THE STORY OF MANKIND'S FIRST JOURNEY TO ANOTHER WORLD
Before we start nitpicking the "data" put forward by conspiracy theorists as the "irrefutable proof of the Apollo program lunar conspiracy", we must carefully analyze the historical context in which the events took place and become familiar with the concepts, terms, support facilities, design and operating features of the spacecraft used, and the flight plan that underpinned the titanic project that took mankind to the lunar surface six times, between 1969 and 1972. While reading, it will be very easy to understand how difficult and profound it was to reach this goal, but above all how many people, from industry all over the country, universities, and public and private bodies, were actively involved in making it all possible. It is an incredible story, a mix of pragmatism, political tension and pure spirit of exploration.
The historical context of the events ...
As the smoke from the ruins of the Second World War cleared over a Europe gutted by relentless fighting that over six long years had cost the lives of as many as 85 million people, the world was not sliding toward a lasting peace, but toward a new, icy form of conflict. 1945 marked not only the end of the Third Reich, but also that of the Empire of Japan, forced by the Americans to surrender with the first weapon of mass destruction in history. On August 6, 1945 the first atomic bomb was dropped on the city of Hiroshima, followed three days later by a second on Nagasaki. Those fateful acts of war effectively marked a boundary, a turning point in the new world order taking shape at the end of the fighting, an order of which the atomic bomb would clearly be the deterrent that kept it in place. The data 
The Hiroshima Prefectural Industrial Promotion Hall, one of the few buildings that survived the atomic bombing.coming from Japan, however, showed that the new weapon had such extreme and catastrophic characteristics that, to use it successfully on a large scale, speed of delivery, possibly automatic, had to be an absolute priority. At the time, the delivery of strategic weapons depended solely on heavy, slow bombers that could be intercepted and shot down very easily by the enemy. What was needed was something extremely fast and surgical, able to swoop down on the target without giving the enemy time to take countermeasures. It had been clear for some years, above all to the British, who had been its main victims, that the Nazi regime had managed to build something suited to that purpose: the first guided ballistic missile in history, which the Allied powers had seen at work on the city of London, in all its potential deadliness. It became clear that this futuristic weapon, suitably reengineered, would soon have the capabilities required by the nuclear bomb. Looking at the parabolic trajectories those missiles followed shortly before impact, moreover, it was easy to understand that they could easily reach the edge of space, build up dizzying speeds and then plunge onto their target with great kinetic energy, which was very probably the main cause of the greatly amplified destructive effect observed, adding to that of the warhead carried. The Allied superpowers, the United States of America and the Soviet Union first and foremost, knew they had to get their hands on that futuristic German technology as soon as possible, because that rocket was not just a war trophy to put in a museum, but the key to world dominance in the near future. And so, as the war in Europe drew to a close, among the ruins of a Germany brought to its knees,
A V2 guided missile (Aggregat 4) lifts off toward London with its explosive payload. annihilated by the incessant fire of Allied bombs, a manhunt without precedent began. In the depths of the weapons workshops of Peenemünde, in fact, Allied intelligence services knew very well that the most brilliant minds of the Nazi regime were hiding, who, at the cost of the atrocious labor of an unheard-of number of prisoners, were the true creators of the V2 (short for the German "Vergeltungswaffe 2", or "retaliation weapon 2"), the long-range ballistic missiles that had sown so much terror in the United Kingdom. The secret American operation known as Paperclip and the Soviet one, Osoaviakhim, were the first moves in a planetary game of chess. The United States managed to seize the most coveted prize: Wernher von Braun, the genius behind the V2, along with much of his technical staff and wagonloads of documents, designs and components. At the same time, the Soviet Union rounded up technicians, facilities and machinery, deporting thousands of specialists to Russia to rebuild the secrets of Nazi rocketry under the guidance of the enigmatic "Chief Designer", Sergei Korolev. Thus began a forced migration of brains that would turn instruments of death into vehicles for military dominance of the skies, but also of dreams and national ambitions. Needless to say, thanks to the meticulous work of intelligence agents and military police, both sides were well aware that the alliance that had so 
Autumn 1944. London counts the damage caused by the German V2s.contributed to the defeat of the Third Reich was in reality turning into something hostile. But the die was cast, and the resulting international tensions began to shape a postwar period of great geopolitical tension, in which the ideological opposition between the Communist Soviet side and the Capitalist American side marked the harsh confrontation between the two superpowers. In a short time an unprecedented arms race began, including the development of a full-fledged nuclear arsenal, whose destructive capacity was greatly increased by the German technology they had just seized. In this "icy" war, aptly named the "Cold War", where the fear of mutually assured destruction and the risk of a nuclear holocaust prevented a direct clash between the two sides, the battle moved to the terrain of propaganda and technology. In this theater of shadows and tensions, outer space was no longer a poetic abstraction, but the vertical extension of the battlefield. Whoever dominated space with rocket technology would surely dominate the world! However, while the Soviet Union progressed frighteningly fast with its rocket program, under the iron fist of Communism and under Korolev's leadership, America found itself paralyzed by fratricidal competition. In the 1950s, rocketry in the United States was a matter of egos and bureaucracy among the various branches of the armed forces: on one side the U.S. Navy with Project Vanguard, on the other the U.S. Army with Von Braun and his Redstone, Juno and Jupiter rockets. The political choice to bet on Vanguard, considered more "civilian", turned out to be an unprecedented public relations disaster when the rocket blew up miserably on the launch pad in 1957, shortly after the Soviet Sputnik had already begun mocking American technological supremacy.
Wernher Von Braun. Photo courtesy NASA.Only then did the Pentagon give free rein to Von Braun's team, which, in just 84 days, put Explorer 1, the first American scientific satellite, into orbit. The humiliation of Sputnik also pushed President Eisenhower to a radical move: in 1958 NACA, the austere federal aeronautical research body, was dissolved to create NASA. The new civilian agency was not just a technical office, but the beating heart of a nation that had to make up for lost time. But it was the series of sensational Soviet achievements that woke the Americans from the tortuous path they were following toward their goals. The launch of Vostok 1 carrying the first cosmonaut in history, "Yuri Gagarin", marked the point of no return in the competition between the two superpowers. Behind the rhetoric of peace, the Cold War was fueled by ballistic terror. The rockets that carried satellites and Yuri Gagarin into space were in fact the same ones that could carry nuclear warheads to Washington in less than thirty minutes. The space race was in effect a huge open-air laboratory for perfecting ICBMs (intercontinental ballistic missiles). Whoever controlled Earth orbit potentially controlled the global battlefield! These were the years of the CIA and the KGB, of McCarthyism in the United States and of purges in the USSR. In this climate, secrecy was the norm. While NASA operated in the glare of television cameras (taking on an enormous image risk), the Russians announced their missions only once they had succeeded. This asymmetry fueled constant paranoia among the Americans, convinced they had fallen behind, and pushed the young President John Fitzgerald Kennedy, who had recently succeeded Eisenhower, to force the issue with the Apollo program, in order to close what they believed was the West's "missile gap". In the end, the Moon appeared as the key to success and was no longer regarded as a possible destination, but as the coveted trophy that would establish which ideology would prevail over the other. Without the political tension of those times, the constant fear of mutual nuclear annihilation and the visceral desire to prove the superiority of one's own way of life, it must be said that the funds needed to leave the Earth for space and then for the Moon would very probably never have been allocated. This is where the American administration led by the young, ambitious President found the strength to react. And it did so with a stirring speech to the nation at Rice University on September 12, 1962, under a scorching Texas sun. It was not a simple political rally; it was the founding act of a new modern mythology, a call to arms addressed to all the brilliant minds of the country. If Apollo's technology would be the body of the mission, Kennedy's speech was its soul! Before 40,000 people, Kennedy spoke words that turned an engineering competition into a crusade for the dignity of the human spirit. He did not try to reassure the nation by saying it would be easy; on the contrary, he exalted the difficulty of the undertaking. The most famous passage was a masterpiece of rhetoric and far-sighted vision:
"We choose to go to the Moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win."
The young President was very skillful in linking the conquest of space to the American pioneering tradition. He compared space to a new ocean on which the United States had to sail to maintain its moral and technological leadership. But there was also a sharp pragmatism: Kennedy knew that to obtain the astronomical funding needed (at its peak NASA received over 4% of the US federal budget), he had to convince the people that space was not just a place to explore, but the front where it would be decided whether the future would be written in English or in Russian. The speech had a devastating psychological impact on the adversaries and a galvanizing one on the United States. From that moment on, going to the Moon was no longer "a possibility", but a solemn commitment made before history! With his famous words, Kennedy gave the program a very tight deadline, "before this decade is out", turning every delay into a matter of national honor. To the great sorrow of the whole nation, the young President did not live long enough to see his dream fulfilled, but his vision remained the unmoved mover that drove engineers to work day and night, even when all seemed lost after the Apollo 1 tragedy. Under this new banner, the American space program accelerated dramatically. On May 5, 1961, Alan Shepard became the first American astronaut in history with his 15-minute suborbital flight as part of Project Mercury, which served to show that a man could survive in microgravity; it was the Gemini program, however, that taught the Americans how to work in space, perfecting orbital rendezvous between spacecraft and spacewalks, which would then be fundamental for the Apollo program.
But the real weapon for revenge was still gestating in Von Braun's dreams: the Saturn Project. It was no longer a matter of modifying military missiles, but of building a "cathedral of power", a rocket of gigantic size able to escape Earth's gravity with an unprecedented payload. The development of the Saturn family was not an isolated event, but a huge industrial effort intertwined, day after day, with the Mercury and Gemini missions, in a race against time in which every test fed the success of the next. This gigantic engineering effort took shape in the Saturn family of launch vehicles, whose development proceeded in parallel with the Gemini program, creating a perfect synergy between training the men and testing the machines. While Gemini astronauts were learning to maneuver capsules as nimble as fighter jets in Earth orbit, Von Braun and his team at the Marshall Space Flight Center were assembling the muscles of the lunar program. The first step was theSaturn I. It was not yet the final Moon rocket, but a revolutionary test bed for trying out powerful new propulsion systems, highly sophisticated guidance and control systems, and the concept of the "propulsion cluster", or "engine cluster". Instead of a single, troublesome giant engine, the first stage grouped eight, coordinated to deliver unprecedented thrust. Between 1961 and 1965, while America held its breath with the first orbital flights, the Saturn I flew ten times with a success rate close to 100%, proving that Von Braun's idea was truly a winner. A direct evolution of the Saturn I was the Saturn IB, a more powerful launcher that became the definitive bridge between old and new. As the Gemini missions came to an end in 1966, the Saturn IB began carrying into orbit the first real models of the Apollo Block I spacecraft. It was this very rocket that marked the operational start of the Apollo era, being used for the systems tests of the hardware that was to take man to the Moon.
However, the path to the stars was brutally interrupted by what remains the darkest moment in American space history. On January 27, 1967, during a ground simulation inside the Command Module mounted on top of an unfueled Saturn IB, a fire suddenly broke out in the cabin. In that test, which was supposed to be a simple routine check, the crew made up of astronauts Gus Grissom, Ed White and Roger Chaffee was trapped in an inferno of flames, fed by a pure oxygen atmosphere at high pressure.
Because of a design flaw, the inward-opening hatch could not be forced open by the rescue teams and in just 17 seconds the three astronauts died of asphyxiation. The Apollo 1 disaster shook the very foundations of NASA, leading to a ruthless Congressional investigation that exposed negligence and construction shortcomings. And yet, from those very ashes, the agency drew the strength for a radical transformation: every single component of the spacecraft was redesigned, flammable materials were banned and a new quick-release hatch was introduced. What was supposed to be the final failure became, thanks to unprecedented engineering rigor, the guarantee of safety that would allow the later Apollo missions to bring their crews home safe and sound. But all this was only the prelude. From the ashes the titan was also rising: the launch vehicle that would finally be able to harness all the power needed to break free of Earth's gravity and send man toward the Moon. While Von Braun built up the technology for the Saturn family step by step, an equally crucial battle was being fought on paper and on NASA's blackboards: how to physically get to the Moon? The agency's leadership knew there were basically three methods:
Direct ascent (the "direct ascent" mode) was without a shadow of a doubt the simplest and most intuitive idea, similar to the one described by Jules Verne in the book "From the Earth to the Moon", in which the conquest becomes possible thanks to a single, gigantic rocket that leaves the Earth and then lands on the Moon in its entirety, before taking off again later to return home. To do this, however, the rocket would have had to be mammoth, much bigger than the Saturn V. Carrying all the fuel needed for landing on the Moon and for leaving it again made the mission essentially impossible with the technology of the time, and therefore this method was ruled out from the start.
Earth Orbit Rendezvous , or "EOR", instead involved launching several rockets (perhaps two or more Saturn IBs) that would carry the various components of the lunar spacecraft, and all the propellant needed, into Earth orbit. These components would then be assembled in space, around the Earth, before firing the engines to head for the Moon with the whole stack. This plan also had major practical problems, since it would have required many perfect launches and complex logistics for assembly in orbit, a maneuver that in the early 1960s had not yet been tested.
Lunar Orbit Rendezvous , or LOR, finally, required a single rocket (like the Saturn V) that sent toward the Moon a spacecraft made of two parts: the CSM and the LM. Once in lunar orbit, the two spacecraft separated: the LM descended to the surface, while the CSM stayed in orbit waiting for it. After the exploration, only the upper part of the LM took off again to rejoin the mothership. It was the most efficient method, because it meant carrying only a small, light spacecraft down to the lunar surface, saving an enormous amount of weight and fuel. In NASA's eyes, however, it did not look that way at all, since the mission would have required a meeting between spacecraft trapped in lunar orbit, which would very probably have had little chance of finding each other again for the return rendezvous.
Since all the plans had significant problems to solve, NASA's offices hotly debated which one to adopt and how to improve it to make it as efficient as possible. This is where John Houbolt entered the scene, an engineer at the Langley Research Center who, with a stubbornness bordering on insubordination, began promoting a radical and initially ridiculed idea: LOR (Lunar Orbit Rendezvous). Houbolt argued that the only efficient way was to send two separate spacecraft to the Moon: one for the journey and one, very light, dedicated exclusively to the landing, which would then rejoin the first in lunar orbit. Openly challenging his superiors and writing heartfelt letters to NASA's top management in which he asked, "Do we want to go to the Moon or not?", Houbolt managed to convince Von Braun. The LOR method saved an immense amount of weight and fuel, making the Saturn V, by then almost ready, powerful enough for the mission. This architectural choice was the keystone: it turned a theoretical undertaking into a concrete flight plan, defining forever the true profile of Apollo as we know it today, with its Command Module and its fragile but agile Lunar Module. And so, at last, it arrived: the Saturn V. 110 meters tall, a skyscraper of metal and propellant able to generate a thrust of over 3,400 tons. While the earlier programs had tested the limits of man and of low orbits, the Saturn V was designed for a single, concise purpose: to send a payload of 45 tons beyond Earth escape velocity, toward the Moon. Every Saturn V launch was a seismic event, a show of strength that shook the ground for kilometers. After all, mankind's first journey to another world could certainly not begin in silence!
After the trauma of Apollo 1, NASA did not just try to fly again, but to do so with a precision bordering on perfection. Men returned to space with Apollo 7 in October 1968: Wally Schirra, Walt Cunningham and Donn Eisele tested the new Block II Command Module for eleven days in Earth orbit. It was the acid test for the redesigned machine, a success for NASA that gave it the boldness needed for an unprecedented space move.
The news coming from intelligence services beyond the Iron Curtain, in fact, was not good at all. Rumor had it that the Russians were preparing a Zond space mission headed for the Moon. It was not clear whether the mission would be flown automatically from the ground or by a real human crew, but being beaten by the Russians again, as had happened in Gagarin's day, was one of those things that always put the Americans on high alert. So, instead of proceeding cautiously with another Apollo mission in Earth orbit, it was decided to skip ahead to beat the Russians: Apollo 8, crewed by Frank Borman, Jim Lovell and Bill Anders, was launched at Christmas 1968 not toward a safe orbit, but toward the unknown. They were the first human beings to escape Earth's gravity, to see the Earth shrink to a small blue marble and to gaze upon the far side of the Moon, giving the world the image of Earthrise over the lunar horizon. An unprecedented image that entered humanity's collective emotional memory.
In 1969 the schedule became frantic. Apollo 9 was assigned to test the Lunar Module in Earth orbit for the first time, showing that Grumman's intrepid spacecraft could fly on its own, act as a multirole spacecraft and perform orbital rendezvous, as well as successfully docking with and undocking from the Command and Service Module. The mission was assigned to the crew made up of astronauts Jim McDivitt, Dave Scott and Russell Schweickart.
Apollo 10 was the dress rehearsal for the Moon landing: Thomas Stafford and Gene Cernan took the Lunar Module "Snoopy" down to just 15 kilometers above the rugged lunar surface, "skimming" the craters before climbing back up to rejoin John Young , who had stayed in orbit waiting for them aboard the Command Module "Charlie Brown" in the safety of lunar orbit. Everything was ready for the act that would change the history of human space exploration forever!
On July 16, 1969, the Saturn V of Apollo 11 lifted off from Launch Complex 39A at the Kennedy Space Center in Florida. Four days later, while Michael Collins stayed in orbit, Neil Armstrong and Buzz Aldrin took the Lunar Module "Eagle" down to the Sea of Tranquility, a basaltic plain roughly on the lunar equator. Armstrong, withless than thirty seconds of fuel left, avoided a boulder field and touched down gently on the lunar surface, marking one of the most important moments in human history. That "One small step for a man, one giant leap for mankind" was not just the triumph of a pilot, but the victory of an entire coordinated system and a shining demonstration of how human cooperation can make even the most cherished and seemingly impossible dreams come true. But contrary to what conspiracy theorists and much of the general public believe, the story of human exploration of our natural satellite did not stop with Apollo 11. It went much further!
The following missions turned exploration into pure science. Apollo 12 , after being struck twice by lightning during a launch in the middle of a thunderstorm, demonstrated NASA's surgical precision, with Charles Pete Conrad and Alan Bean landing in the Ocean of Storms, a few steps from the crater named after the robotic probe Surveyor 3, which had landed there automatically about two and a half years before Apollo 12. Richard Gordon waited for them aboard the CSM in lunar orbit.
Then came the crisis of Apollo 13: the explosion of an oxygen tank turned the journey into a desperate fight for survival. NASA's Mission Control Center showed superhuman ingenuity, bringing Jim Lovell, Fred Haise and Jack Swigert back to Earth safe and sound, in what remains history's greatest "successful failure".
With Apollo 14, Alan Shepard (the first American in space) and Edgar Mitchell set off for the Moon with improved oxygen tanks and an additional independent backup supply. They walked on the lunar dust again in February 1971, landing, this time successfully, at the site planned for the ill-fated Apollo 13 mission, the Fra Mauro highlands. During the mission the crew had, for the first time, a wheeled cart called the MET (Modular Equipment Transporter) for carrying equipment and lunar samples. Astronaut Stuart Roosa waited for them in orbit aboard the CSM.
It was with the "J missions" that the Apollo program reached its peak. Apollo 15 took the first Lunar Rover to the Moon, allowing Dave Scott and James Irwin to explore kilometers of surface and collect the "Genesis Rock", a geological specimen almost as old as the solar system. The landing site chosen was Palus Putredinis at the foot of Mount Hadley in the lunar Apennines, right where it is crossed by Hadley Rille, an imposing canyon formed by the collapse of a large underground lava tube, which helped shape the valley explored during the landing. Alfred Worden was in orbit in the CSM.
The Apollo 16 landing site was chosen in the lunar highlands, to allow the astronauts to collect geologically older material than the samples obtained in three of the first four landings. Samples taken from the Descartes highlands and the Cayley Plains disproved the hypothesis that they were of volcanic origin. Apollo 16 involved astronauts John Young and Charlie Duke , who also tested the rover's capabilities in extreme conditions. Ken Mattingly waited for them in orbit in the CSM.
