There's also light-gas guns - significantly higher performance for launch. As for retrieving asteroids, solar thermal (i.e., steam rockets) is probably still the winner if you have the volatiles.
Quote from: QuantumG on 01/02/2018 01:11 amThere's also light-gas guns - significantly higher performance for launch. As for retrieving asteroids, solar thermal (i.e., steam rockets) is probably still the winner if you have the volatiles. The volatile does not have to be water, just something that boils at a low temperature. A low latent heat of vaporization is also good.
Mass drivers are fairly significant enablers for retrieving asteroids, since they can be loaded with asteroid rock for reaction mass.
So it'd be interesting to know how well they could trade against more conventional SEP.