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careysub
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Quote: Originally posted by aga  | ...
Personally i think it would be very interesting to play with magnetic and electrical fields, along with high masses and sharp temperature changes and
electrical discharges, all occurring in varying patterns.
Basically vary all possible dimensions randomly and see what happens. |
And here you have the history of research into controlled thermonuclear power in a nutshell (more or less).
There is certainly no know physical reason why some combination of temperature, pressure (read ICF), magnetic, electrical (read MCF) forces
implemented in some way could not lead to a viable system for producing fusion power. Thats why so many keep trying to do it.
At this point an enormous panoply of schemes have been proposed, analyzed, tested (in decreasing frequency of occurrence). Some have been very
promising for a long time.
The physical conditions for practical commercial fusion energy seem curiously off-limits to close approach from any side.
Making hydrogen bombs was really easily. But approaching commercial fusion from above - scaling the process down so that something other than a
fission bomb can drive it - has proven impossible so far, with the NIF, the last biggest effort hitting a dead end after 20 years and 4.5 billion
dollars was spent and still ridiculously far from the performance needed for practical use. They even had successful test of ICF targets using a
nuclear bomb as the energy driver to show that the scheme could work, if you had enough driver energy (these were the Centurion/Halite test series,
the driver energy is classified). The empirical (and numerically simulated) scaling laws they depended on apparently did not work.
Magnetic and electrostatic confinement is trying to approach from below, but again everything seems to run into scaling problems far short of the
goal. Tokamak looks like it would actually work - but even an optimistic assessment of the technology once scaled to commercial size makes it
uncompetitive with every other way of making electricity in use today. And that's our BEST candidate.
Polywell fusion is a completely different magnetic confinement scheme, and has put out some good performance as a laboratory fusion plasma source. But
so far we are a long way from being able to envision a commercial power source out of this approach. It is looking more like a niche tool than
anything. It is not unique in this way.
There are a lot of stories like this (usually less successful). If only the physical parameters were 10 or 100 times more favorable that they actually
are... Heck it muons did not stick to fusion fragments quite so much we might have muon-catalyzed fusion today!
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Chemosynthesis
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A few years ago (prior to 2013, but my memory fails me as to when exactly), I had the wonderful opportunity to have a small meal with the then head of
NIF and a couple LLNL researchers after a presentation. I remember that after a technologically impressive speech on the theoretical capabilities of
NIF, her being visibly annoyed was unmistakable when I had asked her what the largest fusion product they had synthesized was. I suppose it didn't
help that most of my subsequent conversation was on tokamak designs and asking about how feasible using the cancelled Superconducting Super Collider
to initiate fusion, possibly with a scaled up version of LHC's "ALICE" experiment, would have been (extreme overkill and not very efficient, I
learned, as according to my old proton-proton chain nucleosynthesis notes even at at T>5×10^6K and ~100 g/cm3, only 1 in 10^22 collisions of 1H +
1H results in a reaction). Anything larger would need more force to overcome the greater Coulomb repulsion.
As for electrons not existing in stars, aga is very correct to point out that ionized, free electrons do exist very much, and this contributes to
Birkeland currents and Marklund convection with sunspots, solar flares and the like. As far as determining quality factors for energy output, at NIF
you have to see if the Q is calculated to take into the facility engineering (laser efficiency) or is just output from the accelerated particle's
kinetic energy. It makes a huge difference.
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careysub
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| Quote: Originally posted by Chemosynthesis | | As far as determining quality factors for energy output, at NIF you have to see if the Q is calculated to take into the facility engineering (laser
efficiency) or is just output from the accelerated particle's kinetic energy. It makes a huge difference. |
Yep. The laser beam-to-fusion ratio achieved is about 2 orders of magnitude short of laboratory break-even. The wall-to-laser pulse efficiency is
something like 1%, and to produce commercial power you need about 10 times laboratory break-even in the energy output.
All together they are five orders of magnitude short (and this is even spotting them a bit on the rounding).
They are three orders short even with a magic 100% efficient driver.
And that ignores the gruesome number for how fast a commercial system would have to cycle to produce cost-effective power, or how cheap those little
targets would have to get.
An ICF explosion might produce about 10 MJ of line current in a commercial system. This is no more than 10 cents worth of wholesale electricity.
Currently those little targets cost several thousand dollars, are still aren't effective enough to break-even. Perhaps even more complex and costly
designs will be needed. For a gigawatt powerplant (probably would need to be larger than this) it would need to cycle 100 times a second.
As far as I know the ICF community currently has no real Plan B.
