How we went to the Moon

Understanding the claims of moon-hoax theorists and the reasons why they're wrong requires at least a smattering of knowledge of the jargon, technology and stages of an Apollo moonshot. This chapter is mostly based on the Apollo 11 mission, the first Moon landing, but the basic concepts apply to all the Apollo lunar flights.

The Saturn V rocket

The Saturn V-Apollo stack (Figure 14) stood 111 meters (363 feet) tall and weighed about 3,000 tons (6.7 million pounds). Even today it is still the most powerful rocket ever built.

Figure 14. Apollo 11's Saturn V on the pad. Detail of NASA photo S69-38660.

The Saturn V consisted of three stages, topped by the Apollo spacecraft, which contained three astronauts. The very tip of the stack was the Launch Escape System, a high-acceleration rocket designed to whisk the capsule with the astronauts to safety in case of an emergency during liftoff.

The first stage, known as S-IC, had a diameter of 10 meters (33 feet) and five enormous F-I engines that gulped 13.3 tons (29,360 pounds) of kerosene and liquid oxygen per second, lifting the entire rocket to an altitude of about 68 kilometers (220,000 feet) and accelerating it to a speed of approximately 9,900 km/h (6,150 mph) in a little over two and a half minutes. The spent S-IC stage was then jettisoned and fell into the Atlantic Ocean.

Figure 15. The Saturn V.

The S-II second stage used liquid hydrogen and oxygen to fuel its five J-2 engines and continue the climb to space, reaching a speed of almost 25,000 km/h (15,500 mph) and an altitude of approximately 182 kilometers (600,000 feet) nine minutes after liftoff. It was then jettisoned like the previous stage. Together, these stages constituted nine tenths of the total weight of the Saturn V.

To reach the speed of 28,000 km/h (17,400 mph) required to stay in orbit at an altitude of 188 kilometers (617,000 feet), the Saturn V needed the extra kick of its third stage, the S-IVB, which had a restartable single J-2 engine.

Less than twelve minutes after launch, the astronauts were already in a parking orbit around the Earth, where they checked the onboard systems. After one orbit and a half, less than three hours after liftoff from Florida, the third-stage engine was restarted and burned for almost six minutes, accelerating the spacecraft to 39,000 km/h (24,200 mph) towards the Moon, which at that time was 403,000 kilometers (250,400 miles) away.⁽⁶⁾
(6) This was the distance for the Apollo 11 mission. Measured center to center, the Earth-Moon distance varies monthly from 363,100 to 405,700 kilometers (225,600 to 252,000 miles).

The spacecraft at this point had the configuration shown in Figure 16 and continued by inertia, with its engines off, towards its destination, gradually slowing down due to the Earth's gravitational attraction and then accelerating as it approached the Moon and was drawn by its gravity.

During the three-day voyage, the three astronauts, with the assistance of the onboard computers and of the measurements and observations made from Earth, corrected their course and performed a crucial and delicate undocking, rotation and redocking to prepare the spacecraft for the Moon landing. They then abandoned the third stage of the Saturn V.

Figure 16. From the top: Command Module, Service Module, Lunar Module and S-IVB stage. Source: Apollo 11 Press Kit (enhanced).

The Apollo spacecraft

The crew traveled in the pressurized cone-shaped Command Module (CM), shown at the top in Figure 16. The CM was 4 meters (13 feet) wide at the base and 3.5 meters (11.5 feet) tall, with a total cabin volume equal to the cargo body of a small van – and no toilet (bags were used for solids; liquids were dumped overboard through a tube). It had small maneuvering thrusters and a heat shield to protect it from the heat of reentry, as it was the only part of the giant rocket that returned to Earth.

Behind the astronauts there was the Service Module (SM), the cylindrical part near the top in Figure 16, which held the fuel for the main rocket engine of the Apollo spacecraft and for the sixteen maneuvering rockets (arranged in four cross-like clusters of four) and most of the oxygen, water, electric power and communication systems required for the mission.

