Kerbal Mun landing
Oct. 30th, 2013 12:22 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
rbandrewsSomething's always bugged me about Apollo.
Every history of the Apollo program mentions John Houbolt. He was an aerospace engineer who had a crazy idea and managed to sell it to everyone: lunar orbit rendezvous. See, the original plan for the moon landings was called "direct ascent": you build a big multi-stage rocket, launch it, fly it toward the moon, dropping stages as you go. Eventually you turn it around and land it on the moon, then take off and fly back.
This has a couple problems. First, most obviously, you need to find someone who can fly a giant tall rocket backwards to land it on the moon. You need to carry a bunch of heavy stuff you don't need on to the lunar surface: parachutes, a heat shield, a bunch of fuel, etc.
So Houbolt had a different idea: make a little rowboat-like thing, drop it from lunar orbit on to the surface, and then fly it back. Rendezvous in lunar orbit with the main ship, then fly that back to Earth. It was a hard sell, because no one knew what a lunar lander would look like or how to build one, and no one yet knew if a rendezvous was possible at all, much less feasible enough to trust the crew's life to doing one in lunar orbit. But he convinced people, and it worked, and we did it seven times.
But, and this has always bugged me, there was a third option: Earth orbit rendezvous.
It works like this: you launch, instead of one big Saturn V, several smaller rockets. A couple just contain fuel tanks, one contains a big engine module, one contains a lunar lander, one contains a reentry module. You dock them all with each other in Earth orbit, where it's easy and you don't lose much if you fail. If you lose one launch, you just try that part again. Eventually, you have a big lunar spacecraft assembled in orbit. Then, you fly the crew up to it, take it to the moon and back, and bring the crew home.
This has problems too: more launches might cost more, even if the rockets are smaller. There's still all the difficulty of a lunar orbit rendezvous, because you still have the lander. There are a lot more missions to screw up, even if each one has lower stakes. Designing something to be built on orbit is hard.
But it's worth all of that, and here's why: after you fly it to the moon, you can reuse the ship. Send up more fuel tanks and more crew, and do it again. Build a bigger one next time and you can go to Mars. Apollo is more or less a dead end; an Earth orbit rendezvous ship would keep being useful, keep having more steps we could try.
And that's essentially exactly what I just did in Kerbal Space Program.
This ship was launched in two pieces: one was the lander, you see here. One was a fuel tank and an engine to carry the lander to the Mun. There would have been a third launch once he got back, to collect the Kerbal from orbit and bring him back to the Kerbin surface. Unfortunately, a glitch in the game immediately after this was taken destroyed the lander, so I'll have to try it again tomorrow. But, what I'm proud of (besides the landing, obviously) is that all the launches used the exact same launch vehicle, with different payloads, and were assembled in orbit. And I can do the same thing later to go to the other planets in the Kerbalverse.
Every history of the Apollo program mentions John Houbolt. He was an aerospace engineer who had a crazy idea and managed to sell it to everyone: lunar orbit rendezvous. See, the original plan for the moon landings was called "direct ascent": you build a big multi-stage rocket, launch it, fly it toward the moon, dropping stages as you go. Eventually you turn it around and land it on the moon, then take off and fly back.
This has a couple problems. First, most obviously, you need to find someone who can fly a giant tall rocket backwards to land it on the moon. You need to carry a bunch of heavy stuff you don't need on to the lunar surface: parachutes, a heat shield, a bunch of fuel, etc.
So Houbolt had a different idea: make a little rowboat-like thing, drop it from lunar orbit on to the surface, and then fly it back. Rendezvous in lunar orbit with the main ship, then fly that back to Earth. It was a hard sell, because no one knew what a lunar lander would look like or how to build one, and no one yet knew if a rendezvous was possible at all, much less feasible enough to trust the crew's life to doing one in lunar orbit. But he convinced people, and it worked, and we did it seven times.
But, and this has always bugged me, there was a third option: Earth orbit rendezvous.
It works like this: you launch, instead of one big Saturn V, several smaller rockets. A couple just contain fuel tanks, one contains a big engine module, one contains a lunar lander, one contains a reentry module. You dock them all with each other in Earth orbit, where it's easy and you don't lose much if you fail. If you lose one launch, you just try that part again. Eventually, you have a big lunar spacecraft assembled in orbit. Then, you fly the crew up to it, take it to the moon and back, and bring the crew home.
This has problems too: more launches might cost more, even if the rockets are smaller. There's still all the difficulty of a lunar orbit rendezvous, because you still have the lander. There are a lot more missions to screw up, even if each one has lower stakes. Designing something to be built on orbit is hard.
But it's worth all of that, and here's why: after you fly it to the moon, you can reuse the ship. Send up more fuel tanks and more crew, and do it again. Build a bigger one next time and you can go to Mars. Apollo is more or less a dead end; an Earth orbit rendezvous ship would keep being useful, keep having more steps we could try.
And that's essentially exactly what I just did in Kerbal Space Program.
This ship was launched in two pieces: one was the lander, you see here. One was a fuel tank and an engine to carry the lander to the Mun. There would have been a third launch once he got back, to collect the Kerbal from orbit and bring him back to the Kerbin surface. Unfortunately, a glitch in the game immediately after this was taken destroyed the lander, so I'll have to try it again tomorrow. But, what I'm proud of (besides the landing, obviously) is that all the launches used the exact same launch vehicle, with different payloads, and were assembled in orbit. And I can do the same thing later to go to the other planets in the Kerbalverse.
