In article ,
Christopher M. Jones wrote:
...just means you have to choose propulsion systems carefully,
avoiding orthodox hypergolics and other systems which spew out condensible
garbage that can easily contaminate optics. Xenon Hall-effect thrusters
or an ammonia arcjet would be good choices.

True, which is why I did not *completely* rule out the
option. Of especial note is that such efforts come with
rather sizeable down sides (and price tags). Low thrust
propulsion requires nearly continual operation...

That's why I mentioned arcjets, which are still low-thrust by chemical
standards but have *much* higher thrust than Hall-effect thrusters.
With them, it should be possible to do occasional corrections rather
than continuous thrusting.

Even resistojets would be worth considering. You don't actually *need*
terribly high Isp for this; the point of the electric thrusters is more
that they can run on storable non-contaminating fluids.

For that matter, you ought to be able to do non-contaminating storable
chemical fuels, if you picked carefully. I would guess that ClF5/NH3
would be non-contaminating. (Don't know if anyone's tried that particular
combination; ammonia is notorious for being difficult to burn well because
it's so stable, but ClF5 is notorious for being so ferociously active that
it gives smooth combustion with anything it gets its hands on.)
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