From: Robert J. Bradbury (bradbury@aeiveos.com)
Date: Wed Jan 08 2003 - 16:20:53 MST
On Wed, 8 Jan 2003, Eugen Leitl wrote:
> I don't know which purpose we're talking about here, but nanotechnology
> and biology needs only traces of the heavier elements.
I would have to sit and go through them in detail but I believe the
existing nanopart designs differ with "natural" abundances quite
significantly. (See Table 6 in
http://www.aeiveos.com/~bradbury/MatrioshkaBrains/MatrioshkaBrains.html)
I agree with the statement that nano-bio-tech only need "traces" of
heavier elements but would offset that with the fact that it seems
unlikely that the element abundances in the outer (or inner) solar
system are likely to provide optimal element utilization.
> Nanotechnology will be very happy with carbon mostly.
Hrmph. The Neon Pump seems to have a ~29%/29% H/C atom allocation
and a 26% Si allocation -- that isn't the common ratio of those
atoms anyplace in the universe that I know of.
> Hydrogen/Deuterium/Lithium is fuel/fuel precursor.
While I agree that Li could be used as a fuel, it may be better
used as an energy (neutron) capture fluid. One of the fundamental
problems with most fusion reactions is *"how do you capture the
energy released?"*.
> I think we can focus energy (beamed microwaves from the inner solar system
> orbiting machinery) towards selected habitats to propel and/or power them.
> Or spin up material from the deep orbits.
But this places a "plutino" at the mercy of its energy source. (Or individuals
that would block the energy path). Unless you have a solar-system wide
system of governence and legal enforcement this is a very fragile situation.
I also think you may be underestimating either the mass requirements for
refocusing a beam across 40-60 AU (or collecting a beam that has spread
across that distance).
> Nanotechnology and lots of hard vacuum and microgravity along with
> cryogenic temperatures (for cryomagnets?) seems to help a lot with
> building reactors.
Not enough IMO though I may be wrong. I don't think this approach has
been studied sufficiently. You still have the problem that you have to
be able to extract the energy from the fusion engine and turn it into
something more user friendly. The technologies for doing that are
very crude at this point -- and we don't know whether or not they
can be significantly improved upon.
> Li abundances:
Eugen, can you cite some references for your table so I can reconcile
it with my tables? [Thanks!]
> Doesn't look too shabby. Li burns too easily in stars, not in fusion
> reactors. So there will be very little lossage of it, to breed tritium.
I'm not worried about Li loss to breed tritium. I'm worried about having
enough of it for optimal capture of the energy being produced by the fusion
reactions. Now it may be that we can go to Na/K energy capture blankets --
if so that is fine -- but this is beyond my level of understanding of fusion
reactor mechanics.
> Light elements are fuel. There's no point in using all of them
> immediately. For that small fraction of them which will be used there is
> enough heavier elements.
This depends in large part on the fuel cycle and the energy capture
cycle of the reactor. I think we are too early in the development
of these paths to state with any amount of certainty how the allocation
of resources will play out and where the element shortages may develop.
Robert
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