With the Artemis Space Program underway, why don't we have a look back at the Apollo Space Program? This was certainly one of the great events of history, the first time a human had stepped onto a celestial body other than earth. For those readers who weren't around yet it was a fantastic time. I followed the moon landings when I was a boy.
There is a compound posting "The Moon", August 2023. There is another compound posting, "Orbital And Escape Velocities And Impacts From Space", November 2014.
There is an important factor in the success of America's space program that I would like to add, the war that made it possible.
Credit to Wikipedia for dates and fact checking. Dates given for each mission are launch dates, unless otherwise specified.
The Space Age began with the launching of the Soviet Sputnik satellite and then Yuri Gagarin being the first man in space, sent to orbit the earth. Alan Shepard would be the first American in space, in a suborbital flight, and John Glenn would be the first American in orbit. The competition was part of the Cold War scenario.
One thing that I don't think gets enough attention as boosting America's space program is the Korean War of 1950-53. This was the first major war in which jet aircraft were widely used. It wasn't thought of at the time but being a combat jet pilot is an ideal background for an astronaut. The three most famous names from America's space age are probably John Glenn, the first American in orbit, Neil Armstrong, the first man to step onto the moon, and Buzz Aldrin, the second man to step onto the moon. All three had been jet pilots during the Korean War.
Before John F. Kennedy was assassinated he expressed the goal of putting astronauts on the moon by 1970 and bringing them safely back home. There is no doubt that fulfilling Kennedy's vision was a primary reason for the success of the Apollo Space Program.
The heroes of the space program were not all astronauts. James Webb was the administrator of NASA during the Kennedy and Johnson Administrations. His service was considered as so valuable that he got the space telescope, which might be the most important space project of all, named for him. The very expensive space program was not universally popular and it took some convincing to get taxpayers to support it.
The moon is about a quarter the diameter of the earth, about 2,000 miles or 3,220 km. It is made of rock and, since it lacks an iron core, is 1/81 the mass of the earth. The moon's surface gravity is 1/6 that of earth, helping the astronauts to carry heavy loads. The average distance to the moon is 239,000 miles, or 384,500 km.
There is no universally accepted definition of where the atmosphere ends and outer space begins. The atmosphere doesn't end suddenly, it gradually fades out. The so-called "Karmann Line" is the altitude at which an aircraft would theoretically have to fly so fast to maintain lift, due to thinning air at higher altitudes, that it would exceed the necessary orbital velocity for that altitude. But that is just a definition with regard to technology.
The earth has an orbital velocity of about 5 miles, or 8 km, per second and an escape velocity of 7 miles, or 11.3 km, per second. But that applies to ballistic objects, not to a rocket with an engine.
Once a rocket is in outer space it is not necessary to keep the engine running. The rocket will keep moving in the direction it is pointed until it encounters a gravitational field. The engine is only necessary to accelerate, decelerate, or change direction.
For a spacecraft to just take off and reach the moon is actually impossible, due to the weight of the spacecraft and the fuel it would have to carry to escape earth's gravity. But we can get around this by using stages. The Apollo rockets had three stages added, besides the Service Module with the engine that would be used in outer space.
Each stage had it's own engine, fuel tank and oxygen tank. The difference between a jet and a rocket is that the jet takes in air for combustion while the rocket, which will be operating in airless outer space, brings it's own oxygen or oxidizer. The first stage is the largest and most powerful. When it has expended it's fuel it drops away and the second stage ignites.
The spacecraft still has the momentum built up by the first stage, but has shed it's weight. With existing fuels, and their weight to energy ratio, this is the only way to reach orbit. The first two stages were finished in about ten minutes and the third in about thirty minutes. One concern in the Apollo Program was the discarded third stage staying alongside the spacecraft, and potentially colliding with it, since the two had the same momentum.
It looks like the Artemis Program uses two stages, instead of three. America's earlier space programs, Mercury and Gemini, also only used two stages because they were only going to low earth orbit. Each successive program increased the number of astronauts by one. Mercury has one astronaut, Gemini had two, Apollo had three, and now Artemis will have four.
