[rescue] Energy

[Chris Byrne]

Well there's a few BIG issues here on the fusion topic

1. Touch off point/break even point.

This is the amount of energy and reactive mass (which are ultimately the
same thing but that's another topic) required to produce a self sustaining
reaction that outputs more energy then it sucks in. Basically how do we get
the damned thing primed. Thus far we have been mostly unsuccessful in
reaching the breakeven point. The few times it was MAYBE achieved it didn't
last long and it was uncontrolled which brings up point two.

2. Controllability

We have no idea how to control a self sustaining fusion reaction, or if it
is even possible to control. The best ideas so far involve massive torroidal
field generators which control plasma flow. Small problem, what happens when
the energy of the fusion reaction vastly exceeds the energy of the fields
controlling that reaction? Oh and assuming we contain the reaction how do we
throttle it without dropping below the touchoff point? Because the natural
tendency of the reaction is to grow til the point where it is either fuel
exhausted, too unstable to continue, or otherwise self limiting for various
reasons.

According to everything we know (which I'll admit isn't a hell of a lot)
these self limiting points are far greater than we can currently handle, or
even have any concept of how we might handle them in the future. If you
don't believe me think about this. The largest fusion reactions we as humans
are able to produce are in the gigaton range, the largest we can control are
in the several molecule range (yes I know there's no basis for dimensional
analysis here because the units are incompatible). These gigaton reactions
are not inherently self limiting in the pure sense, though because of the
methods used to initiate the fusion as well as the materials used in the
devices and produced during the reaction (primarily tritium and helium which
tend to absorb neutron flux) they actually are.

5. Neutron flux and hard alpha

Guess what folks, fusion reactions aren't 'clean' in that they do produce
massive amounts of radiation that is harmful to carbon based life forms.
Primarily these are in the form of neutron flux and alpha particle
radiation.

Neutron flux is one of the primary sources of background radiation in the
universe, all that nice radio noise, microwave radiation through space
etc... But that's at light-years distance. At anything less than half an AU
it starts getting more dangerous.

Hard alpha is the emission of high energy alpha particles. These nasty
little buggers can at most cause the disintegration of your molecular
structure (not atomic structure, molecular structure) and at the least cause
genetic defects in a few cells. It's kind of like shooting marbles with your
molecules, cept the relatively large molecules that make up much of our
bodies are like 1" aggies and the little alpha particle is a BB some asshole
just shot at them.

6. Fuel

SO far the best success we've had with fusion comes from using hydrogen
isotopes (some blend of tritium and deuterium) as the reactive mass. There's
three problems with this. First, too little tritium and deuterium and the
reaction starves out. Second, too much and the reaction absorbs itself
because tritium and deuterium absorb the neutron flux that is generated by
and sustains the reaction. Third, tritium is literally the most expensive
commercially available substance on the planet.

The amount of tritium in a high quality watch is far less than a milligram
and yet costs in the neighbourhood of $10. By comparison a gram of .999 fine
commodity gold is also about $10. Doing the math out that means tritium is
at least a thousand times more expensive than gold.

Also we still haven't figured out a way to produce tritium on a large scale
that doesn't involve nuclear reactors, and there is no way to store it for
long periods of time because tritium has this irritating tendency to decay
into other substances (deuterium helium and hydrogen)

4. Usability

Okay so lets assume we have a controlled self sustaining reaction that
doesn't explode massively,  instantaneously burn all matter on the planet,
or emit so much hard alpha and neutron flux that we all dissolve into
flaming little puddles of semi organic goo that glow like light sticks. Let
us further assume that we have figured out how to fuel these reactions
without bankrupting national economies.

Big assumptions

But let's say we do get past these issues, and I am sure that eventually we
will if we research enough, what do we do with this fusion reaction?

The instinctive gut response is "use the energy". Ok, how? The most
widespread way we as a species have come up with to put energy to use is
electricity. Alright so we turn it into electricity. How?

In the past three hundred years we have come up with precisely three ways
for generating electricity. Interesting chemical reactions, smashing
crystals, and moving magnets near each other.

How is it that we will use the fusion reaction to do one of these things?

Okay how do we use the energy form a fission reaction to generate
electricity? Well primarily we use the waste heat of the reaction to boil
water, which then builds into high pressure vapor, which can be forced
through a turbine.

That process will use what, a millionth of a percent of the energy released
in the fusion reaction, a billionth? And of course the rest will be waste.
That much waste heat will be at minimum interesting to deal with.

Chris Byrne



> -----Original Message-----
> From: rescue-admin at sunhelp.org [mailto:rescue-admin at sunhelp.org]On
> Behalf Of James Lockwood
> Sent: 09 May 2002 18:54
> To: rescue at sunhelp.org
> Subject: Re: [rescue] Energy
>
>
> On Wed, 8 May 2002 dave at cca.org wrote:
>
> > If you look at the Big Picture, fission is a horrible, messy, ugly
> > hack used briefly by civilizations before they figure out fusion.
>
> I thought this was reality, not SF?
>
> "Clean" hot fusion (meaning hazardous-waste-free) is unlikely to be
> possible.  The hypothetical hot fusion reactors of the future will be
> marvelous neutron generators that will create many disposal problems in
> their own right.
>
> > I think we should just wait for fusion. (Well, not passively. :-)
> > We should be funding the hell out of it right now.)
>
> We have been for several decades.  Unfortunately, there is no requirement
> in physics that sub-stellar scale controlled fusion be practical.  Every
> problem that has been solved on the path towards fusion has shown that
> additional issues exist.
>
> At this point I consider orbital solar concentrators to be a better
> possibility.  The engineering needed is far better understood.
>
> -James [and, however convoluted, it brings the topic back to the Sun]
> _______________________________________________
> rescue list - http://www.sunhelp.org/mailman/listinfo/rescue