Re: Re: starship-design: Pellet track

[KellySt@aol.com]

In a message dated 8/18/97 9:17:14 AM, you wrote:

>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.

?? No, You could tap off some energy from the exaust plasma by magnetic
fields or the interaction with the compresion feild.  You'ld want to avoid
direct contact of at all possible.


>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.

True.


>>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.

That asumes theirs a market for it.  Specifically one big enough to pay for
the R&D.  Comercial research in exotic power sources, especially ones
invoving nuclear, died when the fuel crises evaporated.

The system I'm reffering to is agreed (even by the government researchers) to
be a more promising design then Magnetic fusion (possibly more then laser
fusion).  But of course no new research programs are scheduled to be funded.
 (Mag fusion programs are grand fathered in, but only at minimal levels.)


>>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.

The geometry for this system is a hollow sphere by the way.  

>>>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.


We've acheaved fusion be several means.  That doesn't mean they'ld work in a
star drive.  Or that they are stable.  Magnetic confinment is legendary for
its instability.

Kelly