Sunday, August 23, 2009

A Word For The Sceptics

I was looking at the comments to my American Thinker article Fusion Energy and came across an interesting sequence of comments I had missed earlier. The first comment is by a sceptic. There are earlier comments by him in the comment section.
Posted by: WR Jonas Jun 19, 01:18 PM

I have spoken out here about my skepticism based on a provable dynamic and truth. There will always be ample reasons to spend other peoples money. To give this research or any other some noble purpose or cause does not necessarily make the aims correct or worthwhile.

If we were still shooting rockets at the moon and coming up empty or failed we would have stopped it a long time ago. This canard of ,try until we run of money, is the basis for continuing a proven failure. Because it is Navy project doesn't give it any greater chance of success.

So , how about we put the fusion research industry on a time, results or dollar limit to see if it is ever going to produce anything. Any takers?
I added the emphasis. And then there is a reply to the question by Rick Nebel:
Posted by: rnebel
Jun 23, 04:11 PM

Mr. Jonas:

I'll take you up on that.
It seems Rick is confident of getting a yes/no answer on time and within budget for the question "Is it worthwhile to scale up the Polywell Fusion Concept to the size of a modest (~100 Megawatts) net power reactor?

And what is Rick's time frame? The answer Rick gives is "We Will Know In Two Years."

You can learn the basics of fusion energy by reading Principles of Fusion Energy: An Introduction to Fusion Energy for Students of Science and Engineering

Polywell is a little more complicated. You can learn more about Polywell and its potential at: Bussard's IEC Fusion Technology (Polywell Fusion) Explained

The American Thinker has a good article up with the basics. (same article referenced above)

Why hasn't Polywell Fusion been fully funded by the Obama administration?


isochroma said...

First, my hope that Polywell like all other fusion attempts will be a failure.

Second, my prediction that it will be a failure based on either science, market or politics or more.

Third, if Polywell succeeds, it will be used by the US military to continue their program of violent aggression, rape, plunder, and despoliation of land and peoples for many hundreds if not thousands more years to come.

M. Simon said...

Third, if Polywell succeeds, it will be used by the US military to continue their program of violent aggression, rape, plunder, and despoliation of land and peoples for many hundreds if not thousands more years to come.

I'm encouraged by your prediction of an American Empire lasting at least many hundreds of years if not many thousands if Polywell can be made to work.

Devin said...

Nuclear Fusion, unlike the process of nuclear fission (which makes the Atomic Bomb and Hydrogen Bombs work), is not self-sustaining. That means if you remove power from the system or stability is compromised, the reactions will "fizzle out." This is very simply due to the fact that "fission" is the process of releasing energy by-way of splitting large isotopes whereas "fusion" is the process of releasing energy by-way of joining them. Thus, fission self-propagates until the energy density diffuses to a level that is lower than what is required to split neighboring isotopes, meanwhile fusion requires near-constant power-input to maintain the electron-cloud density in the potential well.

Devin said...

or, in other words... "Fusion cannot be used as a weapon (directly)"

Travis said...

Wow, lots of mis-information here.

1) Hydrogen bombs work via fusion. They detonate a fission core to compress deuterium and tritium to fusion conditions (density and temperature) and then you get a tremendous release of energy.

2) Fission is a lot easier than fusion. There are natural fission reactors on earth where the mass of unenriched uranium + water is slightly critical to sub-critical. There's no such place on earth where fusion can occur naturally. Trying to re-create the conditions of the sun, either with magnetic field, lasers or the polywell, is a pretty robust physics and engineering challenge.

3) Fusion can be self-sustaining depending upon the set-up. Most burning fusion concepts thought to be self-sustaining (eg-alpha heating and boot strap current). The sun being the prime example.

Devin said...

Um, no "misinformation" here, Travis. You need to read more carefully.

1) I state that "fission... makes the ... Hydrogen Bomb work". Without compression of the fissal material at the core, there is no subsequent fusion event. Thus the statement that "fission is required to make a functioning Hydrogen bomb" is still very valid (despite neglecting to say that Fusion is also required). However, I feel it perfectly acceptable to omit the statement "Fusion is required to make a functioning Hydrogen bomb" because (a) the point of my statement was that Fusion (by itself) cannot be used as a weapon (directly) and (b) this should already be a given (as the "Hydrogen Bomb" is thusly named for its process of fusing Hydrogen atoms [producing Helium]). If you build a Hydrogen bomb that fails to achieve fusion, you still have a very powerful weapon due to the fission of Uranium-235 or Uranium-238 (note that, though Plutonium can be used, it is rarely, if ever, the "primer"; it is a common misconception that the original A-Bombs developed at Los Alamos where Uranium and Plutonium respectively; the first was U-238 and the second was Plutonium in a Beryllium shell with a U-235 "primer"; so essentially, both Atomic bombs are Uranium based, one with a Plutonium enhancement), whereas if you make a Hydrogen bomb that fails to reach critical fission, you have a dud. Oh, and by the way, the modern Hydrogen Bomb is actually a fission-fusion-fission process, not just-fission, just-fusion, or fission-then-fusion (or vice-versa), but fission, followed by fusion, followed by more fission.

2) Agreed, but I'm confused as to how this contradicts anything that I said. You are correct, sir, on all accounts.

