Where's the beef?

[seedload]

100 million pounds is far too much to invest in an unproven concept unless its well diagnosed and tested so that the scaling laws are verified to a reasonable degree of certainty.

BTW, I have always felt that Bussard's suggestion to jump to a full scale machine was most likely a product of his personal desire to see his life long dream become a reality before the inevitability of his impending death. Given more time, I would assume he would favor at least one other less expensive step in there.

While I question Bussard's motives in some ways, I also respect his ideas. I question the quality of his papers on the subject but I understand the circumstances under which he tried to get this info out there. It is hard to be critical of a man who was dying.

I am very impressed with Dr Nebel. He left on leave from some pretty interesting work with a well respected institution to do this. I fail to see the motivation in that move if it is based on some crackpot ideas. He must believe that it is not. Further, he isn't pussy footing around. He wants to make a machine and show it to the scientific community and get it properly peer reviewed. Heck he wants to build machines and give them out to said community. He is way up front about it. And he isn't over hyping anything. He wants this properly looked at. Until you find that he hasn't followed through on this promiss, you must respect the way he has conducted himself.

I await the WB7 results and then suspect we will see and incrementally larger design at some intermediate scale that leaves you the majority of your 100 million pounds.

<joke>
Come to think of it, it won't use ANY of your 100 million pounds. It will be built with good old American dollars!
I say that Brits and Germans really shouldn't worry about what we Americans spend our dollars on Except, of course, when it is to save one of you from the other ... again
</joke>

[Art Carlson]

Hmmmm, no. Remember, WB trapping was not just discovered in WB-6. It goes all the way back to SCIFE and includes the intermediate machines. The counts are only one piece of evidence.

What is the other evidence? Where is it published?

[Art Carlson]

My personal favorite longshot for fusion energy is the Field-Reversed Configuration.

Field Reversed Configuration - you mean something like these guys are working with -

A High Density Field Reversed Configuration Plasma for Magnetized Target Fusion - Intrator, Park and co - http://fusionenergy.lanl.gov/Documents/ ... tor03f.pdf - vis:

'...Significant progress towards a target plasma
has been achieved, with FRC parameters within a factor of 2-3
of the design goals.....'

sounds promising - so long as you don't mind changing the imploding Aluminium liners a few thousand times a second.

Your reference refers to a rather special incarnation, but that's the same species. I'd rather go the other direction and make a steady-state FRC. You'd have to figure out current drive, but that might be possible with neutral beams, rf waves, or merging. The joker is whether they will still be stable when you make them big. Theoretically even small ones should flip over, but for some reason they don't.

So you are suggesting that 'theoretically' IEC per se can't work at Q>1 (though contrary theories still abound it seems)?

That's what I believe, but it's tough to prove that no conceivable configuration can work.

I'd love to see experiment prove you wrong of course, though I feel we would somehow be cheated of a victory if we couldn't provide a conclusive and convincing theoretical model ahead of any real positive outcome.

I would also love to see an experiment prove me wrong.

Maybe I'm just stuck on Bussards quote - '...the heavens are filled with billions of fusion reactors, and not one of them is toroidal...' - (nor cylindrical i think). Hence its hard to shake a gut belief/hope that 1/r^2 has got to have some intrinsic usefulness in our endeavor.

Just remember that a smallish tokamak running on deuterium has a power density comparable to the sun. If it came down to having a tokamak or a star in your back yard, which one would you think is the better concept?

Can you point me to any more up to date results/methods wrt FRC?

I've been out of the field for a looong time, so I can't say much about the current state or the best reviews. Google seems to turn up a lot, like this white paper.

[MSimon]

The power density of the sun is pitiful. Microwatts per cc of volume.

BFRs will be running in a watts to multi watts per cc regime. If it works.

Solar radius:
6.955E8 m (6.995E10 cm)

4/3 pi r^3 = 1.433678e+33 cc

Solar Output = 3.83E26 Watts

**************************

2.67E-7 W/cc

Pitiful.

[scareduck]

Art's loss-bucket arithmetic is certainly interesting, and perhaps compelling.

I would certainly like to see Dr. Nebel respond.

[Art Carlson]

The power density of the sun is pitiful. Microwatts per cc of volume.

That was my point. Stars are a lousy example to follow.

[rcain]

I've been out of the field for a looong time, so I can't say much about the current state or the best reviews. Google seems to turn up a lot, like this white paper.