Finally, in December 1972, with a technically flawless mission, Apollo 17 brought a wonderful era to a close. Harrison Schmitt, the first scientist-geologist to walk on the Moon, and Gene Cernan spent three days on the surface, exploring the Taurus-Littrow valley on the southeastern edge of Mare Serenitatis. Ronald Evans waited for them in orbit aboard the CSM "America". Cernan was the last man to leave his footprint on the lunar soil during the Apollo program, speaking words of hope before climbing back into the Lunar Module.
As he prepared to take the last human step on the Moon, Cernan said:
"Bob, this is Gene, and I'm on the surface; and, as I take man's last step from the surface, back home for some time to come, but we believe not too long into the future, I'd like to just say what I believe history will record: that America's challenge of today has forged man's destiny of tomorrow. And, as we leave the Moon at Taurus-Littrow, we leave as we came and, God willing, as we shall return, with peace and hope for all mankind.
Godspeed the crew of Apollo 17."
As the program came to a close, mankind had not only won a cold war; it had discovered that it was a species in charge of its own destiny, able to leave its cradle and look at its own planet from a different perspective, as a single, fragile oasis in the infinity of space. From then on, for over fifty years, until the Artemis II mission of April 2026, no human being crossed the deep space separating the Earth and the Moon again, and no one has yet set foot again on that ancient soil which still holds so many secrets, very probably including some about the evolution of life, among its rocks, waiting to be found. The footprints of the Apollo astronauts, the wrecks of the LM Descent Stages, the Lunar Rovers of the last three missions, all the abandoned equipment, as well as the flags now bleached by the Sun's violent rays and the night/day temperature swings, are still there. Intact in the lunar vacuum and lit by the light reflected from the Earth, the planet they came from, waiting for the "hope" Cernan spoke of to become reality with the return of man and of the first woman, perhaps with the Artemis program itself!
The machines of the Apollo space program
Now that we have examined the historical context of the events, between geopolitical tensions and pioneering ambitions, we cannot talk about Apollo without first looking in detail at the machines that allowed man to reach the Moon. It would be a mistake, in fact, to consider them simple means of transport, since they represented the highest expression of 20th-century engineering, a series of complex integrated systems that had to work in perfect harmony in the vacuum of space. Getting into the "guts" of Apollo means discovering how pieces of aluminum, titanium and silicon were turned into a fortress against the unknown, able to protect human life where it was never meant to go. We will therefore start with a specific analysis without going into too much detail, since the accurate, detailed description of the most technical aspects of the machines can be found in our download section, which contains all the original handbooks provided by NASA.
In summary, the human conquest of the Moon was made possible by (you can click on the following links to jump to the desired section):
- NASA'S ROBOTIC PROBES FOR THE PRE-EXPLORATION OF THE MOON;
- THE SATURN V MULTISTAGE LAUNCH VEHICLE;
- THE APOLLO COMMAND AND SERVICE MODULE;
- THE LUNAR MODULE;
- THE LUNAR ROVER;
- THE ALSEP SCIENTIFIC INSTRUMENTS;
- THE A7L SPACESUITS;
NASA'S ROBOTIC PROBES THAT PAVED THE WAY FOR HUMAN EXPLORATION OF THE MOON:
The path to the Sea of Tranquility was not first traced by human crews, but by the mechanical sacrifice of a generation of pioneering machines that faced the vacuum of space when the Moon was still a dark enigma and potentially hostile. Before the Apollo program could get fully under way, in fact, NASA had to answer fundamental questions that tormented the American space agency's engineering team:
- Is the lunar surface solid, or a deep ocean of dust?
- Is it possible to land there safely with heavy machines without the risk of sinking?
- What are the environmental conditions on the lunar surface? Is it very hot? Is it very cold?
- Is it better to land with the Sun high in the sky or in the early morning light?
- Is there dangerous radiation in deep space? And on the lunar surface?
- What are the dangers of micrometeorite impacts? Are they very frequent?
- Where are the craters, mountains and most dangerous areas of the lunar surface?
- How do you navigate precisely toward a moving target 380,000 km away?
All these answers could only come through three specific, complementary robotic programs that NASA had no choice but to carry out to gain a thorough knowledge of deep space and of the lunar surface before sending a man there. These programs were called the Ranger program, the Surveyor program and the Lunar Orbiter program.
The first phase of this robotic assault was entrusted to the Ranger program, conceived with an almost sacrificial philosophy: these probes, designed and built in-house by the Jet Propulsion Laboratory in Pasadena, were technological projectiles fitted with electronic eyes, launched on a direct collision course with the lunar surface. Their job was to transmit as many close-up images as possible before the final crash. After a series of frustrating attempts that called into question the space agency's very capabilities, the success of Ranger 7 in July 1964 finally opened an unprecedented visual window, revealing a landscape tormented by craters of every size but, more importantly, free of the insurmountable obstacles that many feared would make a landing impossible. Once the first close-up views had been obtained, the need for systematic mapping became a priority, leading to the birth of the Lunar Orbiter program, entrusted to Boeing. These probes were not simple cameras, but real miniaturized chemical and photographic laboratories orbiting the Moon. In an era before high-resolution digital photography, the Lunar Orbiters used an ingenious and complex system developed by Eastman Kodak: they took pictures on 70 mm film, developed them automatically on board using a dry process and then scanned them with a beam of light to transmit the data to Earth. It was a triumph of analog engineering that made it possible to map 99% of the lunar surface with such precision that scientists could identify the flat areas needed for the descent of the future lunar modules. It was a Lunar Orbiter that gave mankind the first view of the Earth rising above the desolate horizon of the Moon, changing forever our perception of isolation in the cosmos. However, one fundamental unknown remained that no photograph could solve: the consistency of the ground and the environmental conditions needed for a safe human landing. A widely accepted scientific theory at the time suggested that the lunar surface was covered by a very deep layer of extremely fine dust, capable of swallowing any heavy object like quicksand. To refute or confirm this nightmare, NASA commissioned the Hughes Aircraft Company to build the Surveyor probes. Unlike the Rangers, the Surveyors had to perform an operation never before attempted by the Americans: a soft landing. Using radar and variable-thrust engines, these elegant three-legged structures managed to settle gently on the regolith, showing that the ground was solid and compact and also providing the first photographic evidence of the actual makeup of the lunar surface. Also equipped with small mechanical arms with a scoop, the Surveyors dug small trenches and analyzed, as far as possible, the chemical composition of the soil and the local environmental conditions, such as the temperature over the course of the day, levels of cosmic and solar radiation and the frequency of micrometeorite impacts. All this provided definitive proof that the Lunar Module would not sink into oblivion and that man could explore the surface safely, and with what precautions. This trio of programs, born of the synergy between government laboratories and the giants of the American aerospace industry, thus turned the Moon from an idyllic silver disk far away in the sky into a real, measured territory one could walk on, making the Apollo program no longer a visionary dream, but a logistical challenge most probably within man's reach.
With the era of robotic probes over, having turned the Moon from a cosmic mystery into a mapped and safe destination, NASA faced the most imposing challenge in modern history: turning that data into a human undertaking. It was no longer a matter of launching small robotic laboratories, but of lifting immense payloads and human lives beyond the safe embrace of Earth's gravity ...
The bridge between robotic exploration and the human landing was built on a monumental scale, pushing the limits of engineering to heights never reached before. At the center of this new phase stood a titanic figure, the colossal Saturn V, the king of rockets, the only machine able to generate the power needed to hurl mankind toward its destiny among the stars and born of the experience gained in the field by NASA with Von Braun's team, with the Saturn I and Saturn IB programs; but also the Command and Service Module (CSM), the Lunar Module (LM), the Lunar Rover (LRV), the ALSEP scientific instruments and the legendary A7L spacesuit. We will now analyze them point by point, using the diagram below as a reference ...
THE SATURN V MOON ROCKET
The Saturn V was a multistage liquid-fueled rocket of the "super-heavy lift" class, used by NASA between 1967 and 1973. Designed under the technical direction of Wernher von Braun at the Marshall Space Flight Center, it remains one of the most powerful launchers ever used to carry humans, and the first to take man beyond low Earth orbit, into interplanetary space all the way to the Moon.
The Saturn V was a marvel of engineering made up of about 3 million parts. Its dimensions were colossal , and anyone lucky enough to have seen one in person, perhaps in an American museum, can confirm it! When it was ready for launch, raised on the pad and pointing at the sky, it stood about 110.6 meters tall (like a 36-story building), had a base diameter of 10 meters (the liquid oxygen tank of the first stage could easily have held three semitrailers parked side by side inside it), weighed about 2,970 tons at launch (like some 500 African elephants, 90% of it propellant) and could lift to an altitude of 190 km (low Earth orbit - LEO) the Apollo spacecraft stack (a payload of 140 tons, of which 43 reached lunar orbit) in just 12 minutes of titanic thrust divided into three stages.
The Saturn V was made up of the following parts (you can click on the following links to jump to the desired section):
The Saturn V (pronounced "Saturn Five") had a three-stage architecture, plus a ring at the top known as the "wedding ring", designed to join the Saturn V rocket to the Apollo stack and to house the electronic sequencing control, guidance and navigation system (IU). The Saturn V was designed to use its stages precisely in sequence, dropping them in flight once their propellant was used up, thus lightening the remaining load and allowing it to reach the high speeds required for the various phases of the mission. The three stages were as follows:
1 - FIRST STAGE (S-IC):
The S-IC stage is hoisted onto the MLP to be placed in launch position. Photo courtesy NASA.The S-IC stage (the first stage of the Saturn V) was a colossus of engineering, designed to lift the entire Moon rocket during the first two and a half minutes of flight, bringing it to an altitude of about 68 km and a hypersonic speed of 7,500 km/h (Mach 6.1). To accomplish this demanding task successfully it had to store all the energy needed in the form of an impressive amount of liquid propellant, which inevitably dictated its record-breaking size. Standing 42.1 meters tall (about 38% of the rocket's overall height), it had a diameter of 10 meters. Built by Boeing for NASA, it was powered by five gigantic Rocketdyne F-1 engines arranged in a cross, single-combustion-chamber engines among the most powerful ever built. These engines were the basis of the Saturn V's success because they managed to harness all the power needed to send a very large payload toward the Moon while splitting it among the smallest possible number of engines, thus reducing the chance of a catastrophic failure. The same luck did not, for example, attend the huge Soviet competitor known as the "N1 Moon rocket", which, having a larger number of engines at its base (albeit less powerful ones), never managed to get them to work in unison for the time needed for the mission, turning every launch into a colossal failure, followed by catastrophic explosions that also seriously damaged the launch pads. At the base of the Saturn V were four sturdy stabilizing fins, called "fins", whose total span extended the rocket's footprint well beyond the 10 meters of its cylindrical body. Their function was to keep the rocket aerodynamically stable during the delicate phase of powered flight through the atmosphere. The fins were mounted vertically on four large conical fairings called "Engine Fairings", whose function was to protect the four outboard engines from the aerodynamic load generated by the violent airflow of the climb at very high speed through Earth's atmosphere, whose turbulence could have damaged the engines beyond repair. The voracious engines of the S-IC stage were located at the very bottom, facing backward relative to the rocket's direction of travel.
One engine was fixed in the center, while the other four were mounted outboard on gimbals that allowed them to be tilted by means of huge hydraulic servo-actuators. Their purpose was to precisely control the trajectory followed by the launcher during the first phase of flight. Unlike those you can see today in museums, every F-1 engine assigned to fly on the Saturn V was covered by a fireproof blanket that protected it from the fireball that formed around the rocket when, at high altitude, it began to cross the thinner layers of the atmosphere. Up to an altitude of about 30 km, in fact, the substantial atmospheric pressure squeezed the flames from the engines into a narrow, long column called the "exhaust plume" (up to three times the overall length of the rocket). As the rocket climbed toward Earth orbit, however (if you watch videos of the Apollo launches you can see this phenomenon very clearly), the air pressure dropped inexorably, in accordance with the laws of physics, and so did the force acting on the jets of the F-1 engines.
It was at this point that on television the rocket seemed to be burning down like a candle. The flames, in fact, no longer formed a long trail behind the rocket's path, but tended to bunch up at its base, creating a ball of fire that seemed to move along with the rocket. This fireball could have catastrophic effects on the integrity of the engines and the rocket's structural mechanical parts, as well as on the sophisticated equipment (valves, sensors, manifolds, pumps, heat exchangers, etc.) that made the whole thing work. For this reason they had to be protected by a heat shield, made of a multilayer fireproof blanket called the "Aft Heat Shield", made mainly of asbestos, epoxy resins and Inconel 718. The blanket also worked as an acoustic absorber for the devastating shock waves generated by the engines' combustion (which were nothing more than violent controlled, confined explosions) and which were often the cause of catastrophic structural failures in rockets of such power. Given the mass it had to lift and steer toward Earth orbit, the S-IC stage consumed enormous quantities of propellant. The average flow to the engines was about 13 tons per second, which for each engine meant almost a thousand liters of RP-1 kerosene (an ultra-refined kerosene for rocket propulsion) and 1,500 liters of liquid oxygen (LOX) burned every second in those voracious combustion chambers. This flow produced temperatures of around 3,200°C with combustion pressures of about 70 atmospheres, released through an exhaust nozzle only 3.7 meters in diameter. If the cooling passages built into the nozzles and the combustion chamber had not been continuously cooled by a flow of RP-1 kerosene from the tanks, they would have melted instantly in a huge explosion. In this way the S-IC stage managed to generate the 3,400,000 kg of thrust needed for the mission, with a deafening roar and an impressive glare, so much so that during the night launch of Apollo 17 in December 1972 (the last mission of the program), the rocket's lift-off was seen in the distance even from Cuba, more than 600 km away!
2 - S-IC <> S-II INTERSTAGE
The S-IC<>S-II interstage provided structural continuity between the two adjacent stages and protected the second-stage J-2 engines while crossing the atmosphere. Photo courtesy NASA.The S-IC / S-II interstage ring was one of the most critical structural components of the Saturn V. It was not simply a "connector", but a piece of sophisticated aerospace engineering designed to handle the transition between the brute power of the first stage and the cryogenic efficiency of the second. It was a hollow structural cylinder 10 meters in diameter and 5.5 meters high. It was made of aluminum alloy with a "corrugated" (accordion-like) structure to maximize stiffness without adding too much mass. It had to bear the entire weight of the upper stages and the vibrations imposed on the whole structure by the five F-1 engines at full power, as well as transfer the thrust they produced to the rest of the rocket. The black color (alternating with the white of the rest of the rocket) was not chosen for purely aesthetic reasons, but helped ground technicians visually monitor the roll (rotation about its own axis) of the rocket through long-range cameras. Unlike other rockets built by NASA, the separation between the first and second stages of the Saturn V took place in two distinct steps, all designed to protect the integrity of the second stage's J-2 engines. When the first stage ran out of fuel, in fact, it was jettisoned. However, the interstage ring initially stayed attached to the second stage (S-II). This feature served to create a physical "shield" that protected the five delicate J-2 engines from the violent separation of the S-IC stage, to avoid catastrophic collisions in flight. About 30 seconds after the second-stage engines ignited, when the risk of impact or damage had passed, the interstage ring was jettisoned and fell into the Atlantic Ocean below. The S-IC <> S-II interstage was an extremely crowded and complex environment. Mounted on the outside of the ring were small solid-propellant motors (ullage motors). These fired for a few seconds right after separation to give a small forward push to the second stage, ensuring separation from the now inert S-IC stage , but above all that the liquid hydrogen and oxygen "settled" at the bottom of the tanks so they could be pumped correctly to the engines. Separation took place by means of explosive bolts and linear charges that literally cut the metal in a perfect circle. Since the ring stayed attached to the S-II for the first 30 seconds of that stage's flight, it was still a "dead weight" of several tons that the rocket had to keep lifting for nothing. NASA engineers accepted this compromise for the sake of safety and mission success, to make sure that the J-2 engines were not hit by debris or by the heat of the separation under way.
3 - SECOND STAGE (S-II):
The S-II stage is hoisted on top of the S-IC<>S-II interstage and the S-IC stage. Photo courtesy NASA.Built by North American Aviation, it came into operation right after the first stage separated. If the latter was the "brute force" needed to leave the ground, the S-II stage was the "long-distance runner" that took the rocket almost all the way to Earth orbit, operating in the thinnest layers of the upper atmosphere. The S-II stage was 24.9 meters tall (about 23% of the rocket's overall height) and 10 meters in diameter. It had a dry mass of 36,000 kg , rising to 480,000 when loaded with ultra-cold propellants. It is considered one of the most technically complex stages of the Apollo program because it used liquid hydrogen (LH2) for propulsion, an extremely efficient propellant but very hard to handle. To save weight and reduce the rocket's overall length, the S-II engineers came up with a brilliant solution: the common bulkhead or shared bulkhead. Instead of two separate tanks with an empty space between them, the oxygen and hydrogen tanks shared a single curved dividing wall. The real challenge lay in keeping the very extreme thermal characteristics of the two neighboring propellants unchanged. Liquid oxygen, in fact, was stored in its tank at a cryogenic temperature of -183°C, while liquid hydrogen was kept at -253°C. To prevent disastrous thermal interaction between the two propellants, the common bulkhead separating them, without adding to the rocket's overall volume and weight, was made of two aluminum shells separated by a layer of phenolic honeycomb about 12 cm thick. This insulation was vital: if heat from the oxygen had warmed the hydrogen, the hydrogen would have boiled off quickly with unpredictable consequences; conversely, the oxygen could have frozen if exposed to the more extreme cold required for storing hydrogen, compromising the structural integrity of the stage and, not least, the proper feeding of propellants to the engines. Like the first stage, the S-II was built mainly of aluminum alloy. However, liquid hydrogen posed a unique problem: it was so cold that, in contact with the outside air, it liquefied it and even froze it on the surface of the rocket, not to mention the high humidity naturally present in Florida, which condensed and then froze solid on the outer surface of the rocket. All this unpredictably increased the overall weight and the atmospheric drag at launch, creating risks of aerodynamic instability (above all vibrations and oscillations) during the troubled ride to Earth orbit. For all these reasons, the entire stage was covered with a special insulating foam (polyurethane with isocyanurate additives). In the early versions it was applied by hand in prefabricated shaped panels, but after worrying detachments at lift-off and in flight, a much stronger and more reliable spray-on system was used from the Apollo 13 mission onward, which still gave the rocket its classic translucent white look. The white color of the whole rocket was no accident: its main purpose was to effectively reflect solar glare in flight, as well as during the long pre-launch periods when the rocket stood vertically on the pad at Complex 39 (A/B) of the Kennedy Space Center (KSC from now on), for the final fit-out, the rigorous checks it underwent, the fueling operations and the many tests that had to declare it fit for flight on the day of the mission. This color choice thus prevented insidious solar overheatingof the propellant tanks and of the internal bays housing the rocket's sophisticated systems (electrical, electronic, hydraulic and pneumatic). The S-II stage was powered by five Rocketdyne J-2 engines , also arranged in a cross. The center engine was fixed, while the four outboard ones could be tilted (by means of gimbals and hydraulic actuators) to steer the thrust and control the rocket's course. Unlike the F-1 engines of the first stage, burning RP-1 kerosene and liquid oxygen, the J-2s used the liquid hydrogen / liquid oxygen combination, which offered a much higher specific impulse per unit mass and therefore prodigious amounts of thrust in a vacuum at lower cost and weight. The S-II stage came into operation about 2 minutes and 40 seconds after launch, just as it separated from the S-IC stage, which, no longer held, inexorably fell into the Atlantic Ocean below, roughly 500 / 600 km east of KSC. A few tens of seconds after ignition, the interstage ring that structurally joined the first and second stages was also jettisoned in flight. This ring provided physical separation between the first two modules of the Saturn V, structural continuity, and a protected housing for the J-2 engines while they waited their turn to fire. The powered phase of the S-II stage accelerated the launcher from a speed of 7,500 km/h (imparted by the S-IC stage) to about 25,000 km/h (almost orbital velocity, Mach 20.4), in about 6 minutes of thrust , bringing the payload to an altitude of about 185 km. Once its task was done, it too was jettisoned in flight with a spectacular separation maneuver, also falling into the Atlantic Ocean, roughly halfway between the American and African continents.
