[Spaceships] Mass-driver realism

[Michael Thayne]

In Spaceships, the dominant selling point of the mass driver engine is that you can use anything as fuel. This is especially attractive for mining craft (as seen in designs in both SS6 and SS8). But I know that when it comes to the mass driver's weapon counterpart, the railgun, a major concern is the rails wear out very fast. This is potentially a bigger issue for the engine than the weapon; "able to use anything for ammo" isn't a selling point of the railgun, so if you need also need replacement parts its tolerable, but if you need to carry lots of replacement parts for your mass driver engine it sort of defeats the purpose.

So: is the promise of fee fuel for the mass driver realistic? Presumably they're not maintenance free, but will realistic mass drivers wear out much faster than other engines?

[Anthony]

Mass driver rockets are presumably coilguns, not railguns. They don't have the same erosion problems (they have other issues, but those may not matter in a low thrust propulsion situation).

[Michael Thayne]

Originally Posted by Anthony

Mass driver rockets are presumably coilguns, not railguns. They don't have the same erosion problems (they have other issues, but those may not matter in a low thrust propulsion situation).

What are those other issues?

[Anthony]

Originally Posted by Michael Thayne

What are those other issues?

Typically relatively low acceleration, and it's hard to aim and stabilize the projectile in the barrel. Both can be mitigated by producing a big, low density system, which won't work very well as a weapon but is perfectly okay for slowly pushing an asteroid around.

[Michael Thayne]

Is that likely to be a barrier to getting the kind of performance assumed in Spaceships? Or is the lack of accuracy fine for a propulsion system?

[AlexanderHowl]

Accuracy does not matter for thrust. The real problem with mass drivers are that they are energy hogs because of the inefficiency of ionizing random matter. While people can talk about ISRU with mass drivers, water is more common than dirt in the outer solar system, and a fusion drive that uses water as reaction mass is vastly superior to a mass driver (meaning that mass drivers are only really useful in the Inner Solar System).

[Daigoro]

Originally Posted by Michael Thayne

I know that when it comes to the mass driver's weapon counterpart, the railgun, a major concern is the rails wear out very fast. This is potentially a bigger issue for the engine than the weapon;

I'da thought it be a bigger issue for the weapon as it needs to maintain a pinpoint accuracy that's unnecessary for the engine.