Re: Mass Drivers (was GEV and Grav Vehicles)

>>> owner-gzg-l@CSUA.Berkeley.EDU at internet 12/02/99 06:30AM >>>
>>Michael T Miserendino wrote:
>> A mass driver (AKA a "Rail Gun") uses magnetic attraction between
>> electromagnets to propel a payload.	The electromagnets are made up
of 
coils
>> conducting current which produces magetic fields.  The payload is
stored 
in
>> a bucket coil which makes up one electromagnet.  The other
electromagnets
>> are made up of a series of drive coils which form a tube.  The
>> electromagnetic fields are used to repel or attract each other. 
AFAIK 
the
>> most common mass driver in use now is the pull type using attraction.

Someone wrote:
> Ummmmmm, that turns out not to be the case.

> What you are describing is a "coil gun", not a rail gun.
> A rail gun consists of two long rails.  The electrically
> conducting payload strikes an arc between the rails and
> rides the wave of plasma.

No, I was describing a mass driver.  Thanks for the links.  I now
remember 
what the plasma was used for.  I remember that mass drivers work best in
a 
vacuum for obvious reasons.  The plasma was used to help seal the tube
from 
air leaking in during the firing, not to push the payload.  Plasma 
generation, as stated, is actually optional and I don't believe it was
even 
used in early mass driver experiments.

Mass drivers, as I mentioned earlier, use coils to generate
electromagnetic 
fields to either push or pull a payload.  I think "coil gun" and "rail
gun" 
are just used now to describe variants of the mass driver.  Some early
mass 
driver experiments used magnetic guide strips which is where I think the

first use of the term "rail gun" came from.  The rail gun today appears
to 
use a mass driver as a component of the acceration process with the
initial 
force applied from a gas piston.  Both perform the same job of
accelerating 
a payload using electromagnets.  

Mass Drivers: (check under the research section)
http://www.ssi.org/research.html

Here's some good articles on mass drivers:
1. "Mass Driver III - Construction, testing and comparison to computer 
simulation" by Les O. Snively and Gerard K. O'Neill (Princeton
University 
physics dept.) Space Manufacturing 3, pp. 391-401. 

2. "Mass driver theory and history" F. Chilton (Science Applications,
Inc.), 
Space Based Manufacturing from Nonterrestrial Materials 2 1977, 8 p. 

3. Look for articles about or by Dr. Gerard K. O'Neill and Dr. Harry
Kolm, 
the inventors of the first practical mass driver.

Mike

Michael Miserendino
Senior Software Engineer
Lincoln Re
mtmiserendino@lnc.com