Rocket launch facilities are often located on the east coast of a country. This is because the earth rotates eastward and when the rocket takes off it picks up some of the earth's eastward momentum. So if something should go wrong the rocket will crash into the sea, rather than into a populated area. The moon also orbits eastward and orbits the earth in 29 days. 24 hours divided by 29 = 50 minutes, which is why the moon rises 50 minutes later each day. The launch site doesn't have to be on earth's equator but it's generally more efficient the closer to the equator it is, because the earth's spin is greatest at the equator.
A particularly challenging part of the space program was reentry into the earth's atmosphere when the mission was completed. If an unprotected spacecraft entered earth's atmosphere at the speed it was traveling through space it would burn up like a meteor. The capsule that returned to earth had a blunt bottom. This was designed to create a shockwave that carried away much of the energy involved in reentry, so that it wouldn't be manifested as heat. There was also a heat shield that would peel away layer by layer. Finally the spacecraft would splashdown in the ocean and be recovered by a navy ship.
Outer space is a very hostile environment. Small meteors will burn up in earth's atmosphere but above that there is no protection against meteors that might be traveling faster than bullets. The atmosphere also provides some protection from cosmic rays. The astronauts reported seeing flashes, even with their eyes closed, which were caused by cosmic rays. With no air to redistribute heat the side of the spacecraft toward the sun will get extremely hot while the other side gets freezing cold. This can be remedied by having the spacecraft do a gradual "roll".
The earth is a magnet, which is why a magnetic compass works. The magnetic lines of force through space, between the magnetic north and south poles, are known as the Van Allen Belts. These protect the earth from the stream of charged particles from the sun, which cause aurora, but beyond them there is no protection. This is what causes electronics in satellites to gradually break down.
Without this magnetic shield the charged particles could eventually strip away earth's atmosphere. This may be why the moon has no appreciable atmosphere. Lacking an iron core like earth it has practically no magnetic field.
An Apollo spacecraft would have three modules, besides the initial three stages. The Service Module would have the engine and fuel. The Command Module would house the astronauts. The Lunar Module is what would actually land on the moon, while the Command Module would remain in lunar orbit.
The Lunar Module would be discarded once the two astronauts who landed on the moon returned to the Command Module. The Service Module would be discarded before reentry into the atmosphere, and would burn up in the atmosphere. The Command Module, slowed by parachutes before splashdown, would be the only module that returned to earth.
After the Apollo spacecraft had attained earth orbit, called a "parking orbit", checks would be done from Mission Control, on the ground. Since the moon itself is in earth orbit it is possible to go to the moon without leaving earth orbit. If an object in orbit is given a boost in the same direction that it is orbiting it will then have more orbital energy and will climb to a higher orbit. It can be boosted as high as the moon.
It all works by the Inverse Square Law, an object that is given three times the orbital energy will climb to nine times the altitude but will move at only one-third the speed. Satellites are sometimes placed at an orbital altitude of 22,300 miles, or 35,890 km. At this altitude it will orbit earth at the same rate as the earth rotates. This is known as a geostationary orbit because the satellite can be made to stay over the same point on the earth's surface.
The same side of the moon always faces earth. Obviously all landings were done on the side facing earth because radio communication and television broadcast to earth would not be possible from the far side. Since the moon has practically no atmosphere an orbit at much lower altitude than on earth is possible, and the Lunar Module wouldn't have as far to travel.
The phase of the moon was important so the astronauts would be in daylight on the moon, not in the dark. The earth had to be visible from where the astronauts were to make possible radio and television communication with Mission Control.
This means that a lunar mission wouldn't be done at new moon, as seen from earth, because then it would be the far side of the moon that was lighted by the sun. If the mission was done at full moon that would mean communication and television broadcast to the earth would be done at night. Around the half moon phase would seem to be best. The landing site would be chosen and then it would be lit by the sun at half moon phase, either when the moon was waxing or when it was waning.
