Jon S. Berndt nous apporta ses lumieres en ce 15-12-2006 06:48:
> "Alain" <ele### [at] netscapenet> wrote in message 
> news:45828032@news.povray.org...
>> Jon S. Berndt nous apporta ses lumieres en ce 14-12-2006 22:07:
>>> "Tim Attwood" <tim### [at] comcastnet> wrote
>>> Hey, I kind of like this (I think I've seen something like this in my 
>>> kitchen, too!)
>>> A couple of notes:
>>> 1) There should be no over-expansion of the nozzle, I think. All of the 
>>> flow would be almost all directed aft.

>> The over-expansion is unavoidable. All you can do, is try to minimise it.

>>> 2) I'm sure this is a WIP, but thought I'd mention that there would be 
>>> more to the engine (a lot of equipment creating magnetic fields - coils 
>>> and stuff, supply lines for fuel, etc.)

>> Depending on the scale, that can be all contained within the nozle.

> Visually, what I would like to see is probably best illustrated by looking 
> at a Hall thruster:

> http://fluid.ippt.gov.pl/sbarral/hall.html

> (see Pratt and Whitney thruster at bottom of this page)
> http://www.engin.umich.edu/dept/aero/spacelab/thrusters/thrusters.html

> http://www.adastrarocket.com/Plasma.html

> There is little, if any, overexpansion of exhaust in these images. The image 
> by Tek was very good in this respect.

> Jon


Plasma or ion engines, indeed, don't show overexpansion. The reason is that the 
plasma have very neglegible pressure. It don't have presure as it's not 
accelerated by the presure but by magnetic and electric fields. I was thinking 
more about chemical or nuclear powered rocket engines. In those cases, the 
exaust have a prety high residual presure as it leave the engine, and that 
residual presure is what causes the overexpansion.

-- 
Alain
-------------------------------------------------
When the bosses talk about improving productivity, they are never talking about 
themselves.

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