4 - S-II <> S-IVB INTERSTAGE
The S-II<>S-IVB interstage provided structural continuity between the two adjacent stages and protected the third stage's J-2 engine during the climb to Earth orbit, where the aerodynamic load had not yet disappeared. Photo courtesy NASA.The interstage located between the second stage (S-II) and the third stage (S-IVB) was a unique structural component, easily recognizable by its truncated cone shape. It was made of light aluminum alloy with a honeycomb structure reinforced by internal stringers. It had several small openings that allowed technicians, while the rocket was on the pad, to reach the umbilical connections and the control systems of the third stage's J-2 engine , which remained "enclosed and protected" inside the cone. Unlike the cylindrical ring between the first and second stages, this element had to handle a significant change in diameter. The second stage (S-II), in fact, had an imposing diameter of 10 meters, while the third stage (S-IVB) was much narrower, measuring just 6.6 meters. The truncated cone interstage therefore served to connect these two different sizes, ensuring the aerodynamic and structural continuity of the rocket. It had to transmit the whole weight of the Saturn V above it (made up of the S-IVB, the Lunar Module and the Command Module) down to the structure of the S-II stage below and, conversely, pass all the thrust generated by the S-IC and S-II stages on to the rest of the launcher. While a complicated two-plane separation was used between the S-IC and the S-II, as described above, the separation procedure between the S-II and the S-IVB was relatively simpler. When the S-II shut down, a circular explosive charge cleanly cut through the upper edge of the truncated cone interstage. The interstage stayed firmly attached to the second stage, falling back with it through the atmosphere and then sinking into the Atlantic Ocean. This separation exposed the J-2 engine of the third stage (the S-IVB) to the vacuum of space, now ready for the decisive orbit insertion burn. To ensure perfect ignition, fluid mechanics required a rigorous procedure: just as in the previous phase, here too a slight acceleration was needed to 'force' the ultra-cold propellants to the bottom of the tanks. On the early missions this maneuver was performed by small ullage rockets mounted at the base of the S-IVB. Fired a fraction of a second after separation, they pressed the liquid hydrogen and oxygen against the bottom, ensuring a smooth feed and preventing the J-2's turbopumps from sucking in deadly gas bubbles. However, starting with Apollo 15, NASA decisively optimized the masses: it removed the ullage motors and entrusted the job of settling the liquids directly to the thrusters of the auxiliary propulsion system (APS) built into the body of the third stage itself. This engineering refinement saved precious hundreds of kilograms, to the benefit of the payload sent toward the Moon. At the same time, to ensure a clean and safe separation, four small solid-propellant retrorockets on the outer surface of the interstage fired, pointing in the direction of travel. Their rapid firing abruptly slowed the now inert mass of the S-II, instantly moving it away from the S-IVB, which could then head for Earth orbit completely undisturbed and safe from catastrophic collisions in flight.
5 - THIRD STAGE (S-IVB):
The S-IVB stage is hoisted on top of the S-II<>S-IVB interstage and the S-II stage. Photo courtesy NASA.The S-IVB stage was the third stage of the Saturn V. Built by the Douglas Aircraft Company, it was the component of the rocket with the most versatile and delicate task: it first had to complete putting the Apollo stack into orbit and then, after a two-hour stay in a parking orbit around the Earth (during which the crew checked that all systems were ready for the journey to the Moon), restart and put the spacecraft stack onto the translunar trajectory, performing what in jargon was called "TLI", or Trans-Lunar Injection. It was in fact the last stage of the launcher to stay attached to the Apollo spacecraft during the journey to the Moon. The S-IVB stage was 17.8 meters tall (about 16.1% of the rocket's overall height) and only 6.6 meters in diameter. The S-IVB was powered by a single Rocketdyne J-2 engine, which also burned liquid hydrogen and liquid oxygen. These cryogenic propellants were stored in tanks with the same construction and thermal insulation features as those of the S-II stage. What made the third stage's J-2 engine unique, however, especially compared with the engines of the stage below (S-II), was its ability to restart in flight and in a vacuum. This capability came from a substantial modification made to the propellant feed and pressurization system. The S-IVB's J-2 engine started when the S-II stage was jettisoned in flight, running for about 2 and a half minutes and accelerating the stack from 25,000 km/h to the 28,000 (Mach 22.8) needed to maintain a stable parking orbit around the Earth. Since the S-IVB stage had to remain in this state for a short time (about two hours of revolutions around the planet), it needed an auxiliary propulsion system which, besides maintaining its attitude, would settle the remaining propellant in the tanks just before the engine restarted. In microgravity, in fact, the hydrogen and oxygen floated about randomly inside their tanks, making their intake by the feed lines leading to the J-2 engine's feed pumps unstable and at times impossible. To solve this problem, the S-IVB stage carried at its rear, very close to the stage's own center of gravity, two dedicated independent propulsion modules called the APS (Auxiliary Propulsion System). These small rockets (using hypergolic propellants stored in independent pressurized tanks) provided a minimal thrust along the direction of orbital motion (called an "ullage burn"), forcing the propellants to settle again in an orderly way at the bottom of the tanks and allowing a stable feed and an optimal restart of the engine. The APS thrusters also handled the roll (roll x+/x-), pitch (pitch y+/y-) and yaw (yaw z+/z-) (motion about the three inertial reference axes) of the Apollo stack during all the maneuvers needed in orbit or on the way to the Moon (post-TLI maneuvers) to control the trajectory. When it was time for TLI, the J-2 engine was restarted with extraordinary precision by the dedicated hardware that set it apart from the J-2s of the S-II stage. The burn lasted on average about 5 minutes and 45 seconds (345 seconds) and was one of the most critical and spectacular moments of the whole mission. In that short time, in fact, the rocket had to go from an orbital speed of about 28,000 km/h to the transfer speed toward the Moon's orbit of over 39,000 km/h (Mach 31.8). At that point the spacecraft was no longer in Earth orbit, but traveling along a long, curved ballistic trajectory that would bring it to cross the Moon's orbit at a very precise, precalculated point, about three days after TLI. Interestingly, although the burn lasted less than 6 minutes, it was so powerful that the astronauts felt in their seats a steady but increasing acceleration (as the tanks emptied and the stage became lighter). At the end of the TLI burn the engine shut down abruptly and the astronauts went instantly from about 1.5 G of acceleration to the microgravity that would accompany them for most of the rest of the journey to the Moon. Interestingly, the S-IVB was not designed exclusively for the Saturn V. It was an evolved version of the S-IV stage (used on the Saturn I). It was also used as the second stage (or upper stage) of the smaller rocket called the Saturn IB, used during the program to test the Apollo spacecraft in Earth orbit (as with the Apollo 7 mission, for example, and all the post-Apollo missions to the Skylab orbital laboratory). The fate of the S-IVB stages used on the Apollo missions was truly fascinating. Launched toward the Moon together with the Apollo stack, once its propulsive task was complete it remained inert in flight through space in the direction of the Moon. To prevent it from becoming a danger to the astronauts and to the mission (and to later missions that would pass through those regions again), after separating from the Apollo Command and Service Module (CSM from now on) and releasing the Lunar Module (LM from now on) from its SLA adapter, it was fired up once again. This remotely commanded burn , controlled from Mission Control in Houston on Earth, either put it into solar orbit (forcing it to leave the Earth-Moon system for good) or, as on the later missions, deliberately crashed it into the Moon to create artificial moonquakes for scientific study.
6 - IU INSTRUMENT RING:
The IU Instrument Unit is hoisted on top of the S-IVB stage. Photo courtesy NASA.The Instrument Unit (IU) was the real "brain" of the Saturn V. It was a cylindrical ring only 91 centimeters high (about 0.8% of the rocket's overall height) with a diameter of 6.6 meters. It sat on top of the third stage (S-IVB), just below the Lunar Module's truncated cone SLA adapter. While the various stages of the rocket provided the brute force, the IU provided the intelligence needed to guide the giant from the launch pad all the way onto the course to the Moon. Without this component, the Saturn V would have been just a pile of metal and propellant with no control. It was designed by NASA at the Marshall Space Flight Center and built by IBM. It was made of a light aluminum alloy with a honeycomb structure to ensure stiffness and lightness. Inside it were mounted all the electronic systems needed to manage the flight from launch until the spacecraft was put on its trajectory to the Moon. It could calculate the rocket's position and velocity in real time, control the orientation of the engines (through hydraulic actuators mounted on gimbals) to keep the correct course, sequence at the right times, by analyzing data and sensors, the commands for stage separation and the necessary engine firings, and radio thousands of telemetry readings on the rocket's performance to the ground. The heart of the IU was the Launch Vehicle Digital Computer (LVDC), built by IBM for extreme reliability. Since a computer failure during launch would have been catastrophic, the LVDC used triple modular redundancy (TMR). In practice, three separate channels performed the same calculations at the same time; if one disagreed, the other two "outvoted" it (voting logic), allowing the rocket to keep flying without errors. It had a magnetic core memory of about 32,000 words, housed in a sealed structure to withstand vibration and vacuum. To know where it was in space, the IU used a gyroscopic inertial platform. This system made it possible to maintain a fixed reference point in space regardless of the rocket's movements, while extremely precise accelerometers measured every change in velocity, allowing the computer to correct the trajectory instantly in the event of strong winds or asymmetric engine thrust. The IU's electronics generated a lot of heat, in an environment like space where there was no air to cool it. For this reason it had sophisticated temperature control , and the most critical components were mounted on metal heat-sink plates called Cold Plates. Through these heat exchangers flowed a mixture of water and methanol that absorbed the excess heat and carried it to external radiators, keeping the circuits at their ideal operating temperature. It is a common mistake to think that the astronauts flew the Saturn V during launch. In reality the rocket was controlled automatically by the IU through its computer (LVDC), which ran the software customized for each mission, constantly comparing it with readings from thousands of sensors. Only in a real emergency could the astronauts have taken control of those 3,400,000 kg of thrust through the hand controllers and the guidance computer of the Apollo Command Module. When all went well, however, the crew only had to monitor the rocket's trajectory through the data provided by the onboard instruments and to supervise certain aspects of the flight that often required authorization to proceed, by means of switches and digital settings. Once insertion onto the translunar trajectory was complete, along with the joining of the lunar spacecraft (CSM + LM), the IU would go on managing the S-IVB stage until its impact with the Moon or otherwise for the whole duration of its insertion into solar orbit.
7 - SLA TRUNCATED CONE ADAPTER FOR THE LM
The SLA adapter protected the Lunar Module throughout the powered flight of the Saturn V. Photo courtesy NASA.The Lunar Module Adapter, technically known as the SLA (Spacecraft-Lunar Module Adapter), was a truncated cone structure acting as a "bridge" between the Saturn V rocket and the Apollo spacecraft. Often overlooked compared with the engines or the capsule, the SLA was a masterpiece of structural engineering that performed three critical functions: protection, support and separation. The SLA was located above the third stage (S-IVB) of the Saturn V and below the Service Module of the Apollo capsule. It was about 8.5 meters tall (about 7.7% of the rocket's overall height), with a base diameter of 6.6 meters (to match the Saturn V's IU instrument ring) narrowing to 3.9 meters at the top (to match the Service Module). It was made of aluminum honeycomb panels designed to be extremely stiff yet very light. The main function of the SLA was to house the Lunar Module (LM) during launch and the climb through the atmosphere, providing it with a shield against the aerodynamic load caused by the immense turbulence of launch. The LM, in fact, with its irregular shape covered by the fragile outer layers of Kapton and Mylar that made up its MLI protective blanket against heat and micrometeorites, could not have withstood the stress of air pressure and the frictional heating during lift-off. For this reason the SLA wrapped it completely in its truncated cone fairing, protecting it until it reached the vacuum of space. The LM did not rest on the bottom but literally hung inside the SLA from four attachment points on the descent stage structure. Inside the SLA, the Service Module's main engine (SPS) and the folded-up high-gain antennas that equipped the CSM for deep space communications were also protected from the airflow. One of the most spectacular phases of every Apollo mission was precisely the opening of the SLA at the right moment. This phase, known as "Transposition, Docking and Extraction", took place shortly after TLI, when extracting the LM from its housing became essential to continue the mission correctly. Once the third stage had put the spacecraft on course for the Moon, the SLA adapter was opened on command from the crew. To do this, pyrotechnic separation lines were fired (explosive charges) that split the SLA vertically into four large panels. No longer held and pushed outward by dedicated springs, these panels came away from the S-IVB stage and drifted off in four different directions, moving away from the stack and disappearing into space. Where they ended up is not known for certain: some may have crashed on the Moon after a journey through space of about three days, others probably ended up orbiting the Sun. Jettisoning the SLA fairing made it possible to safely reach the top of the LMand dock with it using the docking probe fitted to the Apollo spacecraft. Once the LM was firmly docked , it could be released from the cradle that attached it to the Saturn V's third stage by means of four more explosive bolts and pulled away to continue the journey together toward the lunar surface.
10 - LES ESCAPE TOWER AND BPC COVER:
An image of a static ground test of the LES escape tower which, with its extremely rapid firing, pulls the Apollo Command Module along with it. Photo courtesy NASA.The escape tower, technically known as the LES (Launch Escape System), was the imposing truss structure at the top
of the Saturn V rocket, placed exactly above the Apollo Command Module. In short, it was the emergency escape system for the astronauts during the most critical phases of launch: the first 120 seconds. Its sole, relentless purpose was to quickly rip the capsule with the crew on board away and pull it as far as possible from the launcher in case of an explosion or imminent failure on the pad or during the early climb. This extreme choreography served to bring the Command Module to an altitude high enough to deploy the three main parachutes, thus ensuring a safe splashdown afterward. The LES solid-propellant motor could generate a monstrous thrust of about 68,000 kg (68 tons) in less than half a second. This brutal but necessary jolt subjected the crew to an acceleration that could reach 15 G, pulling the capsule away at a top speed of 600 km/h in the blink of an eye. The system was constantly supervised by the automatic emergency management system (EDS, Emergency Detection System), able to detect catastrophic anomalies, but the LES could also be triggered manually by the astronauts with a simple handle, or remotely by radio command from Mission Control in Houston, if the crew was unable to do so in time. At the top of the tower, mounted on the side, there was also a small additional solid-propellant rocket called the PCM (Pitch Control Motor), which in the photo on the left can be seen firing, at the top, next to the tip of the main rocket. Its function was vital: to create a sideways thrust vector able to move horizontally the Command Module-LES assembly, making it quickly leave the deadly straight path followed by the failing Saturn V. Once the emergency burn was over, a set of aerodynamic control surfaces known as the Canard Wings deployed automatically at the top of the tower. These lifting surfaces created in flight a turning moment that made the system pivot away from its line of flight, thus placing the Apollo capsule in the
This image shows the LES escape tower, complete with the BPC at its base, completely covering the Apollo 11 Command Module "Columbia". Photo courtesy NASA. right attitude to continue its descent toward a safe splashdown. Once triggered, this whole decisive, lightning-fast choreography was programmed to happen in a completely automated way. This feature avoided the potential inability to carry out the procedures of a crew stunned by the commotion or, worse, unconscious (G-LOC, G-induced Loss Of Consciousness) because of the terrifying accelerations during the sudden intervention of the system. When the launch went smoothly, the LES of course remained unused. During the Apollo missions, the very high reliability of the systems always managed to avert this serious eventuality, something that was not spared the Soviet Soyuz T-10-1 mission, which showed the world once and for all how effective and vital this aerospace rescue technique was. When the Saturn V reached an altitude of about 90 km, essentially close to the Kármán line (the conventional boundary separating Earth's atmosphere from outer space), the air became too thin for the Canard Wings to work aerodynamically and the tower became superfluous. About 30 seconds after ignition of the second stage (S-II), with a spectacular jettison maneuver triggered by the crew, the tower was jettisoned in flight by another small dedicated motor, called the Tower Jettison Motor. This motor, together with the detonation of the explosive bolts holding the LES to the capsule below, pulled the whole structure away at very high speed along with the Command Module's protective cover, called the BPC (Boost Protective Cover). This freed the top of the spacecraft, allowing it to continue its climb to Earth orbit lighter and unhindered. At that point the flight entered abort modes II, III and IV: from then on, any emergency rescue maneuver would be carried out by separating the spacecraft from the rocket and, later in the climb, with the help of the powerful main engine of the Service Module, the SPS (Service Propulsion System). The earlier LES abort sub-modes (IA, IB and IC) involved different LES sequences, depending on the altitude reached by the launcher. The jettison of the escape tower was so violent and fast that the crew noticed only two things: a loud bang described as the classic "clank" of release, and the sudden appearance in the cabin of a burst of light from the blinding Sun at very high altitude, surrounded by the deep black of 
Installation of the Apollo 15 BPC in the upper protection chamber of the MSS. In the center of the photo you can see the reflective outer surface of the Command Module Endeavour, which is then covered precisely by the BPC. Photo courtesy NASA.space. Until then, in fact, the capsule had been darkened by the BPC. For reasons of structural integrity, the BPC had only two reinforced glass windows, located over the commander's rendezvous window and the main access hatch of the spacecraft. The purpose of these openings was to let the pilot see the minimum amount of horizon outside needed to perceive the rocket's attitude , or that of the tower in an emergency. Often mistaken by laymen for the outer metal hull of the Apollo capsule, the BPC was actually the "second skin" of the Command Module during the early phases of launch. Made of a white cone-shaped protective shell in fiberglass with internal insulation of aluminized materials, it completely enclosed the cabin and performed three vital safety tasks. First, it protected the spacecraft thermally during the hypersonic climb through the atmosphere, absorbing the extreme heat generated by friction (especially during the phase of maximum pressure) and preventing the capsule's delicate silvered Mylar heat-reflective surface from being damaged or melted. Second, it provided a formidable shield against the devastating action of the LES escape rocket: if it had fired, its nozzles would have emitted terribly hot, abrasive flames, mixed with corrosive chemical residues, which would have burned through the bulkhead, killing the astronauts. The BPC effectively deflected this jet of fire. Finally, it preserved the integrity of the delicate external systems (such as the docking mechanism, the RCS maneuvering nozzles and the environmental vents), protecting them from bad weather, salt spray, birds, insectsand dust during the long pre-flight periods on the pad. All spacecraft are in fact assembled in a clean room to
A series of close-up frames showing the lift-off of the Saturn V of Apollo 11, the first mission to take man to the lunar surface. The immense column of gas and dust released at lift-off, spreading even to great heights, is clearly visible. Photo courtesy NASA. protect the internal environment in which the crew will live, preventing contamination by foreign bodies that in microgravity could float dangerously around the cabin. Another essential task of the BPC was to keep the windows spotless at launch, openings indispensable to the success of the mission, for star navigation and for docking in space. The lift-off of a Saturn V was a terribly violent and "dirty" event. The exhaust of the giant F-1 engines generated clouds of sticky soot, unburned propellants, stones and sheets of ice breaking off the cryogenic tanks, which were hurled everywhere and dragged upward by the turbulence and the brutal wake of the launch. The BPC cover acted like 
a full-face helmet, absorbing these impacts and keeping the grime well away from the vehicle. Last but of fundamental structural importance, at the very top of the escape tower stood the legendary Q-Ball. Although it looked like just a small decorative metal knob, it was one of the most vital instruments for preventing the colossal rocket from breaking up in flight. In aerodynamics, the letter "Q" stands for the dynamic pressure of a fluid on a body at high speed. About 80 seconds after lift-off, at an altitude of 13-14 km and traveling at Mach 2, the Saturn V went through the point of maximum structural stress, the dreaded Max-Q, where the air pressed against the vehicle with a force of 3,500 kg per square meter. The Q-Ball acted as the rocket's sense organ: it was a spherical head with eight pressure ports arranged with extreme precision. By comparing the air entering these holes (a kind of complex multidirectional Pitot tube ), the system measured and then instantly calculated three critical parameters: dynamic pressure, the angle of attack (the tilt of the nose relative to the relative wind) and the sideslip angle (the vehicle's sideways slip). If the angles of attack or sideslip had exceeded specific limits during Max-Q, the terrifying aerodynamic shear forces would have caused the structural failure of the Saturn V. The Q-Ball constantly sent this data to the LVDC onboard computer in the instrument ring (IU), which instantly corrected the orientation of the F-1 engines to keep the rocket perfectly aligned. Since it only worked inside the atmosphere, the Q-Ball finished its job at an altitude of 90 km and was jettisoned along with the tower. While the rocket stood on the pad, however, these vital pressure ports were protected from the weather and insects by the "Q-Ball cover", a cap that was pulled off by a retracting cable a few seconds before engine ignition, thus unlocking the aerodynamic "senses" of the giant before its leap into space.
