The Apollo Lunar Module

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Podcast Transcript

When President John F. Kennedy set the objective of landing on the moon before the end of the 1960s, no one really knew what it entailed. 

The Apollo program involved many incredible feats of engineering, but perhaps the most impressive was the development of the Apollo Lunar Module. 

The Lunar Module was unlike any spacecraft before or since. It was the first spacecraft designed to fly only in the vacuum of space and the first to land on another celestial body. 

Learn more about the Apollo Lunar Module and the incredible design challenges it had to overcome on this episode of Everything Everywhere Daily.


When people think of the Apollo program, one of the first things that comes to mind is the giant Saturn V rocket. 

To be sure, the Saturn V was indeed an incredible feat of engineering. However, it was not the most impressive engineering accomplishment of the Apollo program.

The Saturn V was just a bigger version of the rockets that had come before it. There had been decades of experiments and progress in rocket design, and the Saturn V was just the culmination of that process. 

The real gem of the Apollo program was the Lunar Module. 

The Lunar Module was completely novel. Nothing like it has been created before or since. It required a host of new innovations never seen in previous spacecraft, and it had to function in an environment that no one had ever experienced. 

The story of the Lunar Module began with President Kennedy’s call to land someone on the moon. 

When the idea of going to the moon was first floated, there wasn’t any agreement on how to do it. Two basic ideas were proposed: direct assent and Earth orbit rendezvous. 

Direct assent would involve building a giant spaceship that would be launched from Earth, land on the moon, and return to Earth. There would just be one ship that would do everything.

The other proposal involved launching multiple rockets into Earth orbit, where a ship would be assembled to go to the moon and return. 

If you remember back to a previous episode, the method that was eventually selected was neither of these. What they went with was called Moon Orbit Rendevous. 

The problem with direct ascent and Earth orbit rendezvous was mass. A large ship that did everything would have to be massive, requiring an enormous amount of fuel. 

Moon orbit rendezvous recognized that a massive ship was not necessary. A smaller shuttle was all that was needed to travel from lunar orbit to the surface. This smaller vehicle would be cheaper, faster to build, and wouldn’t require multiple launches for the same mission. 

Once the decision to go with lunar orbit rendezvous was made, a contractor had to be selected to design and build the vehicle, which was initially dubbed the Lunar Excursion Module, and called the LEM. The name was changed to Lunar Module in 1966, as the word excursion seemed too frivolous, however, everyone kept calling it the LEM. 

Eleven aerospace companies were contacted to submit proposals, and nine of them responded.  The contractor who won the bid was the Grumman Corporation of Long Island, New York. 

Grumman won the bid but faced a massive problem. No one had ever built a lunar module before, so they had nothing to go on. There were no past examples that they could use to determine a timeline or a budget. 

No one was really sure what the surface of the moon was like. Some thought that it was deep in power and that anything that landed on it would sink. 

The biggest issue that the Grumman engineers had to deal with was weight. If you remember back to my episode on the tyranny of the rocket equation, the more mass you have, the more fuel you need, and you need more fuel to launch that fuel. 

Tom Kelley was the lead engineer at Grumman. His engineers mercilessly removed everything that was unnecessary. 

The initial design has seats for the two astronauts and broad windows. It was determined that they didn’t need chairs in zero and low gravity, so the seats were removed, which then allowed for much smaller and lighter windows because the astronauts would be standing closer to it. 

The entire vehicle had to be built out of lightweight materials, mostly aluminum and aluminum alloys. 

Where they could, they even got rid of the aluminum. 

Another problem they had to face was the extreme heat and cold. Depending on whether the ship was facing the sun or the shade, temperatures could range from +200 to -200 degrees Celsius or +392 to -328 degrees Fahrenheit. 

They solved this problem with extremely thin layers of reflective Mylar and Kapton. The reflective surface materials helped protect against the intense sunlight and the cold vacuum of space.

Another engineering challenge was that the LEM didn’t have to worry about traveling in the atmosphere and being aerodynamic. It could be as boxy and ugly as necessary because it only operated in the vacuum of space. 

Another challenge was that the LEM was actually two different spacecraft. At the bottom was the descent stage, with the legs actually touching the surface. 

Nothing of the descent stage was necessary to return to lunar orbit; it was just extra weight. When the astronauts returned to orbit, the bottom descent stage would serve as the launch platform for the assent stage. 

Because the moon only has ? the gravity of the Earth, and because there is no atmosphere to plow through, the amount of fuel needed to get from the lunar surface to lunar orbit was a fraction of what is necessary to get to Earth orbit.

The LEM also had to work flawlessly. Every system had to be checked and double checked because there was no possibility of rescue if something happened on the moon. 

By April 1963, the general design of the LEM had been frozen. That began the process of building and testing every single component and subsystem that would be part of the LEM. 

In addition to the extensive testing, astronauts had to be trained to pilot the LEM. 

The LEM was nothing like any of the astronauts had ever flown. Most astronauts were former test pilots.  Astronaut Gus Grissom joked that instead of test pilots, they should have recruited experienced helicopter pilots because it was the thing most like piloting the LEM.

In 1964, Bell Aerosystems was commissioned to build the Lunar Landing Research Vehicle (LLRV), which allowed astronauts to have more realistic training in an actual flying vehicle. 

