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

[Spike]

> Technotranscendence

> 
> 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?

Ja.  The NASA Glenn facility was an outgrowth of an
effort to create an atomic oxygen test facility which
could produce a stream of cold neutral oxygen atoms
going at 8 km/sec for materials testing purposes.  Other
oxygen testing facilities create hot ionized oxygen
without the kinetic energy, so the usefulness in
materials testing was limited and the results are
related to the real world are by inference only.

So instead of hot, charged and slow, NASA Glenn gives
you cold, neutral and fast, by injecting the previously
stripped electrons back into the ion stream.  An oh by 
the way, would not this make a wonderful ion engine?  {8-]  

Minor problem: the Glenn facility costs a fortune to set
up and fires a few parts per million of copper particles
at your test item, which in some cases wrecks the test.
Also there is radiation from at least two sources: the
UV from the recombination of oxygen ions with electrons,
and the bremsstrahlung from the remaining oxygen ions
hitting your target.

Besides that, we at Lockheeed can do it cheaper.  And
faster too.  I dont know about better.  {8^D  But you
know the old saying about that: pick any two.


> > c) the need for the ion engine to take
> > up its own solar  panels for power (I
> > doubt the designers thought far
> >    enough ahead to include a power
> > outlet on the outside
> >    of the Hubble itself...).

I think the notion is to use the ion engine in
applications where the spacecraft already has
access power generating capacity: it has its own
solar panels which are not always in use or not
fully used always.  Then use the otherwise wasted
power to gently push the craft along, extending
its orbit life.

spike