Thanks for that Dr Carlson, I shall certainly give it a good read through.

A very nice looking approach here - circa 2000 - 'Thick Liquid-Walled, Field- Reversed Configuration - R. W. Moir, R. H. Bulmer & co - https://e-reports-ext.llnl.gov/pdf/240026.pdf (though design concept only so far I think, part of APEX - Advanced Power Extraction programme at LLNL).

Now why on earth hasn't this been built yet?

I can certainly see major advantages in a FRC design - not least of which; it seems actually (slightly) simpler than Polywell to analyse and understand, its smaller and easier to build (theoretically), and there is even an early feasibility paper by Nasa on rocket motor applications - here (1990) - http://ntrs.nasa.gov/archive/nasa/casi. ... 018903.pdf (how quaint - I'm sure Bussard would have approved).

If my small brain understands it right, it takes fuel in one end, holds it, compresses it (mightily), then spews exhaust out the other end - eminently practical my dear Dr Carlson...

As to...

If it came down to having a tokamak or a star in your back yard, which one would you think is the better concept?

well, I think it depends on what sort of box it came in, Vs the spot price on scrap metal at the time.

[TallDave]

Hmmmm, no. Remember, WB trapping was not just discovered in WB-6. It goes all the way back to SCIFE and includes the intermediate machines. The counts are only one piece of evidence.

What is the other evidence? Where is it published?

There should be a pile of data over at EMC2. Bussard was under a gag order for most of that time and could not publish. Inconvenient, yes, but I'll give him the benefit of the doubt at least for the moment.

I'm sure this will all come out in the WB-7 review.

[TallDave]

Now why on earth hasn't this been built yet?

They got $45M from Paul Allen's VC company and may be building it as we speak.

[rcain]

Now why on earth hasn't this been built yet?

They got $45M from Paul Allen's VC company and may be building it as we speak.

Thanks for the info TallDave - I shall certainly be keeping a weather-eye from now on - any idea of their project plan/timescales?

[TallDave]

rcain: Their spokesperson said "more than five but less than fifteen" years.

Google Tri-Alpha for more.

[blaisepascal]

The power density of the sun is pitiful. Microwatts per cc of volume.

Solar radius:
6.955E8 m (6.995E10 cm)
4/3 pi r^3 = 1.433678e+33 cc
Solar Output = 3.83E26 Watts
**************************
2.67E-7 W/cc

Pitiful.

It's not that bad... Only the core is a significant fusion source, which is about 1/5th the size of the rest of the sun. So your 2.67E-7 W/cc is boosted by a factor of 125, or 33.4E-6 W/cc. Much better .

[dch24]

Plus, the energy transport is very slow:

The high-energy photons (gamma rays) released in fusion reactions are absorbed in only few millimetres of solar plasma and then re-emitted again in random direction (and at slightly lower energy)—so it takes a long time for radiation to reach the Sun's surface. Estimates of the "photon travel time" range between 10,000 and 170,000 years.[35]

[Aero]

WB-7 is funded by the navy, isn't it? Is that the same navy that slapped a gag order on Dr. Bussard? Do we have any assurance that Dr. Nebel won't be gagged the same way? I guess I'm trying to ask a question.

Do we know that we will get information about WB-7 experimental performance later this year, or are we just hoping that we will?

[jmc]

While I question Bussard's motives in some ways, I also respect his ideas. I question the quality of his papers on the subject but I understand the circumstances under which he tried to get this info out there. It is hard to be critical of a man who was dying.

Bussard was very creative and imaginative and indeed perhaps we shouldn't be too harsh about mistakes he made on a paper he scribbled out while he was ill of health with cancer.

BTW
Stop going on about IEC being shaped like the sun and tokamaks not being shaped like the sun!!!

I'M SICK OF IT! It's nothing more than a purile dirt slinging contest that oversimplifies the issue of energy confinement in fusion devices to the point of insanity and has nothing to do with any real issues with regard to the feasibility of either devices.


I support Dr. Nebels further investigation, I don't think we have anything like enough information to rule out the Polywell as a viable fusion concept, and to be honest I don't think anyone here, including myself, knows enough about them to rule them out. I just don't like them being oversold with inadequate evidence.

Dr. Nebel is taking a correct conservative approach in attempting to investigate them as rigorously as possible, he is also not trying to derrail ITER or shut down the other tokamak programmes.

I support a pluralistic approach to fusion until one design delivers the goods in the sense of economic power as opposed to net power.