So I am using the VASIMR data of approximately 5N of force per 250kw of power draw. As far as I can see, this scales fairly linearly, so 500kw would result in 10N of force. (Might require two engines, I'm not sure how ion drives actually scale up, but that's a separate question).
However I can't seem to find the propellant (xenon, I think is usually used) usage for that 5N of force.
I do suspect there's an obvious way to work it out from the specific impulse, which I know is Ns/kg.. but I'm not quite sure how I use that information. Does it mean that an engine with a specific impulse of 12000Ns/kg, can put out 1N of force for 12000 seconds, using 1kg of propellant?
(and a second minor question, how do engines like the VASIMR scale up? If you want 50N of force, do you build 10* 5N engines, or can you build a single much bigger engine (I don't know if the technology can be increased in size like that), or can you just pump 200MW into a single normal engine (if you can keep it from exploding). Would be interested in the solution - I suspect the answer is to build 10 engines)