Engineering Phase Spaces, was: Plasma engine calculator

From: Robert J. Bradbury (
Date: Thu Mar 22 2001 - 07:16:19 MST

On Thu, 22 Mar 2001 wrote:

> How many thermo-nuclear fusion reactors are powering cities?
> Zero. And the funny thing is, it might take one of Yudkovsky's Super
> Intelligences to finally develop a working model, if the aren't busy doing
> other things.

Its interesting to wonder if the problem with TNF is that it
fell victim to Moore's Law? The 19th and early part of the
20th centuries, the dreams were always "bigger" and "larger"
(you only have to look at the Saturn C designs or some of
the Russian N-1 or UR-family rocket designs to see that).

But one of the consequences of the Apollo program was the
push for miniaturization that led to the development of the IC
which was the real foundation for Moore's Law. Once we had
that in place, our enchantment with "bigger" got replaced
with "smaller". Since smaller requires less material, its
inherently cheaper. So you shift to pursue this exploration
of the engineering phase space until it bottoms out, presumably
with full blown single-atom nanotechnology. Once you have
that, exploring the phase space of "bigger" gets much cheaper.

Now, one of the problems with TNF, was that the primary
concept was the Tokomak (or variants thereof). This is
inherently a large scale device (and therefore expensive).
They have had to keep scaling this back because the public
and governments don't want to spend the money to build
something this large. It will be very interesting to
see over the long term how small we will actually be
able to make TNF reactors. If you take some of the
ion driven inertial confinement approaches (I think
Berkeley is working on these for example), combined
with nanoscale ion accelerators (right up against the
limits of the laws of physics in terms of acceleration
over distance), I'll bet you can get TNF for a lot lower
mass/power ratio than the Tokomaks. The problem with
the Tokomak and the National Ignition Facility is that
they require such a large amount of matter to create
the energy densities to drive a fusion reaction.

It is worth noting that the NIF, since its using ~10 year
old concepts and the construction is proving quite problematic
will quite likely be obsolete by the time it is finished.
Diode laser technology is moving ahead at a very fast paceu
(the NIF is powered by flash lamps of all things...)
Yet another sign of the singularity -- any "big" technology
instantiation you build is guaranteed to be obsolete by the
time it is finally complete.


This archive was generated by hypermail 2b30 : Mon May 28 2001 - 09:59:42 MDT