3) Yes, the sun is a good example of a self-sustaining system that exhibits fusion (energy released by fission further increases the energy/matter density to the point where fusion is possible, releasing further energy in the form of Alpha particles, etc... thermonuclear physics in effect). I don't know if I would go so far as to say that "fusion is self-sustaining" however. Fission on the other-hand, exhibits the property that it's own release of energy through the decay of the weak nuclear force is further utilized in a self-propagating manner. Fusion exhibits no such property (in which the newly released Alpha particle cannot be used directly to cause another fusion event). Thus, fusion can be sustainable, but it is not sustained by itself (fission, a wholly different concept than fusion, or some other form of high-energy physics, is required to achieve fusion).

Any *perceived* "misinformation" was merely that.

Travis said...

My second point was directed at isochroma. Just b/c we haven't made fusion work yet, doesn't mean we should abandon it yet. Especially given the money that was thrown at fission/atomic weapons/nuclear submarines to get nuclear power to where it is today compared to the money put into controlled fusion research.

Devin, you stated that, "Nuclear Fusion, unlike the process of nuclear fission (which makes the Atomic Bomb and Hydrogen Bombs work), is not self-sustaining. That means if you remove power from the system or stability is compromised, the reactions will "fizzle out.""

Hence my comments that fusion can be self-sustaining via boot strap current and alpha heating. I agree this isn't the same self-sustaining as in fission with a nuclear chain reaction. But is self sustaining none-the-less. Theoretically, fusion can be sustained with out any external power or "other high energy physics" required once the plasma is burning. The caveat being that it's theoretical since we've never produced a self-sustaining, burning plasma on earth. That's ITER's biggest goal though even it may not be totally self-sustaining/may not work in practice.

There's other information in your last post that is incorrect. There is no way the Uranium bomb from the manhattan project was U-238 based. It may have contained U-238, but U238 isn't a fissile material. A large part of the Manhattan project was learning how to enrich uranium such that it was 90-95% U235/5-10% U238.

As for the other nuclear weapons details ... I'm no expert on that and won't venture into that area. But I'd be interested in seeing data (and I'm sure it exists, somewhere) from weapons where the fissile portion of the bomb worked but the fusion portion failed. The majority of a hydrogen bombs energy is released in the fusion reaction not fission. I don't know enough about modern weapon design to say what the weapons yield would be if something like that occurred.

Devin said...

Ah, so when people say that the bomb was U-235/238, they mean "almost entirely 235" rather than "a combination of" or "separate quantities of".

It often seems that there's a lot of common misconceptions out there relating to thermonuclear weaponry physics (as I point out my own misconceptions; thanks for clearing that up for me).

As for fusion sustainability via bootstrap current and alpha heating... definitely a plausible technique for stabilizing the plasma cloud at high densities, but I think I recall reading that Bussard and Nebel were working on a way to convert the released alpha particle directly into electrical current, gaining efficiency by eliminating the waste produced by heat/energy conversion. That is to say that such a mechanism (which I believe to be documented somewhere in something I read from Bussard) would eliminate the need to use a steam turbine or other inefficient mechanism for getting energy out of the system and converting it to electrical power for a nation-wide grid. I hope that it works, and would be a huge step toward achieving a self-sustained plasma for fusion.

All around, I'm definitely anxious to see if they (Nebel and team) can achieve Bussard's plans for a pB11 reactor. Such a reactor, utilizing liquid He3 to cool the super-conducting magnet toroids and direct alpha conversion,... the machine could sustain the fusion process as long as we keep putting pB11 fuel in (since the final product of the pB11 fusion event, after the carbon decays, is He3, which can be [re]used in the SC magnets; of course the current gained from converting the alpha particle can be fed directly back into the electrical needs of the unit). Not to mention that pB-11 doesn't produce dangerous neutron radiation, unlike DD/DT, which destroys the machine in the long run.

I've been following the Polywell storyline (of what little is published regarding their progress) for some years now, and do believe it to be the only real valid attempt at net-producing fusion-energy. Personally, I think the Tokamak, though may teach us something valuable, is likely to prove a waste of time and energy (and money; or at least not worth those things compared to what we learn from ITER).

I would say "it's sad that Polywell hasn't been funded", but I think it currently is being funded by the Navy (hoping to produce WB8 and WB8.1), though I sure would like to know what is going on. For now, all we can do is speculate that "no news is good news" and the fact that it continues to get funding over the years is a good sign.


Loren said...

fission-fusion-fission weapons worked by using the fusion reaction to fission the U-238 tamper wurrounding the fusion stage. Most of hte energy from these devices was from the second fission stage. Modern H-bombs work with a fission trigger just poerful enough to set off the fusion stage, and the second fission stage is optional, producing a bomb that will get most of its energy from fusion.

The trinity shot and fat man(?) were plutonium bombs. They used a small "initiator" which helped increase the neutron flux, boosting efficiency, but the energy was gotten from plutonium fission. Little Boy used a similar initiator. Both bombs had a tamper surrounding them to bounce neutrons back inside, and to hold the bomb together for a few more split seconds, increasing the yield.

If isochroma really thinks that anything can keep the US empire together at this point, let alone for another century or more, he's crazy.

Robert said...

Oooh... These ideal compact and mobile reactors can be dedicated for hydrogen and desalinization plants, as well as powering maglev and even full blown supersonic vactrain rails that will replace the atmospheric heating jumbo jets.