When the astronauts ascended from the moon back to the Command Module it had to be remembered that the moon is effectively rotating once as it orbits the earth every 29 days. If the Command Module was orbiting the moon in a given time frame, and the astronauts were on the moon for two days, it would have to be remembered that the place on the orbit to meet the Lunar Module would be displaced 2/29 of the moon's circumference at that latitude, backwards or forward depending on whether the Command Module was orbiting in the same direction as the moon orbits the earth.
There was so much that had to be taken into account that "rocket science" became a euphemism for any complicated task that required a lot of intelligence.
The Apollo Space Program was preceded by the Mercury and Gemini Programs. The primary difference between the programs was the number of astronauts on board. The Mercury Program carried one astronaut, Gemini carried two and Apollo carried three. The Mercury and Gemini Programs never went beyond low earth orbit, and only required two stages.
The Mercury Program lasted from 1958 to 1963. After satellites had been put into orbit the next step was to get humans into orbit. The first Americans got into orbit on this program. Seven astronauts were initially chosen and Alan Shepard is generally considered as the first American in space, although it was a suborbital flight. John Glenn was the first American to orbit in this program. During this program NASA took over the space program from the Air Force. Because of the initial seven astronauts each Mercury capsule had a 7 in it's name, such as "Friendship 7". The local channel 7 had a morning children's show called "Rocketship 7".
The Gemini Program lasted from 1961-66. Aside from carrying two astronauts the Gemini flights lasted longer than the Mercury. The NASA Mission Control at Houston was first used. Astronauts did spacewalks, outside the capsule.
The Apollo Missions were numbered. Apollo 1 unfortunately ended in tragedy before it even began. The mission was to be the first step to the moon, a three astronaut flight in low earth orbit. On February 21, 1967, during a launch rehearsal, an electric fire started and the three astronauts suffocated. Today the town of Amherst, NY has streets named for Roger Chaffee, Edward White and, Gus Grissom.
Image from Google Street View.
There had been uncrewed Apollo missions the year before but the 1 designation was used for the deceased astronauts.
Apollo 4, November 9, 1967, was an uncrewed orbital test of the new Saturn V (5) rocket. This rocket had three stages, which would be necessary to get to the moon, as explained above. The earlier Saturn 1B had only two stages.
Apollo 5, January 22, 1968, was another uncrewed orbital test. This time a model of the lunar module, that would actually land on the moon, was attached. You can see how the space program was progressing one step at a time. Each mission was just one step ahead of the last. The Apollo missions were each designated by a letter from A to J. The simplest uncrewed test was an A mission. The final few moon landings were J missions.
Remember that the world was watching, lives were at stake, the Saturn V was a completely new rocket and this was something absolutely unlike anything that had been done before. Three astronauts had already lost their lives. It had to be done carefully and one step at a time.
Apollo 6, April 4, 1968, was another uncrewed orbital test, with all modules attached.
Apollo 7, October 11, 1968, was the first crewed mission since the three astronauts died in Apollo 1. It was a test of everything, with an actual crew, in earth orbit. There was some reported tension between the astronauts and Mission Control, and none of the three astronauts ever flew again. A cardinal rule for an astronaut is not to be difficult to work with. The astronauts had backgrounds as fighter pilots or test pilots, and so are naturally used to working alone and thinking for themselves, as opposed to being "team players".
Apollo 8 was the first mission to the moon, around Christmas time 1968. The three astronauts didn't have a real lunar module, to actually land on the moon, but did ten orbits around the moon. A primary objective of this mission, aside from being the next step, was to help select sites for the landings on the surface that would come. In a broadcast to the world the astronauts read the first ten chapters of the Book of Genesis.
Although Apollo 8 didn't actually land on the moon it is the mission that I remember the best. I had just turned 8 years old and had landed in the United States. My new country was sending astronauts to the moon. In the school library I took out the following children's book and have been interested in science ever since.
Apollo 9, March 3, 1969, was a test with astronauts and a real lunar module, but it didn't leave earth orbit.
