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Re: starship-design: Pellet track

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).

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.

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.
    _____     Isaac Kuo kuo@bit.csc.lsu.edu http://www.csc.lsu.edu/~kuo
/___________\ "Mari-san...  Yokatta...
\=\)-----(/=/  ...Yokatta go-buji de..." - Karigari Hiroshi