurd and implausible that forty years ago we could do something that we can’t do today, but there are other cases of journeys to remote places that were made once and not repeated for decades.
For example, mankind first reached the South Pole in 1911, with Roald Amundsen’s team, followed a few weeks later by Robert Scott’s men (who died on the return trip). After that, nobody set foot on the South Pole for all of 45 years, until US Rear Admiral George J. Dufek and his multinational crew landed there with an aircraft in October 1956.
The Marianas Trench, the deepest point of all of the world’s oceans, almost 11 kilometers (6.8 miles) below the surface, was reached for the first time in 1960 by Don Walsh and Jacques Piccard on board the bathyscaphe Trieste. Fifty-two years passed before anyone returned: director James Cameron went there solo in 2012 with the Deepsea Challenger.
The apparent contradiction of past technology being superior to today’s is explained by similar cases in other fields. In the 1970s we had supersonic airliners (the Anglo-French Concorde and the Russian Tupolev Tu-144). Today, for a wide range of reasons, we don’t.
Until July 2011, there was a spacecraft capable of taking seven astronauts and twenty tons of payload into Earth orbit and landing on a runway like a glider: the Space Shuttle (Russia had Buran, a very similar spacecraft, but it flew only once, uncrewed and without a payload, before the project was canceled). Not anymore: the Shuttle fleet has been retired after thirty years of service, and its current replacements are capsules that land under a parachute, like Apollo did. The Space Shuttles turned out to be too costly and unacceptably dangerous.
7.2 How come the Russians didn’t even try? Did they know it was impossible?IN A NUTSHELL: Actually, they did try, and they tried hard, too. But their giant N1 rockets, designed and built specifically for lunar missions, kept exploding during test launches. The Soviet Moon landing project was abandoned and kept secret to avoid international humiliation, as detailed in Chapter 1, but the cover-up was revealed when the Soviet Union collapsed.
THE DETAILS: There actually was a Moon hoax, but not the one most space conspiracy theorists talk about: the Soviet one, meant to hide all evidence of their failed attempts to be the first to fly a crewed mission around the Moon and then achieve a crewed lunar landing.
The secret Russian L1 fly-around project was based on two scenarios. In the first one, a Proton rocket would launch an L1 spacecraft (a stripped-down Soyuz) equipped with an additional Block D booster stage, flying directly to the Moon.
In the second scenario, the same type of Proton launcher would place an uncrewed L1 spacecraft and Block D stage in Earth orbit; a three-man crew would climb to Earth orbit using a second Soyuz on another rocket. Two of the three cosmonauts would then transfer to the L1 spacecraft and accelerate to fly around the Moon, while the third crewmember returned to Earth.
This project was approved and funded by the Soviet authorities and spacecraft manufacturing was started, with the goal of a lunar fly-around by 1967, one year before the Americans. However, the fatal accident of Soyuz 1, which cost the life of cosmonaut Vladimir Komarov, and the reliability problems of the Proton launcher caused delays that allowed the American space program to achieve the first crewed flight around the Moon with Apollo 8 in 1968.
The Russians also had another secret project, the N1-L3, for landing a single cosmonaut on the Moon, as described in Chapter 1. However, the unreliability of the massive N1 launcher (Figure 7-2) once again caused delays that gave the United States the time to perfect their technology and be the first to land a crew on the Moon.
Russia’s last attempt at a lunar fly-around took place a few days before the Apollo 11 landing and failed when the N1 rocket that carried the uncrewed L1 spacecraft exploded catastrophically on the launch pad.
Figure 7-2. Size comparison between the Soviet N1-L3 system (left) and the Saturn V-Apollo stack (right).
The Soviet conspiracy to hide all traces of these attempts and failures was quite successful, so much that even today many Moon hoax believers are blissfully unaware of this aspect of the space race. At the time, the Russian authorities declared that they had never taken part in a race for the Moon, that they had no intention of taking a Russian to the Moon and that they would never risk a Soviet citizen’s life on such a dangerous endeavor, which could be accomplished just as effectively with uncrewed vehicles. That was the official party line.
Many in the Western media fell for the Soviet hoax. Even celebrated newsman Walter Cronkite stated on TV in 1974 that “it turned out there never had been a race to the Moon”.*
* Fifth Anniversary – Apollo in Retrospect, CBS, July 1974, as quoted in Cronkite on Space: Inspiration, not Information, by James Oberg, in Space Review, 6 March 2006.
However, the reality of the Russian attempts to land a man on the Moon, long suspected by Western experts and partly known to US intelligence, became very public with the collapse of the Soviet Union in the 1990s. Today we even have insider’s reports, such as Russian rocket designer Boris Chertok’s four-volume Rockets and People (1994-1999), detailing the Soviet lunar plans.
7.3 Weren’t 1960s computers too primitive?IN A NUTSHELL: No. The Apollo spacecraft’s computer technology was certainly primitive compared to today’s, but it was still adequate, also thanks to the presence of three very powerful additional “computers”: the astronauts, who were all trained to control the spacecraft and calculate trajectories, orbits and rendezvous by hand if necessary. Moreover, most of the computing power wasn’t on board: it was in NASA’s much larger computers on Earth.
THE DETAILS: Moon hoax theorists often point to the fact that a modern cellphone has more computing power and memory than the onboard computer of the Apollo spacecraft and argue, therefore, that it’s unthinkable that anyone could have flown to the Moon with such limited equipment.
But first of all, the Saturn-Apollo spacecraft had five main onboard computers, not one: two Raytheon AGCs (Apollo Guidance Computers), one in the lunar module and one in the command module; one IBM-built LVDC (Launch Vehicle Digital Computer) in the Saturn’s Instrument Unit; a Honeywell SCS (Stabilization and Control System) in the command module; and a TRW-designed AGS (Abort Guidance System) in the lunar module.
It’s true that the computer hardware of the spacecraft was puny compared to today’s standards. For example, the AGCs (Figure 7-3) had about 8,000 bytes of memory each (a laptop computer currently has at least four billion, i.e., five hundred times more RAM) and a 2.048 MHz clock (yes, that’s a decimal point, not a thousands separator). But these computers could focus all their power on a small set of core tasks and didn’t have to waste power on fancy graphical interfaces or other embellishments, so they were adequate for the tasks they had to perform. Moreover, the onboard systems had the backup of Mission Control’s mainframe computers. In other words, the available computing power wasn’t as small as is often thought.
