On 22 Oct 2003 21:14:50 -0500,
(Gordon D. Pusch) wrote:

(Christopher) writes:

Over the weekend I was reading some sites associated with our British
Interplanetary Societys Project Dedalus. It seems to be for the
moment the only practical proposition to get a payload to another
system in a realistic time frame.

Anyhow, on some of the sites concerning the engine, was a discription
to have around the rocket nozzel bell end an O ring of like a cathode,
so the probe can recycle some current/electrocity via the plasma
exhaust plume.

Can they do that, and do you get much electricity via it? It sounds
like a good idea and it could be used on a VASIMR type rocket to get
some payback from the amount of electricity the ship would use to
generate a plasma exhaust.

TANSTAAFL. There Ain't No Such Thing As A Free Luanch. Any energy you
extract from the exhaust slows down said exhaust relative to the vehicle,
and vice versa, because it exerts an equal and opposite reaction force
on the vehicle. Hence, trying to "recycle" the energy simply cuts into the
engine's performamnce. You can't lift yourself by pulling on your own
shoelaces, and you can't "recycle" energy you've used to produce thrust.

The reason why this was acceptable on _Daedalus_ was that the exhaust was
being produced by fusion micro-explosions, i.e., the enegine was a net
_SOURCE_ of energy, which could be tapped for vehicle operations.
By contrast, VASIMR is a net _CONSUMER_ of energy, not a _producer_
of energy.

Right, thanks for the clarification.


Christopher
+++++++++++++++++++++++++
"Kites rise highest against
the wind - not with it."
Winston Churchill