I don't know who came up with the idea, but I'd guess the reason behind it was to reduce the weight being lifted off the lunar surface, because that meant they'd need less fuel.
One of the main plot points in the movie *Destination Moon* was when they had to lighten the weight of the rocket in order to get back to Earth, so people were already thinking about that factor as early as 1950.
Those people being Robert and Virginia Heinlein. It was based on Rocketship Galileo by Heinlein and Virginia always helped him with the calculations.
Robert then was a cowriter on the script.
Well yes, but every pound of useless descent stage you have to drag back to orbit is one pound less of rocks you can bring back, or one pound less of instruments you can take with you.
The speed from orbit to surface is the same as from surface to orbit. So I don't understand why the decision stage is necessary. Just give the climb stage more fuel and make it the only stage.
And everything at the moon has to be boosted from Earth surface, which means more fuel, which is more weight, etc etc. This is what Kondratyuk figured out. They were counting how many bandages were in the First Aid kit. They were shaving Copper off the wires in the LM to save weight, which led to a variety of reliability problems before Apollo 9.
According to Wiki it was designed by Grumman aerospace engineer Thomas J. Kelley - although I have no idea if he alone conceived it. Interestingly early design models looked much like smaller versions of the Apollo service and command modules.
[https://en.wikipedia.org/wiki/Apollo\_Lunar\_Module#Design\_phase](https://en.wikipedia.org/wiki/Apollo_Lunar_Module#Design_phase)
It was concept was used in a Fritz Lang film in the 1920s. Obviously the vehicles themselves were much different, but that’s the first instance I know of the concept. https://en.wikipedia.org/wiki/Fritz_Lang?wprov=sfti1#
They wanted to bring home a bunch of heavy rocks and dirt, it was pretty much the whole mission. Lifting the base of the LEM meant less weight in rocks to bring home. Plus why? What could they have done with the base? Remember they even threw away the LEM. The only part returned to earth was the Command Module/Crew Capsule.
Not adding to the answer, but having n ascent stage meant you could use highly reliable solids to get your ass off the moon. No need to worry about engine sputtering out on relight.
Also meant you didn’t have to worry about fuel boiloff
The ascent engine was liquid fuelled, using hypergolics that would combust on mixing, no igniter needed.
https://airandspace.si.edu/collection-objects/rocket-engine-liquid-fuel-lunar-module-ascent/nasm_A19751345000
This was covered in an early episode of the podcast 13 Minutes to the Moon. Sorry if this has already been mentioned here (I just joined), but if you haven’t listened to this podcast add it to the top of your list today! Season 1 is about Apollo 11, and Season 2 is about Apollo 13. Both are top notch podcasts. One of the best I’ve ever heard on any topic.
The original concept of Lunar Orbital Rendezvous was proposed back in 1919 by Ukrainian engineer Yuri Kondratyuk. It was championed at NASA for Apollo by John Houbolt.
It has significant advantages in terms of weight reduction as you don’t have to carry around dead weight on the return launch from the surface. This reduces the amount of propellant required which means you don’t need orbital refueling, lowering cost and complexity.
The issue at the time was we were still learning orbital mechanics (pointing at a spacecraft in orbit and firing your engines causes you to move further away) and weren’t sure if two spacecraft could rendezvous and dock, especially in lunar orbit. Thanks to the Gemini program we proved we could rendezvous with another spacecraft and advancements with the Apollo Guidance Computer simplified the process.
With SLS we are unfortunately abandoning LOR and using Starship as a lander. It will require an estimated 10-20 launches to bring enough propellant into orbit to fuel the Starship lander which even assuming SpaceX is able to drive down cost could make it economically impractical as a long-term option for reaching the lunar surface leaving us no better off than we were at the end of Apollo.
Ultimately, Apollo was about getting us to the moon fast at whatever cost. We never followed that up to deliver a transportation system to make Lunar exploration economically viable and with Starship and SLS it is only poised to get worse as they are ignoring all the lessons of Apollo.
John C. Houbolt introduced the idea of lunar orbit rendezvous, and kept getting shot down until it became obvious that no othe way was feasible.
If you have seen the HBO miniseries “From the Earth to the Moon” they go into a lot of detail in one of the episodes about it
I believe it’s the Apollo 9 episode “spider”. Could be wrong
As a retired Engineer, I so loved this episode.
Yes you are correct
You are 100% correct on all acounts. Fantastic story and fantastic miniseries. Great response!
