Re: starship-design: Plasma Drive...

[Kevin Houston <Kevin@urly-bird.com>]

At 10:58 AM 9/29/99 -0600, Ben Franchuk wrote:

>I don't think the plasma will scale to make a large space launcher possible.
>My guess is still a air launched pseudo SSTO space plane with a payload in the
>2-3 ton
>range for low earth orbit. The problem is scaling and heat flow. I suspect a
>external field of some kind will be needed to keep the plasma stable for
energy
>addition

Not only that, but you would want one on-board for emergencies, in case you
had a "Flame-out".  So I think that an external elctro-magnetic device
should be built in to the containment vessel.

>and removal. ( Mr Fusion of "Back to the future" comes to mind here for a
>successful reactor
>size wise <grin>). The heat produced from say a 70% efficient engine still has
>to fed through small area.

I wonder if the air-flow could be directed in such a way as to couple with
the rotational component of the plasma, so as to help keep it stable,
instead of breaking it.

>Assuming a 10^9 J? plasma  we are looking at about 3 feet diameter with a 1 
>foot hole.
>That's a lot of heat and external forces wanting to push the  field out of
>shape. I wonder
>how the field would explode if pushed out of shape? Lots of nasty X-rays is my
>guess.

Cherenkov radiation?  It would be one hell of an EMP wouldn't it?  I'll bet
it will be spread out over the EM spectrum in a gaussian shape with some
characteristic frequency peak.

>quick calculations ... 2 ton payload 3 ton unmanned craft ... Isp = 6,000.
g=32
>mi=5 tons
>v 30,000 ft/sec
>Mf = (e(V/(g*isp)-1)Mi  = 1 ton.


>Ben.
>I wonder if C4H would work for fuel?

Any gas/liquid should work as well as any other.  Assuming you mean
methane, it would combust in the reaction chamber while in flight, adding a
little kick, but the main gas for the atmospheric portion will have to be
plain old air.  Once out in space, you'd have to bring your own O2 to
combust the CH4, and that costs extra weight.

I think plain old water would be the best.  You could build the water tank
around the plasma, to provide extra sheilding if the plasma collapsed,
Then the heat leakage from the plasma will help warm the water and keep it
liquid out in space.

What would happen if you threw one these plasma rings at someone?  How
would you do that, and how could you make sure the field collapsed when it
reached it target?  That energy has to go somewhere....

Kevin