Some interesting progress in polywell fusion.
"We're fully operational and we're getting data," Nebel said. "The machine runs like a top. You can just sit there and take data all afternoon."
So was Bussard correct? Will it be worth putting hundreds of millions of dollars into a larger-scale demonstration project, to show that Bussard's Polywell concept could be a viable route to fusion power?
Nebel said it's way too early to talk about the answers to those questions. For one thing, it's up to the project's funders to assess the data. Toward that end, an independent panel of experts will be coming to Santa Fe this summer to review the WB-7 experiment, Nebel said.
"We're going to show them the whole thing, warts and all," he said.
Because of the complexity, it will take some interpretation to determine exactly how the experiment is turning out. "The answers are going to be kind of nuanced," Nebel said.
The experts' assessment will feed into the decision on whether to move forward with larger-scale tests. Nebel said he won't discuss the data publicly until his funders have made that decision.
Let's hope it pans out. If so, Bob Bussard will be smiling from the grave, or wherever he is.
I have high hopes for this.
It seems that the key question to answer is this paper wrong:
http://dspace.mit.edu/bitstream/1721.1/11412/1/33227017.pdf
Can you create and maintain plasmas with non Maxwellian velocity distributions? Or do all plasma thermalize into a Maxwellian distribution?
Bussard thought that the assumptions in the paper were wrong. I've read the arguments both for and against and I just don't have the physics background to decide.
If it works PB11 fusion would be the ultimate power source. It would enable the hydrogen economy, space exploration and in general it would change the world.
It makes me wonder what the anti technology eco-communist crowd would find to oppose.
The answers to your questions are (1) yes, and (2) yes, if not external work is done. This part is straightforward.
The paper is more complex. He's trying to establish theoretical efficiency limits on fusion reactors that rely on nonthermal distributions of velocities of one particle, or different temperatures of two kinds of particles (e.g. electrons and ions) by calculating the least possible power that has to be expended in maintaining the nonequilibrium against the natural tendency to relax to the Maxwell distribution, i.e. the work you have to do to fight the Second Law.
I'd have to read much more of it to know if there are any reasonable criticisms. Essentially, it boils down to whether he has made a completely general e.g. thermodynamic argument, which seals the case, or whether he has made a mechanical argument that relies on a particular mechanism for maintaining nonequilibrium, in which case someone might be able to think up a new mechanism not subject to his limits.
It's a mildly interesting question, I may take the time to read the thing -- well, some of it, it's 300 pages or so -- and if I do I'll report back.
What they will oppose, Paul Breed, is that if run on D-D the thing produces neutrons which can be used to make Plutonium from U238.
Bussard said it will run on D-D easier than on p-B11.
That he feels confident enough to have an independent peer review this summer would indicate to me that the group believes they are meeting their initial goals and...
(a) need this independent verification to expand the project, and
(b) want to avoid the "cold fusion" fiasco
I can hardly wait to see what fall brings after the peer review.
>What they will oppose, Paul Breed, is that if run on
>D-D the thing produces neutrons which can be used to >make Plutonium from U238.
Cat's out of the bag. I believe that there is enough public information about the project that others could recreate it given knowledge that it actually works.
The big secret to keep or share is does it work.
Placing tinfoil hat firmly on head I ask....
Suppose that you had the perfect solution for unlimited fusion power, easy works great, makes lots and lots of neutrons. Would they keep it secret to stop proliferation? P-B11 is aneautronic, but if the system works with P-B11 then it would be an easy tweak to work with D-D making those dammed pesky neutrons....
Unlimited almost free power for the world, unlimited almost free plutonium for the terrorists...
An interesting trade off.
How convenient is it that fission can only happen with a rare and difficult to extract isotope?
Bussard stopped publishing in 1995 due to requests from Navy. In 2006 Bussard knows he is dying of cancer. Dying of cancer he is beyond the reach of man's law.
He believes that the unlimited energy is worth more than the proliferation risk, he makes personal cursade and goes off the reservation to spread the word.
Got to go now, I'm missing my daily Art Bell....
Paul Removes his tinfoil hat,he feels a strange sense of unease he can't quite place. Paul goes back out the the garage to work on his rocket.