Apollo 10, May 18, 1969, was a close rehearsal of the landing that would come on the next mission. The astronauts, from lunar orbit, used the lunar module to approach the surface of the moon just as if they were going to land. They did everything except enter descent mode, that would have taken them down to the surface. They just made sure that everything was in working order, before returning to the Command Module, that was in orbit around the moon, and then back to earth.
They came within 16 km of the moon's surface. In the video you could see the craters close-up. I was near the end of third grade and didn't quite understand why they didn't just land.
There was a story that NASA considered the possibility that the Apollo 10 astronauts might disobey orders in order to be the first on the moon. The astronauts were reportedly told that there wasn't enough fuel in the Lunar Module to get them to the surface of the moon and then back to the Command Module. I suspect that there was enough fuel, just so it wouldn't be a disaster if they did try landing, but they certainly didn't want the astronauts to know that.
The Command Modules are the only part of the Apollo spacecraft that returned to earth, with the astronauts inside. The modules are all in various museums today. The Command Module of Apollo 10 is the only one that was given to another country. I have seen this module in the Science Museum in London.
Finally the day came when humans first walked on the moon. The unforgettable day was July 20, 1969. The mission was Apollo 11. The Lunar Module descent and then ascent stages both worked flawlessly. Neil Armstrong was the first man to step onto the moon, followed by Buzz Aldrin.
I remember a report that there was some tension over who would be on the moon first. But some of the astronauts were still in the military. Neil Armstrong was a civilian and I think it was decided that it would be appropriate to have a civilian step onto the moon first.
The mission went almost perfectly, the American flag that they planted on the moon was too close to the spacecraft and was knocked over when the Lunar Module took off to rejoin the Command Module, which was still in orbit. The Lunar Module was jettisoned after the astronauts were back in the Command Module, and crashed into the moon.
One thing that hadn't been anticipated about the moon is how much it's surface gravity varies from place to place. This caused Apollo 11 to miss it's intended landing site by several km. In 1967 an unmanned spacecraft with a camera, Surveyor 3, had been landed on the moon. In an amazing feat of precision Apollo 12, launched November 12, 1969, landed near Surveyor 3. The astronauts removed it's camera and brought it back to earth.
All had gone well in the space program since the loss of the three astronauts in the Apollo 1 launch rehearsal. That was not to last. Apollo 13, April 11, 1970, was the most tense and dramatic event of the program, except the first moon landing. An oxygen tank exploded on the way to the moon, crippling the spacecraft. The moon landing had to be cancelled.
The astronauts went around the moon to point them back toward earth. The Lunar Module was successfully used as a "life raft" to get the astronauts back home. Fortunately the explosion occurred before they reached the moon so that they hadn't yet discarded the Lunar Module.
The moon has mountains and Apollo 14, explored higher terrain. The astronauts had a "shopping cart" to move the scientific experiments around on the moon's surface. Seeds were brought to germinate in space, growing as the "Moon Trees" back on earth. Alan Shepard, who had been the first American in space in a suborbital flight, finally got to walk on the moon.
If modern computer terminology had been around Apollo 15 onward might have been referred to as "Apollo 2.0". Astronauts began staying longer on the moon and brought a vehicle, the Lunar Rover, to drive around on the moon. Since there is no air on the moon the Lunar Rover had to be electric.
Exactly in the center of the following photo are a large and a small white patch of light. The photo was taken from the Apollo 15 Command Module, in orbit around the moon. The large patch of light is sunlight reflecting off the Lunar Module, down on the moon's surface. The small patch of light looks like sunlight reflecting off the Lunar Rover, parked by the Lunar Module.
Image credit to Wikipedia article "Apollo 15".
Apollo 15 brought the famous televised experiment where a hammer and a feather were dropped from the same height. Because there is no air on the moon both hit the surface at the same moment. A plaque honoring fallen astronauts was placed on the moon. A privately-owned Bulova watch was brought to the moon, which greatly increased it's value.
Trouble came again, with Apollo 16 April 16, 1972. This time it was with the main engine. The decision was made that it was not necessary to cancel the mission, although it was shortened by one day.
