Re: starship-design: Pellet track

[KellySt@aol.com]

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

>KellySt@aol.com wrote:
>>In a message dated 8/9/97 10:47:53 AM, kuo@bit.csc.lsu.edu (Isaac Kuo)
wrote:
>
>>>One thing that a lot of people seem to ignore when discussing traditional
>>>fusion rockets is that any fusion rocket with very high Isp will be
>>>_very_ low thrust, because of power requirements.
>
>>Actually the Bussard Votage compression system I went into seems likely to
>>give 10 to 1 thrust to weigh ratios.  Maybe even a couple times that.  With
>>Isp in the 1-2 million range.
>
>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.  

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'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.


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

>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?

Kelly