Fusion energy

Donald Hosford schrieb:
> Just one question...(no I am not questioning anyone's

There are several paths towards building a fusion reactor that are being
explored. The two that look most promising are plasma confinement and Laser
Implosion fusion. And all use the Deuterium isotope of Hydrogen instead of
plain Hydrogen, because Deuterium is easier to fuse that hydrogen.

For plasma confinement, Deuterium gas is heated to extremely high temperatures
and compressed by electromagnetic fields to a high pressure to simulate
conditions inside a star.

For Laser implusion fusion, you take a small hydrogen pellet and hit it from
all sides with Laser beams. The pellet implodes to produce a
micro-hydrogen-bomb.

None of the methods being explored has, AFAIK yet achieved energy
break-even. That is, there have been fusion reactions, but so few that
the energy pumped in far heating etc. has been rather higher than the energy
from the reactions.

Even if this is achieved and you produce a worthwhile amount of fusion
reactions, there reamin the ddevelopment problem of converting this to energy
at commercially viable rates.

Early fusion plants will probably be about as big as a present-day
power station. The fusion reactor itself probably about he size of a small
house, but there will be generators and all the associated equipment.

It will be a long time before we get it down to the size of an AFV
engine. But that what PSB is for :-)

> At our current stage of fusion development, how did they

Because the basic fusion reactions have been well studied in nuclear
accelerator experiments. You shoot protons (Hydrogen atoms' nuclei) at liquid
hydrogen targets and observe the results. So we know pretty well at which
speeds hydrogen will fuse and what kind of energy and particles will get out.
From this and the laws of thermodynamics, it is fairly easy to calculate the
energy output of a hydrogen cloud under any conditions.

Unfortunately, the accelerator method doesn't scale well to produce worthwhile
amounts of energy (thouhg I think there have been experiments in that
direction).

> In the RPG GURPS Space, they include a fusion reactor for

Seems reasonable (see our earlier discussion) for a power supply. It will
depend a lot on what the energy is used for. If you use the energy to
accelerate the ship to high speeds (near lightspeed) that will eat a lot of
energy. But there would be a lot of assumptions and calculations to do to get
hard numbers.

> After reading Traveller, where the smallest fusion reactor takes 20

1 parsec = 3.26 light years
Hence, that ship is moving at faster-than-light speeds.
That should answer the "real possibility" question.

> If so, that would be super cool! 8-D

Indeed.

Greetings

Hi,

I have been following fusion research as a hobby for over a decade.

On Friday, February 8, 2002, at 02:25 AM, KH.Ranitzsch@t-online.de
wrote:
[snip]

> There are several paths towards building a fusion reactor that are

Another approach that looks promising is termed the z-pinch. A brief
synopsis can be found at
http://www.sciam.com/1998/0898issue/0898yonas.html
One of the really cool features of this technology is that it may scale quite
well. Another really cool feature is the lightning storm it creates;)

> For plasma confinement, Deuterium gas is heated to extremely high

Break-even was first achieved in the mid-90s. The ratio of energy out to
energy in is called "Q". Break-even has Q = 1, but for a commercial
reactor, they are looking for Q > 50. So far, the tokamak design has reached
the highest Q. The current problem is that plasma instabilities quickly halt
the fusion process. Very recently, computer models have shown that it may be
possible lengthen the stable regime through magnetic field feedback.
Basically, as instabilities occur, the confinement field is adjusted to wipe
them out. Only recently has computer power reached the speeds necessary to
make this possible. There are currently several tokamak's undergoing refit to
test this approach.

[snip]

> At our current stage of fusion development, how did they

Linear accelerators, cyclotrons and synchrotrons require a huge amount of
energy to accelerate a very small number of particles. However, a tokamak
still accelerates the particles in the plasma to fusion energies. It just does
it in bulk with a much wider energy spectrum.

The goal of most modern accelerators is to break nuclear matter into its
constituent "fundamental" particles. The energies required are far beyond
those required to initiate fusion, and you pay for that with remarkable
inefficiency. I think that that technology would be better utilised as a
weapon technology.

[snip]

> Greetings
Cheer,