(I submitted Rev 1.02 of my FAA experimental permit today, I have unofficial indication that it will be judged sufficiently complete., I have to fabricate one small cable to connect IIP computer to the catalyst cutoff valve and vehicle hardware is 100% complete.)
Bussard said it will run on D-D easier than on p-B11.
Neutrons/shmootrons - does the thing give off more energy than it takes to run it?
Measure the inputs, measure the outputs, compare. (Yes, I know that measuring can be non-trivial if either one is AC.)
For most of us, the goal is not fusion, it is energy production. We don't much care whether it is actually fusion or just harnessing tiny horses.
Ahhh, but energy production is a whole 'nother ball of wax. WB-7 is not going to produce any electricity. While electrical generation with a polywell is far simpler than building steam loops and turbines, it's still a bit of a challenge, and somewhat irrelevant to the issue of determining whether it *could* do so.
The first tests will be used to determine if the math works, by presence of enough evidence to estimate how much net power *could* be achieved if the power generation system was built.
In addition, I'm not sure that WB-7 would ever truly hit breakeven by itself. There's a lot of scaling involved; for commercial power plants, I've heard the 10m diameter number tossed around a lot.
It doesn't even have to make break even on energy production to be of interest to make plutonium.
Don't get me wrong, I think we need this. Proliferation is a red herring anyway. Any *government* that wants nuclear weapons will get them regardless of the method.
Some of the "no-go" results in the literature don't apply to low-Z fuels like DT, D3He, or (I think) DD. Energies are lower, the electron density is much lower (since the ions have lower charge), and the rate of free-free radiation is also strongly dependent on Z. DD also doesn't necessarily have the issues that arise from ions of different charges and masses.
Of course you have the complications of neutrons, but that's "just engineering".
There are plenty of neutron sources (for example, some isotopes and bombarding light elements with alpha particles) and one only needs the seed neutron source to start the conversion of uranium 238 to plutonium 239 in a breeder reactor. The reaction is (so I understand) self-substaining since plutonium 239 and its decay products tend to release several neutrons. If someone were really blocking D-D fusion on the basis of that, then that's highly irrational and ineffective.
Karl,
Unfortunately rationality or lack thereof doesn't seem to cut much ice when it comes to energy production. There are people who think you can run a technological civilisation on Pixie Dust and Good Intentions.
Mr Dietz seems to be backing off from his earlier stance of "it can't work because Rider said so".
"Cat's out of the bag. I believe that there is enough public information about the project that others could recreate it given knowledge that it actually works."
Indeed. I've often wondered if China (and others) are quietly watching...
If it works, the space-based applications almost scream at you. I wonder what the boron-11 abundance on the Moon is? Do we know?
Mr Dietz seems to be backing off from his earlier stance of "it can't work because Rider said so".
Not at all. Have you read Rider? He himself said his results don't rule out non-Maxwellian schemes for DT (for example). My criticism was always about the aneutronic fuels, particularly p-11B, the one Bussard pushed in the slideware. I stand by the position that that is snake oil.
>There are plenty of neutron sources
>that's highly irrational and ineffective.
When did highly irrational and ineffective.
stop the eco communists?
On a different note if it was so easy to set up a any old neutron source and make a plutonium breeder reactor why did north Korea Pakistan Iran etc... go the route of uranium centrifuges?
I think a neutron source capable of doing industrial scale U238 -> plutonium transformation is something to be worried about.
Clearly the detailed engineering to make a Plutonium weapon is a lot harder than a gun type U235 thin man device, but its also a lot smaller and hence more dangerous in terrorist hands.
On a different note if it was so easy to set up a any old neutron source and make a plutonium breeder reactor why did north Korea Pakistan Iran etc... go the route of uranium centrifuges?
Because, as you said, uranium bombs are really easy but plutonium bombs are really hard.
Yours,
Wince
Paul Dietz:
If the Bussard - Nebel machine is non - Maxwellian on D-D it will be the same on p - B11 surely? Drive voltage will change though.
This machine at least has the possibility of p - B11 fusion, unlike Tokamaks.