9 - THE APOLLO COMMAND AND SERVICE MODULE (CSM)
The Apollo spacecraft was the first ark of our century in which human beings left the Earth to visit another world. It was not a single, self-contained spacecraft, but a modular system of docked spacecraft , extremely advanced for its time, designed to carry three men to the Moon, keep them alive for up to two weeks in the hostile environment of space and bring them back safely to Earth. The complete system (which formed the top part of the Saturn V Moon rocket) was made up of two main parts: the Command Module, or CM and the Service Module, or SM. Together they formed the Command and Service Module, or CSM.
APOLLO COMMAND MODULE (CM):
The Command Module (CM) was the beating heart of Apollo. Designed and built for NASA by North American Aviation, it was the only spacecraft of the entire docked stack of CSM and LM designed to return intact to Earth, and the only part of the giant Saturn V Moon rocket to survive. The Command Module was not designed to be a reusable spacecraft for several missions, far from it! The stress it underwent during the flight to the Moon and back was so great that, for safety reasons, NASA required a brand-new one to be built for every mission. It was much more than a simple "space capsule" like the Mercury or Gemini capsules of the programs that preceded it. The Command Module was a full-fledged spacecraft, designed entirely to be launched toward the Moon by the most powerful rocket in the world and to operate far from Earth in deep interplanetary space: a place never reached by human beings before. For all these reasons it was fitted with many features to ensure the success of the mission, preserving the precious human cargo inside and sheltering it from the rigors of space. These were mainly: the deadly vacuum of space, unimaginable temperature swings (as much as 200°C difference between light and shadow), ionizing radiation of solar and cosmic origin, and deadly micrometeorites. To deal with all these factors, the Command Module had every precaution built in to avoid disaster. After the Apollo 1 fire on the launch pad, which tragically cost the crew their lives, the spacecraft known as Block I was completely redesigned, replacing all the flammable materials on board with fireproof ones, greatly improving the emergency systems and optimizing the escape routes. This gave birth to the Block II spacecraft, the one we will deal with in this chapter of our analysis. When the Apollo Command and Service Module (CSM from now on) was mounted on top of the Saturn V more than a hundred meters up, the only way to get to it was by means of the top access arm of the launch umbilical tower, which led to the White Room. This was a special antechamber that formed a small access balcony at the main hatch of the Apollo capsule itself. This hatch provided an airtight seal to ensure internal pressurization and, at launch, like the rest of the Command Module (CM from now on), it was covered by a hinged extension of the BPC described above. Once through the main hatch, you entered the pressurized cabin of the CM , and after taking your place in the crew couches and finishing configuring and testing the systems, you were ready for launch. The CM had a truncated cone shape. Overall it was 3.2 meters high, with a base diameter of 3.9 meters, and weighed about 6 tons. The habitable volume inside was just 6 cubic meters (about the size of a large van). The hull was divided into three parts. The top part, not habitable, contained the probe and the docking mechanism for the Lunar Module (LM from now on), the reentry parachute compartment, the uprighting balloons for splashdown and part of the tunnel that would allow the crew to move from the CM to the LM at key moments of the lunar mission. In the center of the CM was the pressurized cabin where the crew lived. It contained all the instruments and hardware needed for the spacecraft's uninterrupted operation, for navigating it through space and for providing life support and comfort to a crew of three astronauts: a Mission Commander, abbreviated "CDR", a Command Module Pilot, abbreviated "CMP" and a Lunar Module Pilot, or "LMP". These men lived, worked, ate and slept inside the cramped CM, on missions that could last as long as 15 days. The astronauts spent most of the flight to and from the Moon floating in microgravity inside the capsule, or strapped into their couches during the key parts of the mission, such as launch, engine burns and reentry. Inside every Apollo command module, therefore, there were three couches. The center couch could be folded away to let the crew move around more freely. The other two side couches, on the other hand, were fixed. The central part of the CM had five windows designed to allow views outside both to the sides and to the front of the Module. These windows had several layers of transparent materials , resistant to the large temperature swings of the space environment. They were also able to filter harmful radiation, first and foremost ultraviolet rays and infrared radiation from the Sun. They were also bulletproof, able to withstand impacts from the dreaded micrometeorites moving through space on unlikely collision courses at several tens of km/s. Windows no. 1 and no. 5 were square and located on the sides. Window no. 3 was round and set in the middle of the main hatch of the CM. Windows no. 2 and no. 4 , on the other hand, were "wedge-shaped" and were the only ones that allowed you to look forward along the spacecraft's longitudinal axis. Their particular position earned them the name "rendezvous windows" because, by allowing a forward view, they made it easier for the CSM to dock with the LM in orbit.
Under the crew couches there was a habitable compartment, where the astronauts stowed the bulkiest equipment needed for 15 days of life in space. This was also where a large container held the folded spacesuits and the stowed helmets and pressure gloves when they were not in use. In this area the astronauts also set up their sleeping bags so they could sleep comfortably in microgravity, shielded from the light of the instruments on the main control console, which stayed on round the clock for the whole planned duration of the mission. At the foot of the crew couches there was also another compartment, called the lower equipment bay or "Lower Equipment Bay". This housed the navigation station, with a sextant and a telescope, needed to align with the stars a complex, precise inertial reference platform (IMU), which, once calibrated, provided the correct attitude vectors to the AGC guidance computer for trajectory calculations. This area also housed much of the electronic equipment that kept the whole spacecraft running, including: the radio transceivers, the transponder, the telemetry systems, the AGC guidance computer, all the logic controls for the attitude thrusters (RCS, or Reaction Control System, from now on) and for the SPS engine, the systems for managing, distributing, measuring and converting electrical power, the galley for preparing food, much of the stowage areas for mission equipment , the toilet (made up of the relief tube and the sealed storage for fecal bags), and the system for general crew hygiene. In front of the couches was the main control console , which housed some 560 switches, about twenty electrical and hydraulic selector knobs, the DSKY (pronounced "Disky", which was nothing more than the human-machine interface of the AGC guidance computer , with numeric data displays and a keyboard for entering them) and as many as 24 instruments (mostly analog needle gauges) and 56 indicator lights to manage every system, from cabin air conditioning (with an internal temperature kept steady at about 24°C by the ECS environmental control system, even though outside the temperature ranged from +120 to -180°C depending on whether you were in direct sunlight or in the darkness of space), to guidance and navigation of the spacecraft on its journey through space. Not only that: through the main console it was also possible to control the electrical systems of the whole spacecraft, the health of the fuel cells that produced power and the status of the spacecraft's precious consumables. It is important to point out that the main console showed only the most important data that the crew could act on immediately. All the rest of the immense onboard monitoring network, in fact, fed into the remote telemetry system, an automatic spacecraft system that every second acquired data from thousands of sensors scattered throughout the CSM, packing the logic states and numerical values into a single radio signal sent continuously to the ground for constant, accurate evaluation by the flight controllers at Mission Control in Houston and their support teams. Nothing, therefore, was left to chance, and an identical system equipped the LM, completely independent of the CSM. The CM was also equipped with a unique cabin air-conditioning station. Known as the ECS (Environmental Control System), it was a masterpiece of 1960s engineering. Its job was not just to "let" the astronauts breathe, but to create a tiny, self-sufficient ecosystem able to protect them from the vacuum of space and from extreme temperatures. Unlike modern spacecraft (such as the ISS), which use a mixture of nitrogen and oxygen similar to Earth's, the Apollo CM used 100% pure oxygen at a reduced pressure of about 5 psi, about one third of Earth's atmospheric pressure, which, if you think about it, is even higher than the partial pressure of oxygen (about 3 psi) in the air we normally breathe here on our planet at sea level. This feature had an advantage: it greatly simplified the operation of the ECS (... and simplicity in space means reducing the risk of catastrophic accidents) and, above all, it allowed a lighter capsule to be built, since the structure had to withstand a much lower internal pressure. The ECS was strategically placed inside the CM bulkhead, right next to the left couch occupied by the Mission Commander, so that the manual controls (oxygen knobs and coolant valves) were always within reach in an emergency. The complete system (including its surge tank and the active filtering system) took up about 0.56 cubic meters (20 cubic feet). It may not seem much, but in a cabin of just 6 cubic meters in all, it took up almost 10% of the available living space. To better understand how the Apollo spacecraft was laid out, let's take a little guided tour inside the Apollo 11 Command Module "Columbia", now on display at the National Air and Space Museum in Washington D.C. (we recommend watching in full screen and raising the playback resolution as high as possible):
... and now some artistic reconstructions that show how big the Command Module was and how the hardware that allowed three men to survive on board throughout the journey to and from the Moon was arranged ...
The ECS was not only responsible for supplying oxygen to the cabin and maintaining a constant pressure. Its job was also to remove the carbon dioxide exhaled by the crew through dedicated lithium hydroxide (LiOH) filters, eliminate odors generated by the crew (sweat, flatulence, etc.) with special charcoal filters, regulate humidity, regulate cabin temperature, but above all cool the onboard electronics, which would otherwise have been prone to catastrophic failures. In space, in fact, the problem is not just the cold beyond the bulkhead, but also getting rid, in a vacuum, of the heat generated by the devices that keep the spacecraft running, as well as by the astronauts' own bodies. A mix of water and ethylene glycol therefore circulated in a closed loop, absorbing heat inside the cabin and radiating it into space with the help of special panel radiators on the outer surface of the SM. In critical phases (such as reentry or high heat loads), the system could also use another remarkable device of the ECS: the evaporator. This device fed water into a special porous membrane in contact with the vacuum of space, to rapidly and 
After the Apollo 1 accident, the main hatch of the Block II CM was completely redesigned and could be opened in a few seconds. The photo above shows the main hatch with window no. 3.very efficiently cool the water-ethylene glycol mixture flowing through the cooling loops. The water the system needed was produced by the fuel cells in the SM which, besides producing prodigious amounts of electrical power by combining gaseous oxygen and hydrogen, produced as a by-product a considerable amount of water (hot and cold). For safety reasons the ECS had two separate loops: one for air-conditioning the whole cabin, the other dedicated to air-conditioning the spacesuits alone. If, in the event of a sudden structural failure, the CM had lost its ability to keep a habitable atmosphere inside, the astronauts could have worn their spacesuits until splashdown, simply by switching the ECS over to suit pressurization. The ECS was so efficient that it could maintain a breathable cabin pressure of at least 3.5 psi for about 15 minutes, even with a hole in the bulkhead 6.5 millimeters in diameter. This extraordinary redundancy had been calculated specifically to give the crew a vital margin of time against deadly hypoxia. In the event of a structural puncture (caused, for example, by the impact of the largest micrometeorite statistically predicted by NASA's mathematical models, about 6.5 mm) the astronauts would have had the precious minutes needed to put on and safely seal their spacesuits, saving their lives before the cabin completely depressurized into the vacuum of space. The CM had two functional ends: the top, containing the docking and undocking mechanism (Docking Probe) for the Lunar Module, the transfer tunnel between one spacecraft and the other , fitted with a removable pressurized hatch , and the parachute section. The bottom of the CM, on the other hand, was attached to the SM, the section below the Apollo capsule that supplied oxygen, water, electricity, attitude control with the RCS thruster system and the thrust of the SPS main engine needed for course corrections to and from the Moon, as well as the burns needed to enter and leave lunar orbit in a stable way. When the Apollo CM and SM were docked in flight, together they formed theCSM , or Command and Service Module. The CM was separated from the SM just 15 minutes before entering Earth's atmosphere. At that moment its base, with its slightly rounded shape, became the undisputed protagonist of the success of the lunar mission. It housed the heat shield that protected the crew during the last phase of the mission: the spacecraft's reentry into the atmosphere before splashdown in the Pacific Ocean. The peculiar rounded shape of the heat shield had two main functions: 1) to generate lift during the delicate phases of reentry in order to make the descent less violent , splitting it into two distinct parts so as not to overstress the shield itself; 2) to moderate the shock wave generated at the moment of maximum atmospheric penetration, deliberately deflecting the white-hot plasma into the long trail that inevitably formed, thus dissipating the immense heat generated by friction with air particles. The ablative layer of phenolic resins it was made of, in fact, by rapidly vaporizing, absorbed most of the incoming heat, keeping it away from the spacecraft's lower aluminum bulkhead, which faced precisely in the direction of motion. On every reentry, in fact, a CM coming back from the Moon fell toward the Earth, hitting its atmosphere at a speed of about 40,000 km/h, generating temperatures on the heat shield that could reach 2,800°C, while keeping the internal temperature at about 25-30°C. Once the atmospheric braking phase was over, the final descent of the capsule had to be slowed further for a safe splashdown. To do this, the CM deployed a set of parachutes in sequence: two small ones to stabilize the capsule at about 7,000 meters, three intermediate ones whose job was to pull out the three big, iconic orange-and-white striped main parachutes, which slowed the spacecraft to a splashdown speed of about 35 km/h.
APOLLO SERVICE MODULE (SM):
The Service Module provided propulsion, attitude control, electrical power, radio communications and breathable air to the Apollo Command Module. Photo courtesy NASA.The Service Module (SM) was the "engine", the storage area for the consumables needed for the mission and the "power plant" of the Apollo spacecraft. If the CM was the head and heart of the mission, the SM was its muscles and lungs. Also designed and built by North American Aviation for NASA, it was an aluminum cylinder 7.5 meters long, 3.9 meters wide and weighing 24,500 kg. It was positioned between the CM and the Saturn V's SLA adapter. Inside, the module was divided into six sectors arranged radially around a central cylindrical compartment. These sectors were not pressurized; they were deliberately exposed to the vacuum of space in order to improve thermal insulation between internal components, keep the structure light and ensure fire protection in an environment where extremely reactive substances were stored and which, at the same time, also housed very critical, vital components for the success of the mission. Sectors 2, 3, 5 and 6 contained the large propellant tanks (oxidizer and fuel) for the main engine. Sector 4, on the other hand, was the heart of life support. This was where the fuel cells or FCs (which produced electricity, heat and drinking water), the cryogenic liquid oxygen (LOX) tanks and the cryogenic liquid hydrogen (LH2) tanks were located. The oxygen tanks also held the crew's entire breathing supply. Finally, sector 1 was not used on the early missions, but from Apollo 15 and then on missions 16 and 17 (called the "J" scientific missions) it was devoted entirely to housing the SIM Bay (Scientific Instrument Module), a technical bay designed to hold scientific experiments, such as high-resolution cameras and sensors for studying the Moon from orbit. One of the most important subsystems housed in the Service Module was the SPS (Service Propulsion System) engine. An Aerojet-General Corporation AJ10-137 engine that could be gimbaled by electric servo-actuators, it was located at the base of the SM. Its large bell nozzle, 2.5 meters in diameter at the exit, protruded outside to allow the exhaust gases to be expelled into space , producing the powerful thrust the engine was capable of. It was an incredibly simple engine, designed never to fail! It had no complex electrical ignition systems , nor pumps to move the fuel and oxidizer. What made it infallible was the type of propellant used to generate thrust, called "hypergolic". Made up of Aerozine 50 as the fuel (a 50/50 mixture of hydrazine and unsymmetrical dimethylhydrazine , or UDMH) and nitrogen tetroxide as the oxidizer, the winning feature of these propellants was that they ignited spontaneously on contact with each other, producing, when confined in a combustion chamber, prodigious amounts of thrust. The SPS was the engine that slowed the CSM (almost always docked with the LM) to enter a stable orbit around the Moon, performing a precise maneuver called Lunar Orbit Insertion (LOI) and, above all, the one that accelerated it out of orbit and back toward Earth, with another extraordinary burn called Trans-Earth Injection (TEI). If the SPS engine had failed to fire at the time of return, the astronauts would have been stranded in lunar orbit forever, with all the tragic consequences that implies. Unlike modern spacecraft, which often use solar panels, Apollo's power plant was made up of three fuel cells ( fuel cells ) built by Pratt & Whitney Aircraft. Each was about 1.1 meters tall and weighed around 110 kg. Each cell generated between 563 and 1,420 watts of power, with an output voltage between 27 V at full load and 31 V at idle. The nominal voltage was 28 V on buses A and B , which redundantly distributed electrical power to all the spacecraft's systems. Each cell could deliver a peak of 2,300 watts in case of extreme need. Their remarkable operation depended on the electrochemical recombination of a gaseous mixture of hydrogen and oxygen, which reacted at porous nickel electrodes separated by a potassium hydroxide (KOH) electrolyte. The resulting ionic recombination, through a well-conceived and well-developed electrochemical process, produced all the electricity needed to run the onboard systems. The Apollo fuel cells also produced two vital by-products that a spacecraft flying in deep space certainly could not do without: liquid water (hot and drinkable , for personal hygiene, crew hydration and food preparation), and a continuous supply of cold water, needed for cooling the onboard electronic systems. The heat released by the fuel cells was also used to heat the CM, thus ensuring comfort on board. Excess heat, on the other hand, was dissipated into space through a set of radiators on the outer surface of the SM or through the sublimator of the CM environmental control system (ECS - Environmental Control System). The SM also housed most of the radio, video and telemetry transmission systems to and from the Earth, made up of a set of omnidirectional VHF antennas for communications close to the planet, and a set of steerable high-gain dishes, called the HGA (High Gain Antenna) for deep space communications. The SM also contained the main attitude control system , or RCS (Reaction Control System) , the most powerful of the whole spacecraft (the other one was housed in the CM but was used only during reentry , when it flew on its own shortly before splashdown). The SM's RCS was made up of four quads set about 90° apart, containing small hypergolic rockets that positioned the spacecraft in space along the three inertial reference axes (roll, pitch and yaw), during small trajectory correction maneuvers or to steer the CSM precisely during docking with and undocking from the LM. About 15 minutes before reentering the atmosphere, the SM was separated from the CM by a dedicated sequential separation device. While the astronauts returned to Earth protected by the heat shield, the SM, with no protection, was moved well away from the astronauts' trajectory by a last automatically controlled firing of its RCS thrusters and finally burned up completely in the atmosphere over the Pacific Ocean, thus ending its vital role.
8 - THE LUNAR MODULE
The Lunar Module (LM), affectionately nicknamed "the spider" because of its unusual shape, was the first spacecraft in history designed exclusively to operate in the vacuum of space and on the lunar surface, with no regard for aerodynamics. Built by Grumman Aerospace, the LM was the only component of the Apollo program that allowed a crew of two astronauts to touch down gently on the lunar surface. Once there, it also served as a base for the whole stay and then later allowed them to take off again for lunar orbit, so that the astronauts could rejoin the CSM. The LM was therefore not a simple space machine, but a multirole spacecraft made up of two interconnected modules, which operated in a predetermined way depending on the phase reached by the mission itself. The two distinct interconnected sections were designed to work together during the descent and separate at the right moment for the climb from the lunar surface. For this reason the two modules making up the LM were called the Descent Stage and the Ascent Stage.
