2. An Apollo Overview
When talking about Apollo, I’m likely to use such terms as “Command Module”, “Lunar Module”, “descent stage” and “ascent stage” without thinking; to me, and any fellow enthusiast who lived through the era, these names are simply part of the language, and I tend to take it for granted that others will know what they mean. But it occurs to me that some younger readers may not be familiar with the Apollo spacecraft and its components – so before I begin the main body of this dissertation, I’ll give you a brief description of the spacecraft, so that the meanings of these terms, which I’ll frequently use, will be clear. This is quite important, as some of the conspiracy theorists’ arguments centre around ridiculous claims – made by people who are clearly ignorant of basic physics and engineering – that the spacecraft wasn’t fit for its purpose!
I’ll also briefly describe how a Moon landing mission was carried out.
Those who are familiar with Apollo can skip this section!
2.1. Anatomy of the spacecraft
Apollos 8-17 were all launched by the huge three-stage Saturn V rocket, the biggest launch vehicle ever built. ( Apollo 7, the first manned test flight, flew only in Earth orbit, and was launched by a smaller Saturn 1B rocket. ) At launch, the whole assembly stood 363 feet tall, and weighed over 2800 tons. ( Younger readers – please excuse me using imperial units; these were the figures which we oldies learned at the time, and I still know many of them by heart! ) The engines of the first stage produced an incredible 7.6 million pounds of thrust.
The first two stages accelerated the spacecraft almost to the velocity required to go into Earth orbit. ( I’m assuming that the reader is familiar with the principle of multi-stage rockets. ) The third stage was fired twice – once to complete the acceleration to orbital velocity ( about 17500 mph ), and again later, to accelerate the spacecraft to its escape velocity of about 24500 mph, which it required to leave orbit and travel to the Moon.
Fig. 1 is a representation of the entire assembly at launch; note the small size of the Apollo spacecraft itself, in comparison with the Saturn V.
Just to give you a sense of the immense scale of the vehicle, take a look at the engine nozzles at the bottom of the first stage ( there were actually five of them, though only three are visible in this view ). Fig. 2 shows one of these close up; it’s on display in the “Rocket Park” of Kennedy Space Centre. That's a very youthful me standing in front of it!
Fig. 3 is an expanded view of the Apollo spacecraft, showing its various components, or modules.
The Launch Escape System ( LES ) was the tower-like structure at the very top of the assembly. As its name implies, it provided a means of escape for the crew, in case anything went wrong on the launchpad or during the first two minutes of the launch. Had the Saturn V exploded, or malfunctioned in any way which caused the mission to be aborted, the LES’ small rocket engine would have lifted the Command Module clear of the rocket to safety; the CM would then have parachuted to the ground. The LES was jettisoned about two minutes into the launch.
Fortunately, no American manned spacecraft ever had to use its LES – though one Soviet Soyuz mission did. Thankfully, it worked!
The conical Command Module ( CM ) was the one which housed the crew, and was the only part of the spacecraft to return to Earth. It was 13 feet across and 12 feet high – not much room, for three men to live in for up to 12 days! - and weighed 6 tons. It had no propulsion system of its own, and was supplied with power, oxygen and water from the Service Module; the CM was capable of operating independently for only a very short time. The base of the CM was the heatshield, which enabled it to survive the intense heat of re-entry into the Earth’s atmosphere. In its nose was a docking mechanism which enabled it to link up with the Lunar Module, and a hatch through which the crew transferred to the Lunar Module.
The cylindrical Service Module ( SM ) – 24 feet long and weighing 24 tons – was the “power station” of the combined spacecraft. It contained the fuel cells which generated electrical power, and the oxygen and water tanks. Though the SM was inaccessible to the crew, they depended upon it for their vital life support systems.
The SM’s rocket engine was used to slow the spacecraft down to enable it to enter lunar orbit, then to accelerate it back towards Earth, and finally to position the CM for re-entry. It was also used to perform mid-flight course corrections.
The combination of the CM and SM formed the Apollo “mother ship”. The two were joined, and operated as a single spacecraft ( referred to as the CSM ) for all except the final few minutes of the flight. Just before re-entry, the SM was jettisoned, and the CM alone re-entered the atmosphere, and landed by means of parachutes.
