h a l f b a k e r yContrary to popular belief
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Fusion. It's really jolly good, and when we can do it in a
controlled way, it'll be even better. It'll happen
sometime
in the next 30 years (or, if you're reading this in the
future, it'll happen sometime in the next 30 years).
Basic problem with nuclear fusion: you have to keep the
fusing
atoms very, very hot in a confined space. Way
hotter than the vaporisation temperature of any known
material. Hence the tokamak - which attempts to
contain
the fusing material using magnetic fields.
Howevertheless, neither tokamaks nor anything else
have
yet achieved useful, sustained nuclear fusion. The
plasma
keeps escaping from the magnetic field.
If only there were some material that could withstand
fusion temperatures...
"But wait!" you hear me cry. "If all known materials are
vaporised at fusion temperatures, why not just use the
vaporised material as the fuel?"
So here's the plan. We take some metal which will fuse
under the right conditions. Maybe beryllium (just don't
inhale). From this metal, we make a bunch of rods in
the
form of long five-sided prisms.
We mount these rods on feeders, so that all the rods
converge on the centre of an imaginary sphere. Because
the rods are pentagonal, we have a dodecahedral space
in
the middle, entirely surrounded by the end-faces of the
rods.
Now we light the blue touchpaper, and get some fusion
going in this dodecahedral space. Almost immediately,
the
ends of the rods are vaporised. So, what we do is simply
move all the rods inward, as fast as they are vaporised.
In other words, the walls of our fusion chamber are
continuously replaced, and their continuous vaporisation
provides the fuel for the ongoing fusion reaction.
So, there you go. Problem solved. Happy to be of
service,
mankind.
General Fusion
https://en.m.wikipe...wiki/General_Fusion
[xaviergisz, Aug 19 2015]
Ball of Confusion...
https://www.youtube...watch?v=SyMPXvpvkI8
..by The Temptations. [DrBob, Aug 25 2015]
[link]
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You may not believe this, but I proposed this exact
principle many years ago, and it was denied the billions in
funding I requested to develop it further. |
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so beryllium doesn't melt, but simply sublimates ? |
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No, I'm sure beryllium will melt first, but at fusion
temperatures it will go on to boil (and, indeed, to
ionize). |
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Is it a problem if the walls vaporize faster than the fuel can be spent? Can your fusion ball become too "rich?" |
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How do the material and thermal products of the reaction escape? |
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//How do the material and thermal products of
the reaction escape?// |
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You could feed the rods in just a liiiiiittle bit
slower, so that excess beryllium vapour had a
chance to escape. In fact, with a bit of luck, the
thing would be self-regulating (if the reaction gets
too exciting, the rods vaporise faster than they're
being fed in, leaving gaps through which plasma
can escape, thereby slowing the reaction). |
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Another possible outcome is that the system would
oscillate between fusion and non-fusion, venting
bursts of beryllium gas between cycles. This
would be very satisfying, as it would sound a bit
like a gigawatt steam engine. |
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I'm pretty sure beryllium will tend to fission, not fuse. It
has just one little neutron holding two alpha particles
together, and they don't really want to be together. Supply
enough nuclear agitation to set the neutron loose, and the
two alphas will happily zing elsewhere, separately. And
you won't even get more energy out, than you put in!
