[Henning]

Rezwan wrote: We’ll have to set up a “Brian Bingo” game.

I’m all for it.

[Henning]

jamesr wrote:

I thought that with these very large currents the majority of the current flows on the outside of the electrode rather through the conductor anyway??

Exactly – that’s the problem. The current flows through a thin surface layer & hence all the resistive heating is concentrated there. Although it is the fast rise time (ie frequency) or the current flow that causes it to flow in the skin.

Isn’t only the charge located on the surface, being static? Why do I need on the other hand big copper wires to transport current over land lines? If that would be the case, a thin pipe of copper could replace solid copper lines, thus decreasing costs. Okay, they’re aluminium anyway…

Therefore I think the 20nm skin wouldn’t suffice. Correct me if I’m wrong. I’d love to be wrong here!

Okay, James quotes a different analysis here:

jamesr wrote:
I’m not sure I can go as far as percentages but here are a few figures from analysis done by Doug Olsen in 2003 (not verified):

For a copper anode, if the current is treated as a 1/4 sinusoidal rise to 600kA in 2us the skin depth is ~0.18mm. Integrating the current as a function of radius gives a maximum temperature rise of ~26C at the surface – for one shot. This diffuses into the bulk of the anode over time so after 40us or so the surface has dropped to 15C above its pre-shot temperature.

[Henning]

Colonising deserts is much more doable and desirable than any onwater or underwater scenarios.

Onwater land-maintenance is expensive (boats, tanks, or what), for a desert that’s free. Desalination is needed for both. Desert colonies need water transported by pipelines, but so does New York.

Doesn’t rule out a onwater/underwater/inspace tourist resort. But there self-sustainability is not a real goal.

[Henning]

nemmart wrote: Also, I think in Eric’s google tech talk, he mentioned 330 hz.

No, that 330Hz is just a fantasy-value developed within this forum on the base that the American Electrical System (tm) has a cycle of 60Hz. The rest of the world uses 50Hz, therefore a rate of 300Hz or 350Hz would be correct for the World’s Electrical System (tm). It was introduced for eliminating output capacitors. Eric talks about a variable rate of up to 1kHz.

For embedded systems (ie. aeroplanes) without any external connection this requirement does not apply at all.

It is even benifitial to synchronise the shot frequency with rounds of the propeller.

[Henning]

Glenn Millam wrote: You wouldn’t want to put FFs on an airplane. X-ray shielding alone will make the weight prohibitive.

That’s the neutron shielding that requires that heavy water (1 ton per m^3), but that compensates the tons of fuel required.

See also here in the forums: Space and Aerospace Design in a Focus Fusion World

[Henning]

Or maybe Deuterium and Bor-10? With higher Deuterium contents? So first D-D reacts to T + p and He-3 + n, providing initial boost for D + B-10 reactions? Possibly the energy for the neutrons is wasted, though.

[Henning]

Brian H wrote: We’re in the coldest part of the interglacial since about 10,000 years ago (see attached graph).

Nice cherry-picking.

[Henning]

I don’t follow this discussion because it disgusts me, but there’s a quite fitting article on Ars Technica:

When science clashes with beliefs? Make science impotent.

Okay, I’m telling you “read this”, whilst not reading what you’ve written above. Yes I know, it’s quite ignorant, but that’s how I am. And it’s how everyone here is…

[Henning]

Maybe something like “Civilization” can be used too. It simulates an civilization from 4000 BC until 2100 AD. Fusion Energy is part of the achievable technology advances you can develop whilst playing.

There is an open source implementation called FreeCiv. Maybe it is possible to get them implementing a “grassroots fusion device”? A DPF? Requirements: Internet, Grassroots Collaboration, Search Engine, Plasma Physics.

BTW:
Question: What do you get, if you’re convincing people that energy will be eventually free?
Answer: They will waste more energy now, because tomorrow it will be free anyway. But how far is that tomorrow away? One year? Ten years? Fifty years? Thousand years? Million years? After the sun dies?