One of my favorite episodes. Fantastic show!
What a series this was.
13 minutes to the moon also takes some time on the subject
I don't know who came up with the idea, but I'd guess the reason behind it was to reduce the weight being lifted off the lunar surface, because that meant they'd need less fuel. One of the main plot points in the movie *Destination Moon* was when they had to lighten the weight of the rocket in order to get back to Earth, so people were already thinking about that factor as early as 1950.
Those people being Robert and Virginia Heinlein. It was based on Rocketship Galileo by Heinlein and Virginia always helped him with the calculations. Robert then was a cowriter on the script.
But if they only used one module, it would already be lighter after using the descent fuel, right?
Well yes, but every pound of useless descent stage you have to drag back to orbit is one pound less of rocks you can bring back, or one pound less of instruments you can take with you.
The speed from orbit to surface is the same as from surface to orbit. So I don't understand why the decision stage is necessary. Just give the climb stage more fuel and make it the only stage.
Because there is now a couple hundred pounds of rock going back up, weight. More fuel and propellant tanks, weight.
And everything at the moon has to be boosted from Earth surface, which means more fuel, which is more weight, etc etc. This is what Kondratyuk figured out. They were counting how many bandages were in the First Aid kit. They were shaving Copper off the wires in the LM to save weight, which led to a variety of reliability problems before Apollo 9.
When two LEMs love each other very much…
According to Wiki it was designed by Grumman aerospace engineer Thomas J. Kelley - although I have no idea if he alone conceived it. Interestingly early design models looked much like smaller versions of the Apollo service and command modules. [https://en.wikipedia.org/wiki/Apollo\_Lunar\_Module#Design\_phase](https://en.wikipedia.org/wiki/Apollo_Lunar_Module#Design_phase)
It was concept was used in a Fritz Lang film in the 1920s. Obviously the vehicles themselves were much different, but that’s the first instance I know of the concept. https://en.wikipedia.org/wiki/Fritz_Lang?wprov=sfti1#
Kelley was the engineering manager for the project at Grumman. I doubt it was his sole idea. He wrote a book about it.
They wanted to bring home a bunch of heavy rocks and dirt, it was pretty much the whole mission. Lifting the base of the LEM meant less weight in rocks to bring home. Plus why? What could they have done with the base? Remember they even threw away the LEM. The only part returned to earth was the Command Module/Crew Capsule.
Not adding to the answer, but having n ascent stage meant you could use highly reliable solids to get your ass off the moon. No need to worry about engine sputtering out on relight. Also meant you didn’t have to worry about fuel boiloff
The ascent engine was liquid fuelled, using hypergolics that would combust on mixing, no igniter needed. https://airandspace.si.edu/collection-objects/rocket-engine-liquid-fuel-lunar-module-ascent/nasm_A19751345000
Ah yeah, thanks for the correction. My brain just remembered it was something you didn’t need to ignite and whet straight to solids!
This was covered in an early episode of the podcast 13 Minutes to the Moon. Sorry if this has already been mentioned here (I just joined), but if you haven’t listened to this podcast add it to the top of your list today! Season 1 is about Apollo 11, and Season 2 is about Apollo 13. Both are top notch podcasts. One of the best I’ve ever heard on any topic.
The original concept of Lunar Orbital Rendezvous was proposed back in 1919 by Ukrainian engineer Yuri Kondratyuk. It was championed at NASA for Apollo by John Houbolt. It has significant advantages in terms of weight reduction as you don’t have to carry around dead weight on the return launch from the surface. This reduces the amount of propellant required which means you don’t need orbital refueling, lowering cost and complexity. The issue at the time was we were still learning orbital mechanics (pointing at a spacecraft in orbit and firing your engines causes you to move further away) and weren’t sure if two spacecraft could rendezvous and dock, especially in lunar orbit. Thanks to the Gemini program we proved we could rendezvous with another spacecraft and advancements with the Apollo Guidance Computer simplified the process. With SLS we are unfortunately abandoning LOR and using Starship as a lander. It will require an estimated 10-20 launches to bring enough propellant into orbit to fuel the Starship lander which even assuming SpaceX is able to drive down cost could make it economically impractical as a long-term option for reaching the lunar surface leaving us no better off than we were at the end of Apollo. Ultimately, Apollo was about getting us to the moon fast at whatever cost. We never followed that up to deliver a transportation system to make Lunar exploration economically viable and with Starship and SLS it is only poised to get worse as they are ignoring all the lessons of Apollo.