Figure 7-3. The display and keyboard of an Apollo Guidance Computer (AGC).
The astronauts were also trained extensively to control all the spacecraft’s systems, to calculate trajectories, rendezvous and orbits using slide rules and precomputed charts, and to navigate using the stars. They acted, in a way, as additional computers, making up for the limitations of the automatic systems available at the time: consider, for example, the manual override decided on the spot by Neil Armstrong during Apollo 11 to avoid landing in an unexpected boulder field that the onboard and ground computers couldn’t detect, or the manual realignment performed by James Lovell during Apollo 13 after the automatic navigation system had been shut down to conserve power after an oxygen tank failure crippled their ship.
7.4 How is it possible that everything went so smoothly?IN A NUTSHELL: It didn’t. NASA went out of its way to give this impression, but the truth was quite different. Three astronauts died on the launch pad (Apollo 1). Apollo 13 suffered an explosion that scrubbed its lunar landing and almost killed the crew. Apollo 12 was struck by lightning at liftoff. Apollo 11 had a computer overload as it was landing on the Moon. Every mission had its significant malfunctions, equipment failures and close calls, and many crews were struck by nausea, vomiting and diarrhea, but all this wasn’t widely publicized.
THE DETAILS: Moon hoax theorists often express their sarcastic amazement at the perfection of the Apollo flights to the Moon. How is it possible that such incredibly complex and powerful machines, which pushed the envelope of 1960s technology, could work so flawlessly? And how could astronauts be so impeccably cool and professional on such life-threatening journeys?
Actually, this perfection is only an impression driven by superficial knowledge of the events and by the fact that the political importance of the lunar missions prompted NASA and the media to gloss over the errors and failures and the less dignified aspects of the endeavor. National prestige was at stake, so problems were played down in public. Some failures, however, were too big to be brushed under the carpet.
As a matter of fact, out of seven Moon landing missions, one failed (Apollo 13). Three astronauts died on the launch pad (White, Grissom and Chaffee, Apollo 1). All the missions had problems that brought the crew close to disaster or abort. Here are a few examples taken from the technical mission reports. A more extensive list of the various critical and non-critical malfunctions that affected the various missions is in the Discrepancy Summary section of the Post-launch Mission Operation Reports.
Apollo 7Water from the cooling systems pooled in the cabin, posing a serious danger in an environment crammed with electrical wiring.
The crew was plagued by a cold that blocked their nasal passages: a serious problem in spaceflight, because in weightlessness fluid accumulates instead of draining and blowing one’s nose can cause severe ear pain, and because during reentry, with their head enclosed in the helmet, the astronauts would be unable to clear their ears and therefore compensate for cabin pressure changes, with the risk of eardrum damage. Despite NASA’s strong disagreement, the crew performed reentry without wearing their helmets and suffered no physical consequences.
The Apollo 7 crew also refused orders from Mission Control, and commander Walter Schirra had no uncertain words about the unprecedented workload of the maiden flight of the Apollo spacecraft, speaking openly of “tests that were ill prepared and hastily conceived by an idiot” and declaring that he’d “had it up to here” and that his crew was “not going to accept any new games... or going to do some crazy tests we never heard of before.” This was one of several underreported rebellions of spaceflight crews.*
* Apollo: the Epic Journey to the Moon, by David Reynolds and Wally Schirra.
Apollo 8The first crewed flight around the Moon was troubled by bouts of vomiting and diarrhea during the first day of flight, nearly forcing an early return home.
Three of the five spacecraft windows were fogged by sealant leaks, hindering viewing and lunar photography. Water formed dangerous pools in the cabin.
Jim Lovell accidentally erased part of the computer’s memory, and the crew was forced to compute and reenter the correct data by hand.
Apollo 9Astronaut Rusty Schweickart vomited repeatedly due to nausea induced by weightlessness forcing cancellation of the emergency procedure test (a spacewalk from the Lunar Module to the Command Module) that he was scheduled to perform.
One of the maneuvering thruster sets of the command and service module and the tracking lights of the lunar module failed due to a misplaced switch: these were crucial components, since the two modules had to maneuver and fly separately, 185 kilometers (115 miles) apart, in Earth orbit and then find each other and dock again, otherwise the two crewmembers in the LM would have died in orbit, unable to return to Earth. Rendezvous was achieved despite these failures thanks to the skill of the astronauts.
Apollo 10When the ascent stage of the LM separated from the descent stage, just 14.45 kilometers (47,400 feet) above the lunar surface, an incorrect switch setting made the spacecraft spin wildly about two axes, coming dangerously to a so-called gimbal lock (loss of orientation of the navigation system). Astronaut Gene Cernan let slip a heartfelt “Son of a bitch!”, which was picked up by his open radio mike and transmitted live to world audiences back on Earth.
Apollo 11During the first Moon landing, the lunar module’s computer overloaded repeatedly. The preprogrammed flight path would have taken the spacecraft to a boulder-strewn area, where landing and liftoff would have been prohibitive if not impossible. Only Armstrong’s manual intervention to change landing site saved the mission.
Radio communications in lunar orbit, after separation of the LM from the command module, were so poor and broken up that Armstrong and Aldrin in the LM didn’t hear the “go” to initiate descent to the Moon from Mission Control. Fortunately it was picked up by Michael Collins, in the command module, who relayed it to his colleagues.
After landing on the Moon, one of the propellant lines of the descent stage failed to vent correctly due to freezing, leading to a potentially explosive pressure buildup. Mission Control noticed the problem and was discussing it guardedly with the crew when it cleared itself up by thawing.
After the moonwalk, the astronauts realized that the knob of a circuit breaker required for arming the ascent engine was broken, probably because it had been struck by Aldrin’s backpack. If that circuit could not be operated, liftoff from the Moon would be impossible. The astronauts improvised by using a felt-tipped pen to operate the failed breaker.
