Re: starship-design: Pellet track

[kuo@bit.csc.lsu.edu (Isaac Kuo)]

KellySt@aol.com wrote:
>In a message dated 8/14/97 1:42:21 AM, kuo@bit.csc.lsu.edu (Isaac Kuo) wrote:

>>Well, I make a flat assumption that outside of special circumstances,
>>the waste heat pumped into the ship itself will be a significant
>>percentage of the energy going into the exhaust.  (Special circumstances
>>would include isolation from the exhaust and its power source by
>>superconducting coils.  Superconductors are inherently capable of
>>doing certain things with seemingly magical 100% efficiency.)

>>Assuming a .1% percentage, a rocket with a 10:1 thrust/weight ratio
>>and 1 millions sec Isp would be absorbing 10^12 watts/kg in waste
>>heat.  Without massive heat rejection systems (which would adversely
>>affect the thrust/weight ratio), that's going to melt the rocket in
>>a fraction of a second.

>>Therefore I don't consider the Bussard Votage compressions system
>>to truly offer a plausible chance at such high thrust/weight ratios,
>>considering how various components are directly impacted by fusion
>>products (thus implying a significant waste heat problem).

>Actually the Bussard system use anti-nutronic fuels that convert virtually
>all the power of the fusion reaction into the kinetic energy of the charged
>waste particals.  Efficency is about 99.9+%.  (give or take).  Most of the
>waste can just be vented to the sides.  

However, in order to get the electric energy from it, you propose
terminals which directly contact some of those charged particles.

Even without this assumption, you need to plasmatize the reactants,
and electrically charge them, and you need to create and maintain
the electric potential field.  All of these things will not be
100% efficient.

>Super couductors arn't quite as majical as you seem to think.  They can't
>deal with radiation, heat, have limited load capacities etc.

I know they aren't all powerful.  However, I find what they do do
to be very counterintuitive.

>I'm also pulzeled why you make such distinctions between other fusion systems
>and your ram fusion system?  If anything the dificulty of grabing, fusing,
>and reacting off of fuel blasting at you at relatavistic speeds seems to
>dwarf other fusion systems.  Other factors would be similar.

Primarily because in order to acheive high thrust, I expect the ram
fusion system to be a low Isp rocket drive.  In other words, it
would sacrifice exhaust velocity (exhaust velocity difference)
for thrust capability.

With a normal rocket, you can't do this because your propellant
requirements will blow up exponentially.

With a ramjet, the requirements go up more modestly.

That said, the way in which I conceived of this fusion ramjet is
specifically designed to prevent any need for the starship to
funnel any power to or from the main drive.

>>As for the efficacy of electric field containment for fusion power,
>>I'll admit I haven't read the reference articles on this compressions
>>system, but it seems very optimistic to assume it will even work well
>>enough to break even, much less provide power.

>I can't follow this.  Why do you assume its so dificult?

Because if it were so easy, it would already be giving us cheap
fusion power.

>Certainly it couldn't require more power then the scoop or
>conventional magnetic confinment systems.

There are difficulties in dealing with charged plasma, since
the more charged it is, the more it wants to fly apart (even
more).  The less charged it is, the more you need a stronger
electric potential difference.  Setting up that potential
difference in the right geometry is challenging as well.

>>When fusion power is acheived, by any method, I'll gladly cheer
>>if I live long enough to see it.  But until then, it seems like
>>the more we learn, the more we learn that it's not so easy.

>Magnetic plasma confinement is a pain, and designs that use it should be
>avoided.  But their are several other designs.  Laser fusion for example
>developed far ahead of mag-confine while it was under comercial development
>in the '80's.  However your suggestions also use complex magnetic fusion
>concepts.  So why list them and attack the others?

Magnetic plasma confinement is a pain, but it is a pain we know.
The technology we do have is mature, so it can be safely used in
speculations of future technology.  We can and do acheive fusion
with magnetic confinement.  We just don't do it well enough to
acheive sustained fusion.
-- 
    _____     Isaac Kuo kuo@bit.csc.lsu.edu http://www.csc.lsu.edu/~kuo
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