THE LM DESCENT STAGE:
The LM Descent Stage was a concentrate of lightness, strength and technology. Here we see it ready to be mated to the Ascent Stage, already covered with its protective MLI blanket. Photo courtesy GRUMMAN- NASA.It was the lower part of the lunar module, with an octagonal base , to which four shock-absorbing, deliberately crushable legs were hinged at the sides, allowing the whole spacecraft to make solid, stable contact with the lunar surface. The Descent Stage was built of reinforced aluminum , and inside its sturdy body it contained: the hypergolic landing engine , or DPS - Descent Propulsion System, four propellant tanks to feed it (two for Aerozine 50 as fuel and two for nitrogen tetroxide as oxidizer), a large supply of breathing oxygen for the crew, a large supply of water for cooling the systems and for crew hydration , four large silver-zinc batteries that supplied most of the electrical power needed to run the LM during the lunar mission, the stage separation devices used for lift-off from the lunar surface, the ALSEP scientific equipment to be installed permanently on the lunar surface and, on the last missions, the folded-up lunar Rover. The sturdy body of the Descent Stage was protected by a special outer covering that allowed it to withstand the rigors of space during the long days spent on the lunar surface, protecting it from the large temperature swings of the lunar day, as well as from the danger of impact by micrometeorites drifting through space or falling freely onto the lunar surface. This covering was called MLI, or Multi-Layer Insulation , and in the Apollo photos it always appeared a crinkled silvery gold color, which gave the LM as a whole the look of a clumsy, fragile vehicle or, as Moon hoax theorists love to say, "made entirely of tinfoil". MLI, however, was actually a sophisticated passive thermal protection system for the LM, made up of layers of extremely light materials (up to 25 layers), each with a specific function. It was well known in the aerospace world (it is no coincidence that it is still used on satellites today) that about 1.5 centimeters of this multilayer insulation had the same insulating power as a brick wall several meters thick. The main material used was Kapton, an amber polymer that gave it its typical "gold" color. It was used for the outermost layers because it withstood very high temperatures (up to 400°C), allowing almost total reflection of incoming sunlight. Under the Kapton were several layers of Mylar, another special heat-resistant polymer that gave it the typical "tinfoil" look. Just below were many layers of Dacron, a tough polyester fiber, a forerunner of technical fabrics like the Kevlar used today in bulletproof vests , whose job was to soften the impact of micrometeorites, slowing them down so that the Whipple shields underneath could stop them completely before they could damage the load-bearing body and, inevitably, the innermost pressurized shell containing the precious human cargo. Throughout the descent from lunar orbit to the surface, the DPS engine of the Descent Stage provided all the thrust needed to slow down the whole LM from orbital speed to the speed that would allow a safe touchdown on the lunar surface. The DPS was an engineering masterpiece, one of the first rocket engines whose thrust could be throttled (like a car's accelerator) to allow a soft, safe landing and, before that, to calmly look for a suitable spot to touch down. In the minutes before contact with the lunar surface, in fact, the DPS, suitably throttled by the crew, could hold the LM in hovering flight like a helicopter. Just before the LM's legs touched the lunar surface, special probes about 1.7 meters long , connected to sensors and to the legs themselves, warned the crew that the ground was near by lighting up a large blue light on the Ascent Stage control console. At that point, to prevent the DPS engine from being damaged because it could no longer expel its exhaust gases properly, given the approaching rough lunar surface below, the crew shut it down for good, allowing the LM to fall freely for the last meter, settling forever at the chosen landing site, an indelible witness to the spectacular human adventure that had taken place there. The Descent Stage then served as a support for the Ascent Stage, whose pressurized cabin housed the crew, sheltering and protecting them for the whole planned stay. On one of the four legs of the descent stage was the famous nine-rung ladder the crew needed to reach the ancient dusty surface of the Moon. The last meter and a half separating them from the history books! Throughout the stay on the lunar surface, the Descent Stage supplied the Ascent Stage with breathing oxygen for the crew, drinking water and water for cooling the systems, part of the electrical reserve through its batteries , a stable support and stage separation at lift-off from the lunar surface. Its fate, however, was already sealed: it would stay on the Moon forever! Once the exploration of the landing site was over, in fact, the last function of the Descent Stage would be to serve as a stable, shock-absorbing launch pad for the Ascent Stage with the crew inside, which, equipped with another dedicated hypergolic engine of lower, constant thrust, would leave the Moon for lunar orbit to rejoin the third crew member (the CMP, or Command Module Pilot), who was waiting for them in the CSM and organizing the return.
THE LM ASCENT STAGE:
The Ascent Stage being completed before mating to the Descent Stage. Here we see it already fitted with its MLI covering and its Kapton micrometeorite panels. Photo courtesy GRUMMAN- NASA.It was the nerve center of command for the whole lunar exploration mission. Ungainly and angular in shape, only seemingly fragile because of the protective coverings against heat, particle radiation and micrometeorites that covered the structured, sturdy aluminum body underneath (hence the reckless Moon hoax claims that the LM was a movie prop made of tinfoil especially for the conspiracy set), it held the precious human cargo of two astronauts (CDR - Mission Commander and LMP - Lunar Module Pilot). The LM Ascent Stage was essentially a pressurized cabin with a complex internal air-conditioning system (called the LSS - Life Support Section) that worked very much like the Apollo Command Module's, but with one substantial difference: a special recharging station for the spacesuit backpacks (PLSS - Portable Life Support System) needed to provide life support during the extravehicular activities on the dusty lunar surface. The LSS supplied breathing oxygen to the crew, removed the dangerous carbon dioxide they exhaled, kept the internal pressure at about 5 psi, and regulated temperature and humidity. A special activated charcoal filtering system also removed odors and dust from the air of the cabin, making life much easier in those cramped quarters, no bigger than a couple of telephone booths side by side. Inside the Ascent Stage was also the main control console for the whole LM, from which every function of the intrepid lunar spacecraft could be controlled, configuring it as needed according to the phase reached by the mission. The main console also included two flight stations from which the crew flew the spacecraft in the desired direction, changing its trajectory when needed using dedicated hand controllers. The direction of motion was carefully monitored through the onboard instruments and two large triangular multilayer windows. The Ascent Stage also had a telescope navigation station for aligning the guidance and navigation inertial platform (IMU) with the stars, a mission computer called the LGC (Lunar Module Guidance Computer) , similar in some ways to the Command Module's AGC but with specific software for landing and lifting off from the surface, and finally another computer called the AGS (Abort Guidance System) , with safety functions, which would have helped the astronauts abort the mission if necessary, giving them the best possible chance of a safe return to lunar orbit to meet the CSM. The Ascent Stage also contained an RCS attitude control system, needed for all the course or attitude corrections required during descent and ascent, as well as a fixed hypergolic engine called the APS (Ascent Propulsion System). This engine allowed lift-off from the lunar surface and a safe return to orbit once the surface exploration mission was over. Like the SPS, this engine too was built for simplicity of operation so that it would never fail! If it had not fired for lift-off, in fact, it would have been impossible for the astronauts to leave the lunar surface, condemning them to die there within a short time. Fortunately, the APS engine was a marvel of technology and, in the nine missions in which it was used, it never caused any problems whatsoever. The Ascent Stage also contained the hypergolic propellant tanks dedicated to feeding the APS engine (and, in an emergency, the RCS too), of course separate from those used for the DPS, which were installed in the Descent Stage. The structure of the Ascent Stage looked boxy and angular for two main reasons: first, because it was to operate exclusively in the vacuum of space, where an aerodynamic shape would have been completely unnecessary; second, to save weight and make the spacecraft lighter and easier to carry, which meant a significant saving in the propellant needed to launch the Saturn V, as well as a larger allowance for the equipment and resources needed to explore the lunar surface. At the top of the Ascent Stage was the conical docking system for the CSM, as well as the circular pressurized hatch giving access to the half-tunnel connecting the two spacecraft. When the LM was firmly connected to the CSM, the tunnel, about 80 cm wide, was completed, solidly joining the two spacecraft by means of a sophisticated docking system with 12 latches. The purpose of the tunnel was to allow the crew to move safely from one spacecraft to the other without going out into space. When the spacecraft were docked, the tunnel was pressurized by the spacecraft's environmental systems, providing a sturdy, safe passageway without the need for dangerous extravehicular activities in orbit.
The LM Ascent Stage also carried all the equipment needed for exploring and living on the lunar surface, such as: various tools, clothing for spaceflight, medicines, personal items, spacesuits and their accessories, food rations for two people, a reserve of breathing oxygen and drinking water, independent of the Descent Stage, for crew hydration and system cooling, all the avionics and electronics needed for spaceflight and for running the whole spacecraft, a flight station complete with console and navigation and control hand controllers, and a sophisticated set of radio transceivers providing communication
The LM Ascent Stage in the Grumman workshops, photographed after the mechanical assembly of its sturdy inner body. It would soon be fitted with the external hardware and the micrometeorite and thermal insulation covers that gave it that seemingly fragile appearance. Photo courtesy NASA.s between the two spacecraft when they flew separately in lunar orbit, as well as with Earth during the descent and the stay on the Moon. The LM also had two radars: one, on the Descent Stage, needed to measure the altitude above the lunar surface during the descent; the other, on the Ascent Stage, called the "rendezvous" radar, needed during the climb from the Moon to track and interrogate the CSM's transponder and inform the guidance computers of the two spacecraft about their relative orbital positions, their relative velocities and the remaining distance. Without this valuable instrument, an orbital rendezvous between the spacecraft would still have been possible, but rather complicated. It must be said, however, that since the days of the Gemini space missions crews had been trained to deal effectively with this kind of situation too. Once on the lunar surface, the Ascent Stage served as a permanent base for all the days planned for exploring the lunar site. It offered a safe shelter for the astronauts , where they could eat, rest and sleep, as well as put on their spacesuits and prepare to go outside. The Ascent Stage could be depressurized several times during the mission so that the astronauts could safely open the main hatch. Opening that historic door gave access to the ancient lunar surface, the most remote, hostile, yet at the same time extraordinary place man had ever reached. The final fate of an Ascent Stage was almost always the same. After bringing the astronauts up to the CSM's orbit and allowing the crew to be reunited and the lunar samples and personal effects to be transferred to the orbiter, the tunnel was closed for the last time and finally depressurized. This allowed the crew to jettison in flight, through a final separation of the spacecraft, the Ascent Stage, which, with a last burn commanded automatically through the RCS attitude control system, was sent crashing onto the Moon for two reasons: first, to clear lunar orbit of potential accidental collision hazards for future missions venturing to those places and altitudes; second, to generate artificial moonquakes detectable by the seismometers placed on the Moon at sites previously visited by other Apollo missions, in order to study the Moon's internal geological structure . The Apollo 11 Ascent Stage, however, was left in lunar orbit, and only the LM of the Apollo 10 mission, called "Snoopy", was sent into solar orbit with a powerful final engine burn. It still orbits the Sun today, periodically coming close to the Earth, and in 2019 astronomers identified an object observed by telescopes that could be it.
THE SPACE TRAIN (CSM + LM):
The Apollo space train was made up of the docked CSM and LM. Throughout the cruise between the Earth and the Moon, the lunar spacecraft flew through deep space in this configuration.The "space train" (or spacecraft stack) , formed by joining the CSM (Command and Service Module) and the LM (Lunar Module) in flight, was the complete operational configuration of the Apollo spacecraft during the journey to the Moon. In this phase the two spacecraft were joined "nose to nose" in what is called the Docked Mode or docked configuration. At departure from Earth, in fact, the LM was inside its truncated cone adapter , called the SLA, on top of the last stage of the Saturn V rocket (S-IVB), right behind the CSM. To form the "space train", therefore, the astronauts first had to complete the translunar injection maneuver, or TLI (Trans Lunar Injection) and only then perform a very delicate maneuver called TD&E (Transposition, Docking, and Extraction). In this operation the CSM physically separated from the structural grip of the LM's SLA adapter, firing dedicated pyrotechnic separation lines that joined them, triggered by the crew once the stack was stabilized on its way to the Moon. These charges split the SLA adapter into four individual panels which, no longer held and pushed outward by four dedicated springs, drifted away in four different directions and were then lost in space. This opening, besides freeing the CSM, which could finally fly on its own, exposed the top of the LM Ascent Stage, right where the docking tunnel was, closed at that moment by a dedicated drogue waiting for the CSM to arrive. The CSM, on the other hand, carried at its top an extendable probe called the "docking probe", whose head ended in three spring-loaded capture latches. The function of these devices was to snap into a locked position once inserted into the LM's drogue, precisely during docking, matching perfectly with the hole at its bottom. This initial docked configuration, stable but not 
Faithful reconstruction of the wedge-shaped rendezvous window that allowed the forward view from the CM during docking with the LM. In the center, the backlit COAS sight.final, was known as a "soft dock". After separating from the SLA, therefore, and using the SM's RCS thrusters, the crew flew the CSM forward about 50 meters along the direction of travel of the whole stack and then, again using the same attitude controls, performed a 180° turnaround. This rotation brought the LM sitting on top of the Saturn V's S-IVB stage, previously completely out of sight, into view from CM windows no. 2 and no. 4 (the wedge-shaped ones that allowed a forward view). When the spacecraft were correctly aligned, the CSM was pushed forward with the RCS thrusters onto a slow collision course with the LM, taking care to keep the correct attitude throughout. All this was possible by referring to a special illuminated and dedicated target , shaped like a "T", mounted on the roof of the LM Ascent Stage right next to the docking tunnel where the CSM's probe was to be driven home. The aiming and the whole maneuver were handled by the Command Module Pilot , or CMP, with the help of a collimating sight installed in CM window no. 2 , through which the CSM could be carefully guided into a delicate, safe approach. If the CMP managed to keep the two references aligned throughout the approach, at some point the CSM's extended probe slid perfectly into the drogue in the LM's tunnel, allowing the three latches of the docking probe to snap firmly into the hole in the LM's drogue, thus establishing the long-sought physical and mechanical connection between the spacecraft. When this maneuver succeeded, the LM was said to have been "captured". At that point the spacecraft were not yet rigidly joined, but only connected by a pivoting joint (the extended probe, precisely), which still made it possible to rotate the CSM about its longitudinal axis (the axis of travel), in order to align the inertial reference vectors of the spacecraft. This feature was extremely important, because once in lunar orbit the guidance computer of the intrepid lunar spacecraft had to be specially configured to fly on its own and reach the designated landing point. To do this, however, it needed to know precisely its initial orientation in space. These vectors were provided by the CM's AGC guidance computer and then converted by hand with mathematical calculations (gimbal angle conversions, or more precisely the correspondence between the gimbal angles) for the LM's LGC computer. So the closer the LM's reference axes were to the CSM's when the spacecraft docked, the less complex this operation was. Aligning the LM with the CSM's attitude as precisely as possible was therefore an absolute necessity on every mission. When the axes were finally aligned, the crew retracted the probe.
This maneuver drew the spacecraft together for good, allowing the CSM's docking ring around the tunnel to lock the two spacecraft together mechanically and airtight . The CSM's docking ring had a dedicated flange with 12 latches, whose hooks snapped shut when the spacecraft came together, trapping the raised edge of another flange of the same diameter installed on the LM, also around the top tunnel. The pressure created by the mechanical contact between the spacecraft, drifting slowly toward each other, automatically triggered the 12 latches , joining the CSM to the LM in a "rigid" or "hard dock" right at the tunnels and at two concentric silicone seals that were compressed by the rims of the flanges, thus ensuring the airtightness of the cylindrical inner passage that had been created. Thus the space train was formed, a single spacecraft flying through deep space, joined by a tunnel connecting its two halves. The following video shows how docking between the CSM and the LM took place:
From that moment on, the two docked modules formed an assembly about 16 meters long (excluding the S-IVB still attached to the LM) with a total mass of over 45 tons. Joining two such different spacecraft radically shifted the center of gravity of the assembly. The Command Module's onboard computer (AGC) had to be told the new total mass so that it could fire the maneuvering thrusters (RCS) correctly without making the whole assembly spin around. The connecting tunnel thus created, although sturdy, had a certain elasticity. Firing the main engine (SPS), for example, needed for course corrections toward the Moon or to enter a stable lunar orbit, could subject the whole "space train" to significant oscillations, which the astronauts had to monitor carefully precisely to avoid overloading the 12 latches holding the spacecraft together. Although the LM had its own engines, in fact, during the journey to the Moon it was always the Service Module (SM) that did all the correction work, assisted by the RCS. Once the mechanical connection between the spacecraft was established, the transfer tunnel had an effective length of 46 cm (of which 30 cm belonged to the Command Module and 16 cm to the Lunar Module) and a diameter of 80 cm. Bare dimensions, but enough to allow an adult man to pass, even when encumbered by the bulky A7L spacesuit. At either end of this short passage were the pressurized hatches of the respective cabins, which sealed the compartments airtight to prevent disastrous decompression into the vacuum of space. Opening these hatches, however, was not at all immediate: the flight checklist first required a rigorous check of the airtightness of the docking seals. To carry out the test, the crew opened a dedicated equalization valve on the CM hatch, letting air into the sealed tunnel. Then, using a dedicated pressure gauge, they monitored the pressure for at least 10 minutes. A drop in the readings would have meant unmistakably a deadly air leak into space; a steady reading, on the contrary, certified that the seals were doing their job perfectly. Only then, with the pressure stabilized, could the astronauts turn on the tunnel's internal lighting, inspect it carefully through the hatch window and finally open it safely for transit. 
