Digging through some NASA archives...

[Kelderek]

If this has already been posted here before then I apologize...

I came across the official Apollo 11 Press Kit released July 6, 1969. This document is some 250+ typed pages with all manner of charts and diagrams in a single PDF file.

Totally fascinating stuff! The detail is amazing. I didn't look for it, but I bet the items from Neil Armstrong's private stash that were just discovered this week are probably listed in there somewhere.

Some things that caught my eye:

* After playing so much KSP, it really started to make me realize how dumb we Americans are for still using measurements in feet instead of meters, lol.

* I didn't realize that the Apollo mission orbited the moon in the opposite direction than how they orbited the earth. Is this due to how the moon is tidally locked to Earth, always showing us the same side? I guess I hadn't given it much thought before, but that might make sense. Should we try to orbit and land on the Mun in KSP in the way?

* It is also interesting how close to the night/day line (is terminus the right word for that?) that they chose for landing. I know they did that for shadow contrast on the terrain during landing.

* This document is the plan for the mission before it happened, this is not recorded data afterward. The full scale of everything they had to think of and plan for really looks crazy when you see it like this - it really was a huge undertaking and they left nothing to chance.

Anyway, this was a mesmerizing read for me, I hope you guys find it fun to look through too.

[Streetwind]

* I didn't realize that the Apollo mission orbited the moon in the opposite direction than how they orbited the earth. Is this due to how the moon is tidally locked to Earth, always showing us the same side? I guess I hadn't given it much thought before, but that might make sense. Should we try to orbit and land on the Mun in KSP in the way?

The retrograde lunar orbit was the result of the figure-eight "free return trajectory" that the Apollo missions flew. It is less efficient than a standard Hohmann transfer. However, it was tuned in such a way that if the crew decided to skip their lunar capture burn, the spacecraft would simply continue on its way and return to Earth - even intersecting the atmosphere without having to perform a deorbit burn.

This is what saved the lives of the brave men aboard Apollo 13, when they suffered a catastrophic hardware malfunction shortly before entering lunar orbit. Because they were on a "free return" trajectory, they were able to ride their wrecked craft home despite being unable to operate its main engine. (They did have the use of the lunar module's engine as backup though, which helped to shorten the trip.)

Edited February 12, 2015 by Streetwind

[Motokid600]

Can that figure 8 flight path be simulated in KSP without n-body physics? Ive never attempted a free return trajectory.

[Karriz]

I think the orbit direction is because that way they have a free-return trajectory in case something goes wrong on the way there, just like happened with Apollo 13.

Going other way would basically mean using Moon for a gravitation slingshot, which could throw the spacecraft to solar orbit.

I think it also takes less fuel to get into lunar orbit if you're coming in from a free-return trajectory rather than a slingshot.

http://en.wikipedia.org/wiki/Free_return_trajectory

I try to do it that way in KSP usually, though it takes a bit more fine-tuning than a counter-clockwise orbit.

[Streetwind]

It works in KSP, yes. It's a bit fiddly but you can get it to work by adding more dV to the burn and moving the encounter further ahead on the Mun's orbit.

It won't be a completely faithful representation of real life due to the patched conics simplification, but it will give you a figure-eight trajectory that loops you retrograde around the Mun and then returns you to low Kerbin orbit if you decide not to capture. So it's the same for almost all purposes

Edited February 12, 2015 by Streetwind

[LordFerret]

An interesting read: http://nssdc.gsfc.nasa.gov/planetary/lunar/apollo13.pdf

[Kelderek]

Well for me, the amazing part of this Apollo 11 document is that it represents what they HOPED would happen, before they were actually able to do it. That and the sheer volume of planning that the whole thing took.

[Streetwind]

Remember, there were several prior missions that tested everything out. Famously, the poor people onboard Apollo 10 got to do the entire mission all the way down to the moment of initiating the landing burn... and then abort and go home. All to pave the way for someone else to do what will be remembered for the rest of human history. Talk about a bummer!

[PakledHostage]

I try to do it that way in KSP usually, though it takes a bit more fine-tuning than a counter-clockwise orbit.

It can also be done without any fine-tuning at all... At the risk of being accused of shameless self promotion, here's a link to a forum challenge that I completed back in January 2012, long before MechJeb or the patched conics trajectory projection system even existed: free-return trajectory.

Per the challenge, I jettisoned everything but the command pod and parachute immediately after completing my TMI burn. I had no way to adjust my trajectory after that but the boys still made it home on the first try.

[How2FoldSoup]

I just read the Apollo 13 pdf...What a ride!