On returning from the lunar surface, when the LM docked with the command and service module, the slightly incorrect alignment of the two spacecraft triggered an uncontrolled rotation that the onboard computers both tried to correct, contrasting each other and worsening the spin. Only Collins and Armstrong’s skills allowed to correct manually the chaotic tumbling of the mated vehicles.
Apollo 12The lightning that struck the Saturn V during liftoff caused widespread instrument malfunctions and a total loss of meaningful telemetry. Only an unusual suggestion by John Aaron in Mission Control (the request to set “SCE to AUX”), radioed up to the astronauts, allowed them to restore telemetry and prevented the mission from being aborted immediately.
During the live TV broadcast from the Moon, the TV camera was pointed accidentally at the sun and its delicate sensor burned out, ending TV transmissions for the mission’s moonwalk.
At the end of the flight, during atmospheric reentry, the wind caused the command module to swing beneath its parachutes and the astronauts were subjected to 15 g of deceleration on impact; a camera fell from its holder and struck Alan Bean on his temple. Had it fallen slightly differently, it would have caused a potentially fatal head trauma.
Apollo 13As already mentioned, an oxygen tank in the service module ruptured explosively, depriving the astronauts of air and power reserves. It became necessary to use the LM as a lifeboat and return hurriedly to Earth after looping around the Moon. James Lovell had to align the navigation systems manually by star sighting.
Apollo 14On the way to the Moon, the docking mechanism between the LM and the command module failed five times before finally working. This meant that it might fail again when the LM returned from the Moon, forcing the astronauts to perform a dangerous spacewalk to transfer from the LM to the command module, but the decision was made to go ahead with the landing nonetheless.
An errant solder ball in the LM caused the onboard computer to receive a false abort signal, which during lunar descent could have triggered an unnecessary emergency climb back to orbit, canceling the Moon landing: in the nick of time, NASA and MIT managed to reprogram the computer to ignore the false signal.
Apollo 15One of the three splashdown parachutes failed to open fully (Figure 7-4), leading to a violent impact with the ocean. The malfunction was probably caused by venting propellants, which could have caused all three parachutes to fail, with fatal consequences for the crew.
Figure 7-4. Apollo 15’s splashdown with a malfunctioning parachute. Detail of photo AS15-S71-42217.
Apollo 16The command and service module main engine, crucial for returning to Earth, reported a malfunction while the spacecraft was in orbit around the Moon. The Moon landing was almost scrubbed.
7.5 Why do a rendezvous in lunar orbit? It makes no senseIN A NUTSHELL: Actually, it does. Lunar rendezvous was chosen despite its dangers because it reduced drastically the fuel and payload requirements. It’s riskier than doing it in Earth orbit, or avoiding it completely by landing directly on the Moon with a single spacecraft instead of using a two-part vehicle, but these alternatives would have required a truly gigantic rocket, far bigger than the already massive Saturn V.
THE DETAILS: Some Moon hoax believers find it preposterous that NASA chose to perform intricate undockings, redockings and rendezvous between the command module and the lunar module, and to perform them near the Moon instead of in Earth orbit, which offered better chances of rescue. Better still, why not follow the classic method featured in so many science fiction movies and land directly on the Moon with the main spacecraft, without using a separate lunar module?
Actually, NASA’s initial plan was indeed to land on the Moon with a single, large, tall spacecraft: a concept known as tailsitter. However, a direct flight to the Moon would have required a colossal rocket, the Nova (Figure 7-5), which didn’t exist yet and could not be completed in time for President Kennedy’s deadline. The only booster that could be developed in time was the Saturn V, which was relatively smaller.
Figure 7-5. The giant Nova booster (right) compared with the C-5, precursor of the Saturn V (center). Document M-MS-G-36-62, April 1962.
Mission planners also considered using a first Saturn V to launch an uncrewed tailsitter spacecraft into Earth orbit, followed by a second Saturn with the fuel. This was known as Earth Orbit Rendezvous and was NASA’s favored plan for some time. However, it entailed two closely coordinated launches and a dangerous transfer of fuel in space.
An alternative option was to split the tailsitter into two separate vehicles: the main one would remain in orbit around the Moon and the secondary one would be a stripped-down, specialized Moon lander. This approach reduced weight and fuel requirements so much that it allowed to launch the entire mission with a single Saturn V rocket. However, the savings came at the cost of a risky rendezvous in lunar orbit (hence the name Lunar Orbit Rendezvous or LOR), which entailed certain death for the moonwalkers if it failed. A high-stakes gamble, in other words, but a perfectly logical one.
The lunar orbit rendezvous plan wasn’t new: it had been conceived in 1916 by Russian spaceflight theoretician Yuri Vasilievich Kondratyuk. Nevertheless, NASA was very reluctant to take this perilous and untested path. John Houbolt, a relatively low-ranking aerospace engineer in the agency, is often credited with turning Wernher von Braun and NASA management around on this matter in 1962.
7.6 Why don’t we just point a telescope at the landing sites?IN A NUTSHELL: Because even the most powerful telescopes currently available on Earth can’t see such small features. Trigonometry and the laws of optics dictate that seeing any detail of the vehicles and equipment left at the Apollo landing sites from Earth would require a telescope with a mirror at least 45 meters (150 feet) in diameter. No current ground-based telescope comes even close.
THE DETAILS: The resolution of a telescope, i.e., the detail that it can see, is determined by the laws of optics, specifically by a formula known as Dawes’ limit, and depends essentially on the diameter of the main lens or mirror. Adding a lens to magnify the image acquired by this main telescope component will not yield more detail – only more blur.
The largest objects left on the Moon by the Apollo astronauts are the descent stages of the lunar modules, which measure approximately 9 meters (30 feet) across diagonally opposite footpads. A little trigonometry shows that at the minimum Earth-Moon distance, which is about 355,000 kilometers (220,600 miles), seeing the descent stage is equivalent to seeing a US one-cent coin from 740 kilometers (460 miles) away.
No current earthbound telescope can do that; not even the Hubble Space Telescope (Figure 7-6), which at the distance of the Moon can resolve nothing smaller than about 80 meters (262 feet).