Diagram showing the configuration of the CSM and LM during the flight of the docked space train from the Earth to the Moon. The two spacecraft were mechanically connected by the pressurized tunnel, which allowed the astronauts to move from one spacecraft to the other without going out into space.At that point the CM hatch was removed and the crew checked that all 12 latches had locked firmly. If not, they could be locked manually by pushing them into place by hand and then tightening them hard using a special tool carried by the crew. Then the umbilical electrical connections between the modules were made, allowing the CSM to supply electrical power to the LM throughout the outbound journey. The aim was to save the Lunar Module's precious batteries as much as possible for the landing, while also powering the lander's precious telemetry systems, which kept Mission Control in Houston informed about the health of the dormant, intrepid lunar spacecraft. And that's not all! Through the umbilical electrical connection between the spacecraft, the CSM's power system kept the LM's sensitive devices warm , which would otherwise have risked freezing in the extreme cold of space while on standby. At that point the tunnel was almost ready for human transit: it was in fact blocked in the middle by the docking probe on the CM side and by the drogue on the LM side. These had to be removed. The CM's probe was a marvel of technology that worked by means of springs, latches and pneumatic pistons, moved by dedicated solenoid valves that allowed it to extend or retract on electrical command from the astronauts. The astronauts also positioned, armed or removed it by hand as needed, as well as the drogue on the LM side. Once the whole assembly just described had been completely removed and properly stowed out of the way, the crew could reach the last obstacle along the way: the LM hatch closing the tunnel on the other side. Before opening it, they had to make sure that the pressure in the Ascent Stage matched that of the CM, by checking that the dedicated valve in the hatch itself had been left open for this purpose by the launch pad teams. And it always was! Once this check was done, the hatch was opened and the crew made their first visual inspection of the LM cabin to make sure that the spacecraft had survived the incredible violence of launch and the jolts of docking unharmed. Then, as a precaution , because of the torsional risk to the tunnel from the course correction maneuvers that would be needed during the journey, and so as not to overload the Command Module's ECS, the LM hatch was closed again and the crew withdrew into the orbiter for the whole transfer to the Moon. The LM, however, was not powered up and remained on standby to save the batteries needed for the mission on the lunar surface. Pressurization of the two spacecraft was therefore handled by the CM's ECS. Once the LM was firmly docked to the CSM, the time came to continue the journey to the Moon without the bulky S-IVB stage. By firing four explosive bolts holding the four folded legs of the Descent Stage to the Saturn V, the CSM could then perform a backward maneuver with the space train, again by means of the RCS thrusters. This operation made it possible to extract the LM from its housing and move well away from the S-
PTC (Passive Thermal Control) consisted of slowly rotating the space train about its longitudinal axis at a rate of three revolutions per hour.IVB stage, which inevitably went on to its spectacular fate as a derelict in solar orbit or as a scientific projectile aimed at the Moon to generate artificial moonquakes. Thus began, for the space train made up of the CSM and the LM, the cruise to the Moon , which would last about three days. During that time the astronauts could watch through the windows as the Earth shrank hour by hour and, if the course allowed, the Moon grew larger and larger, while the docked spacecraft glided silently through the depths of deep space. The transfer trajectory to the Moon began at the extraordinary speed of 39,000 km/h , but it did not stay constant over time. Earth's gravity, in fact, constantly slowed down the Apollo stack by pulling it back (slowing it down progressively to about 3,000 km/h), until, at a point about 5/6 of the way along the outbound path (about 62,000 km from the Moon), the space train entered the lunar sphere of influence, where lunar gravity began to prevail and draw it into its own gravitational slingshot , speeding it up again. During the three-day journey between the two bodies, on average about 384,000 km apart, the spacecraft had to perform a special protective maneuver so that it would arrive unharmed at the Moon. This choreography was called PTC, or Passive Thermal Control, jokingly nicknamed by the astronauts "Barbecue Roll Mode" (or the barbecue maneuver). Since in space there is no atmosphere to spread heat evenly, it was a fundamental maneuver for the health of the systems and the astronauts. A spacecraft sitting motionless in space between two worlds, in fact, is always exposed to brutal radiant heat from the Sun 24 hours a day. On the sunlit side of the space train, therefore, high temperature peaks could quickly build up, easily approaching +120°C within a couple of hours. Conversely, the shadowed side radiated heat away into space, cooling down to -180°C. This large temperature difference could lead to a structural weakening of the spacecraft, risking deforming or cracking its structure because of the stress on the surface metal. The propellant tanks and electronic systems deep inside the space train could also have been damaged by the violent temperature swing, boiling on one side or freezing on the other. For this reason, once the S-IVB stage had been left to its fate, the crew, with the help of the guidance computer, started PTC, which consisted of slowly rotating the space train about its longitudinal axis at a rate of three revolutions per hour. Like a chicken on a rotisserie, every part of the spacecraft was exposed to the Sun's heat for a time long enough to warm up, then rotated into the shade to cool down , thus keeping an average temperature between +7 and +15°C over the whole surface of the docked spacecraft. When PTC was active and stable, the astronauts could finally rest. The maneuvering thrusters (RCS) were turned off so that their firings would not disturb their sleep or cause annoying jolts. During these hours, the only sound in the cabins of the docked spacecraft was the constant hum of the ECS fans, the noise of the electronics and the running power inverters , and the ticking of the mechanical instruments, while outside the windows the Earth, the Moon and the Sun began to alternate rhythmically in the deep black of space.
12) THE LUNAR ROVER: DRIVING AMONG THE LUNAR CRATERS!
The Apollo 15 LRVThe Lunar Roving Vehicle (LRV), better known as the "lunar Rover", was the first crewed four-wheeled vehicle to cross the soil of another world. Built for NASA by Boeing (with the participation of Delco/General Motors), it was introduced on the last three Apollo "J" -type missions (15, 16 and 17), turning them from simple exploration expeditions into real long-range geological research missions. The rover had to meet an extreme engineering challenge: to be very light, withstand extreme temperatures and take up very little space during the journey. It had a chassis built of aluminum alloy, 3.1 meters long and weighing about 210 kg on Earth, but able to carry almost 500 on the Moon of astronauts, samples and equipment. It had four extraordinary wheels! Since rubber would have worn out too quickly in contact with the abrasive lunar regolith, or would have become too brittle in a vacuum, the wheels were made of a mesh of zinc-coated steel piano wire, with titanium treads for traction. This design made it possible to move effectively on the soft lunar dust (regolith) without sinking, and also provided an enviable compression suspension system. The Rover was a fully electric vehicle, powered by two non-rechargeable silver-zinc batteries. Each wheel had its own independent electric motor of 0.25 HP (for a total of 1 HP). If one motor failed, the other three wheels could go on driving the vehicle normally. Both axles (front and rear) could steer, allowing a very tight turning radius (3 meters), as well as "crab-style" maneuvers. There was no steering wheel, but a joystick shaped like a "T" placed between the two seats, which could therefore be operated by either astronaut. Pushing it forward accelerated, pulling it back braked.
Since GPS was not yet available at the time of the Apollo missions (let alone around the Moon), nor a compass sensitive enough to detect and use the Moon's extremely weak magnetic field, the rover used a directional gyroscope and odometers on each wheel to constantly calculate its position relative to the Lunar Module. Mounted at the front of the vehicle was a deployable umbrella-type dish antenna, which had to be pointed manually at the Earth every time the rover stopped, in order to transmit high-quality color television pictures (for the time, of course) from the camera on the lunar dune buggy. This camera could also be controlled remotely by an operator at a dedicated console in the MCC in Houston. Thanks to the staff taking turns at the control console on Earth, Mission Control could follow the astronauts' explorations almost in real time (there was a delay of about 3 seconds for the radio signals to travel between the two worlds and back) as they moved across the lunar surface, as well as film the lift-offs of the LMs from the surface as the astronauts left it forever. Perhaps the most incredible aspect was how the rover traveled to the Moon. It was folded into a compact package and stowed in quadrant no. 1 of the LM descent stage. Once on the Moon, the astronauts worked a series of tapes and lanyards which, thanks to an ingenious system of springs and pulleys, allowed the rover to unfold, literally opening by itself and locking its wheels and chassis into operating position in less than 15 minutes. The deployment was designed not only to open the Rover, but also to lower it to the ground without any direct physical effort by the crew. It must be said, however, that once deployed the rover was not very heavy in the Moon's reduced gravity. More than once, in fact, before setting off again, the crew partly lifted it by hand to point it in the desired direction. This is why in some Apollo photos showing the LM on the lunar surface, no tracks from the rear wheels can sometimes be seen in the lunar dust. The top speed recorded by the Rover on the lunar surface was about 18 km/h. The record was set by Gene Cernan and Harrison Schmitt during the Apollo 17 mission. This extraterrestrial record still stands today. In all, the three rovers covered about 90 kilometers on the Moon and greatly extended the area visited by the astronauts. To this day, the wrecks of the rovers still lie inert on the lunar surface, a few steps from the LM descent stages, and are still clearly visible in high-resolution photos taken by orbiting robotic probes from several countries.
13) THE ALSEP SCIENTIFIC PACKAGE:
The Apollo 17 ALSEP stationThe LM Descent Stage was organized into quadrants, that is, dedicated sections with bays holding the propellant tanks, the DPS engine, the batteries, the oxygen tanks, the drinking water tanks and the Lunar Rover. However, some of these (called SEQ) also held the package of scientific instruments to be left on the Moon to continue the scientific study of the site even after the lunar crews had left. This scientific package was called ALSEP (Apollo Lunar Surface Experiments Package). It was a set of instruments designed to be installed by the astronauts on the lunar surface and to operate autonomously for years, sending data to Earth by radio. If the Lunar Module was the means of transport for reaching the lunar surface, the ALSEP was the permanent research station. Each ALSEP station was made up of a Central Station (the control and transmission center) and several experiments connected by shielded flat cables (which coped better with the temperature swings of the lunar surface and were less vulnerable to the disruptive impact of micrometeorites). The Central Station received commands from Earth, distributed power to the instruments and transmitted the scientific data. Since batteries would not have survived the freezing lunar night (which lasts 14 Earth days) or the scorching midday Sun, the ALSEP was powered by a Radioisotope Thermoelectric Generator (RTG-SNAP-27). This generator used the heat from the decay of Plutonium-238 to produce about 70 watts of steady electricity, ensuring operation for over a decade. The makeup of the ALSEP varied from mission to mission, but some instruments were almost always present. Among them was a Passive Seismometer, called PSE , the most iconic instrument ever taken to the Moon. It was used to measure "lunar earthquakes" (moonquakes), meteorite impacts and even the vibrations caused by the steps of astronauts moving nearby, as well as the very distant ones from the crashes of the S-IVB stages of the Saturn V rockets used during the Apollo missions. By interpreting this data, scientists worked out the internal structure of the Moon, dividing it into a core, a mantle and a crust, just like the Earth. Another instrument taken to the Moon was the LSM magnetometer , which precisely measured the lunar magnetic field at the surface. The experiment showed that although the Moon does not have a global magnetic field like the Earth's, there were areas with local residual magnetism that was still very strong. Another noteworthy instrument was the HFE Heat Flow Experiment. To set it up, the astronauts had to drill into the lunar soil to a depth of up to about 2.3 meters and insert probes to measure how much heat was flowing out from inside the Moon. It was essential for understanding the thermal history of our satellite. Finally, another historic passive instrument left on the Moon was the Laser Ranging Retroreflector, or LRRR. Technically it was not part of the electronic package (it needed no power), but it was placed next to it. It was made up of a set of prism mirrors able to reflect back along the line they came from special beams of tightly collimated laser light modulated into pulse trains, sent by dedicated telescopes on Earth. This instrument, if conspiracy theorists want proof, is still used today to measure the Earth-Moon distance with the extraordinary precision of a few millimeters, and has helped confirm the predictions of celestial mechanics, according to which the Moon is steadily moving away from the Earth by about 3.8 cm per year. The astronauts carried the ALSEP in two packages stowed in an outer compartment of the Lunar Module (the SEQ Bay). To take them to the installation site (away from the LM, so that dust kicked up by the violent exhaust gases at lift-off would not damage or soil the instruments), they used a carrying bar joining the two packages, carrying it on the shoulder. Installation took about an hour of meticulous work: the central station had to be leveled, the antenna pointed at the Earth and the plutonium fuel element inserted into its housing inside the RTG. The ALSEP stations were among NASA's most incredible successes. They were designed to last one or two years, but some instruments remained in operation until September 30, 1977, when they were deliberately switched off remotely, only because of a lack of funds to keep the receiving stations on Earth running, even though the instruments were still sending back valid data.
11) THE A7L SPACESUIT:
The A7-L and A7-LB spacesuits were a technological marvel of the twentieth century. They were in every respect a wearable spacecraft that protected the astronaut from the rigors of space. Photo courtesy NASA.The A7-L (built in two versions, the A7-L for the short-duration Apollo missions A7/14 and the A7-LB for the extended-duration "J" missions A15/17) was the spacesuit used by NASA astronauts during the Apollo program, between 1968 and 1972. Made by ILC Dover, it is considered one of the masterpieces of 20th-century engineering, having allowed man to survive and work on the hostile lunar surface and in deep space during the extravehicular activities between the Earth and the Moon on missions 15, 16 and 17. It was an anthropomorphic pressure suit, designed and made to measure for each astronaut, to provide protection against the vacuum of space, solar radiation, dangerous micrometeorites, the extreme temperatures of deep space and the Moon, which as we have seen could range from -180°C to +120°C, depending on whether the astronauts were exposed to sunlight or not. In short, it was a full-fledged wearable spacecraft . Unlike earlier suits, the A7L was "integrated", meaning that it served both as a protective garment worn by the crew during lift-off from Earth and reentry, and as an autonomous survival system for extravehicular activities in space or on the lunar surface. The suit was made up of no fewer than 21 layers of different materials, which can be grouped into three main systems. Let's look at them in detail: 1) the Liquid Cooling Garment (LCG), a special undergarment in direct contact with the astronaut's skin, with a dense network of small tubes through which chilled water flowed to absorb the astronaut's body heat and then get rid of it into space; 2) the Pressure Layer, a dedicated layer of rubberized nylon (neoprene) designed to keep the internal pressure steady at about 3.7 psi (0.25 atm) of pure oxygen; 3) the Thermal Micrometeoroid Garment (TMG), the protective outer layer made of aluminized Mylar for thermal protection, Dacron for structural stability and micrometeorite protection, and Beta cloth, a Teflon-coated glass fiber, fireproof and resistant to the abrasion of lunar dust (also known as "regolith"). Before putting on the spacesuit and LCG, the astronaut fitted the UCD (Urine Collection Device) device, a sort of personalized "anatomical adapter" that led to a collection bag called the UCP (Urine Collection Pouch), which was strapped around the lower abdomen and one thigh. This device allowed the astronaut to urinate without any worry during the long hours spent on the lunar surface. The set was completed by the FCS (Fecal Containment System) device, a sort of diaper designed to effectively absorb any "solid evacuations" that might become necessary during extravehicular activities in the spacesuit. It should be pointed out that the astronauts followed a low-residue diet before launch and during the mission, so as not to have to use it during moonwalks. Around the opening for the astronaut's head, the A7L suit had an airtight locking ring, needed to attach the pressure helmet. The helmet was made of clear polycarbonate, extremely resistant to impacts and temperature swings, while also offeringa wide field of view. The A7L helmet had a cushion at the back of the head, which the astronaut rested against when lying in the Command Module couches. On the transparent polycarbonate bubble, roughly at mouth level, there was also a special sealed valve that allowed a water-dispensing straw or predetermined bags of freeze-dried food to be inserted into the helmet without losing suit pressure, so that the astronaut could drink and eat even if the spacecraft had lost pressure in space. At the front of the helmet, low down so as not to block the view outside, there was also a small soft plastic stick that let the astronaut scratch his face (but above all his nose) in case of an irresistible itch while working in space or on the lunar surface. When the astronaut's head was in the helmet, it was always covered by a special two-tone Teflon cap, called the "Snoopy Cap", which prevented stray hairs from floating near the astronaut's face, causing irritation and itching. Inside the Snoopy Cap were also the headphones through which the astronaut listened to radio communications, as well as the boom holding the dual microphone , which reached to the corners of the mouth: both were used for communications and to reduce background noise as much as possible , so that the astronaut's communications were always clear. Inside the neck ring joining the helmet to the suit there was also a spring-loaded dispenser of multivitamin, high-protein energy snacks, which let the astronaut grab them with his teeth, tear them off and eat them more easily, thus providing precious nutrients to the astronaut during the long, exhausting moonwalks. During the lunar landings, the helmet was always covered by the LEVA (Lunar Extravehicular Visor Assembly), a sort of protective over-helmet , also made of polycarbonate but protected on the outside by the TMG covering. In front of its line of sight were two vertical side shades and one horizontal shade, as well as a pivoting gold visor which, like a pair of special sunglasses for space, filtered the Sun's violent UV and IR rays, cut down the extraordinary glare of visible light and reduced the radiation reflected from the lunar surface. At the wrists there were two more locking rings that connected the A7L suit to the special silicone pressure gloves, which during the moonwalks were also covered by special TMG over-gloves. The suit was a one-piece garment and could easily be put on simply by stepping in from the back, first slipping the legs into the pressurized trousers and then lifting and closing a special pressure-sealed zipper at the back . Some straps inside helped the astronaut get into the suit, making it more or less easy (but this was subjective), even in the most cramped spaces, such as the pressurized cabins of the LM Ascent Stages. The boots were built into the suit's trousers. They had a special grip sole that allowed the astronaut to attach himself firmly to the Velcro strips on the floor of the LM cabin. This precaution was used when the crew was flying the LM, especially during the lunar descent, when stability at the controls was a crucial safety factor. On the sides of the trousers there were also two metal attachment rings that allowed the suit to be clipped to special carabiners connected to wire restraints that further steadied the standing astronaut throughout the approach to the lunar surface, as well as during the final jolt when the LM touched the ancient lunar surface. From the Apollo 13 mission onward, the commander's spacesuit was marked with red stripes on the helmet and arms. This made it easier to tell the crew members apart in television pictures and photographs. Before starting their lunar exploration, the astronauts put on special overshoes, designed to provide stability, as well as thermal and mechanical protection for the feet, while walking through the rugged lunar regolith. The sole was made of high-strength silicone rubber, with deep horizontal grooved treads that allowed them to grip the very fine lunar dust as well as possible. This material stayed flexible even at very low temperatures. The outer upper, on the other hand, was covered with a flexible metal fabric called Chromel-R. It was extremely resistant to cuts and abrasion caused by lunar rocks as sharp as glass, while the inside was made of many layers of aluminized Mylar, alternating with Dacron felt, whose purpose was to provide effective thermal insulation, to prevent the heat or cold of the ground (which can reach +120 or -180°C) from burning or freezing the astronaut's feet. These overshoes, aptly called "Moon Boots", were responsible for the peculiar, iconic footprints left by the astronauts on the lunar surface , seen in all the photographs of the missions. The A7L suit could not work without the special backpack the astronauts carried on their shoulders. Called the PLSS (pronounced "Pliss"), or Portable Life Support System, this backpack was in every respect the astronaut's only means of survival during the long hours of exploration on the lunar surface. On the first lunar missions, the PLSS could support extravehicular activities of no more than 4 hours (for the A7-L suit), which were extended to 8 during the "J" missions (A7-LB suit). It was 66 cm long, 46 wide and 25 deep, and during the journey it was stowed in the LM in dedicated recharging compartments for gas and water. On Earth it weighed about 38 kg. On the Moon, the whole system (A7L suit + PLSS) was much lighter thanks to the gravity reduced to 1/6, but it was designed to help keep the center of gravity of the suit in a precise, stable position, even when the astronaut walked clumsily across the lunar surface. When it was connected to the suit pneumatically, hydraulically and electrically, the PLSS turned the A7L suit into a real miniature "autonomous spacecraft". Without the PLSS the astronaut would have been tied to the LM by umbilical cables and hoses, just as on the spacewalks in Earth orbit during the Gemini missions. Thanks to the PLSS, on the other hand, the astronauts could explore the surface of the Moon freely, moving away from the LM up to a maximum permitted distance of 6 km. This limit was not arbitrary : it was considered the safe distance that gave the astronaut a very good chance of survival with the PLSS consumables to walk back to the LM in case of problems with the Lunar Rover. The PLSS had to perform five tasks, all extremely critical for the astronaut's survival in such an extreme environment: 1) pressurize the suit once it had been put on and sealed around the astronaut, supplying pure oxygen for breathing and keeping the internal pressure steady at 3.7 psi (about 1/4 of an atmosphere). 2) Remove or reduce the heat produced by the astronaut's metabolism and the heat absorbed by the suit from sunlight. 3) Circulate air inside the protective garment , sending it to every cavity, helmet, arms, legs and torso, to help the LCG get rid of heat and to help sweat evaporate. 4) Actively remove all contaminants from the suit's air, such as: the carbon dioxide exhaled by the astronaut (through a special lithium hydroxide, LiOH, filter), dust, floating fibers from the rubbing of the inner garments, any intestinal and/or gastric gases and, last but not least, the dry skin the body sheds every day. 5) Allow radio communication between crew members and with Mission Control in Houston on Earth, also packaging and transmitting the data from the biomedical sensors the astronaut was always connected to, such as body temperature and ECG (electrocardiogram). To do all this, the PLSS, which was not a simple tank but an extremely sophisticated closed-loop system , contained a full-fledged air-conditioning and air purification station . This consisted of a sublimator specially sized to get rid of heat effectively in the vacuum of space, supported by a large water supply to operate it at the right rate in BTU. This supply was held in a tank with a capacity of 6 liters. Another bag inside the suit, on the other hand, kept the astronaut hydrated, through a straw with a spring-loaded valve inside the helmet. The PLSS also contained an electronic system for radio communications and the astronaut's biomedical telemetry , a disposable battery for each moonwalk, a compressed oxygen tank to pressurize the suit and let the astronaut breathe for the hours of the moonwalk, and two integrated circulation systems, one for the suit's cooling water through the LCG and another for the distributed air. The sublimator was certainly the most ingenious part. Since there is no air in space , heat cannot be dissipated with fans; for this reason the PLSS used precisely the physical principle of sublimation in a vacuum. Water from the LCG undergarment passed through a system of external and then internal tubing to a special porous metal block exposed to the vacuum of space, which was the heart of the PLSS sublimator . There, the water, moved by a dedicated pump, froze in the pores in contact with space, subliming more or less quickly as needed (that is, going from ice to vapor) directly into space, subliming (that is, going from solid to gas without melting) and carrying away with it the astronaut's body heat and the unwanted heat absorbed by the suit from sunlight. The thermostat regulating this process could be set through a special console that the astronaut wore outside the suit, on the chest, called the RCU (Remote Control Unit). This unit was the operational control center of the A7L suit. Since for obvious reasons the astronaut could neither see nor reach the backpack (PLSS) on his shoulders, the RCU acted as a "remote" interface mounted directly in a place easily reached by hands made clumsy by the pressure gloves. It was a silver box covered by the protective TMG layer, small but packed with controls, which let the astronaut monitor his own parameters, manage life support and control the radio, all with one hand. Its functions were to: monitor the status of the precious consumables (oxygen and water), monitor vital parameters such as the temperature inside the suit and pressurization, set the thermostats that controlled the cooling or heating of the LCG water and, last but not least, adjust the VHF radio settings, such as: headphone volume, microphone gain and selection of transmission bands. When the astronaut was inside the A7L suit, he could not look straight down at the RCU from the pressure helmet, because the edge of the neck ring and the bulk of the suit made it completely impossible. To get around this, the astronauts had a small mirror mounted on the wrist of the suit.