Think more of glass breaking, than some nitrogen-rich
chemical compound decomposing explosively. |
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Hmmm. Well, I could go with lithium if you prefer. |
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To me, it still doesn't sound like you have compressed the sun's size and mass environment into a human scale machine. |
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Would it help if I read this out in a Stephen Hawking
voice? |
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Nope, still not imagining feasible containment. |
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Well, OK, imagine the initial system. The ends of the
rods are pressed together hard, creating a sealed
dodecahedron. |
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Then fusion gets going and, in the first few
microseconds, vaporises a millimetre of the ends of
the rods; but during those microseconds, the rods are
all pushed inward by a millimetre. |
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Not only feasible, but feased. |
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Where does the exhaust gas go? Your Lithium Deuteride (because that's what you should use) rods seal off the dodecahedron. The deuterium is liberated, and an energetic neutron splits the Lithium into two Tritium nucleii - fine. Now even supposing you can achieve fusion conditions inside the core, how will it be sustained? Any fusion events that occor will result in alpha particles (and lots of very energetic neutrons, but most of them will escape the core - might want some lead lined lab coats) clogging up the space. Surely, [Max], you know the difference between continuous and discrete processes? The challenge for any continuous process is cycling through reactants to prevent dilution. |
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...Anyhow, methinks you're underestimating the pressure (and temperature, but mostly pressure) requirements for fusion, by maybe a few tens of orders of magnitude. [Do you know the secondary in a thermonuclear device is compressed not by explosives, but by the recoil forces arising from the ablation of it's surface by x-ray heating?] Your rod feed mechanisms are going to have to be able to index the rods inwards against the pressure in the core, which I understand to be in the hundreds-of-terapascals range. In fact I think your rod feed mechanism will be your real achievement here, and will make "canned fusion" look like childs' play. |
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Every time I see the word tokamak I think of the sign at
Steak and Shake that glows a neon 'Takhomeasack.' Come
to think of it some of their fries might be the perfect
candidates for fusion trials. |
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I just think that mony a tokamickle maks a tokamuckle. |
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//Come to think of it some of their fries might be the
perfect candidates for fusion // |
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With the far superior British chip, actual fusion can be
achieved with ease. Plenty of gravy and just the right
amount of vinegar. |
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I'm pretty sure it will work, [Max]. It looks like it just needs
maybe 30 years of development work. |
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I have always imagined the plasma in the sun like the Mathmos lamp, doing twisting and turning blobby motions. Mind you at a different speed and scale. |
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I wonder if the Tokamak is missing a set of natural sun motions, inside the magnetic bottle, which would be the basis of a sustained reaction? Maybe continuous fed motion deflection plates could be the answer. |
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//With the far superior British chip, actual fusion can
be achieved with ease.// |
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I think you're confusing this with that other energetic
nuclear reaction. British fission chips are well-
known. |
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// it will eat the vessel voraciously at operating
temperatures and pressures// |
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Yes, it will. On the other hand, the only
consistently-over-unity* non-bomb, non-star fusion
reactor as far as I know is the Z-Machine. It
operates for about a microsecond at a time, after
which several tons of components have to be
replaced. |
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*In terms of fusion energy out divided by electrical
energy in. |
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Isn't the Tokamak totally designed around containment ? and nothing to do with macro patterns that effect nuclear species in our sol. Just getting it hot enough might not be enough. For one major thing, gravity would be a bit different. |
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Maybe a Tokamak on the end of hyper-centrifuge. |
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Just wondering; why a dodecahedral space with pentagonal prisms and not, say, a tetrahedral space with triangular prisms, or a cubic space with ... oblongs? I'm guessing the oblongs would be easier to machine. |
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Anyway, there's a small knot of disgruntled platonic solids out here wondering why they didn't make the grade. |
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Because (a) dodecahedra look way cooler than cubes
or tetrahedra and (b) I think the closer you get to a
sphere, the better this will work. |
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Not necessarily true. In a tokamak, the requisite
pressure still has to be contained. It's contained by
magnetic fields, but those fields still react against
the machinery. |
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[bigs], I agree completely with everything you say,
except for the wrong bits, which is all of it. |
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Many things about me are strange to the
inexperienced. |
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//the closer you get to a sphere// |
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The icosahedron is now bouncing up and down with equal parts of excitement and indignation. |
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Again, triangular prisms. |
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The problem is the combination of a strong enough feed
mechanism close enough to the active tips of strong enough
rods. |
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Basically, if you've got a mechanical drive mechanism that
can press the rods together with enough force, it's going to
be massive enough that you won't be able to get close
enough to the tips of the rods to prevent them from
buckling. |
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Depends on the scale. The stiffness of the rods (that
is, their resistance to buckling) goes up as way more
than the square of their thickness. |
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I just had an imaginary picture of a constant buckyball like frame and a whole lot off rods being squeezed inside as there ends vaporise. A bit like playdough through a mould press and with a kid eating the outcome. |
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I wonder if the vaporising bubbly end would supply the pressure needed. Even a strong magnetic buckyball might be the seal needed. |
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I just had an imaginary picture of a constant buckyball like frame and a whole lot off rods being squeezed inside as there ends vaporise. A bit like playdough through a mould press and with a kid eating the outcome. |
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I wonder if a strong seal is even necessary when the vaporising could act as a seal. A strong woven magnetic buckyball shape around the rods might be the seal needed. |
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Isn't the sun just two burns with fuel used up? Any boxed section of the sun's process would have to be a production line of fuel consumption. |
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I shall have words with him. |
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[Ah - the previous annotation appears to have fused
and vaporised.] |
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Ah Yes, the problem of editing thoughts outside the mind. |
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Meanwhile, the actual sphere is sulking like Obelix "Of course, I don't get any, because I fell in a non-euclidean surface when I was a baby". |
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So the only true interface to an actual sphere, is any phagocytosis in which the sphere still still keeps the attributes that make it a sphere. Obelix does like his boars. |
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