"John Thingstad" wrote in message
news
On Thu, 11 Nov 2004 00:02:36 GMT, Christian Ramos
wrote:


VASIMR, seems to me like a technology toy looking for a real life
solution.
How would you envisage VASIMR being used. Although, given a space based
research program that furthers our understanding into magnetics and
plasmas
things could change, but the benefits are more likely to flow through to
technologies such as the Russian MPD thrusters.



I've looked over MPD and it seems like it produces far lesser thrust per
wight of
gas. I might be wrong.

It may, although it would be interesting to compare end to end conversion of
the energy to thrust output. MPD is also on my list of a propulsion system
that I "should" be able to build at "home", VASIMR on the other hand is not.
My thinking was along the lines that further research into plasma dynamics
and magnetic fields is going to have more direct bearing to MPD first and
then vasmir later. That is, their is much more room for performance
improvement on the MPD side which may then flow through to things such as
VASIMR.

.. The idea of VASIMR is to get variable thrust of
significant
% of g force and be able to maintain it over a long time. Getting the
energy from a
reactor greatly reduces the amount of propellant needed. As I've said a
nuclear fission
produces approx 1 000 000 times the amount of energy you would get from a
chemical reaction.
(Not that you can utilize all of it..)

Well the question I would ask is, if you have a reactor on board your craft,
would you not be better to pump the fuel directly through the reactor rather
than convert to electricity then convert back to heat the propellant. This
is a numbers question though, have you ever compared?

Also, given our limited understanding of plasma and magentic sciences, are
we even sure that such a device would work well in "Outer Space" with all
kinds of external plasma and magnetic interactions This later is a question
I've never seen addressed so perhaps I'm being paranoid.

I see it used for manned interplanetary flight.
Particularly continous acceleration means that the peaple are exposed to
cosmic radiation and zero g for much lesser periods of time.

I always have a problem with these types of solutions of long term
acceleration. Once you get to such speeds that make Interplantary travel
viable, arent you also going to be at a speed where even the impact of dust
particles could devastate your ship. Your ability to maneuver is also
compromised with such a solution.