Figure 7-6. The Hubble Space Telescope.
That’s an apparently counterintuitive fact. After all, telescopes can see incredibly distant galaxies, so why can’t they get a good picture of a 9-meter (30-foot) object on the Moon, which is in our back yard, astronomically speaking?
The reason is that galaxies are enormous, while the Apollo objects on the Moon are tiny, and their closeness doesn’t compensate for the difference in size.
For example, the Andromeda galaxy is two million light years away (19 million million million kilometers or 12 million million million miles), yet it’s bigger than the full Moon in our night sky; it’s hard to see with the naked eye because it’s very faint. That’s why large astronomical telescopes are designed more to collect light from these remote objects than to magnify them.
Dawes’ limit dictates that even in ideal conditions, seeing the Apollo lunar module descent stages on the Moon from Earth as nothing more than a bright dot would require a telescope with a primary lens or mirror at least 45 meters (150 feet) wide. Resolving any details of the spacecraft would require even more colossal telescopes.
The largest single-mirror telescopes on Earth are currently just over ten meters (33 feet) in diameter. Even the future record holder, the aptly-named European Extremely Large Telescope, which is scheduled for 2018, will be inadequate, because its composite primary mirror will only span 42 meters (138 feet).
A technique known as interferometry, however, allows astronomers to pair two telescopes to obtain a sort of “virtual” instrument that has a resolution equal to a single telescope with a primary mirror as large as the distance between the two telescopes. The Very Large Telescope in Chile, one of the best-equipped observatories for this kind of science, in ideal conditions could achieve a resolution of 0.002 arcseconds: enough to show the LM on the Moon as a handful of pixels (dots forming a digital image). That sounds promising, but there’s a catch.
Interferometry doesn’t produce directly viewable images, but only interference patterns, which require computer processing to extract meaningful information. This means that there’s no way to put a Moon hoax theorist in front of a massive telescope and tell him or her to peer into the eyepiece to see the Apollo landing sites in any significant detail.
However, it is quite possible to take a telescope close to the Moon, point it at the Apollo landing sites and view them with enough detail to make out the Apollo spacecraft. This is what several space probes of various countries have done, as detailed in Chapter 3 and below.
7.7 How come nobody sends probes to take pictures of the landing sites?IN A NUTSHELL: Actually, several countries, such as India, China, Japan and the United States, have sent science probes to the Moon and have surveyed its entire surface, including the Apollo landing sites. Their images confirm that there are vehicles and science instruments exactly where NASA said it placed them.
THE DETAILS: Over the course of the four decades since the Apollo crewed landings, the Moon has been visited and mapped in progressively greater detail by uncrewed probes sent by China, India, Japan and the United States. Some of these spacecraft are currently in operation in orbit around the Moon, sending fresh images and science data.
The 1994 Clementine probe, launched by NASA, was able to image a patch of differently reflective soil exactly where NASA said that Apollo 15’s LM had landed. This is compatible with the soil color changes expected as a consequence of the displacement of surface dust and the exposure of differently-colored underlying rock caused by a spacecraft rocket motor.
The same site was photographed in more detail in 2008 by the Japanese Kaguya probe (Figure 7-7), in 2009 by India’s Chandrayaan-1 and in 2012 by the Chinese Chang’e-2 spacecraft, confirming the Clementine findings and revealing a dot at the center of the patch: presumably, the descent stage of the Apollo 15 LM or its shadow.
Figure 7-7. The bright halo is located where Apollo 15 landed. Credit: JAXA/Selene.
Kaguya also performed altimetric measurements of the Moon, generating a 3D terrain map that matches exactly the terrain shown in the Apollo photographs.
In 2009 the United States’ Lunar Reconnaissance Orbiter (LRO) became the first probe to image directly the Apollo vehicles as well as the science experiments, the lines of footprints of the astronauts and the wheel tracks made by their electric car. Its first pictures were released in July 2009; some are shown in Chapter 3.
7.8 How could the large Moon buggy fit inside the small Lunar Module?IN A NUTSHELL: It was folded up inside the Lunar Module’s descent stage.
THE DETAILS: Many people compare the sizes of the Lunar Roving Vehicle or Rover (the electric car used by Apollo 15, 16 and 17) and of the lunar module and wonder how the Rover could fit inside the LM. The Rover was 2.96 meters (116.5 inches) long, 2.06 meters (81 inches) wide and 1.14 meters (44.8 inches) tall and at first glance seems to be incompatible with the dimensions of the lunar module, whose descent stage was about 4.3 meters (14.1 feet) wide and also had to accommodate the descent rocket engine and its fuel.
The answer is quite simple: the LRV was designed to fold up for transport so that it would fit in one of the wedge-shaped recesses provided in the descent stage frame, covered only by a thermal protection sheet.
The Rover was simply an aluminum chassis with four small electric motors for driving the wheels and two additional motors for actuating the steering system, a battery pack and two tubular frame seats. On Earth it weighed just 210 kilograms (462 pounds). It required no gearbox, no transmission shafts and no wheel axles (the wheels were coupled directly to the motors) and so it could be folded up into a very compact shape (Figure 7-8).
The TV footage of the moonwalks show very clearly how the Rover was extracted and unfolded into its configuration for use.
Figure 7-8. The Apollo 15 Rover, compactly folded into a wedge-like shape with its wheels clustered together, is ready to be stowed in one of the equipment recesses of the LM descent stage. Detail of photo AP15-71-HC-684.
7.9 How come Apollo didn’t reach escape velocity?IN A NUTSHELL: Because it didn’t need to. Getting to the Moon doesn’t require escape velocity: a spacecraft only has to achieve a speed that produces a highly elongated orbit around the Earth that reaches a maximum altitude equal to the distance of the Moon, without ever escaping from the Earth’s pull.
THE DETAILS: This pro-conspiracy argument is a fine example of the misuse of science jargon and factual data to give an impression of competence and knowledge. Its premise is that the escape velocity, the speed required to escape the Earth’s gravity field, is 11.2 kilometers per second (about 7 miles per second), i.e., 40,320 kilometers per hour (about 25,000 mph). This is correct. However, NASA reported that the top speed of Apollo 11 during its climb to the Moon was about 39,000 kilometers per hour (about 24,250 mph). This, too, is factually correct.
