2.1 The Saturn V rocketThe Saturn V-Apollo stack stood 111 meters (363 feet) tall and weighed almost 3,000 tons (6.5 million pounds). Even today it is still the most powerful operational rocket ever built; only the failed Soviet N1 exceeded it in terms of total thrust.
Apollo 11’s Saturn V on the launch pad. Detail of NASA photo S69-38660.
The Saturn V consisted of three stages, topped by the Apollo spacecraft, which carried three astronauts. The very tip of this stack was the Launch Escape System, a high-acceleration rocket designed to whisk the crew compartment with the astronauts to safety in case of an emergency during liftoff.
The first stage, known as S-IC and manufactured by Boeing, was 42 meters (138 feet) tall, had a diameter of 10 meters (33 feet) and was equipped with five enormous F-1 engines that gulped 13.3 tons (29,300 pounds) of kerosene and liquid oxygen per second at liftoff, lifting the entire rocket to an altitude of about 67 kilometers (220,000 feet) and accelerating it to a speed of approximately 9,900 km/h (6,180 mph) in a little over two and a half minutes. The spent S-IC stage was then jettisoned and fell into the Atlantic Ocean.
The Saturn V-Apollo stack components. Credit: Boeing Space, 2018.
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 24,000 km/h (14,800 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 two stages constituted nine tenths of the total weight of a Saturn V.
To reach the speed of 28,000 km/h (17,400 mph) required to orbit the Earth at an altitude of 190 kilometers (617,000 feet), the Saturn V needed the extra kick of its third stage, the S-IVB, which had a single restartable 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. The spacecraft at this point had the configuration shown below.
From the top: Command Module, Service Module, Lunar Module and S-IVB stage. Source: Apollo 11 Press Kit (enhanced to highlight the LM and CM).
After one orbit and a half, two hours and forty-four minutes 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 was approximately 400,000 kilometers (250,000 miles) away (the Earth-Moon distance varies every 27.3 days from 363,100 to 405,700 kilometers (225,600 to 252,000 miles), measured center to center).
The spacecraft began coasting with its engines off towards its destination, gradually slowing down due to the Earth’s gravitational attraction.
2.2 The Apollo spacecraftThe crew traveled in the pressurized cone-shaped Command Module (CM), which 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. Bbags were used for solids; liquids were dumped overboard through a tube.
It had small maneuvering thrusters, a heat shield to protect it from the heat of reentry, and three parachutes, as it was the only part of the giant rocket that returned to Earth.
Behind the astronauts there was the cylindrical Service Module (SM), 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 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 light 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 were sacrificed, so the astronauts flew the LM while standing.
The LM was 7.3 meters (23 feet) tall, weighed approximately 15 tons (33,000 lb) and was divided into two stages, shown separately below.
Cutout drawing 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 storage compartments for scientific equipment, water, fuel and (from Apollo 15 onwards) an electric Moon buggy (the Lunar Roving Vehicle).
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. After touchdown, they exited the vehicle by crawling backwards in their bulky spacesuits through a narrow square hatch and then 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. They then began their exploration of the Moon.
An unused LM at Washington’s National Air and Space Museum. Credit: Wikipedia.
At the end of their stay on the Moon, the astronauts lifted off in the ascent stage, using the descent stage as a launch pad. The descent stage was left on the Moon.
2.3 Crucial maneuversSuccess 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 to be achieved while in orbit around the Moon.
A few hours after liftoff, the crew separated the Command and Service modules (CSM) from the rest of the spacecraft and positioned them slightly ahead by using the SM’s 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.
Extraction of the Lunar Module. Animation by Michael Quinn.
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 scientists 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 forward. 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 100 to 120 kilometers (54 to 65 nautical miles) and a speed of approximately 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 (in the more advanced lunar landing missions, the CSM carried the LM closer to the Moon before undocking, in order to conserve the lander’s limited fuel). After flying in formation 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, so descent depended entirely on the flawless operation of the descent stage’s single rocket engine, which had to reduce the spacecraft’s speed from 5,900 km/h (3,700 mph) to zero in about 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 and none for second attempts.