A conical aerodynamic fairing, shown in phantom lines in Figure 16, connected the command and service modules to the third stage of the Saturn rocket (S-IVB) and enclosed the Lunar Module (LM), the spider-like spacecraft that would be used by two of the three astronauts to land on the Moon while the third waited for them in the Command Module.

Since the Lunar Module was to be used only in the vacuum of space, it didn't need to be streamlined and instead had to be as lightweight as possible in order to reduce the fuel requirements and maximize its payload. Accordingly, it was stripped down to the absolute minimum: even the seats had been sacrificed, so the astronauts flew the LM while standing.

The LM was 7 meters (23 feet) tall, weighed approximately 15 tons and was divided into two stages, shown separately in Figure 17.

Figure 17. Cutout view of the lunar module.

The descent stage was the lower octagonal part, which had a single engine to brake the descent to the Moon, four shock-absorbing landing legs and compartments for scientific equipment, water, fuel and (from Apollo 15 onwards) for an electric Moon buggy.

The top part of the Lunar Module, known as ascent stage, contained the cramped crew cabin, some oxygen, food and water supplies, the onboard computers, the radio and television equipment and the single rocket engine used to climb back to orbit from the Moon. The ascent stage was equipped with sixteen attitude control thrusters (in four clusters of four, as in the Service Module) with their propellant tanks.

The astronauts viewed the lunar surface during landing through two small sloping triangular windows at the front of the ascent stage and exited the vehicle by crawling backwards in their bulky spacesuits through a narrow square hatch.

After touchdown, they climbed down along a ladder attached to one of the legs of the descent stage, as shown by the LM on display at the National Air and Space Museum in Washington, D.C. (Figure 18), and began their exploration of the Moon.

Figure 18. An unused LM at Washington's National Air and Space Museum.

At the end of their stay on the Moon, the astronauts lifted off in the ascent stage and used the descent stage as a launch pad.

Crucial maneuvers

Success of the mission and survival of the astronauts depended on some very tricky undocking and redocking maneuvers during the outbound journey and on a vital rendezvous while in orbit around the Moon.

Three hours after liftoff, the Command and Service modules (CSM) separated from the rest of the spacecraft by using the maneuvering thrusters. The four panels of the fairing were released, exposing the lunar module. The astronauts then turned the CSM around, docked with the LM and extracted it from the S-IVB, the third stage of the Saturn V rocket (Figure 19).

Figure 19. Extraction of the Lunar Module. Source: NASA Press Kit.

The CSM and the LM then continued their flight towards lunar orbit, while the S-IVB rocket motor was restarted to nudge the spent stage away into an orbit around the Sun or, from Apollo 13 onwards, to crash into the Moon and produce a man-made moonquake, which was picked up by the seismometers placed on the lunar surface by previous missions, allowing to probe the interior structure of the Moon.

The docked Lunar Module was linked to the CSM by a tunnel, through which the astronauts crawled to power up and check the vehicle and prepare it for descent to the Moon.

As the spacecraft approached the Moon, the drag of Earth's gravity that had been gradually slowing it began to fade and Apollo's speed started to increase due to the pull of lunar gravity. The astronauts turned the spacecraft around so that the Service Module's powerful main engine was pointing forwards. They had to achieve multiple carefully timed burns of this engine, as they swung repeatedly around the far side of the Moon, out of radio contact with Earth, in order to slow down and gradually achieve a stable, almost circular orbit around their destination, at an altitude of 114 to 138 kilometers (374,000 to 453,000 feet or 62 to 75 nautical miles) and a speed of 5,900 km/h (3,700 mph).

The two astronauts that would walk on the Moon transferred into the lunar module, while their colleague stayed in the Command Module, and the two vehicles undocked. After flying together to visually inspect each other and run a final check of all onboard systems, the LM pointed its descent engine forward and fired it to begin the landing phase.

On the Moon there's no atmosphere to glide through with wings or parachutes. Descent depended entirely on the single rocket engine, which had to reduce the spacecraft's speed from 5,900 km/h (3,700 mph) to zero in twelve minutes and then allow the LM to hover just above the lunar surface long enough to find a safe landing spot. Fuel reserves were tight and left little margin for error.