In other words, Apollo 11’s stated maximum speed was about 1,230 kilometers per hour (765 mph) slower than escape velocity. So, the argument goes, how could the spacecraft escape Earth and reach the Moon?
The answer to this apparent contradiction is that escape velocity is required only if the spacecraft seeks to escape Earth’s attraction permanently. Anything traveling at this velocity will never fall back to Earth and will continue to climb away from it indefinitely without requiring any additional thrust (more specifically, it will escape from Earth’s gravity field yet will still be in the grip of the Sun’s gravitational attraction).
A spacecraft doesn’t actually need to reach escape velocity to get to the Moon. It just has to achieve a speed that produces an elliptical orbit around the Earth that stretches out to the distance of the Moon and is timed so that the Moon is at the opposite end of the ellipse when the spacecraft gets there. So the Apollo flights didn’t have to reach escape velocity to land on the Moon or fly around it.
Actually, staying below escape velocity is a safety bonus, because it allows to use a so-called free return trajectory (Figure 7-9): the spacecraft will fall back to Earth spontaneously, without requiring additional maneuvers or thrust from its rocket motors. This is particularly useful in case of major malfunctions, as in the case of Apollo 13.*
* More specifically, Apollo 13 began its flight on a free return trajectory and then fired its main engine to leave this trajectory and fly towards the Moon. After the onboard explosion, the thrust of the LM’s descent engine was used to inject the astronauts into another free return trajectory.
Figure 7-9. The main trajectories used by the Apollo missions. From the Apollo 11 Press Kit.
7.10 Is it true that the Saturn V wasn’t powerful enough?IN A NUTSHELL: No. A mathematical analysis of the liftoff footage of the Saturn V, published by Russian scientist Stanislav Pokrovsky, appears to prove that the first stage of the lunar rocket didn’t reach the speed stated by NASA and therefore could carry to the Moon far less payload than officially stated. However, the analysis is based on highly inaccurate estimates and on an incorrect premise: the actual work of getting the astronauts to the Moon was performed by the third stage, not the first one, which like the second one was only designed to place the spacecraft in Earth orbit and did so correctly, even according to Pokrovsky’s analysis.
THE DETAILS: A highly complex, math-heavy analysis published in Russian by Stanislav Pokrovsky and available in English from pro-hoax site Aulis.com (which describes Pokrovsky as a “scientist”) argues that the actual speed of the Saturn V Moon rocket when it exhausted the fuel of its first stage and separated from the rest of the spacecraft was only half of the speed claimed by official documents.
Pokrovsky claims that the F-1 engines of the Saturn’s first stage were not powerful enough to carry to the Moon the 46-ton payload constituted by the command and service module and lunar module. His calculations suggest that the low speed entailed that the maximum payload that could be delivered to the Moon was approximately 26 tons. Since the CSM weighed over 30,000 kilograms (66,000 pounds) and the LM weighed over 15,000 kilograms (33,000 pounds), Pokrovsky argues that NASA could fly one or the other, but not both, to the Moon, and therefore the best it could achieve was a flight around the Moon, without landing.
However, despite the impressive charts and formulas, the entire analysis is based on an estimate of the progressive apparent distance between the Saturn V and the exhaust plume of the first-stage retrorockets; an estimate made purely by examining blurry footage from one of NASA’s tracking cameras (Figure 7-10). It is quite hard to measure the exact point where a rocket plume ends.
Figure 7-10. The frames of the liftoff footage analyzed by Pokrovsky.
Moreover, Pokrovsky assumes that the retrorocket plume somehow stopped in mid-air, instantaneously losing the tremendous speed of the spacecraft that generated it, and therefore can be used as a fixed reference point to calculate the speed of the Saturn V rocket. But the first stage separated from the rest of the spacecraft (Figure 7-11) at an altitude of over 61,000 meters (200,000 feet), where the atmosphere is approximately 10,000 times thinner that at sea level, so there was no significant air resistance to slow the plume or stop it. By inertia it would continue to climb, chasing the rocket and thus biasing any visual estimate of distance and speed.
Figure 7-11. Separation of the first stage of the Saturn V during the Apollo 11 flight. Detail from NASA photo S69-39958.
Apart from the inaccurate data, Pokrovsky’s analysis is invalidated by the fact that the Saturn V’s first stage, together with the second stage, only had the task of placing the third stage and the Apollo spacecraft into Earth orbit (with some help from the third stage). The first two stages did not contribute to the actual trip from Earth orbit to the Moon, which was instead powered by the third stage.
Since Pokrovsky acknowledges that Earth orbit was achieved by the Apollo vehicles, all his remarks and calculations regarding the actual speed of the first stage are simply irrelevant in terms of how many tons of payload could be sent to the Moon.
Moreover, in the laws of physics that govern orbital flight what matters is the final speed of a spacecraft, which must be sufficient to stay in orbit without falling back to Earth. The speed during the climb to altitude is only relevant in terms of fuel consumption and crew comfort: a faster climb uses less fuel, but subjects the astronauts to higher acceleration stresses (up to 4.7 g for the Saturn V; Gemini’s Titan launchers reached 7 g). In principle, a slow climb to orbital altitude followed by acceleration to orbital speed would still achieve orbit. Therefore Pokrovsky’s issue of first stage speed is irrelevant.
7.11 How could the tiny LM climb back from the Moon?IN A NUTSHELL: It didn’t have to fight against air resistance, it only had to cope with one sixth of Earth’s gravity, and it only had to reach one quarter of the orbital speed required to orbit the Earth. The fuel demands of a lunar liftoff are far lower than terrestrial ones and the payload was minimal (two astronauts, some Moon rocks and a tiny, ultralight spacecraft). Also, the LM only had to achieve lunar orbit, not lunar escape velocity, since the thrust for the trip back to Earth was provided by the service module’s main engine.