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.
Buzz Aldrin on the Moon during the Apollo 11 EVA. NASA photo AS11-40-5872.
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 car, 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, in which the third crewmember 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. With narrow margins for error, if the engine didn’t fire at the right time, with the right thrust and 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.
The final rendezvous between the Command Module and the ascent stage of the Lunar Module required docking the two spacecraft so that the moonwalkers could return to the Command Module with their priceless cargo of science data, Moon rocks, photographs and film footage.
The Apollo 11 LM climbs back from the Moon. NASA photo AS11-44-6643 (cropped).
The ascent stage of the LM was then jettisoned, subsequently crashing onto the Moon, while the instruments placed by the astronauts 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 again to accelerate and leave lunar orbit, heading home to Earth. The return journey took approximately three days.
2.4 Fiery returnShortly before contact with the Earth’s atmosphere, the Service Module, too, was 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 no braking rockets.
Air resistance slowed the spacecraft but also generated tremendous heat. Its heat shield had to cope with temperatures up to 2,700°C (5,000°F), and reentry had to occur at a very precise angle, between 5.5 and 7.5 degrees.
If the reentry angle was too shallow, the CM would slice through the thin upper layers of the atmosphere without losing enough speed and would end up in space again, with no chance of safe return. An excessively steep angle would overload the heat shield, turning the spacecraft and its occupants into a deadly fireball.
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, 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 science cargo.
Splashdown of Apollo 16. NASA photo AP16-S72-36293 (cropped).
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. 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.
Armstrong, Collins and Aldrin with US President Richard Nixon during the astronauts’ quarantine.
2.5 The true cost of ApolloThe crewed Moon landings did not come cheap. In 1973, the total cost of the Apollo program was reported as 25.4 billion dollars over a ten-year period. In 2004, the Congressional Budget Office estimated this cost to be equivalent to roughly 170 billion in 2005 dollars [House Subcommittee on Manned Space Flight of the Committee on Science and Astronautics, 1974 NASA Authorization, Hearings on H.R. 4567, 93/2, Part 2, page 1271; A Budgetary Analysis of NASA’s New Vision for Space, Congressional Budget Office, September 2004].
The Apollo project was widely perceived as an unsustainable and exorbitantly costly endeavor, despite the fact that the money was all spent on Earth and helped to train a whole generation of scientists and engineers and to develop countless technologies that we still use today. This misperception contributed to the early cancellation of the project once its primary political goal had been achieved.
Through the years, the cost of Apollo and of space ventures in general has been consistently and greatly overestimated by American public opinion. For example, a 1997 poll reported that Americans believed on average that NASA drained 20% of the entire US budget, although the actual figure has always been less than 1%, with the exception of the Apollo era, when it peaked at 2.2% in 1966 [Public Opinion Polls and Perceptions of US Human Spaceflight, Roger D. Launius (2003); The Manhattan Project, Apollo Program, and Federal Energy Technology R&D Programs: A Comparative Analysis, Deborah D. Stine (2009)].
By way of comparison, in 2005 the total expenditure for US defense was 493.6 billion dollars, social security outlays were 518.7 billion and Medicare/Medicaid outlays totaled 513 billion, according to the Congressional Budget Office. In other words, in recent years the US spent on defense each year three times the cost of the entire Apollo program.
Looking at it another way, getting to the Moon cost each one of the 202 million Americans alive in 1969 the grand sum of 84 dollars a year for ten years (in 2005 dollars). That’s roughly equivalent to twenty packets of cigarettes per year per person. In fact, two years of US consumer spending on tobacco products, which is 90 billion dollars per year according to 2006 CDC estimates, would pay for the entire Apollo project.
But in politics as in public opinion, perception often matters far more than reality.
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This, in summary, is how a Moon mission was accomplished with 1960s-era technology: high costs, minimal margins for error, high chances of failure, no rescue options, with the whole world watching live on TV and a nation’s prestige at stake. No wonder nobody has gone back to the Moon since.