Could we fly up rocket sections piecemeal and assemble them in orbit at the ISS? How large a rocket could we assemble? What could it buy us in terms of flight time/payload size to Mars?
I understand that we would want to limit exposure of astronauts to interplanetary space to 3 months. Is that achievable with chemical rockets using this scheme? Also, would such rockets need to fire at full power or could they gradually be throttled up? Would that have any advantages if possible?
Thanks,
Rob
Yes, it would be possible to design an interplanetary spacecraft that could be launched in several pieces and put together in orbit. That’s how the ISS itself was built, after all. The size is only limited by the number of launches you can afford. But the extent of “assembly” should be limited to just connecting the modules together.
I don’t think you’d want to do the assembly at ISS though. Each piece must be able to fly to the ISS and rendezvous with it anyway. You might as well have them fly into a more desirable orbit and connect to each other.
Shortening the flight time isn’t possible in practice for a normal (chemical) rocket, because instead of coasting for almost the entire flight you’d have to keep firing.
The flight time can only be shortened by a rocket with higher specific impulse, with an electrical or nuclear drive.
Not necessarily. The Hohmann transfer orbit is the minimum-energy path. But you can use a more powerful chemical rocket and get into a transfer orbit that’s more elliptical than the Hohmann orbit. This will allow you to coast to the destination more quickly. Of course you’d also need more fuel to decelerate at the destination.
Seems like it would make more sense to build an empty rocket on the moon, then have a facility there to extract/compose fuel from moonrocks (and ice that may be hidden in crater shadows at the poles) and solar power. This would save you from having to bring the weight of the fuel up from the surface of the earth, since the fuel seems to be the largest part of the weight of a heavy launch vehicle. Not only that, but you’d be launching from a low-gravity environment (moon gravity ~= 1/6 earth), so you could achieve your desired transit speed with far less fuel.
Instead, you’d have to bring up the weight of all the mining and processing equipment, and all the people and fuel to run it …
The ISS doesn’t contribute anything to this effort. It is in the wrong earth orbit to assist in launching spacecraft. The orbit was picked to allow access from Russian launchpads. Good thing to, since without the Russian ferries there would be no ISS since those are the lifeboats and the only way to get to the station for a good part of it’s life. In addition, safety rules prevent any storage of rocket fuel near the ISS. Th shuttle and the Soyuz don’t care a large fuel supply since all they have to do is return to earth.
So, it is pointed in the wrong direction and can’t store fuel. Not much of a waystation.
That is one reason why NASA is planning to deorbit the ISS in about 10 years. It was a great learning experience, but not worth maintaining.
True, but it’s possible a future Mars mission would be a collaboration with Russia as well. In which case a similar orbit may be optimal for assembling the spacecraft.
Why would you need fuel in a place you’re making fuel? Solar cells and long lunar weatherless days would be your energy source.
Plus once you got the stuff up there you could make fuel for additional rockets.
Gravity wells are gravity wells. The more you can do weightless the better off you are.
Does a moonbase have any usefulness at all as a launch platform or intermediary? Maybe, debatably, if all the materials are easily accessible and we can somehow put fabrication plants on it. Since that’s highly unlikely I can’t see the moon used that way.