THE DETAILS: The truly minuscule size and fragile appearance of the LM’s ascent stage used to return from the Moon (Figure 7-12) are a striking contrast to the colossal size of the Saturn V required to leave Earth. Some people doubt that such a tiny spacecraft could be adequate and wonder, for example, where all the fuel needed to climb and accelerate to orbital speed could be stored.
Figure 7-12. The Apollo 16 ascent stage. Detail from photo AS16-122-19530.
Actually, the comparison is quite misleading, because it would be harder to find two more dissimilar liftoffs. The Saturn V had to lift its own huge initial mass of approximately 2,900 tons against Earth’s gravity and against air resistance (aerodynamic drag) up to a speed of 28,000 kilometers per hour (about 17,400 miles per hour) and inject a 130-ton payload into Earth orbit, at an altitude of 190 kilometers (118 miles).
The LM’s ascent stage instead had to lift an initial mass of 4.5 tons (of which 2.3 were fuel, leading to a very large loss of mass during the climb as the fuel was used) and accelerate it to approximately 6,600 kilometers per hour (4,100 miles per hour), raising a payload of 2.2 tons to a maximum altitude of 83 kilometers (approximately 51 miles). Moreover, on the airless Moon there was no atmospheric drag and the gravity was one sixth of the Earth’s.
The idea of having to reach escape velocity is also wrong: as mentioned in section 7.9, escape velocity is required only to fly away indefinitely from a celestial body without further fuel consumption. But the LM didn’t need to do that: it only had to reach a speed that allowed it to enter an elliptical orbit with a minimum altitude of 16.6 kilometers (10.3 miles) and a maximum altitude of 83 kilometers (about 51 miles).
The extra thrust required to leave lunar orbit and fly back to Earth was provided by the rocket engine of the service module, which stayed in lunar orbit indeed to avoid landing and bringing back up additional mass. NASA’s choice of a lunar rendezvous was made for this very reason: to achieve great mass and fuel savings.
All these factors drastically reduce the power requirements of a lunar liftoff, so approximately 2,350 kilograms (5,181 pounds) of fuel, constituted by 910 kilograms (2,006 pounds) of Aerozine 50 and 1,440 kilograms (3,175 pounds) of dinitrogen tetroxide, were sufficient to lift the stripped-down ascent stage into a low lunar orbit.
That may sound like a lot of fuel to store in such a small spacecraft, but these substances have a density of 0.903 g/cm3 and 1.443 g/cm3 (56.372 and 90.083 lb/ft3) respectively, and therefore the quantities reported by NASA have a volume of approximately 1 cubic meter (35.3 cubic feet) each, which fits quite adequately in the two spherical tanks located in the bulges at the opposite sides of the cylindrical crew compartment of the ascent stage (Figure 7-13 shows the Aerozine 50 tank).
Figure 7-13. A cutout view of the LM ascent stage published by Grumman.
7.12 How could the Lunar Module be so stable?IN A NUTSHELL: The irregular shape of the LM, with its odd bulges and single central rocket motor, seems strangely top-heavy and as unstable as a football balanced on a finger, ready to tip sideways at the slightest wobble: apparently impossible to fly. But if you look at its internal structure it turns out that it was actually easier to stabilize than a conventional pencil-shaped rocket, because its main masses were located at or below the center of thrust of the motor and therefore its center of mass was quite low.
THE DETAILS: Moon hoax theorist Bart Sibrel claims that the Apollo lunar module had a high center of mass that made it too unstable to fly. Sibrel is not an aerospace specialist, yet he appears to believe that he can judge the stability of a spacecraft just by looking at its picture. Actually, a less superficial examination based on some elementary physics reveals that the LM was easier to stabilize than a conventional rocket.
In the descent stage and in the ascent stage, the fuel tanks, which are the most important masses of the vehicle, were located as low as possible, laterally with respect to the motor (Figure 7-14).
Figure 7-14. Arrangement of the fuel tanks in the LM descent stage.
This is a far less unstable configuration than a conventional rocket, in which the tanks (and therefore their great masses) are located above the engines. Placing these tanks laterally and at opposite ends actually helped to stabilize the vehicle, somewhat like the pole of a tightrope walker.
Moreover, the main engines were not underneath the spacecraft, as a cursory inspection of the LM might suggest, but were deep inside it, with only the nozzle protruding below. The ascent stage’s engine was actually inside the crew compartment (Figure 7-15). This meant that the center of thrust (the imaginary point, located at the top of the nozzle, on which a vehicle “rests” when its engine is on) was close to the center of mass, which was an ideal situation in terms of stability.
Figure 7-15. Cross-section of the LM ascent stage: the main rocket motor is shaded. Source: Apollo Operations Handbook, volume 1, with added shading.
Finally, the sixteen maneuvering thrusters were placed at the end of outriggers, as far as possible from the thrust axis of the main engine, so as to augment their effectiveness in a lever-like fashion.
The asymmetrical shape of the lunar module was actually dictated by the choice to balance it: in the ascent stage, for example, the dinitrogen tetroxide tank was placed closer to the engine thrust axis than the tank that stored the Aerozine 50 because this fuel component is considerably lighter than dinitrogen tetroxide for an equal volume.
7.13 How come the astronauts didn’t unbalance the tiny LM?IN A NUTSHELL: Because their movements had a very small effect and were compensated automatically by the onboard computers.
THE DETAILS: In Fox TV’s Did We Land on the Moon?, Ralph Rene alleges that the movements of the astronauts in the cabin of the lunar module would have shifted the center of mass continually and therefore would have caused the spacecraft to tip over uncontrollably and crash. Therefore, he argues, the LM could not fly and accordingly the Moon landings are fake.
The facts are quite different. First of all, the LM had not one, but two automatic stabilization systems that controlled the maneuvering thrusters (the ones clustered at the end of the ascent stage’s outriggers) to compensate constantly for any imbalance. The astronauts didn’t stabilize the spacecraft manually. The computer-controlled stabilization can be noticed in the liftoff footage, which shows a characteristic periodic oscillation induced by the automatic firing of the thrusters as soon as an imbalance was detected.
