For those unfamiliar with the tradeoffs: Hall effect thrusters make fairly efficient use of the reaction mass - about 2000s, compared to ~250 for solid rockets or ~300-400 for liquid rockets. That means a considerable increase in your delta-v - since you only need 10-20% as much reaction mass for the same impulse, you get 5-10x more delta-v. Great, right?
The trouble is that you need a power source. Liquid fuel rockets just burn the propellant. Hall effect thrusters (and other ion thrusters) need a power source in addition to the propellant.
This is a great tradeoff for stationkeeping on satellites - you only need tiny amounts of thrust, so you can easily generate enough power using solar cells or a RTG. Thus the very efficient use of reaction mass means a much longer useful life, or more useful payload in your satellite for a given launch mass, etc. It's just plain more efficient.
But this isn't like that. They seem to want to use them to perform the Hohmann tranfer [wikipedia.org]. That means having a very high thrust for a short duration - not just because you want to get there more quickly, but because it's much more efficient than a long continuous burn.
They're talking about 100KW. That seems low. Ballpark 5000 newtons of thrust... Compare to the Apollo command/service module at ~90,000 newtons. Thus they'll need a fairly long burn at that power. How the heck are they generate that kind of power for a long duration?
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