The Lunar Module ( LM ) was – not surprisingly – the vehicle which actually landed on the Moon. It stood 23 feet high and 31 feet wide across its landing legs, and weighed about 15 tons. It consisted of two stages ( Fig. 4 ), called the descent stage and ascent stage – names which are pretty self-explanatory! The ascent stage, naturally, housed the astronauts; this sat on top of the descent stage, which rested on its spider-like landing legs. When the crew left it through a hatch, they descended onto the lunar surface by means of a ladder attached to one of the landing legs.
I’ve included a detailed diagram here, as several of the “conspiracy” arguments relate to the design of the LM, and its suitability for its purpose.
Note the LM’s ungainly shape; as it was designed to operate in a vacuum, it didn’t need to be at all streamlined or aerodynamic! The complete LM descended to the lunar surface, powered by the descent stage engine. On leaving the Moon, the descent stage was left behind, and became a platform from which the ascent stage took off, using its own engine to ascend back into orbit and dock with the CSM. The docking mechanism, and the hatch through which the crew transferred between LM and CM, were located at the top of the ascent stage. After the crew had returned to the CM, the LM ascent stage was jettisoned, and crashed back onto the Moon.
The LM carried enough power and supplies to sustain its crew for up to three days.
During launch, as can be seen in Fig. 3, the LM was housed inside the aerodynamic fairing which joined the SM to the Saturn V third stage. After the spacecraft had been boosted onto its translunar trajectory, and the third stage had shut down, the LM was extracted from its housing as follows:
The CSM was detached from the rocket, manoeuvred a short distance away, and turned through 180°. The fairing around the LM was jettisoned; the CSM then manoeuvred to dock with the LM, then backed away. For the remainder of the passage to the Moon, the two spacecraft were combined as shown in Fig. 5.
Each of the last three landing missions, Apollos 15-17, also carried a Lunar Roving Vehicle ( LRV ), or Lunar Rover for short. This was an electrically-powered “Moon car”, which allowed the astronauts to carry out a much more extensive exploration, travelling several miles from their LM, as opposed to just a few hundred yards, as the earlier crews had done. The LRV was ingeniously stowed in a compartment in the side of the LM descent stage.
N.B. In some sources, you may see the LM referred to as the "Lunar Excursion Module", or LEM. This was its original name, but the "Excursion" was later dropped, and it became officially known as simply the Lunar Module - though many people in NASA continued to pronounce the abbreviation as "the LEM".
2.2. Anatomy of an Apollo flight
The first four manned Apollo flights, Apollos 7-10, tested the spacecraft and various phases of a Moon landing mission, prior to attempting the first landing. Apollo 7 was simply the first manned test flight of the CSM, in Earth orbit.
Apollo 8 was the first manned spacecraft to be launched by a Saturn V, and the first manned flight to the Moon. It didn’t carry a LM; the CSM spent 20 hours in lunar orbit, then returned to Earth.
Apollo 9 only flew in Earth orbit, but carried the LM for the first time. The crew separated the LM from the CSM, and flew it to simulate the descent to and ascent from the Moon, testing the manoeuvrability of both stages.
Apollo 10 was a full “dress rehearsal”. The complete spacecraft flew to the Moon, and the LM descended to within a few miles of the lunar surface, then returned to orbit. The mission did everything except actually land on the Moon.
Apollos 11-17, between 1969 and 1972, were the landing missions themselves; six of these were successful. The exception was Apollo 13, which suffered a catastrophic explosion in its SM during the outward flight. The Moon landing was abandoned, and with the CM deprived of its power and oxygen supply, the crew used their LM as a “lifeboat”, to keep themselves alive while their spacecraft swung around the Moon and headed back to Earth. Their successful rescue was one of the most dramatic stories of the Space Age.
After the Moon landings ended, four more Apollo CSM spacecraft, launched by Saturn 1B rockets, were used for Earth orbit missions. Three of these carried crews to and from the Skylab space station in 1973-74; the last was used in the Apollo-Soyuz Test Project in 1975 – the first experimental docking of a US spacecraft with a Soviet one.
The following paragraphs describe the main sequence of events during an Apollo Moon landing mission.
An Apollo crew consisted of three men – the Commander, the Command Module Pilot ( CMP ) and the Lunar Module Pilot ( LMP ). The Commander and LMP landed on the Moon, while the CMP remained in the CM throughout the mission. The duration of the mission was 8 days for Apollo 11, but increased to 12 days for the last three flights.