The concept is not at all unusual: any rocket has the same problem of compensating for shifts in the center of mass (for example due to fuel displacement or depletion). In the atmosphere, fins can be used; in space, gimbaled main engines and small maneuvering thrusters are used. This is a solution shared by all spacecraft of all countries, including the Space Shuttle.
Secondly, the astronauts stood very close to the center of mass of the lunar module and didn’t have much room to move anyway (Figure 7-16).
Figure 7-16. The position of the astronauts in the LM during flight. The main engine is between them; the fuel tanks are at the opposite sides of the outline. Detail of Figure 1-6 of the Apollo Operations Handbook.
Moreover, the astronauts weighed far less than the fuel tanks, which had a mass of 910 and 1,440 kilograms (2,006 and 3,175 pounds) respectively. The crew’s movements, therefore, couldn’t affect the balance of the spacecraft to any great extent. The main challenge to stability was the sloshing of the fuel in the tanks as they gradually emptied, but this was handled by the computer-based stabilization systems.
7.14 How come the LM simulator was so unstable that it crashed?IN A NUTSHELL: Neil Armstrong narrowly escaped from a crash of the lunar landing simulator. But that doesn’t mean that the Lunar Module was unstable. The simulator was a completely different vehicle than the LM, and anyway the crash was caused by a rare malfunction of the vehicle, not by Armstrong’s inability to control it. The simulator had flown normally over 790 times without loss of control.
THE DETAILS: The Apollo astronauts familiarized with the unique characteristics of the lunar module by using two types of flying simulator, known as Lunar Landing Research Vehicle (LLRV) and Lunar Landing Training Vehicle (LLTV). These were essentially bare frames on which a gimbaled jet engine was mounted vertically, so that its thrust supported five sixths of the weight of the ungainly craft. The remainder (the weight it would have had on the Moon) was supported by two throttleable rocket engines (Figure 7-17).
Figure 7-17. An LLRV in flight in 1964. Detail from NASA photo ECN-506.
Like the LM, these vehicles had sixteen small thrusters for attitude control. An electronic system kept the main jet engine constantly vertical and adjusted its thrust so as to simulate the effects of the reduced vertical acceleration that occurs on the Moon. Flights lasted only a handful of minutes, but were long enough to practice landing from an altitude of approximately 1,200 meters (4,000 feet).
Two LLRVs were built first, followed by three LLTVs. Armstrong’s accident occurred on May 6, 1968, with an LLRV (Figure 7-18): the pressurization system of the attitude thrusters failed, a gust of wind caught the vehicle, and Armstrong had no choice but to eject, landing safely under his parachute while the LLRV crashed and burned.
Figure 7-18. Neil Armstrong parachutes to safety after the malfunction of his LLRV.
During the training flights, these experimental vehicles suffered two more accidents, in December 1968 and in January 1971, leading to their destruction. The pilots were unharmed.
Conspiracy theorists make it sound as if crashing was the normal conclusion of the flights of these vehicles, but in actual fact the five simulators that were built flew a total of 792 flights with successful landings. Armstrong’s LLRV had flown without mishap 281 times before the crash.*
* Unconventional, Contrary, and Ugly: The Lunar Landing Research Vehicle, by Gene J. Matranga, C. Wayne Ottinger and Calvin R. Jarvis with C. Christian Gelzer. NASA SP-2004-4535 (2005), p. 142.
7.15 How come all the technical problems suddenly vanished?IN A NUTSHELL: They didn’t. Problems occurred throughout all the missions and the first uncrewed flights were designed, as usual, to shake down the vehicles and correct or reduce their defects before the actual crewed missions were flown.
THE DETAILS: A recurring argument among hoax theorists is that the early Apollo missions were plagued with problems, leading to very public delays and cancellations, but all the troubles disappeared just in time for the flights to the Moon.
For example, Mary Bennett and David Percy claim that “[the Saturn V] performed flawlessly throughout the entire Apollo program. But the early Saturn V F-1 engine tests were absolutely disastrous, with catastrophic explosions on the test stand.” They add that “The problem of combustion instability [...] known as the ‘pogo effect’ (the industry term for those internal oscillations we mentioned earlier) was in evidence from early testing of the Saturn rocket right through to the ‘Apollo 10’ launch – after which everything worked perfectly!” And Bill Kaysing asked “Why was Apollo 6, a total fiasco, followed by six perfect moon missions which in turn were followed by the manned orbiting lab debacle?”*
* Mary Bennett and David Percy, Dark Moon, p. 127-128; Bill Kaysing, We Never Went to the Moon, p. 8.
Actually, if you check these claims against the mission reports, it turns out that the Saturn V’s performance wasn’t “flawless” at all. It always got the job done, but nearly all flights reported substantial problems. Far from working “perfectly” after Apollo 10, as Bennett and Percy claim, the Saturn V was troubled by the pogo effect during Apollo 11 and 12 as well, leading to violent vibrations of the central F-1 engine of the first stage. For Apollo 13, vibrations were so intense that the central J-2 engine of the second stage had to be shut down automatically during ascent to Earth orbit to prevent it from tearing the spacecraft to pieces. Changes made for Apollo 14 finally made the problem manageable. Section 7.4 of this chapter covers in detail the major malfunctions and problems that affected the Apollo missions.
As regards the “catastrophic explosions on the test stand,” that’s why rocket designers have tests and use test stands: to iron out the worst kinks before actual flights. Indeed, celebrated Russian designer Boris Chertok noted repeatedly, in his monumental book series Rockets and People, that one of the key reasons for the failure of the Soviet moonshot attempts was the unwise decision to avoid building a full-scale test firing rig for the giant N1 rocket, opting instead to test the engines directly in a series of uncrewed flights. This decision led to four consecutive catastrophic failures of the N1, after which the project was scrubbed and buried.
The successful performance of the Saturn V was the result of extensive testing not only on the ground, but also in flight. There’s a reason why the first actual crewed Apollo flight, after the Apollo 1 fire that killed Grissom, White and Chaffee on the pad during a test, was number 7: all the previous ones were uncrewed test launches.
Test flights AS-203 and AS-202, launched in 1966, respectively tested the S-IVB, which would become the third stage of the Saturn V (Figure 7-19), and flew the command and service modules, testing the heat shield at reentry speeds similar to those expected for a return from the Moon and also qualifying the Saturn IB for crewed flights.
