Re: Prelude to the "grape drive"? [was: NASA Successfully Tests Ion Engine.]

Dear Ilmari Karonen:

"Ilmari Karonen" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> On Sat, 29 Nov 2003 07:58:47 -0700
> "[EMAIL PROTECTED] \(formerly\)" <[EMAIL PROTECTED]> wrote:
> >
> > I'd worry about "selectively ionizing" a molecule for propulsion.  >
Since the number of electrons stripped off provides the handles for
> > accelerating the mass, the more electrons removed means the faster you
> > can accelerate the molecule.  But the more electrons you remove the
> > weaker (or smaller) the molecule fractions become.  So your C60
> > becomes just 60C, and you are back to accelerating a bunch of light
> > nucleii.
>
> C_60 is pretty stable, though, and, like any molecule, will hold on
tighter
> to its remaining electrons once it's already lost some.  Some quick
> googling suggests C_60 can lose at least 3 electrons without breaking up,
> but will start shedding C_2 ions at some point after that.  I don't know
much
> about ion drives, but I'd think that'd be good enough.

I wouldn't expect that to be of much help.  That is a lot of mass, and very
little net charge.  The accelerator path would have to be "long".

> What I'd be more worried about is carbon buildup on the grids.  If even a
> small fraction of the molecules sticks to the charged surfaces (and those
> C_2 fragments are likely to be particularly sticky) the resulting soot
buildup
> might well become a problem over time.

If you strip electrons, just leave a net positive charge on the "nozzle"
(or an AC with a positive bias to invoke any diamagnetism).

I would wonder if you couldn't *add* a few electrons, to either C60, or
some long polymer chain.  In fact, I seem to recall that some ions were
trapped *inside* C60 (how they'd stay ions seems the $64 question).  In
other words, shoot the cat and then the rubber rod out the back...

David A. Smith