Henry Spencer wrote:
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.

Are there arcjets large enough for this task? I was
under the impression that there were none large enough
for main propulsion tasks. Although for simple orbital
maintenance, something that large might not be needed.


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.

Agreed (or solids, of course). And perhaps solar sails or
electrodynamic tethers, though those are much less easily
compatible with telescope operation than even ion engines.