Figure 7-19. Liftoff of AS-203.
Apollo 4 was the first flight of the giant Saturn V rocket (no flight was ever formally designated Apollo 2 or 3); this uncrewed test validated, among other things, the radiation shielding of the crew cabin and was considered very successful. It was an “all-up” flight: a bold gamble to test all the main components at once, rather than one at a time in separate flights.*
* Saturn V Launch Vehicle Flight Evaluation Report – AS-501 Apollo 4 Mission.
The next flight, Apollo 5, was likewise uncrewed because it was an automatic test of the lunar module in Earth orbit, using a Saturn IB booster. Both of the LM’s engines were fired and stage separation was performed. The flight also tested the automatic flight management systems (Instrument Unit) in the configuration that would later be used by the Saturn V.
Apollo 6 (Figure 7-20) was the second uncrewed “all-up” test flight of the Saturn V, also checking the capability of the command module to shield the crew from radiation during their brief transit through the Van Allen belts. It was affected by violent pogo oscillations caused by structural resonances; two of the five engines of the second stage underwent a premature shutdown (one because of the oscillations and one due to incorrect wiring); and the third stage yielded less thrust than expected. These problems were analyzed and addressed in later flights by changing the resonance frequencies of some components, adding dampers and scheduling additional wiring checks. That’s what test flights are for. Despite this, the crewed flights of Apollo 8 and 10 were troubled by pogo oscillations in the central engine of the second stage.
Figure 7-20. Apollo 6: separation of the ring between the first and second stages, filmed by an onboard automatic camera.
7.16 Why is there no engine noise in the Moon landing audio?IN A NUTSHELL: Because the astronauts kept their microphones very close to their mouths, so as to cut out background noise, and because the mikes were designed to pick up only sounds at close range, just like aircraft pilot microphones. Anyway, in a vacuum the rocket exhaust doesn’t interact with an atmosphere, which is what produces most of the familiar roaring noise.
THE DETAILS: Bill Kaysing, in Fox TV’s Conspiracy Theory: Did We Land on the Moon?, says that “the noise level of a rocket engine is up into the 140/150-decibel range. In other words, enormously loud. How would it be possible to hear astronauts’ voices against the background of a running rocket engine?” Indeed, the recordings of the astronauts’ communications during landing and liftoff, while the rocket engines are running, contain no engine noise.
This apparently unusual fact is actually quite normal and occurs not only in the Apollo recordings, but also in Shuttle liftoff recordings. Moreover, when we take a plane and the captain makes a passenger announcement, his voice isn’t drowned out by the noise of the engines, even though the same noise is audible in the cabin.
The explanation is quite simple: the microphones were designed to cut out background noise and were kept very close to the mouth. Bill Anders (Apollo 8, Figure 7-21) reportedly called them “tonsil mikes” because he said that he had to shove them down his throat to make them work. This allowed the voice to drown out the roar of the engines – if there was any to begin with. Kaysing’s claim is in fact incorrect: the noise of a spacecraft engine is not always “enormously loud”.
Figure 7-21. Bill Anders prepares for the Apollo 8 mission. Note the microphones on either side of his chin. NASA photo 68-H-1330.
When a rocket engine operates in vacuum, its exhaust expands without encountering any obstacle: it doesn’t collide at supersonic speed with an atmosphere and therefore it doesn’t generate the shockwaves that instead cause the loud noise that is heard on the ground when a large rocket is launched.
Both Apollo astronauts and current spacecraft crews report that when they are in space, sometimes they hear a bang at the moment of ignition, before combustion stabilizes, and they feel occasionally intense vibration; but apart from this, they say that the engines are noiseless. It seems unlikely that they’re all lying.
7.17 How could the fragile LM withstand temperature extremes so well?IN A NUTSHELL: There’s a good reason why the lunar module could stand on the Moon with one side exposed to the sun and the opposite side in shadow, without overheating or freezing: it was insulated by a highly efficient multilayer thermal blanket. This gave it its characteristic “tin foil” appearance, which made it seem fragile while it was actually better protected against temperature variations than the rest of the Apollo spacecraft.
THE DETAILS: During the voyage to and from the Moon, the great thermal differences between the side of the spacecraft that was in full sunlight and the side in shadow required the astronauts to slowly roll the Apollo vehicle about its longitudinal axis to prevent it from overheating on one side and freezing on the other. This was known formally as Passive Thermal Control and less formally as barbecue mode.
However, the apparently fragile lunar module, when it landed on the Moon, could no longer roll. It kept the same side exposed to the incessant heat of the sun and the opposite side exposed to the cold darkness of shadow for up to three days, without overheating or freezing.
This apparent technical contradiction actually has a very practical explanation: the service module and the command module were more sensitive to thermal variations than the LM. In the service modules, the fuel tanks for its sixteen thrusters were close to the outer skin and had to remain within very strict temperature and pressure ranges. The command module also had a heat shield that would crack and flake if left to cool off in shadow in space for more than thirteen hours, becoming unusable and leading to crew loss upon atmospheric reentry. The slow roll was introduced to provide a more uniform and less extreme heating and cooling of these components of the Apollo spacecraft.
The LM instead didn’t have these limitations: differently from the other modules, it didn’t have to cope with the aerodynamic stresses of the liftoff from Earth (during which it was protected by a streamlined fairing), it didn’t have a delicate heat shield to protect and it had no fuel tanks in direct contact with the outside skin. Accordingly, it could be equipped with a more effective thermal control system, which included a thermal blanket made of multiple layers of Mylar or Kapton. Spacers formed an insulating gap between the blanket and the pressurized crew compartment. The LM also had a sublimator similar to the one used for the spacesuits.
The apparently fragile, tin foil-like appearance of the LM was produced by this thermal blanket, which concealed the normal underlying metal structure shown in Figure 7-22.
Figure 7-22. A prototype of the Lunar Module, preserved at the Smithsonian National Air and Space Museum, reveals the metallic structure inside the thermal protection covering. Credit: NASM.