Low gravity space shipyard vs micro gravity shipyard

Question

If you had a device, similar to a Stargate, but that allowed seamless two way transfer, and that could be moved (You could essentially strap a rocket on it, and fuel it from Earth), you could just leave it in orbit, and shove a satellite into orbit, or "anchor" the gate on a space shipyard, and funnel materials and components, and manpower, through it.

Let's say you want to build more traditional science fiction space ships (Crew quarters, command bridges, engines, science stations and scanners, the whole Star Trek-shebang), and you can't pass a whole one through the gate; the gate is too small, and making one big enough is cost prohibitive.

But just as you can have a micro gravity space shipyard in orbit around Earth, you could also have a low gravity launch facility and shipyard on the moon.

Would the low gravity of the moon, be of benefit to a large scale ship building program, or would it just be better to skip the middle staging ground, and build the ships already in orbit around Earth?

Assume that no artifical gravity technology exists (A rotating shipyard is acceptable), and that the presence of a new Stargate on a newly built ship means fuel reserves can be kept low until in orbit around the moon, and launch cost itself is therefore a minor benefit to keeping the construction in orbit.

Answer 1

I'd be doing all my large-scale construction and assembly in low Earth orbit.

This has three major advantages. Firstly, although you're no longer protected by the Earth's atmosphere you are still protected by its magnetosphere, whereas the moon is mostly not. Secondly, lunar dust is an absolute nightmare. It gets everywhere, it has all sorts of unpleasant electrostatic effects, it is sharp and abrasive, probably toxic (and probably carcinogenic, too) and all these features make working on the moon sound extremely unappealing. This sort of dust is probably present on other airless bodies in the system, too... Martian dust will also be extremely fine and abrasive but with the added bonus that it is full of reactive chemicals, too.

Finally, in the event of a problem with the stargate, Earth is right there. Radio communications are easy, round trip delay times are low, and you can even have re-entry lifeboats if needs be. All good things.

Exceptions can be made for stuff that is intended to be deployed a long way away. You may as well build your starships in the Oort cloud, and ships intended for use in the outer solar system in the outer solar system and avoid all the hassle of flying them out there in the first place.

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You might also consider the fact that having the ability to create flying stargates largely removes the need to muck about in space in the first place. Why go up there? It is full of things that'll kill you. Fly your stargates somewhere nice, then get out at the other end. Much safer, comfier and probably cheaper, too.

Answer 2

From a purely structural point of view, building a spaceship in microgravity means that the structure will have to cope only with the intended acceleration assumed during the design.

Building it on a body with its own gravity means that it will have to be factored into the calculation for the structure, potentially adding weight but in any case resulting in additional design time.

All the rest equal, then, building in microgravity saves design time and is to be preferred.

Answer 3

Lower gravity has many advantages. Primarily, it is easier to move things around, and you don't need (much) scaffolding, and structural integrity of whatever you are building is practically no issue.

Yet, since all that has been mentioned, i would like to look at the flipside of the coin: provided you have humans working on the construction of your vessel, they might actually prefer somewhat higher gravity. First, it's what we are used to, so you need less training than when working in micro- or zero gravity. and second, if you want to tighten a bolt or use a hammer, it is extremely practical if newton's third law would not send you flying away every time you paid a bit less attention than you should. That means, the higher the gravity, the more use a worker can make of his own mass. Think about pushing a door open: That works fine, because you can transfer forces into the ground, which in turn is possible because gravity pushes you to the floor, thus providing enough friction between the floor and your feet. Without gravity, you would need to hold on to the wall in order to push the door open, meaning you need two hands for the job.

So, as with every engineering issue i know of, there is not one clear and correct answer, but you have to balance the pros and cons.

You want gravity as low as possible to facilitate lifting things and preventing them from falling down, yet you want enough gravity to keep things together and give your workers something to stand on.