Apollo 17, December 7, 1972, would be the last time humans have been on the moon. Apollo 18-20 had been cancelled. There was great interest in the geology of the moon and Harrison Schmitt was a professional geologist. Five mice were brought along, to test their exposure to cosmic rays. Since the earth is rotating, and the moon is moving around earth, there is a "launch window" for the spacecraft to most efficiently reach the moon. This meant Apollo 17 had to be launched at night.
After the trouble with Apollo 16 there was a story that Apollo 17 was pushed back until after Election Day so that it wouldn't risk costing Richard Nixon the presidency if it should end in disaster. I don't know how true the story is.
The Apollo astronauts left scientific equipment on the moon, some of which is still in use. There are sensitive seismometers that can detect the impact of a discarded Lunar Module anywhere on the moon. There is a laser reflector so that the precise distance to the moon can be measured. It is known that the moon is moving away from the earth by a few cm per year because the tides caused by the moon in the earth's oceans are transferring earth's rotational energy to the moon's orbital energy.
The Apollo Space Program was followed by Skylab, and then the Space Shuttle. Skylab was placed in earth orbit and was crewed, at different times, by three astronauts doing various experiments and making observations.
Skylab's orbit eventually deteriorated and it burned up in the atmosphere. Parts of it were found in a remote area of Australia. I saw it go by on one of it's final orbits. It was after dark but the sun was still shining on it so it looked like a bright moving planet.
The Space Shuttle was like a partially reusable space plane. Five were originally built. Like the earlier space programs it couldn't just take off into space, it was attached to a large external fuel tank and two solid fuel booster rockets which got it into orbit. Remember that direct flight into orbit is not possible with the weight of the spacecraft and existing fuels. It accomplished tasks like delivering the Hubble Space Telescope to orbit, and later servicing it.
The Space Shuttle had a crew of seven and there were two fatal mishaps, both of which killed the entire crew, the Challenger in 1986 and the Columbia in 2003. The Challenger was destroyed while taking off and the Columbia while re-entering the atmosphere. I was watching the Challenger launch live on television and wasn't sure why there were multiple lines of smoke all of a sudden.
I wonder if the Space Shuttle being designed for seven astronauts is a reflection of the original seven astronauts and Mercury missions all having a '7" in the name.
I think the greatest benefit by far of the Apollo Program were the technological spinoffs. Ronald Reagan tried to repeat the boost to the economy in the 1980s with the Strategic Defense Initiative.
There were inevitably stories that the moon landings were faked. There are places in Nevada that look like the moon. But for the moon landings to be faked, hundreds upon hundreds of people would have to be in on the secret. There is an old saying that the life expectancy of a secret is inversely proportional to the number of people that are in on it. Theories about the moon landings being faked are the domain of tabloids, not of serious media outlets.
The Apollo Space Program has left a lot for archaeologists of the future. With no water or air on the moon there is no erosion and the astronauts' footprints might last forever, unless struck by a meteor. The Lunar Modules, except for the one used to get the crew of Apollo 13 back to earth, all crashed into the moon after being discarded.
The descent stages of the Lunar Modules remain at the landing sites, along with the Lunar Rovers of the later missions, and whatever else the astronauts left behind. There were a number of Swedish-made Hasselblad cameras left on the moon. Some of the ejected rocket stages, for the trip to the moon, remain in orbit around the sun.
But the 1960s vision of regular space travel with colonies on the moon and other planets never came to be. One reason the Apollo Program was curtailed is that public interest in it was waning, and it was tremendously expensive.
The Space Age mostly ended up giving way to the Computer Age. Anyone could never fly into space but anyone can have a smartphone. We also have to question the wisdom of sending people into space. During the Apollo years computer technology was extremely primitive. Now that has completely changed and we could just send robots, with artificial intelligence, into space. They don't need food, other than power, oxygen, or water. They don't have human emotions and we don't have to worry about getting them back home safely.
Space today is as active as ever but it is mostly about communication satellites in earth orbit and unmanned space probes out into the Solar System. But now we are back to sending humans to the moon.