[Henning]

Continued from previous post:

Much more can be, and has been, said by the world’s scientific societies, national academies, and individuals, but these conclusions should be enough to indicate why scientists are concerned about what future generations will face from business-as-usual practices. We urge our policy-makers and the public to move forward immediately to address the causes of climate change, including the un restrained burning of fossil fuels.

We also call for an end to McCarthy-like threats of criminal prosecution against our colleagues based on innuendo and guilt by association, the harassment of scientists by politicians seeking distractions to avoid taking action, and the outright lies being spread about them. Society has two choices: We can ignore the science and hide our heads in the sand and hope we are lucky, or we can act in the public interest to reduce the threat of global climate change quickly and substantively. The good news is that smart and effective actions are possible. But delay must not be an option.

P. H. Gleick,* R. M. Adams, R. M. Amasino, E. Anders, D. J. Anderson, W. W. Anderson, L. E. Anselin, M. K. Arroyo, B. Asfaw, F. J. Ayala, A. Bax, A. J. Bebbington, G. Bell, M. V. L. Bennett, J. L. Bennetzen, M. R. Berenbaum, O. B. Berlin, P. J. Bjorkman, E. Blackburn, J. E. Blamont, M. R. Botchan, J. S. Boyer, E. A. Boyle, D. Branton, S. P. Briggs, W. R. Briggs, W. J. Brill, R. J. Britten, W. S. Broecker, J. H. Brown, P. O. Brown, A. T. Brunger, J. Cairns, Jr., D. E. Canfield, S. R. Carpenter, J. C. Carrington, A. R. Cashmore, J. C. Castilla, A. Cazenave, F. S. Chapin, III, A. J. Ciechanover, D. E. Clapham, W. C. Clark, R. N. Clayton, M. D. Coe, E. M. Conwell, E. B. Cowling, R. M Cowling, C. S. Cox, R. B. Croteau, D. M. Crothers, P. J. Crutzen, G. C. Daily, G. B. Dalrymple, J. L. Dangl, S. A. Darst, D. R. Davies, M. B. Davis, P. V. de Camilli, C. Dean, R. S. Defries, J. Deisenhofer, D. P. Delmer, E. F. Delong, D. J. Derosier, T. O. Diener, R. Dirzo, J. E. Dixon, M. J. Donoghue, R. F. Doolittle, T. Dunne, P. R. Ehrlich, S. N. Eisenstadt, T. Eisner, K. A. Emanuel, S. W. Englander, W. G. Ernst, P. G. Falkowski, G. Feher, J. A. Ferejohn, A. Fersht, E. H. Fischer, R. Fischer, K. V. Flannery, J. Frank, P. A. Frey, I. Fridovich, C. Frieden, D. J. Futuyma, W. R. Gardner, C. J. R. Garrett, W. Gilbert, R. B. Goldberg, W. H. Goodenough, C. S. Goodman, M. Goodman, P. Greengard, S. Hake, G. Hammel, S. Hanson, S. C. Harrison, S. R. Hart, D. L. Hartl, R. Haselkorn, K. Hawkes, J. M. Hayes, B. Hille, T. Hökfelt, J. S. House, M. Hout, D. M. Hunten, I. A. Izquierdo, A. T. Jagendorf, D. H. Janzen, R. Jeanloz, C. S. Jencks, W. A. Jury, H. R. Kaback, T. Kailath, P. Kay, S. A. Kay, D. Kennedy, A. Kerr, R. C. Kessler, G. S. Khush, S. W. Kieffer, P. V. Kirch, K. Kirk, M. G. Kivelson, J. P. Klinman, A. Klug, L. Knopoff, H. Kornberg, J. E. Kutzbach, J. C. Lagarias, K. Lambeck, A. Landy, C. H. Langmuir, B. A. Larkins, X. T. Le Pichon, R. E. Lenski, E. B. Leopold, S. A. Levin, M. Levitt, G. E. Likens, J. Lippincott-Schwartz, L. Lorand, C. O. Lovejoy, M. Lynch, A. L. Mabogunje, T. F. Malone, S. Manabe, J. Marcus, D. S. Massey, J. C. McWilliams, E. Medina, H. J. Melosh, D. J. Meltzer, C. D. Michener, E. L. Miles, H. A. Mooney, P. B. Moore, F. M. M. Morel, E. S. Mosley-Thompson, B. Moss, W. H. Munk, N. Myers, G. B. Nair, J. Nathans, E. W. Nester, R. A. Nicoll, R. P. Novick, J. F. O’Connell, P. E. Olsen, N. D. Opdyke, G. F. Oster, E. Ostrom, N. R. Pace, R. T. Paine, R. D. Palmiter, J. Pedlosky, G. A. Petsko, G. H. Pettengill, S. G. Philander, D. R. Piperno, T. D. Pollard, P. B. Price, Jr., P. A. Reichard, B. F. Reskin, R. E. Ricklefs, R. L. Rivest, J. D. Roberts, A. K. Romney, M. G. Rossmann, D. W. Russell, W. J. Rutter, J. A. Sabloff, R. Z. Sagdeev, M. D. Sahlins, A. Salmond, J. R. Sanes, R. Schekman, J. Schellnhuber, D. W. Schindler, J. Schmitt, S. H. Schneider, V. L. Schramm, R. R. Sederoff, C. J. Shatz, F. Sherman, R. L. Sidman, K. Sieh, E. L. Simons, B. H. Singer, M. F. Singer, B. Skyrms, N. H. Sleep, B. D. Smith, S. H. Snyder, R. R. Sokal, C. S. Spencer, T. A. Steitz, K. B. Strier, T. C. Südhof, S. S. Taylor, J. Terborgh, D. H. Thomas, L. G. Thompson, R. T. TJian, M. G. Turner, S. Uyeda, J. W. Valentine, J. S. Valentine, J. L. van Etten, K. E. van Holde, M. Vaughan, S. Verba, P. H. von Hippel, D. B. Wake, A. Walker, J. E. Walker, E. B. Watson, P. J. Watson, D. Weigel, S. R. Wessler, M. J. West-Eberhard, T. D. White, W. J. Wilson, R. V. Wolfenden, J. A. Wood, G. M. Woodwell, H. E. Wright, Jr., C. Wu, C. Wunsch, M. L. Zoback