After landing, the astronauts performed one or more moonwalks (Extravehicular Activities or EVAs) to gather science data and samples under the watchful eye of a television camera that broadcast their activities live to Mission Control and to a worldwide audience back on Earth.

Figure 20. Buzz Aldrin on the Moon. NASA photo AS11-40-5872 (cropped).

The Apollo moonwalkers had fully autonomous spacesuits, with oxygen, cooling systems and radio links in their backpacks. In the more advanced missions, they also used an electric buggy, the Lunar Roving Vehicle or Rover, to cover distances of as much as 35 kilometers (22 miles) during Apollo 17, the lunar mission which also set the total EVA duration record, with over 22 hours spent outside the Lunar Module during three moonwalks.

Once their lunar excursion was complete, the astronauts threw out all unnecessary weights and lifted off in the ascent stage of the LM. The timing and execution of this liftoff had to be very accurate in order to rendezvous with the Command and Service Module, which was waiting for them in lunar orbit. If the single ascent engine failed to fire, the lunar astronauts would be trapped on the Moon, with no chance of rescue. If it didn't fire at exactly the right time and with the right thrust for the right duration, or if the trajectory was incorrect, they would not achieve the rendezvous and would perish in orbit or crash back onto the Moon. The third astronaut would have no choice but to abandon them and return to Earth alone.

Figure 21. The LM climbs back from the Moon. NASA photo AS11-44-6643.

With the LM and CSM safely docked together, the moonwalkers returned to the Command Module with their priceless cargo of science data, moon rocks, photographs and film footage.

The ascent stage of the LM was then jettisoned, subsequently crashing onto the Moon, while the instruments placed on the lunar surface radioed their data to scientists back on Earth.

The astronauts then rested, checked all the spacecraft's systems, and fired the Service Module's main engine to accelerate and leave lunar orbit, heading home to Earth. The return journey took approximately three days.

Fiery return

Shortly before contact with the Earth's atmosphere, the Service Module was also jettisoned. Of the 111-meter (363-foot) behemoth that had left Earth a few days earlier, only the small conical Command Module remained. It hurtled into the Earth's atmosphere at about 38,000 km/h (23,600 mph), with its heat shield facing forwards to dissipate the tremendous heat (up to 2,700 °C or 5,000 °F) produced by friction and compression of the surrounding air, which braked its speed.

The tiny spacecraft had to reenter the atmosphere at a very precise angle, between 5.5 and 7.5 degrees. If the reentry angle was too shallow, it would literally bounce off the atmosphere back into space. If it was too steep, the heat shield would fail and the spacecraft and its occupants would not survive.

The astronauts also had to deal with violent deceleration (up to 7 g, which is equivalent to having seven times one's own weight). The heat of high-speed reentry also produced a wall of ionized air, which blocked radio communications.

The people in Mission Control, who had guided and supported the entire flight with their vast technical skills and resources, had no way to know the outcome of reentry until the spacecraft slowed sufficiently to resume radio contact. Small drogue parachutes opened at an altitude of 7,000 meters (23,000 feet), followed by the main chutes at 3,000 meters (10,000 feet).

The Apollo capsule splashed down in the Pacific Ocean (Figure 22), where it was reached by a recovery helicopter, which hoisted up the astronauts on a winch with the aid of frogmen and then flew the returning spacefarers to a nearby aircraft carrier. Another chopper later recovered the spacecraft and its precious cargo.

Figure 22. Splashdown. NASA photo AP16-S72-36293.

At the end of the early Moon landing missions, the astronauts donned airtight suits when they exited the Apollo spacecraft and were then quarantined in sealed quarters to guard against the remote chance of Moon germs (Figure 23). From Apollo 15 onwards, this precaution was dropped and the astronauts were free to join the celebrations for their safe return from a fantastic voyage.

Figure 23. Armstrong, Collins and Aldrin with US President Richard Nixon.

This, in summary, is how a Moon mission was accomplished with 1960s-era technology: enormous costs, minimal margins for error, high chances of failure, no rescue options, with the whole world watching and a nation's prestige at stake. No wonder nobody has gone back to the Moon since.