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January 17, 2008

A Fusion Reactor In Your Garage

1920s Vacuum-Tube Technology

"The World's Simplest Fusion Reactor, And How to Make It Work," by Tom Ligon, originally published in the December, 1998, edition of Analog Science Fiction and Fact, online at http://www.fusor.net/newbie/files/Ligon-QED-IE.pdf

Also, a revisited version, supplementary to the above, published in the January/February, 2008, issue of Analog and online at http://www.fusor.net/files/EMC2_FusionToPost.pdf

A must read for anyone enthusiastic for the eventual success of practical fusion power. After 30 years or so, and twelve billion dollars' worth, of research on the promise of thermonuclear fusion, we are assured that a great deal of progress has been made. For another ten to twelve billion we can hope to see a net power demonstration reactor in 20 years time, followed, for a further twenty-five billion, by a workable power plant in 45-50 years. By present indications, the resulting structure, based on the tokamak principle of magnetic confinement in a toroid, looks like having the volume and mass of an aircraft carrier, a lifetime of several years, and a formidable array of "challenges" to be overcome.

When "light" (i.e. in the lower part of the Periodic Table) atomic nuclei fuse together, the mass of the resulting nucleus is less than the sum of the original parts, and the energy equivalent of the difference is released as high-velocity particles from the reaction. Since nuclei are positively charged, for fusion to happen they have to be moving fast enough to overcome their mutual repulsion. In a hydrogen bomb this is achieved by utilizing an initial fission reaction to generate temperatures high enough to promote the required particle velocities. This was well understood and working by the early 1950s, and the logic was thereby born that the key to controlled fusion lay in creating and confining suitably high temperatures. Hence thermonuclear fusion.

But the simplest, most straightforward way of accelerating ionized nuclei (stripped of one or more of the atom's electrons) and other electrically charged particles to hight velocities is by electric fields. Laboratories were doing it in the 1920s, and Ligon describes in detail for the more practically inclined how you can build your own reactor for an outlay of a few thousand dollars or less. Don't expect to be disconnecting from the utility as a consequence, but it does illustrate that maybe an easier and more direct route to this particular Holy Grail is getting less attention and support than it should be.

Electrostatic fusion is not without problems of its own, but Ligon goes into some studies by Dr. Robert W. Bussard--of Bussard ramscoop fame--on how they might be overcome by using magnetic attractor grids instead of metal ones. Besides the enormous implications for the world's energy future, successful economic implementation would revolutionize the prospects for space travel and colonization, effectively reducing the size of the Solar System to that of the terrestrial globe for the Rennaissance navigators. Bussard's calculations indicate a Low-Earth-Orbit to Mars transit in the order of 33 days, and LEO to Saturn's moons in two months, with payloads in the order of 15-20%--inconceivable for any form of chemically propelled behemoth, and not an option for aircraft-carrier-size-tokomaks.

Nature's own ways of engineering tend also to take advantage of the easiest ways of doing things rather than wrestle with the most complex. Prejudices and preconceptions aside, and forgetting our schooling in what "everyone knows," it's intriguing to look again at the case that some theorists have been developing in recent decades, that the fusion occuring in the Sun and other stars isn't taking place in the core at temperatures and confinement pressures due to gravitation, but through intense electrical acceleration at the surface, whose spectrum observers since the 1940s have been commenting strongly resembles that of an arc discharge, and where the heavier elements produced by fusion are found. See, for example, http://www.holoscience.com/news.php?article=by2r22xg , http://www.thunderbolts.info/tpod/2005/arch05/050413electric-stars.htm, and http://www.thunderbolts.info/tpod/2006/arch06/060120solar1.htm

Thanks to Dave Durgee for pointing me to this.

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