* To whom correspondence should be addressed. E-mail: petergleick@pacinst.org

Notes

* 1. The signatories are all members of the U.S. National Academy of Sciences but are not speaking on its behalf.
* 2. Signatory affiliations are available as supporting material at http://www.sciencemag.org/cgi/content/full/328/5979/689/DC1.

[Henning]

On this subject an open letter from 255 members of the US National Academy of Sciences, including 11 Nobel laureates, was published in Science Magazine:

Climate Change and the Integrity of Science

We are deeply disturbed by the recent escalation of political assaults on scientists in general and on climate scientists in particular. All citizens should understand some basic scientific facts. There is always some uncertainty associated with scientific conclusions; science never absolutely proves anything. When someone says that society should wait until scientists are absolutely certain before taking any action, it is the same as saying society should never take action. For a problem as potentially catastrophic as climate change, taking no action poses a dangerous risk for our planet.

Scientific conclusions derive from an understanding of basic laws supported by laboratory experiments, observations of nature, and mathematical and computer modeling. Like all human beings, scientists make mistakes, but the scientific process is designed to find and correct them. This process is inherently adversarial—scientists build reputations and gain recognition not only for supporting conventional wisdom, but even more so for demonstrating that the scientific consensus is wrong and that there is a better explanation. That’s what Galileo, Pasteur, Darwin, and Einstein did. But when some conclusions have been thoroughly and deeply tested, questioned, and examined, they gain the status of “well-established theories” and are often spoken of as “facts.”

