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Re: Re: starship-design: Pellet track

In a message dated 8/23/97 12:37:20 AM, kuo@bit.csc.lsu.edu (Isaac Kuo)

>KellySt@aol.com wrote:
>>In a message dated 8/19/97 11:04:14 AM, kuo@bit.csc.lsu.edu (Isaac Kuo)
>>>KellySt@aol.com wrote:
>>>>In a message dated 8/18/97 9:17:14 AM, you wrote:
>>>>>>>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
>>>>the R&D.  Comercial research in exotic power sources, especially ones
>>>>invoving nuclear, died when the fuel crises evaporated.
>>>At the very least, this means that there is a significant R&D cost
>>>associated with it.  However, the potential profit is so great,
>>>that the perceived risk must also be great for commercial concerns
>>>to avoid it.  (The perceived risk being that even after all that
>>>R&D it won't work.)
>>You forget.  We are awash in cheap fuel, few new power plants of anykind
>>planed in the next 20+ years, and a fusion plant might mot be any cheaper
>>then conventional.  Add to that the general expectation (and stated claims
>>them) that eco groups will attack Fusion plants as rabidly as nuclear
>>(the power companies are still smarting over that), and you have some very
>>reluctant investors.
>Actually, a fusion plant only has to compete with fission plants to
>acheive great profit potential.  The initial and running costs for
>motive fission plants are so great that they're now restricted to
>aircraft carriers and nuclear submarines.  The running costs for any
>practical fusion plant would be much less than fission or conventional,
>so that just leaves initial cost--including R&D.

Actually the weight of the power plants reduces them to fairly large craft.
 Legal restrictions complicated their use so the navy does use them on all
large ships.

Besides your assuming a fusion plant would be cheaper then a fission or other
design.  We don't know that they would be, and with current fuel gluts were
in no pressing hurry to find out.

>For various reasons, naval power plant sales would be the first venue
>for any "easy" fusion power plant.  Civilian power plants, bigger and
>with more restrictions, would come later--but not very much later if
>it were so easy.
>>>I personally think magnetic target fusion offers the brightest
>>>potential (it's a pulsed fusion concept), but even so the concept
>>>is too new and the technology too immature to bank on it.  The
>>>numbers look a _lot_ more acheivable than either magnetic
>>>confinement or inertial confinement.
>>Haven't heard of it.  Whats it like?
>It is sort of a mix between traditional magnetic confinement fusion
>and inertial confinement fusion.  For some reason, no one thought
>of doing it until a couple years ago.
>The idea is to start off with a magnetically contained bit of plasma,
>like what we can acheive in magnetic confinement fusion reactors
>today.  This bit of plasma is then compressed using a surge of
>electricity through the magnetic coils.  This initiates a relatively
>extended burst of inertial confinement fusion.
>The temperature and density of the initial plasma obviously
>doesn't have to be anywhere near what's needed for fusion, while
>the compression is provided by a pulse of magnetic field (which
>is easier to do than a pulse of lasers) over a period of time
>longer than the laser pulse of ICF.  The products also fuse
>over a longer period of time, making it easier to tap energy
>from the products.
>The fusion ramjet concept is similar to this, except that the
>pulse of magnetic field is provided by the motion of the pellet
>plasma into a fixed "bottleneck" of strong magnetic field.
>>>>>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.  
>>>Huh?  A conductive hollow sphere cannot generate an electric
>>>potential gradient inside it.  You'd have to inject electrons
>>>into the center in order to attract the (positively charged)
>>>fuel particles to it, and rely on the charge of those electrons
>>>alone to acheive compression.
>>You charge the hollow sphere.  The ionized gas is repeled from it toward
>>center.  Which effectivly gets a oposite charge.  Fusion products blast
>>outward, out of the potential well.
>This does not work.  The ionized gas will _not_ be repelled from
>the surface of the sphere.  Honest.  The net force on a charged
>particle on the inside of an evenly charged hollow sphere is 0.
>For the same reason, you would be weightless on the inside of a
>"hollow Earth", and couldn't stand on it.  This has to do with
>the fact that both gravity and electric force are inversely
>proportional to the square of the distance.
>Any second semester Physics course with Calculus uses this
>example.  You know, you get a homework assignment where you
>have to derive the electric field around various geometrically
>shaped objects.

Well thats how I read the explanation in Bussards Papers and diagrams.  You
could get copies through your university libray if you'ld like to check up on