Codicil about those ion drives (since you too encountered Teflon
volatilization in space-related projects, Jerry):

I handled such a drive in the 1970s at a space laboratory, but did not work
on it. In conventional chemical rocket fuels, a classic objective is
concentrated energy, formally "specific impulse" (SI). Also known as oomph.

High-performance chemical fuels deliver SI circa 200 or 300 seconds or more.
(For any unfamiliar reader, the number has practical meaning, it's the time
a fuel can produce thrust equal to its own weight -- so to speak, lift
itself off the ground.) Chemicals with higher SI tend also to be harder to
handle.

In the 1970s, ion drives were said to deliver 40,000 seconds or more of SI.
They actually got their energy from electricity. If you have a space probe
that is well away from any planet, a long gentle thrust can get you going
very fast. You burn a Teflon "candle" hot enough to make a plasma, which
will take an electrical charge. Then you use your solar panels as a source
of electric field to accelerate the ions and send them out the back.
Inevitably if they go one way, you go the other. I understand it produced
low accelerations (much less than earth gravity) so not useful for launching
a craft from the ground, but very useful in interplanetary space where also
the sun is much brighter, and electricity is "free."

Think of this, next time you marvel at the nonstick properties of your
properly used Teflon cookware!


-- Max