By turning their arm, they could read the dials and labels on the RCU, which for safety reasons were printed in mirror image in some places, precisely to make them easier to read in the mirror. On the front of the RCU control box there was also another metal bracket on which the astronauts mounted the Hasselblad camera they used to capture the key moments of the mission. For safety, the PLSS was designed to support the integrity of two spacesuits connected to each other in an emergency. Auxiliary connectors on the outside of the A7L suit, in fact, allowed the two exploring astronauts to connect their suits to each other, sharing cooling water and LCG temperature control in situations of serious danger on the lunar surface. This feature allowed the crew to survive if, for whatever emergency reason, one of the two PLSS units suddenly stopped working, thus offering a chance of getting back to the Lunar Module and saving both their lives. On top of the main PLSS, moreover, was mounted a second, smaller unit called the OPS , or Oxygen Purge System. This system was the emergency and backup unit of the Apollo life support system. If the PLSS was the "main engine", the OPS was the emergency parachute, a system designed to ensure the astronaut's survival if the main backpack or the suit itself suffered a catastrophic failure. Physically, it was the rectangular unit mounted on top of the PLSS, easily recognizable by its "box" shape crowning the top of the astronaut's back. Unlike the PLSS, which was a closed-loop system (the oxygen was recycled), the OPS was an open-loop system, and on its top was the VHF radio antenna for the astronaut's radio communications. When activated, the OPS fed a continuous flow of fresh oxygen into the suit, pushing carbon dioxide and heat out of it through an exhaust valve called the PRV , or Pressure Relief Valve. The OPS emergency system maintained pressurization even with a small leak in the suit, giving the astronaut precious minutes to take action. The OPS unit was relatively simple and extremely reliable, since it had to work mechanically even without electrical power from the PLSS. Inside it held two spherical steel tanks filled with oxygen at about 390 bar and a pressure regulator that allowed the suit to be pressurized without overdosing the astronaut. While the PLSS units were almost always left on the Moon to save weight, many OPS units were brought back to the Command Module. This was because they provided a reserve of breathable air for any extravehicular activities that might be needed on the way back and an emergency reserve in case of serious problems during reentry or the recovery phases at sea. Each OPS weighed about 18 kg on Earth and had 30 minutes of endurance in "high flow" mode (in case of a suit leak), extendable to 75-90 minutes in "low flow" mode. It was attached to the PLSS by a pair of sturdy quick-release brackets. The astronaut could activate the OPS in either of its two modes simply by pulling the dedicated handle at the front at the top of the A7L suit, or by means of the famous red knob, better known as "the red apple of the A7L suit", visible in all the photographs of the astronauts on the lunar surface more or less near the waist. The A7L suit was a spectacular piece of equipment. It made all the Apollo missions possible, withstood extreme temperature swings, sudden falls and heavy contamination by abrasive lunar dust , and helped protect the astronaut as he ventured into the most hostile place man had ever set foot in, all without ever presenting a significant problem. The A7-L version was used on the early, short-duration Apollo missions (A7/A14). The A7-LB version, on the other hand, was used for the extended-duration "J" missions (Apollo 15-16-17). These offered greater freedom of movement and excursions on the lunar surface of up to 8 hours. The A7-LB suit, not by chance, was the forerunner that led to the development of the EMU, still used today for extravehicular activities in orbit on the International Space Station , or ISS.
The essential support facilities on the ground
To sustain the colossal technological effort of the Apollo program, NASA had to devise an unprecedented ground infrastructure. To grasp its scale, it is essential to imagine an operational square spanning the United States, in which each corner represented a fundamental area of expertise:
(you can click on the following links to jump to the desired section).
The success of the Apollo missions, in fact, did not depend only on the unquestionable courage of the astronauts who took part in them. Although extremely important and irreplaceable in expertise and undoubted ability, this was only the most visible and deserving part of a titanic infrastructure made up, in reality and at its core, of some 400,000 people (directly employed and in supporting industries) spread across the country. These were grouped mainly into specific, well-defined key centers, each with its own specific, unparalleled mission. Without perfect synchronization between these centers, the Saturn V (derived from the rocket experience of the German team from Peenemünde and then matured within the hectic American space program), the Apollo Command and Service Module - CSM (derived from all the experience gained in earlier space programs with the Mercury and Gemini capsules), the Lunar Module - LM, the Lunar Rover - LRV, the ALSEP scientific package and the A7L spacesuit (derived from field experience with the Navy Mark IV of Mercury and the G4C of Gemini) would never have been conceived, and the conquest of the Moon would have remained an unattainable utopia.
NASA's design brain therefore brought together, standing out for their expertise and professional skills, the best technology companies in the country, some of which reported to a general supervisory center, as in the case of building the mammoth Saturn V launch vehicle. This gigantic rocket, in fact, took shape step by step in the project's engineering and technological supervision arm, called the Marshall Space Flight Center (MSFC), based in Huntsville, Alabama. It was here that, under the direction of the German scientist Wernher von Braun, a team of German and American engineers brought the technological miracle to life, building, in internal competition with the United States Navy, first the Redstone missiles, then the Juno, then the Jupiter and finally the Saturn. Marshall was responsible for the design, coordination, development and testing of all the engines and rocket stages on test stands, while the country's major aerospace companies and their vital subcontractors (Boeing, McDonnell Douglas, North American Aviation and IBM) took care of the construction and logistics. The development of the Saturn project therefore built on solid previous experience, but it nonetheless required a meticulous step-by-step approach, which over time led to the creation ofthree intermediate experimental rockets: the Saturn I, the Saturn IB and finally the Saturn V. Each step built the next as experience grew, maturing the project until the final result. A reverse approach, or a much more direct one aimed straight at the final result, would have failed. The size of the machines being created, in fact, combined with their technological complexity and the unheard-of thrust they were trying to harness to launch spacecraft toward the Moon, could certainly not be achieved overnight. The development of the CSM and the LM followed the same path. The first, for example, was built mainly in Downey, California, at the aerospace technology laboratories of North American Aviation, as well as by its main subcontractors, such as Beech Aircraft Corporation in Boulder, Colorado, and Aerojet Space Technology in Sacramento, California. These companies, supervised as a whole by NASA, designed and built all the components that would make up the Apollo spacecraft as a whole, giving birth first to the "Block I" spacecraft, intended for systems tests on the ground and then in Earth orbit , and finally to the "Block II" version, which instead was intended to fly all the way to the Moon. It is sadly well known that the development path of the Apollo capsule was not immune to accidents and tragedies. We must remember the one that befell spacecraft AS-204, later sadly renamed "Apollo 1" in honor of its crew, in which astronauts Gus Grissom, Edward White and Roger Chaffee died tragically in a sudden, devastating cabin fire. The accident happened during a routine ground systems test on Launch Complex 34 at the Kennedy Space Center on January 27, 1967. After the accident the Apollo program entered its darkest hour, suffering a severe setback that inevitably brought it to a standstill for many months, following the necessary government investigation loudly demanded by members of the United States Congress. The investigation established serious responsibilities on the part of both NASA's leadership (which was pushing to speed up the development of the program in order to meet the deadlines set by the late President Kennedy, champion of the human exploration of the Moon) and North American Aviation , because of questionable design choices made along the way in order to meet NASA's pressing demands for the urgent construction of the Block I spacecraft. The investigation reached its verdict quickly, bearing in mind above all that America was competing in the space race with the Soviet Union, in a context of great international tension known as the Cold War. It allowed NASA to continue the undertaking and North American Aviation to complete the construction of the Block II spacecraft, demanding that all the substantial modifications and precautions be implemented to avoid new accidents on the ground and in space. This, as history soon showed, was done successfully. The Lunar Module, on the other hand, turned out to be the toughest, most complex, intricate and expensive spacecraft that had ever taken shape in a space program. For these reasons it suffered considerable production and testing delays, which greatly affected the timeline of the Apollo program. No one, in fact, had ever built anything like it. The LM was a spacecraft designed to operate in reduced gravity and in the vacuum of space. It also had to have special features that would allow it to perform multiple roles during the lunar mission and, above all, to be stowed on the Saturn V in a dedicated truncated cone adapter called the SLA, or Spacecraft-LM Adapter. In addition, NASA had strongly recommended that the LM be light, but at the same time that this should not compromise crew safety, the sturdiness of the system or the ease of piloting and control it needed, in order to land gently and then return safe and sound. As if that weren't enough, it all had to be done in just 9 years. Anyone faced with those demands would have shuddered, but not the managers of the Grumman Aircraft Engineering Corporation of Bethpage (Long Island, New York), who managed to win the contract. The project was led by Thomas J. Kelly, also known as the "father of the Lunar Module", and by his large team, made up of hundreds of technicians and engineers with the most varied aerospace expertise in history and, inevitably, a large number of secondary subcontractors. Needless to say, the time was ripe for success, since the same enthusiasm found at Grumman spread to every other part of the country and many companies were competing to take part. Completing this mosaic of excellence was the irreplaceable contribution to the Apollo project of the public and private research centers scattered across the country, which together formed NASA's design brain, where people of the caliber of Creola Katherine Johnson worked, as well as universities, first and foremost MIT in Cambridge. Under the direction of Charles Stark Draper, the Apollo Guidance Computer (AGC) was conceived, later adapted as the LGC for guiding the LM, the first multitasking electronic computer to use integrated circuits to combine lightness and computing power. If Draper's hardware was the electronic brain of the Apollo Project, the software written by Margaret Hamilton and her engineering team was its soul: the pioneering Colossus (for the Command Module AGC) and Luminary (for the Lunar Module LGC) programs allowed the onboard computer to manage the key phases of the flight to the Moon, as well as priorities during the critical phases of the landing, turning software once and for all into an engineering discipline fundamental for the future of mankind.
NASA'S OPERATIONAL HEART: THE JOHNSON SPACE CENTER (JSC):
NASA's operational heart, on the other hand, was located at the Johnson Space Center (JSC) in Houston, Texas. Known at the time as the Manned Spacecraft Center , or MSC, it was (and still is) the home of the astronaut corps and of the management of space missions with a human crew. In the Apollo era, the JSC was where the lunar missions were planned and where the prime and backup astronauts were selected , along with all the related support teams. The huge complex also housed all the simulation and training facilities that allowed the crews to practice every phase of the mission in preparation, working actively and closely with the controllers of the Mission Control Center (MCC), who would then follow them, step by step, on the real mission to the Moon. The MCC, in fact, took full control of the flight from the exact moment the Saturn V, lifting off toward space, cleared the launch tower at the Kennedy Space Center (KSC). Their job was to support the astronauts intensively, guiding them and managing every moment of the mission and any emergency that might occur in Earth orbit, in deep space or on the Moon. Houston's Mission Control Center (MCC) also housed the most sophisticated computers the world had at that moment in history, whose job was to continuously analyze the telemetry arriving by radio (picked up by the global tracking antennas of the NASA Deep Space Network - DSN) from the lunar spacecraft and calculate the crucial trajectories Apollo needed to complete every operational phase of the mission successfully. The telemetry data arriving from space was sorted by the computers by area of expertise and sent to the MCC controllers' consoles and those of their support teams working behind the scenes, to be constantly evaluated, compared, analyzed, predicted , and to find quick and precise solutions or countermeasures to any anomalies that might arise at any moment during the mission. It was in fact impossible for a crew flying in space, and under a certain stress because of it, to take care of all this. The crew was responsible for the fundamental part of the mission, such as flying the spacecraft, navigation, looking after the spacecraft entrusted to them and physically exploring space and the lunar surface. The Mission Control Center in Houston employed the best minds in the country. Flight controllers took turns at the consoles, divided by area of expertise and into teams, each with its own specialists and its own Flight Director, to give the astronauts their vital support from lift-off to splashdown, for all the days of the mission, 24 hours a day.
NASA'S EXECUTIVE ARM: THE KENNEDY SPACE CENTER (KSC):
NASA's executive arm, on the other hand, was located at the Kennedy Space Center (KSC) at Cape Canaveral, Florida. This was the departure port for the Moon and for space. KSC was where components produced all over the country were assembled into the final spacecraft that would then set sail for the Moon. Through monumental facilities such as the Vehicle Assembly Building (VAB) and Launch Complex 39, KSC turned millions of separate parts into a single system ready for launch. The VAB was not just an imposing cube-shaped building, but one of the most imposing engineering monuments of the 20th century. Located on Merritt Island at Cape Canaveral, it was conceived and built specifically to allow the vertical assembly of the Saturn V, protecting the rocket, machinery, equipment and technicians from the weather and hurricanes of the southern Atlantic coast. After the Apollo program it was used to assemble the Space Shuttle and is still used today for the mammoth SLS launch vehicle, the new lunar launcher of the Artemis space program, which will soon take man back to the Moon. The imposing VAB structure is visible from tens of kilometers away and remains one of the largest single-volume buildings in the world, so large that, under certain humidity conditions, it can generate its own internal microclimate. To prevent clouds from forming on the upper levels, in fact, special air-conditioning units are installed in its upper part, removing the moisture trapped in the structure and preventing its possible condensation. The figures describing the VAB are almost hard to picture: an overall height of about 160 meters (roughly a 50-story skyscraper), with a footprint at the base of about 3.2 hectares. The internal volume is 3,665,000 cubic meters , so vast that the Statue of Liberty could fit inside it entirely, pedestal and all. It also has the four largest vertical sliding doors in the world (139 meters high). Each door takes about 45 minutes to open or close completely. It is divided into four large vertical bays, in each of which an entire Saturn V could be stacked using a dedicated majestic bridge crane (with a capacity of up to 250 tons).
The lower bays, on the other hand, were used for the transit toward the high bays of all the parts to be assembled into the rockets, such as the various stages arriving from the suppliers and everything needed to fit them out properly before mounting them on the Moon rocket. The building had huge shaped, self-propelled platforms that closed when needed around the rocket at various heights, allowing technicians to reach every centimeter of the Saturn V without having to raise, lower or move it from its base. Assembling a Saturn V rocket was done in stages. First of all, a huge tracked transporter called the Crawler-Transporter (or simply the "Crawler") brought into the designated high bay of the VAB the Mobile Launcher Platform (MLP) , complete with its Launch Umbilical Tower (LUT) , the umbilical tower to which the rocket would be attached during assembly, supporting and feeding it until lift-off. The Mobile Launcher Platform (MLP) was much more than a simple base: it was a real self-propelled technological interface that accompanied the Saturn V through every phase, from assembly in the VAB to the first seconds of lift-off. If the rocket was the heart of the mission, the MLP was the skeleton that supported it and fed it until the moment of its vertical departure for Earth orbit. The platform was a huge rectangular steel structure, 49 meters long and 41 wide. The base platform body alone was about 8 meters high. In the center it had a huge square opening for venting the exhaust gases generated by the five voracious F-1 engines of the first stage. Around this square exhaust opening, set 90° apart, were four massive controlled-release clamps , called Hold-down Arms , which held the Saturn V launch vehicle to the base, keeping it upright until a few moments before lift-off. At that moment they were programmed to release their grip in a controlled way and gradually, as lift-off thrust built up. This feature avoided disastrous jolts of the rocket at release which, combined with the acceleration built up by the engines, could have caused the rocket to hit the LUT next to it. The Hold-down Arms were designed to hold the Saturn V firmly upright while its engines built up to full thrust and, if something went wrong before release, to keep it on the pad while the engines were safely shut down. The Hold-down Arms had protective hoods of hardened steel that closed like a shell once their job was done. The purpose was to protect them from the devastating columns of turbulent fire and the immense shock waves released by the exhaust nozzles of the Saturn V's F-1 engines, which at that moment, running at full power as they rose into the sky, emerged for the first time from the exhaust opening where they had sat, flooding the launch pad with a hurricane of fire. Next to the Hold-down Arms were the Tail Service Masts, three retractable arm structures used to feed propellants into the base of the first stage. At lift-off they too were quickly retracted and immediately protected by heavy hinged steel hoods, which covered them effectively to protect them from the devastating action of the Saturn V's exhaust plume. The most visible element of the MLP was the gigantic red tower, known as the Launch Umbilical Tower (LUT). About 120 meters high, this tower was essential for two reasons: first, it had nine swing arms that connected the tower, and therefore the launch pad, to the Saturn V electrically, pneumatically and hydraulically . These arms supplied the cryogenic propellants for the launcher's huge tanks, made up of liquid hydrogen and oxygen, RP-1 kerosene, gaseous nitrogen and helium, water, electrical power, data and telemetry lines, remote control lines and support for cooling or heating the launcher's delicate systems. At launch these arms detached automatically from the Saturn V's umbilical connections, swinging into a safe position just a few seconds before (some at the exact moment of) lift-off.
This coordinated retraction was meant to clear the rocket's vertical path of the potential risk of a catastrophic collision in flight. At the top of the LUT tower, at about98 meters high, was access arm no. 9, which included the elevator landing and the balcony access walkway ending in the "White Room" (the "white room"). This was an iconic place , charged with emotional tension, being literally the last room the astronauts passed through before leaving the Earth and shutting themselves inside the capsule to reach another world. The Apollo White Room was a small area kept at positive pressure, carefully cleaned, designed to prevent dust, humidity and germs from getting into the capsule, where they could have caused short circuits or malfunctions in the spacecraft's delicate electronic systems. Germs, moreover, could have made the crew seriously ill during the mission. For this reason the technicians who worked there (the famous Close-out Crew - Close-out Crew) wore sterile white coveralls, caps and gloves while supervising the pre-launch preparation of the spacecraft and the crew's boarding. In the White Room each astronaut boarded sealed in his own spacesuit , which, besides getting him used to breathing pure oxygen at 5 psi , as provided by the Command Module's Environmental Control System - ECS, would also protect him from any deadly depressurization , always a risk at every launch. On the way from the astronaut quarters to the launch pad, each crew member wore yellow rubber overshoes, which were removed by the Close-out Crew before entering the spacecraft. This further helped keep the environment of the Command Module uncontaminated. The White Room also provided working space next to the capsule's access hatch, giving the technicians of the Close-out Crew enough room to move. They had the delicate task of helping the astronauts (encased in their spacesuits) slide into their couches, fasten their safety harnesses and connect to the spacecraft through the umbilical hoses and electrical cables. At the same time, all the safety pins and switch covers installed earlier precisely to prevent accidental or disastrous activation during the long tests on the pad were removed with great care. The White Room was also where the iconic pre-launch hatch closing took place. This was the most delicate operation. The hatch, in fact, was sealed and its airtightness was tested. Once it was closed, the astronauts were officially cut off from the outside world. The most important figure in the White Room was the Pad Leader (the head of the pad crew). For almost the whole Apollo program and part of the Shuttle program, this role was held by the legendary Guenter Wendt, German-born and known for his iron discipline and his sense of humor. There was a tradition among the astronauts: giving Wendt a small gift or a "joking token" before entering the capsule (for example, a giant key to the rocket or a fake fish). Wendt was the last man the astronauts saw on Earth and the last to shake their hands, wishing them good luck and a good flight.
