What are the breaktrhrous required for the Polywell to work?

[Breakable]

Breakable,
I think it is more like 300+ toks give you a 50% chance. It is not like taking marbles out of a basket.

Mine is a very optimistic prediction when each Tocamac-like-project is exploring some different approach.
On the other hand it is possible to build 500 identical machines and not learn anything.
50% chance sounds a little more realistic

[D Tibbets]

The correct formula should be to multiply all probabilities (instead of averaging them as I thought before), so the outcome is:

Polywell
0.05*0.001*0.001*0.00001*0.5 *100% = 0.000000000025%

Tokamak
0.05*0.2*0.4*0.8 *100% = 0.32%

ICF
0.001*0.01*0.2*0.5*0.02*0.5 *100% = 0.000001%

DPF
0.05*0.2*0.2 *100%=0.2%



So the conclusion is that we just need another 500 DPF or 312.5 Tokamaks and we should be there with 100% probability. Alternatively we just need one very very very lucky Polywell

Anyone cares to discuss the odds?

Keep in mind that the predictions, at least for the Polywell, is from an outsiders perspective that is starved for data. The confidence of insiders is presumably based on potentially much more/different detailed knowledge. That is part of the fun of speculation. With details it becomes more mundane, whether plus or minus.

Dan Tibbets

[Breakable]

Yes, I wish there were more details available. Unfortunately the Polywell contract does not let them disclose any details. On the other hand an outsider could be more objective when evaluating a number of approaches.

[TallDave]

Eh, the odds are all pretty arbitrary.

Personally I think Polywells are about 10x as likely as tokamaks to be economical producers of energy within 50 years. I would say FRCs are about half as likely as Polywells, and DPFs are a hundred times less likely.

[chrismb]

Eh, the odds are all pretty arbitrary.

Personally I think Polywells are about 10x as likely as tokamaks to be economical producers of energy within 50 years. I would say FRCs are about half as likely as Polywells, and DPFs are a hundred times less likely.

Now, that's a different quesiton again, but, yes, so far only I have ventured a few punts at likelihoods. What do you see as the big issues, and the probability of their resolution?

[D Tibbets]

Yes, I wish there were more details available. Unfortunately the Polywell contract does not let them disclose any details. On the other hand an outsider could be more objective when evaluating a number of approaches.

Everything is realitive (where have I heard that before?). It depends on how you define an outsider. Someone like me with my modest knowledge (coff!) is definatly and outsider. A plasma physist or expert in electrostatics is less so. But, only those with an intamate knowlege of the data, and perhaps expertise could be considered a true insider.
My impression of "outsiders" making decisions are politicians depending on reported climate warming predictions in which the methods and honest confidence levels are not disclosed. Even those who are considered insiders can jump to subsequently disproven conclusions. I have been mildly amused by the firm convictions expressed by human evolutionests. Things like humanoids walked upright because they evolved in grasslands and had to see over the grass, Hand development led to tool use. both now in disfavor based on the newest research. The enviornment was much more unstable and varied, no evidence of stone toolmaking has been found untill a larger brain size developed and long after human like hands had developed. And don't forget Einstin's mistakes, steady state, Heisenberg's insistance that fission bombs were impossible (opinion possibly based on political reasons). Most meteor craters were thought to be volcanic in nature till clarified by Shoemaker. Reverse field configuration plasmas were concidered unstable till disproved. And, in the late 19th century, after Maxwell's work, the contention by at least some experts that all knowledge had been obtained and science (physics?) was at the end of the road ( a myth, I don't know if it is true).
So, skepicism is appropiate when listening to outsiders or insiders. Just make sure you answer test questions that conform to the experts view, but keep in mind the answer may change in 10 years.

Dan Tibbets

[TallDave]

chris,

As you say, the unknown unknowns are the killer. I suspect that if Polywell doesn't work it will be for reasons we don't expect. So I'll try to stick with the big issues.

The major question mark in Polywell is the loss scaling. (Rick didn't seem concerned about the vacuum pumping, and since we don't know how the arcing works and he has the data...) There are reasons to think (or at least hope) Bussard was right about it.

The big problem with toks is low beta. Even the ARES designs have lower power density than fission nukes. Stellerators are even worse in my understanding, and vastly more complex, and have higher losses.

We know even less about FRCs than we do about Polywells. I suspect compact toroids in or out of a cylinder are not the way to go, though.

DPF, electrode erosion. Haven't heard anything to suggest they can solve it.

Piston-driven fusion (General Fusion approach) -- it just sounds crazy. It probably is. I'll still pay money to see a prototype in action, though.

[Art Carlson]

We know even less about FRCs than we do about Polywells.

That is flat-out wrong. A small community, but consisting of several scientists at each of 3 or 4 different sites, has been building, measuring, simulating, theorizing, and publishing on FRCs for decades. The little we know about polywells is pitiful in comparison, not even a single publication of a confinement time on one machine at one set of conditions.

[Breakable]

I would consider an outsider someone that has intimate knowledge of plasma physics, but does not work on a specific problem. It makes little sense to ask shoe salesman to evaluate a physics project if he does not have the education. Of course it would be good if the expert has an understanding of the limitations of his knowledge, and is unbiased.
But in any case crowd-sourcing (if properly done) could cancel-out most of the preexisting biases, and fill in the gaps in knowledge.

[TallDave]

Art,

Well, yes and no. In terms of papers, sure (but one could argue IEC research similarly tends to apply to Polywell). In terms of how the attempt to build a net power reactor is going, no. The Tri-Alpha guys aren't releasing anything afaik. Bussard at least gave some talks explaining the concept before he died, and the Navy contracts are public.

We might hear something next year.