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Fusion Wired

Posted: Tue Sep 23, 2008 12:53 am
by MSimon
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http://www.wired.com/culture/culturerev ... 0/pl_print

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Dreams of a utopian future have driven decades of research into fusion power, the explosive union of atomic nuclei that fuels the stars and liberates colossal quantities of energy. Its pursuit has pushed scientists to the abyss, spawned crackpot schemes (nuke the moon!), and given rise to reactors with names like the Stellarator, the Thermotron, and the Perhapsatron. Although no fusion reactor has ever produced more energy than it consumes, every new advance, real or imagined — cold fusion, bubble fusion, microfusion bombs — is met by media frenzy. In his Sun in a Bottle: The Strange History of Fusion and the Science of Wishful Thinking, Charles Seife has no doubt why: "Fusion is as close as science gets to something for nothing. It offers a theoretically clean, perfectly free, inexhaustible source of energy that nothing else offers. As soon as the theory was born — that you could make atoms stick together and get energy — scientists said, 'We have to make it work.'"

Posted: Tue Sep 23, 2008 1:26 am
by icarus
However hip and fun the article maybe there is not one hint to answer the screaming title "Why Fusion Proves Elusive".

Of course, if one knew the answer as to "why controlled fusion power is elusive" then you could probably subsequently produce it, so I wasn't expecting much after just reading the title. All hat, no cattle.

Posted: Wed Sep 24, 2008 10:37 am
by jmc
I've though about this question myself.

I think the simplest way to phrase the answer regarding why fusion is so elusive is with three points.

1) The universe has a tendency to spontaneously increase its own entropy

2) The universe is 15 billion years old

3) Nuclear fusion energy represents the single greatest store of untapped entropy in the universe.

The conclusion you could draw from these three points is that if fusion was easy, the universe would have already found a way to fuse all, or atleast most of, the fusion fuel available, long before 15 billion years passed by.

Entropy is like the opposite of water, it always tries to find the highest level. And the bigger the body of water you want to store above sea level, the thicker the wall you need to hold it in.

Posted: Wed Sep 24, 2008 1:20 pm
by Barry Kirk
That is a fabulous way of explaining it...

Their is no Boran 11 or at least very little in the sun. Stars burn it very quickly.

The biggest roadblock to fusion in stars is the reaction p + p -> H2 + e-

That reaction is limited by the low strength of the weak force and sets a limit to how fast a star can fuse.

Their is an alternative catalysed path using carbon, but I'm not sure what percent of the sun's energy is derived from that reaction.

Posted: Wed Sep 24, 2008 7:40 pm
by MSimon
Barry Kirk wrote:That is a fabulous way of explaining it...

Their is no Boran 11 or at least very little in the sun. Stars burn it very quickly.

The biggest roadblock to fusion in stars is the reaction p + p -> H2 + e-

That reaction is limited by the low strength of the weak force and sets a limit to how fast a star can fuse.

Their is an alternative catalysed path using carbon, but I'm not sure what percent of the sun's energy is derived from that reaction.
IIRC most of it.