Neil Armstrong was almost killed in an accident involving the LLRV in 1968. He managed to eject moments before it crashed into a fiery ball. 

The Apollo 1 disaster in January of 1967 delayed the entire program and gave the engineers more time for testing and safety checks. 

After the testing phase was complete, several testing and prototype LMs were built, and the production of actual LMs began in 1968. 

Each LM had to be built by hand with custom-made parts. There was no assembly line or mass production. This made construction slow and extremely expensive. 

Each LM was numbered, and there were 15 production LMs made in total. 

LM-1 flew on Apollo 5 in January 1968. This was an unnamed mission designed to test various Apollo systems in space. Apollo 5 was designed to test the LM engines to see if they would fire, especially if the ascent engine would fire when still attached to the descent stage.


LM-1 burned up upon reentry into the Earth’s orbit.

LM-2 was built for testing and never actually flew in space. 

LM-3, nicknamed Spider, flew in March 1969 on Apollo 9. This was the first manned flight of the LM in space. The LM traveled 115 miles or 185 kilometers from the command module before returning and performing the first orbital rendezvous of manned spacecraft. 

LM-3 also burned up on reentry into the atmosphere. 

LM-4, nicknamed Snoopy, flew on Apollo 10 in May 1969. Apollo 10 was a dress rehearsal for the actual moon landing. The mission went into lunar orbit, separated the LM from the command module, and came within 14.4 kilometers or 7.8 miles of the lunar surface. 

The descent stage crashed somewhere on the moon. The ascent stage is somewhere in orbit around the sun, and it is the only surviving Apollo LM ascent stage that still exists. It might have been accidentally discovered when it was confused for an asteroid. 

LM-5, nicknamed Eagle, was the first manned spacecraft to land on the moon in July 1969 with Apollo 11. The descent stage was left on the surface, and the ascent stage was jettisoned and crashed somewhere on the moon. This was the fate of all LM ascent stages which successfully landed on the moon. 

LM-6, nicknamed Intrepid, landed on the moon with Apollo 12 in November 1969.

LM-7, nicknamed Aquarius, famously never landed on the moon with the ill-fated Apollo 13 mission. The LM ended up saving the crew’s life when they retreated to it to serve as a lifeboat.  The entire LM was destroyed when it reentered the atmosphere. 

LM-8, nicknamed Antares, landed on the moon as part of Apollo 14 in January 1971.

Around this time, Congress cut funding for the Apollo program, eliminating the missions that would be Apollo 18, 19, and 20. 

LM-9 was supposed to fly on Apollo 15, but it never did. That was because plans had to be moved up after three missions were eliminated.  Apollo 15 became the first of the J missions rather than the last of the H missions. 

J missions were intended to be advanced missions for more extensive exploration of the lunar surface. These missions introduced the Extended Lunar Module. 

The Extended Lunar Module had increased fuel storage and capacity. Its payload increased from 15,200 kg or 33,510 pounds to 21,500 kg or 47,400 pounds.

This increased capacity was used to carry the lunar rover and bring back more moon rock samples. 

The Extended Lunar Module also had upgraded engines on both the ascent and descent stages, as well as improved life support, increasing the amount of time astronauts could spend on the surface to 75 hours. 

LM-10, the first Extended Lunar Module, nicknamed Falcon, was launched in July 1971 as part of Apollo 15. 

LM-11, nicknamed Orion, flew on Apollo 16 in April 1972. 

LM-12, nicknamed Challenger, flew on Apollo 17 in December 1972. This was the last lunar module to ever fly into space and land on the moon. 

Construction began on LM-13, 14, and 15, which were to fly on the canceled Apollo mission. However, they were never completed and were scrapped. 

If you paid close attention, you might have noticed that a couple of the LMs never flew into space. These lunar modules have been donated to museums and can be visited today. 

Before the production of actual lunar modules, there were several prototype and testing versions that were created. They can be found at the Cradle of Aviation Museum in Long Island, NY, the Kansas Cosmosphere and Space Center in Hutchinson, KS, the Franklin Institute in Philadelphia, PA, the White Sands Test Facility in New Mexico, and the Johnson Space Center in Houston, TX.

Three actual production LMs never flew. LM-2 can be seen at the National Air and Space Museum in Washington, DC.

LM-9, which was supposed to be on Apollo 15, is on display at the Kennedy Space Center in Florida. 

Finally, LM-13, which would have flown on Apollo 19, was partially completed by Grumman and is on display at the Cradle of Aviation Museum. 

If you ever have a chance to visit any of these museums, I highly recommend it as these are the only places on Earth you can see an actual Lunar Module. 

New plans for lunar landers have been proposed with the renewed interest in returning to the moon in the 21st century. Not all of these involve lunar orbit rendezvous. Space X has proposed repositioning one of their Starships as a lunar lander, a ship that normally would be an orbiter.  The Starship lander would be more of a direct ascent lander like the type originally proposed at the start of the Apollo Program. 

Despite the initial design of the Apollo Lunar Module now being over 60 years old, it remains one of the most impressive engineering accomplishments in history and is still the only piloted spacecraft to have landed on another astronomical body.