The spacecraft was launched from Cape Canaveral. The first two stages of the Saturn V, and the first burn of the third stage, lifted it into Earth orbit, at a height of about 116 miles and a velocity of 17500 mph. This orbit was known as a parking orbit; it was necessary, as the third stage engine had to be fired again at a predetermined point in the orbit, in order to boost the spacecraft onto the correct trajectory to reach the Moon.
After a couple of orbits, the third stage fired again at the right time, accelerating the spacecraft to escape velocity – about 24500 mph. After the rocket shut down, the crew detached the CSM from it, and extracted the LM from its housing, as described above. The spent third stage was then briefly fired one last time, to alter its course slightly and take it safely clear of the Apollo. On the earlier missions, the rockets missed the Moon and went into an orbit around the Sun, where they remain to this day; on the later flights, they were targeted to crash onto the Moon, so that the effects of the impact could be measured by seismic experiments left in place on the lunar surface by the earlier crews.
The flight time to the Moon was about two and a half days. About 85% of the way, the spacecraft passed the point at which the gravitational influence of Earth and the Moon balanced each other. By this time, its speed had been slowed by Earth’s gravity to a mere 2200 mph; after this point, it accelerated again under lunar gravity, so that by the time it approached the Moon, it was travelling at about 5000 mph. The SM’s engine was then used to slow the spacecraft down to about 3700 mph, and put it into orbit around the Moon, at an altitude of about 50 miles.
After a few lunar orbits – each orbit took about two hours – the Commander and LMP entered the LM through the connecting hatch, while the CMP remained aboard the CM. The two spacecraft separated, and the LM descended to the surface of the Moon. Though it was guided by its onboard computer, the astronauts were able to override this and take manual control during the final approach, to ensure that they landed in a safe spot.
In a way, you could say that being a CMP was the loneliest job of all time. While their crewmates were on the Moon, the CMPs became the most isolated people in history; at the far point of each orbit, as the CSM passed over the far side of the Moon, the CMP was separated by over 2000 miles from the nearest other human being! At the same time, for half of each orbit, he was unable to speak either to his colleagues or to anyone on Earth, as radio communication was impossible while the spacecraft was “behind” the Moon.
The duration of the astronauts’ stay on the Moon steadily increased throughout the series of flights. On Apollo 11, it lasted only 21 hours; Armstrong and Aldrin made a single “moonwalk” ( correctly known as extravehicular activity or EVA ), lasting 2½ hours. After all, the purpose of that flight was simply to “land two men on the surface of the Moon, and return them safely to the Earth”, thereby achieving the goal set by the late President Kennedy. They were simply proving that it could be done, without bothering too much about actually doing anything useful while they were there! What little science was done – deploying a couple of experiments on the surface, and returning some rock samples – was regarded as a bonus.
But on the later flights, they spent longer times on the Moon, with the emphasis much more on exploration, and obtaining scientifically useful results. The final flight, Apollo 17, included a stay on the surface of just over three days, during which the astronauts made three EVA’s, totalling 22 hours, and drove over 20 miles in their Lunar Rover. That crew also included a geologist, Dr. Jack Schmitt – the only scientist to have walked on the Moon.
When they left the Moon, the LM’s ascent stage took off, leaving the descent stage behind, accelerated into orbit and rendezvoused and docked with the CM. After the astronauts had transferred back to the CM, the ascent stage was jettisoned, and crashed back onto the Moon.
The SM’s engine was fired again, to accelerate the CSM to about 5000 mph, and onto its return trajectory. This was the opposite of the outward flight; after passing the point where the gravitational fields balanced, the spacecraft accelerated “downhill” under Earth’s gravity. By the time it approached the Earth, it was again travelling at over 24000 mph.
Just before re-entry, the SM was jettisoned. The CM, now powered by its own batteries, hit the upper layers of the atmosphere at 24000 mph, and began to decelerate due to air resistance. Its interior was protected from the intense heat thus generated, by its ceramic heatshield, which gradually vapourised. During re-entry, the crew were subjected to a deceleration of up to ten gravities!
Finally, the CM’s descent through the atmosphere was slowed by parachutes, and it landed with a “splashdown” in the ocean, where it and its occupants were recovered by US Navy helicopters and carried to the deck of a waiting aircraft carrier.
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