Re: Nuclear heater for Expeditions

Hara Ra (
Thu, 08 Jan 1998 23:35:38 -0800

Dan Clemmensen wrote:

> > and the other is based on sonoluminescence (SL). SL is still a
> > macroscopic process but I could imagine a SL reactor in the kilogram
> > size range.
> >
> nanotech is not magic. As 'gene says, it may not even be feasible. My
> guessitmate is that is feasible. The requirement for fusion is that
> atoms must slam into each other fast enough. The requirement for
> useful fusion is "engineering breakeven": The process must emit
> more useful energy with no external input. In the particular
> application we're discussing, the useful energy is low-intensity
> heat, which is the easiest goal to reach.
You must recover enough high quality energy to operate your device. So
all fusion devices need a lot of high quality energy.

> It's not proven that SL is blackbody rediation and therefore
> indicative of near-fusion conditions, and the phenomenon is
> not well enough understood to find a useful set of conditions
> whereby you can extract useful energy: currently, SL is observed
> only at temperatured near the freezing point of water. Don't count
> on SL for micro-fusion.
An announcement in Photonics Spectra (photonics trade magazine) stated
a supercomputer simulation of SL, with the right kind of driving pulses
reach fusion temperatures.

> I envision an D-D fusion reactor based on a form of inertial-confinement
> fusion, using a truly tiny holraum and starting in an environment with
> very high static pressure. The environment is the center of a set of
> diamondoid spheres, each of which contributes a megapascal or so of
> pressure differential.

Your geometry won't work. Each shell must be larger than the previous
one. In the end your maximum strength is no larger than that of the bulk

> The D-D reaction emits no primary neutrons.
> The innermost sphere brings the interior static pressure up to the
> highest level that remains consistent with diamondiod nanotech and
> diamondoid compressive and tensile strength. The nanotech machinery
> contained within the inner shell then delivers a transient implosive
> pulse to the holraum (mechanically, or with lasers, or with explosives)
> to cause fusion.

I rather suspect that nanotech becomes quite limited at high pressures.
At extremely high pressures the forces of chemical bonds are of the same
magnitude and you just can't build nanotech.

> This geherates a lot of heat, raising the temperature
> of th interior. The reactor uses the thermal gradient from inside to
> outside to capture the energy neeeded to drive the next pulse.

High pressure and temperature only reinforce my point.

> Agreed. Given nano, you can get very efficient in every way. In
> particular, forget the tent. Just reconfigure your body's resident
> clothing nanos to provide an insulating skin of the type you describe.
Tents are nice, they provide privacy. Of course your clothing could
reconfigure into a tent.

BTW, I think a "mister fusion" is like backpacking a Winnebago...

> Some elements capture neutrons very efficiently, but I want to
> start with a reaction that doesn't emit neutrons at all.

Ok. You have: Neutrons, skip those. Ok, energetic alphas - still capable
of considerable nano mayhem. (and you gotta have alphas, ok?). Then
there's betas, which have a range of inches, at least. OH, and I forgot
the gammas, with a range of several feet even in rock.... Nice device
you have here...

> > So, how do you catch these anyway??
> >
> That's not a percentage of neutrons, that's a percentage of waste atoms.
> you catch the atoms by recognizing that they are atoms of elements
> (heavy metals) that don't belong here.
Just a logical argument here. Either you catch them (and separate them)
or you don't.

> It doesn't have to be efficient. It doesn't even have to
> break even. It just has to be able to bust up these ugly big
> radioactive isotopes that are not amenable to destruction by other
> means.

Using precious high quality energy here. I can see it now. 100 KW, of
we budget 10 KW to run the Mr Fusion, and 10 KW to run the accelerator,
80 KW of waste heat!

> The problem is that for esthetic and political reasons we want this
> tiny accelerator to be contained within the "mister fusion" housing.
> What I'm banking on here is a major deux ex machina, even worse than
> the inertial confinement system above: There are ways to use lasers
> to pump energy into a particle beam with extreme efficiency, yielding
> a very high change in Mev per meter of acelerator.

Catch is the efficiency of making dose laser beams.

> I further assume that
> an accelerator built via nanotech to atomic precision can achieve the
> nearly the theoretical efficiency limit.

Gotcha on this one! The nucleus is 10^5 times smaller than the atom. No
way can you create this precision with nanotech.

> This should permit each nasty
> heavy radioneucleotide atom to be bashed with extreme precision into
> little pieces that are more tractable, all (I hope) in an accelerator
> that's less than a meter long.

And you expect all those random flying bashed pieces to be nice? hah!

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