For instance, there is compelling scientific evidence that our planet is about 4.5 billion years old (the theory of the origin of Earth), that our universe was born from a single event about 14 billion years ago (the Big Bang theory), and that today’s organisms evolved from ones living in the past (the theory of evolution). Even as these are overwhelmingly accepted by the scientific community, fame still awaits anyone who could show these theories to be wrong. Climate change now falls into this category: There is compelling, comprehensive, and consistent objective evidence that humans are changing the climate in ways that threaten our societies and the ecosystems on which we depend.

Many recent assaults on climate science and, more disturbingly, on climate scientists by climate change deniers are typically driven by special interests or dogma, not by an honest effort to provide an alternative theory that credibly satisfies the evidence. The Intergovernmental Panel on Climate Change (IPCC) and other scientific assessments of climate change, which involve thousands of scientists producing massive and comprehensive reports, have, quite expectedly and normally, made some mistakes. When errors are pointed out, they are corrected. But there is nothing remotely identified in the recent events that changes the fundamental conclusions about climate change:

(i) The planet is warming due to increased concentrations of heat-trapping gases in our atmosphere. A snowy winter in Washington does not alter this fact.

(ii) Most of the increase in the concentration of these gases over the last century is due to human activities, especially the burning of fossil fuels and deforestation.

(iii) Natural causes always play a role in changing Earth’s climate, but are now being overwhelmed by human-induced changes.

(iv) Warming the planet will cause many other climatic patterns to change at speeds unprecedented in modern times, including increasing rates of sea-level rise and alterations in the hydrologic cycle. Rising concentrations of carbon dioxide are making the oceans more acidic.

(v) The combination of these complex climate changes threatens coastal communities and cities, our food and water supplies, marine and freshwater ecosystems, forests, high mountain environments, and far more.

To be continued in next post.

[Henning]

I mean you would need something like rapid prototyping for the anode/cathode to include cooling structures. The electrodes would need an uniform material (beryllium, or boron, or…) with a low number of protons. Just because of the complex inner shape of the electrodes rapid prototyping is preferable.

Then on the other hand for the x-ray capturing, layers of different materials are needed. That’s what laminating provides well. And as Tulse writes, a box constructed out of flat panels would be fine, but it still needs cooling channels running through. We just call it the onion, because of its layers (okay maybe also the shape on Torulf’s pictures, but this seems secondary).

Aeronaut: If you mean chemical vapor deposition with CVD for building the x-ray capturing device this could also work. So laminating and CVD would be two solutions to the problem the x-ray converter poses. Maybe even combine these two steps, first do laminating for the outer layers, and then continue with CVD.

Did I sound like I was ruling out that possibility? Wasn’t my intent. Yes, you’re right, we also discussed x-ray capturing in that other thread. Maybe I’ve confused it with rapid prototyping for the onion in one go.

[Henning]

benf wrote: Ah, I see this subject has already been discussed in a previous thread, “New Anode Cooling ‘Limits’ Likely”, so I’ll stop being redundant with my 2 cents. Glad to see you all have been thinking about material impacts.

Actually the “New Anode Cooling ‘Limits’ Likely” thread is about the construction and cooling of the electrodes. But the x-ray capturing onion needs cooling too, and it’s not going to work with rapid prototyping, one needs the laminating technique presented here. So keep on thinking about it.

[Henning]

benf wrote: Also, there are other useful metal alloys out there that could include cooling components as part of there structure. Are these being considered?

MIL composites

This actually describes a possible solution for fabricating the x-ray harvesting onion structure around the focus device. Laminating metallic foils is what’s needed for the production of the onion. They investigate Al – Al3Ti composites, so it needs to be adapted to the materials we need.

The high structural stability adds the advantage of having cooling tubes running through, and pushing the coolant through with high pressure. Still one needs to take care of the tubes not collapsing (see figure 11) during the manufacturing process. Maybe a material filling the holes and which is flushed by a solvant later is the solution here.

[Henning]

You could also take a look at MatWeb which has information about thousands of materials. There you can compare Beryllium with other materials.

I would suggest pure beryllium is preferable to BeO, because oxygen got more protons and here it’s not a gas but a solid (much higher concentration of atoms).

[Author]

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