If the Bussard - Nebel machine is non - Maxwellian on D-D it will be the same on p - B11 surely?
The rate at which it relaxes back to a Maxwellian distribution matters, as does the rate of energy loss to and/or by electrons, as does the fusion rate. Rider's results were that the lower bounds on these losses for DT (and, I think, DD and D3He) were much less than the rate of fusion energy production, while for 'aneutronic' fuels the recirculating power to maintain the non-Maxwellian distribution was much greater than the rate of fusion energy production.
Clearly the detailed engineering to make a Plutonium weapon is a lot harder than a gun type U235 thin man device,
Boy that's a mouthful. IIRC, that (getting the implosion right) was the hardest part of the Manhattan Project.
but its also a lot smaller and hence more dangerous in terrorist hands.
It can be smaller, if you are very good at designing a perfectly -- and I mean perfectly -- spherical implosion to achieve criticality in a smaller pit. But that's difficult, especially if you don't have the capability to do a lot of testing to refine your engineering, or access to good simulation codes. "Fat Man" was actually a bit heavier, and certainly bulkier, than "Thin Man."
1D or 2D implosion, on other other hand, is quite a bit easier to arrange than 3D implosion. Planar or cylindrical shocks can be set up by flying plate techniques, without the need for explosive lenses.
The resulting device will be bulkier and less efficient than a spherically imploded one, but this may not matter for terrorists.
Say what? Paul, what the heck is a 1-D implosion? We live in a 3D world, so by me that's flat impossible. If you squish something in only one dimension -- say you squeeze it only along its length, leaving its width and depth alone -- it will just "squirt" out in the directions you're not squeezing. When you push down on a jelly sandwich, you don't get compressed jelly, you just get jelly shooting out the sides and making a mess.
If you try to confine the sides, so there's no "squirting," then of course you're back to "3D" compression. Furthermore, since at these temps and forces the material behaves pretty much like a gas, I can think of no advantage to having a non-isotropic (i.e. nonspherical) compression. There would also seem to be significant disadvantages, namely that it would be nearly impossible to keep the density constant throughout your material. That means you're either wasting energy overcompressing some of it, or wasting fissile material by undercompressing some of it, or both.
Maybe I'm misunderstanding you; if you're just talking about fast assembly, the trick you have to do with a U-235 supercritical bomb, then OK, whatever, anything will do so long as its fast enough. If you're talking about squeezing a subcritical assembly to make it go critical, which is what they do with small Pu bombs, then I'm mystified. Please explain.
Check out talk-polywell.org if you want a lot more technical detail and discussion.
About the proliferation issues: it's definitely something to consider, but if you have the technical sophistication and capability to use this (polywell) technology to create fissile materials for a nuclear bomb, you probably also have the capability of doing so without this technology.
Say what? Paul, what the heck is a 1-D implosion?
This is where a planar shock wave is used to compress a solid material along one axis. The compression you get is less than if you compress in 2 or 3 dimensions, but you do get compression.
1D compression is regularly used in laser-driven shock experiments.
If you squish something in only one dimension -- say you squeeze it only along its length, leaving its width and depth alone -- it will just "squirt" out in the directions you're not squeezing.
Matter has this wonderful property called 'inertia'. You'd get some compression before it can 'squirt', particularly if you set it up so that the initial along the direction(s) being compressed are less than the dimensions in the uncompressed direction(s).
the initial along
Missing word: ...the initial thinkness along...
Also, Carl wrote:
Furthermore, since at these temps and forces the material behaves pretty much like a gas,
Well, no, the equation of state is considerably stiffer than a gas. But even if it were a gas, it's a gas of very high density, and it cannot move out of the way too quickly without violating conservation of energy. There is only so much kinetic energy available for it to squirt with.
If you don't think 2D compression can work, btw, then you must think thermonuclear weapons don't work. They (or, at least, the ones I've read about) exploit 2D compression in a cylindrical secondary.
I believe modern newest generation US thermonuclear weapons use more complex 3D compression of the fusion secondary. The W88 nuclear warhead, for example, allegedly has a "peanut" shaped hohlraum and a spherical secondary. However, other systems which used/use 2D compression were/are most definitely functional.