Below is another extremely accurate video (we recommend enlarging the window) showing the route taken by the crew to board the Apollo Command Module at the top of the Saturn V, through the White Room at the end of LUT arm no. 9. Video created by the masterful Drew Swenson:
If something serious had happened on the pad during boarding, the White Room was an escape route until a few minutes before lift-off. The astronauts and technicians would have had to run out, cross access arm no. 9 and use a high-speed elevator or, in extreme cases, a slide-wire escape system to quickly reach an armored bunker under the pad, called the "Rubber Room" (room of rubber), which we will talk about shortly. The Saturn V was assembled inside the VAB as follows. After the Mobile Launcher Platform (MLP), complete with its Launch Umbilical Tower (LUT), had been placed inside the chosen high bay and connected to the local electrical, control and pneumatic support systems, the S-IC stage was brought in from the low bay ; attached to the overhead hammerhead crane fitted to every LUT, it was lifted and placed on the Hold Down Arms of the MLP, where it was connected to the propellant feed lines, the control lines and electrical, hydraulic and pneumatic supply lines provided by the Tail Service Masts and by the two designated swing arms. Then, using the same lifting method, the S-II stage, was hoisted and installed, mechanically attached to the S-IC stage by means of the S-IC<>S-II interstage ring, built for convenience of construction and handling into the base of the S-II. After the second stage had also been connected to the LUT by means of the three dedicated arms that retracted at launch, the third stage, or S-IVB, was hoisted. This stage was lifted and attached to the S-II stage by means of its dedicated S-II<>S-IVB truncated cone interstage , which adapted the 10-meter diameter of the second stage to the 6.6 meters of the third. The S-IVB was then connected to the LUT through two dedicated swing arms. Next came the installation of the IU instrument ring, which contained the electronic brain, the "inner ear", and the guidance and sequencing control of the whole launcher. Finally, on top of the rocket, by now 85.6 meters tall, was hoisted the last piece of the gigantic technological puzzle: the space train bound for the Moon, the 25-meter-high Apollo stack. It was made up of the truncated cone SLA adapter (Spacecraft-LM Adapter) , containing the Lunar Module (LM), the Service Module (SM), the Apollo Command Module (CM) and part of the LES (Launch Escape System) escape tower. Since the BPC would be fitted once the whole assembly had reached the launch pad, the space train was protected from the weather by a white waterproof protective cover, visible in all the photos of the rocket on its way to the pad. Every assembly step described required grueling verification and compatibility tests, all aimed at certifying the components for flight and at finding and solving any critical issues. The whole assembly and checkout process took weeks of intense, hard work, carried out by specialist teams working in 10-hour shifts , 24 hours a day, seven days a week. Below is another extremely accurate animation (we recommend enlarging the window) showing the vertical assembly of the Saturn V inside the VAB , created by the very talented Drew Swenson:
Below is another extremely accurate video (we recommend enlarging the window) showing the vertical assembly of the Apollo 15 Saturn V inside the VAB with historic photos from the time, also created by the very talented Drew Swenson:
Only when all the planned checks had been successfully completed was the rocket declared fit for transport and installation on the launch pad. This operation again required the Crawler-Transporter, which, driven by a dedicated team of specialized technicians, went back into the VAB, positioned itself under the MLP, locked onto it firmly, stabilized it, leveling it to the millimeter, and then began the slow journey along the Crawlerway , about 6 km long, leading to the launch pads of the adjacent complexes 39A or 39B. Transporting a Saturn V from the VAB to the launch complex took on average between 5 and 8 hours, moving at a top speed of 1.6 km/h. The Crawler-Transporter, still in use today, was built for NASA by the Marion Power Shovel Company and still holds world records for size, carrying capacity and the power it can deliver for moving and lifting its load. About 40 meters long and 35 wide, it has an area comparable to a baseball infield and an empty weight of about 2,700 tons. The total weight pressing down through its huge tracks on the Crawlerway when it moved fully loaded, with a Saturn V, MLP and LUT on board, came close to 6,000 tons. Despite its enormous bulk, the Crawler-Transporter was called the fussy giant, since it had a hydraulic system for millimeter-precise leveling, called JEL , or Jacking, Equalizing and Leveling, able to keep the Saturn V perfectly vertical as it climbed the ramp to the pad, with grades of up to 5%. The precision was such that the tip of the rocket never swayed more than the diameter of a coin!
The Crawler-transporter, carrying the Saturn V, the MLP and the LUT , moved with such power that it could brave winds of up to about 65-70 km/h (about 40 knots). It was truly a masterpiece of diesel-electric engineering. To move such a mass, in fact, a traditional mechanical transmission could not be used: what was needed was a self-propelled power plant. Inside were two Alco diesel engines of 2,750 horsepower each (for a total of 5,500 hp). These engines did not turn the immense tracks directly, but drove four 1 MW electric generators. The electricity produced by the generators powered 16 direct-current electric motors, each able to deliver 375 horsepower. It was these motors, distributed over the trucks, that provided the torque needed to move the titan. The Crawler-Transporter also carried two more 1,065 hp diesel engines driving two 750 kW generators, used for the onboard systems: lighting, ventilation and, above all, the powerful hydraulic pumps for steering and the hydraulic leveling jacks. The Crawler consumed a frightening amount of fuel: about 350 liters of diesel for every kilometer traveled. The structure rested on eight huge tracks, paired two by two at the four corners of the vehicle. Each single track was about 12 meters long, 3 high and made up of 57 shoes. Each of these was a piece of cast steel weighing about 900 kg (almost a ton for every single "step"). This configuration spread the colossal weight of the Saturn V, MLP and LUT over a very large area, preventing the vehicle from damaging the surface of the Crawlerway. During movement, moreover, to prevent the friction and heat generated from damaging the steel shoes of the tracks under that immense weight, the surface of the Crawlerway was continuously cooled along the line of travel by special water trucks, while the track system was lubricated with a special dedicated oil. The Crawlerway, moreover, was not a simple road, but a civil engineering work designed and built specifically to bear loads that would have crumbled any normal concrete or asphalt highway. NASA called it the "giant's path", a route about 6 km long connecting the VAB to the pads of Complex 39. To bear the nearly 6,000 tons of the assembly in transit, the road was built with a multilayer structure about 2 meters deep. The top layer, in direct contact with the tracks of the Crawler-Transporter, was made of 20 cm of Alabama river gravel. This choice was not aesthetic: river stones are round and smooth. This allowed them to roll over each other under the Crawler's tracks, acting as a sort of "natural ball bearing" that drastically reduced friction and prevented the generation of sparks. Beneath the gravel layer were about1.2 meters of crushed, compacted limestone, which provided the rigid, stabilizing base. The last, deepest layer was made mainly of compacted sand, which, besides preventing rainwater from collecting, further stabilized the marshy Florida ground. Below is another extremely accurate video (we recommend enlarging the window) showing the Saturn V's journey to the launch pad and its positioning there, created by the very talented Drew Swenson:
The Crawlerway was not a single strip, but looked more like a double-track railway line. It was made up of two parallel lanes about 12 meters wide each, separated by a grassy median. This layout matched exactly the position of the tracked trucks at the four corners of the Crawler-transporter. The total width of the whole roadway was about 40 meters, similar to an eight-lane American highway. When the Crawler-Transporter passed over it, the noise you heard standing next to it was not just that of an immense diesel engine revving, but the deep, constant sound of billions of stones being shifted and ground by the bulk of the Crawler, a sound that told the whole of KSC that the journey to the Moon had officially begun. When the Crawler-Transporter climbed up to the launch pads, it set the MLP with extraordinary precision on special, massive support columns, designed to anchor the assembly, supporting it and holding it down until the lift-off of the Saturn V launch vehicle for Earth orbit. Below is another extremely accurate video (we recommend enlarging the window) showing the precise positioning of the Saturn V on the launch pad, created by the very talented Drew Swenson:
The Crawler was then disconnected and began its slow return to the designated parking area , a huge apron next to the Crawlerway about 1 km from the VAB. This area was also where the Mobile Service Structure (MSS) , which we will talk about shortly, was parked. Launch pads 39A and 39B (Launch Complex 39, or LC39A and LC39B) were not simple concrete platforms, but complex technological ecosystems designed to tame the most destructive forces ever handled by man, second only to nuclear weapons. Located in the Merritt Island National Wildlife Refuge, they were placed at a safe distance of about 2.5 km from each other, so that the accidental explosion of a Saturn V on one pad could not destroy both launch platforms.
Each pad was an imposing artificial hill with an octagonal plan, about 12 meters above sea level. In the center was a deep chasm called the Flame Trench , or trench of flames, 137 meters long and 18 wide. Inside it was the Flame Deflector, a massive steel wedge weighing 635 tons, coated with ablative ceramic material. Its important function was to split in two the column of fire released at ignition and then at lift-off by the five F-1 engines and deflect it horizontally along the trench, preventing the acoustic energy and heat from bouncing back up and destroying the rocket. The ignition of the F-1 engines, in fact, generated sound waves so powerful that they could shatter the very structure of the rocket. To counter this phenomenon, a water deluge system was installed (the forerunner of the Sound Suppression Water System of the Shuttle era), a huge network of pipes that at launch poured tens of thousands of liters of water per minute onto the platform and the deflector. Besides cooling the pad engulfed by the devastating flames of the engines, the water absorbed part of the acoustic energy and helped form that iconic cloud of white steam that enveloped the base of the rocket at lift-off. The water came from gigantic tanks and reservoirs that could be seen in aerial photographs of the Saturn V on the pad. At the sides of the launch platform stood two huge spherical tanks, like giant thermos flasks: one for liquid hydrogen (LH2), kept at a cryogenic temperature of -253°C, the other for liquid oxygen (LOX), kept at -183°C. The kerosene (RP-1), more stable and needed by the F-1 engines of the S-IC stage, was stored in simpler tanks . During the countdown before launch, kilometers of insulated cryogenic piping transferred these propellants into the rocket through the MLP at the base of the rocket, the LUT and the umbilical arms of the tower. The base of the launch pad also stored all the other gases needed to operate the rocket, such as supercritical helium and compressed nitrogen, part of which was blown under pressure around the base of the F-1 engines to create an inert, fireproof atmosphere, as well as into the internal compartments of the rocket housing the control electronics and the flight batteries. Also at the base of the pad were all the technical rooms used to supervise the loading of propellant into the rocket, as well as those dedicated to telemetry monitoring and to carrying out all the commands coming from the Launch Control Center (LCC) next to the VAB. Under the pad, moreover, in the heart of the concrete structure, was the bunker already mentioned, called the "Rubber Room" (room of rubber). In a very serious launch emergency, pad personnel could jump into a chute leading to this isolated emergency room, fitted with massive insulated steel doors and mounted on huge rubber shock absorbers, which would absorb the shock wave from the devastating explosion of a Saturn V on the pad, thus ensuring the survival of the personnel for as long as needed until they could be rescued once the fire was under control. Once the rocket was finally secured on the launch pad, it had to be prepared for lift-off. Since the LUT could only provide limited access to certain areas of the rocket (those connected to the swing arms), the Mobile Service Structure (MSS) was brought to the pad (by the Crawler-Transporter) and stayed next to the rocket until 11 hours before launch, when the Crawler came back to take it away to its parking area at a safe distance from the pad.
It was about 125 meters high and weighed over 5,000 tons. The function of the MSS was to provide 360-degree access to the levels of the Saturn V that needed it, just as had been done earlier in the VAB. It had multi-level platforms that closed around the rocket, creating work areas protected from the weather and allowing technicians to carry out any necessary maintenance, the fitting-out planned for the mission and the logistic loading of the spacecraft (CSM and LM) and rocket stages, systems calibration, necessary interfacing, hypergolic propellant loading, as well as the important pre-launch preparations of the Saturn V, along with long testing sessions and final on-site checkouts. Under the protection of the MSS, moreover, the BPC cover was fitted around the Command Module and the LES escape tower was statically tested (without firing it, of course!) and then finally armed to do its job if needed. Below is another extremely accurate video (we recommend enlarging the window) that shows how the MSS worked, created by the very talented Drew Swenson:
The Mobile Service Structure (MSS) had a physical limitation: it did not give technical access to the base of the rocket. In that configuration, in fact, the lower end of the launcher was anchored to the four Hold-down Arms and was literally hanging over the huge square exhaust opening of the mobile platform (MLP). To solve this layout problem, from the assembly phase inside the VAB, a special metal scaffold was pre-installed under the rocket, called the Engine Service Platform (ESP). This scaffold gave technicians vital access for preparing the electronic and pneumatic systems located in the thrust structure of the S-IC stage. It also made it possible to complete the delicate final assembly of the five colossal F-1 engines and their hydraulic actuators. Of course, once all the pre-flight checks were finished, and strictly before launch, the ESP was completely removed and moved to a safe distance from the rocket, to prevent it from being disintegrated by the inferno of flames at lift-off. This was done with a self-propelled platform that could pick up the ESP and carry it elsewhere. In this extremely accurate video (we recommend enlarging the window), created by the very talented Drew Swenson, you can see it clearly at work:
Another very important facility of Launch Complex 39, without a shadow of a doubt the nerve center of launch operations, was the Launch Control Center (LCC) , KSC's launch control center. It was an iconic building, not only for its architecture but for the crucial role it has played from the Apollo missions to the present day. The LCC, in fact, was built at the south end of the VAB, about 6 km from launch pads 39A and 39B. This distance was no accident, but specifically calculated to protect personnel and the building if the rocket on the pad exploded. The building became famous for its huge sloping windows facing the pads, protected by armored louvers that were lowered during launch to withstand the acoustic shock wave.
The LCC windows were not made of simple glass, but were multilayer structures designed to withstand the sound pressure generated by the F-1 engines of the Saturn V, which was so powerful that it could burst the eardrums of a person two kilometers away or kill someone less than a kilometer from the launch pad. Despite this protection, the flight controllers assigned to supervise the Apollo launches described the ignition and then the lift-off of a Saturn V as a powerful earthquake close by, in which everything vibrated and shook , driven by the immense roar of the engines. The arrival of the earthquake was always preceded by a few seconds by a powerful yellow-red glow, a sign that the rocket had begun to release the powerful jets of fire that lit up the surrounding area. Inside the LCC were the "Firing Rooms" (launch control rooms). Historically there werefour, of which no. 1 was used for all the Saturn V launches of the Apollo program (except Apollo 7 , which lifted off from Launch Complex 34) and Skylab (with the launch of the orbital laboratory and its operational missions), up to the first launch of the Space Shuttle STS-1. Firing Room no. 2, on the other hand, was used mainly for pad control and test operations, while no. 3 was used for the Space Shuttle missions of the program. Firing Room no. 1, renovated, is still used today by NASA for the Artemis program , while other rooms have been made available to commercial operators such as SpaceX or Boeing. Each room contains hundreds of consoles where technicians monitor every single parameter of the rocket on the launch pad, such as: tank pressures, the status of the electrical systems, telemetry, engine performance, all short- and long-range safety operations and, last but not least, the weather conditions at the site. During a countdown, the most important launch figures sit in the LCC, such as the Launch Director (LD), who is the supreme authority for the launch and the only person who can give the final "Go", the Test Director (NTD), who coordinates all ground operations and the personnel at the various consoles , and the Safety Officer (SO), who oversees and makes sure everything is done within the safety parameters for personnel and the environment. It is important to point out that the LCC has always managed the rocket from the moment it leaves the VAB until, lifting off, it "clears the tower" ("Tower Clear"). Once the rocket has risen above the LUT, supervision of the whole mission passes to the Mission Control Center (MCC) at the Johnson Space Center (JSC) in Houston, Texas, which then manages the whole mission until splashdown. Below is a sequence of the lift-off of the Apollo 11 Saturn V, filmed by the armored camera on the MLP (Mobile Launcher Platform), right next to the LUT (Launch Umbilical Tower) and at the base of the Saturn V.
NASA'S COMMUNICATIONS ARM: THE DEEP SPACE NETWORK (DSN):
NASA's communications arm. During the Apollo program, all ground-to-air communications between the CSM, the LM and the MCC were made possible by the coordinated action of a sophisticated NASA radio support team spread across the globe and called the Deep Space Network , or DSN. To communicate with a spacecraft heading for the Moon, in fact, a simple transceiver with a single antenna was not enough. The Earth rotates on its axis in 24 hours , and a single, fixed station would have lost the signal after a few hours, when the spacecraft or the Moon dropped below its horizon. To make up for this and ensure uninterrupted communications with the crew and the onboard electronic systems, NASA created a network of three large complexes of giant dish antennas placed about 120° of longitude apart, so that at least one station always had the spacecraft or the Moon in view , depending on the phase reached by the mission. These large transmitting and receiving complexes were (and still are) located at Goldstone in the Mojave Desert in California, Madrid in Spain and Canberra in Australia. Instead of using different frequencies for each type of data, NASA developed the Unified S-Band system. This made it possible to send on a single carrier frequency (S band at 2 GHz) a voice channel (ground-to-air communications between the crew and the MCC), telemetry (countless complex technical data accurately describing the status of the spacecraft's systems and of the astronauts), trajectory and velocity tracking data (tracking) and a video channel for onboard or lunar surface television broadcasts. Relaying the information on the ground, that is, routing the data received from the Moon from the DSN to the MCC and vice versa, was done through ground transmitting and receiving stations, which used the American satellite network (then in its infancy), undersea telephone cables or shipborne radio communication stations to transfer them from one continent to another. The ships, in particular, were used mainly when the Apollo capsule was very close to the Earth (for example at launch, in the parking orbit or shortly before reentry), when the huge DSN dish antennas could not track it accurately during its fast movement from one horizon to the other.
The journey from the Earth to the Moon
Now that we have outlined the historical context of those historic events and, above all, analyzed in depth the machines and ground support facilities that allowed man to reach the Moon, let's get to the heart of the Apollo Project, analyzing point by point how a typical journey of the time unfolded, from the Earth to the Moon. First of all, it must be said that a mission to the lunar surface was a titanic undertaking and as such required a titanic commitment that could not be delegated to a small circle of people, but needed the involvement of hundreds of thousands of people, each with a specific area of expertise, who together would make it possible to reach the ambitious goal. It is no coincidence, therefore, that the whole Apollo Project enlisted, from top to bottom, a real army of people in the United States of the time, belonging to the American space agency (NASA), to public, private and university research bodies, and to aerospace and other industries across the country. It is estimated that about 400,000 people actively worked on the Project, with an unheard-of combination of minds and forces that at that time led to a real industrial revolution across the whole nation. Every Apollo mission, in fact, had to be planned well in advance in every detail, both from the extremely complex point of view of the flight plan (structured and designed to reach a specific area of the Moon) and from the point of view of preparing the machines, the science and the support facilities that would make the undertaking possible. Planning also covered the small details that engineers sometimes considered insignificant, such as planning what the astronauts would eat during the mission and, above all, how many hours of rest they would need so that the inevitable stress of the mission would not undermine their ability to act. Any error in this complicated, coordinated machine could have led irreparably to disaster , putting the very lives of the astronauts at risk. It is precisely in this very delicate balance between mathematical calculation and human daring, between the collective genius of an entire nation and the heartbeat of three men launched into the void of space, that the journey I am about to tell you comes to life. To let you breathe the smell of lunar dust up close, the tension and wonder of that unrepeatable epic, I have captured this extraordinary adventure in my book:
A work designed to guide you, page after page, inside those spacecraft, revealing to you not only the technical marvels that bent the laws of physics, but above all the soul, the sacrifices and the emotions of those who made the impossible possible. Are you ready to climb aboard and relive the greatest adventure of all time?
Coming soon for purchase on this website.
To reserve your copy, write here: pubblicazioni@siamoandatisullaluna.com
