ion engine was RE: [extropy-chat] Saving the Hubble

[Robert J. Bradbury]

On Tue, 20 Jan 2004, Technotranscendence wrote:

> > The mission cost was $110m Euros ($126M).
>
> Which still does not tell us how much the propulsion system cost.
> Hopefully, it would be much lower than 110M Euros.

True.  Wild-2 had 16 individual chemical rocket engines on it.
(Nothing like redundancy to make sure things work...).  My guess would
be that you are talking a maximum of $15-20M.  Probably more
like $2-5M.  I can't believe that NASA would be sinking multi-10's
of millions into the ion engine development that Glenn & JPL
are doing.  I mean what are we talking here - a xenon tank,
a few control valves, microwaves generators to do the ionization
(on the new engines), perhaps a wire mesh to do the neutralization,
some magnets and transformers to generate the HV field, perhaps
some transformers(?) and some packging to hold it all together.

> NASA has done some work, I recall reading, on long-term use of ion
> thrust.

Yep, the tests so far on both the old and newer high power engines
have gone well.

> My understanding of ion thrust is that the ions are neutralized during
> or after exiting as exhaust.  If not, all ion propelled craft would be
> lowering their efficiency, no?

I've always wondered about this.  In theory if one didn't neutralize
the ions the spacecraft would pick up a negative charge.  The only
thing I can imagine is blasting the ions through a wire mesh that
was heated up to boil off electrons like a vacum tube.

Robert