Looking at LLNL, I see they are still keeping the pretense of ICF Power! It's almost here! In any day now we are going to be producing 10-100 times
breakeven (instead of 1/130 breakeven) and we can build a demonstration powerplant (LIFE, little more than vu-graph engineering at this point) in the
2020s!
The hype is so far from reality that you just shake your head in wonder.
(Oh, and then there is the problem with NIF's availability for real science, not weapon research. LLNL requires outside researchers to pay the
operating cost for any experiment, which runs more than $1 million per shot. Currently U.S. investment in science as % of GDP is at a 60 year low.
Only weapons program have that kind of dough.)
[And that provides yet another yardstick to show how far the NIF technology is from commercial feasibility. The cost needs to drop 8 orders of
magnitude to a penny a shot or so, and the repetition rate need to increase 7 orders of magnitude, from once a day, while also improving performance
by 4 orders of magnitude.)
[Edited on 8-12-2014 by careysub]
[Edited on 8-12-2014 by careysub]
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neptunium
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yeah it does popo up every so often in the news... i was excited the first time too. now its just media sensationnalism..
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Chemosynthesis
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| Quote: Originally posted by careysub |
(Oh, and then there is the problem with NIF's availability for real science, not weapon research. LLNL requires outside researchers to pay the
operating cost for any experiment, which runs more than $1 million per shot. Currently U.S. investment in science as % of GDP is at a 60 year low.
Only weapons program have that kind of dough.)
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So true! It's kind of odd when you put it in perspective with how relatively inexpensive and easy the old gun type nukes are to make now, assuming you
have highly enriched uranium-235 or plutonium (latter if you could mitigate premature criticality). Even "fizzle yield" is useful in a weapon.
I can't remember any specifics in this story, so I hope I don't butcher it too much, but as a .gov proliferation thought experiment, a group of
scientists/engineers were stuck in one of the modules of LLNL, I believe, and told essentially not to come out until they made a gun type weapon
design from open source materials which should be feasible for a dedicated rogue nation state to produce. Their simulations were run for them to see
if their design would work. They finished so far ahead of the expectations and deadline that they had to try to make an implosion device because it
was "too easy" to go with a gun type.
I know we've obviously come a long way since then (probably much more than I am remotely aware), but it is stark to contrast how different open
progress has been between fission and fusion (pure fusion in the case of weapons), and yet we still have announcements such as this: http://www.forbes.com/sites/jamesconca/2014/10/17/a-working-...
At least that million or so bucks spent at LL gets you a nice view of the wildlife, and should be a treat for some avian enthusiasts.
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careysub
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| Quote: Originally posted by Chemosynthesis | | Quote: Originally posted by careysub |
(Oh, and then there is the problem with NIF's availability for real science, not weapon research. LLNL requires outside researchers to pay the
operating cost for any experiment, which runs more than $1 million per shot. Currently U.S. investment in science as % of GDP is at a 60 year low.
Only weapons program have that kind of dough.)
|
So true! It's kind of odd when you put it in perspective with how relatively inexpensive and easy the old gun type nukes are to make now, assuming you
have highly enriched uranium-235 or plutonium (latter if you could mitigate premature criticality). Even "fizzle yield" is useful in a weapon.
I can't remember any specifics in this story, so I hope I don't butcher it too much, but as a .gov proliferation thought experiment, a group of
scientists/engineers were stuck in one of the modules of LLNL, I believe, and told essentially not to come out until they made a gun type weapon
design from open source materials which should be feasible for a dedicated rogue nation state to produce. Their simulations were run for them to see
if their design would work. They finished so far ahead of the expectations and deadline that they had to try to make an implosion device because it
was "too easy" to go with a gun type.... |
You are referring to the "Nth Country Experiment":
http://www2.gwu.edu/~nsarchiv/news/20030701/nth-country.pdf
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Chemosynthesis
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Thank you very much! I was almost certain you'd know exactly what I was talking about, not surprisingly better than I.
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MrHomeScientist
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This is why I love this site. Even a trolling post can spawn a wonderful thread full of great information. So many skilled and knowledgeable people
here!
I thought it would be fun to calculate exactly how much gold ASocialSurvival's "half a million dollars worth gold in my pocket" would be. It turns out
this equates to a cube about 3.5 inches to a side, which would weigh about 29 pounds! Reasonably pocket-sized, actually, though a cube would make
quite a noticeable bulge. And you'd need a good belt to hold up the weight. The extreme density of gold always surprises me.
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whiteshadow
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you guys need to check this link out very badly http://www.lockheedmartin.com/us/products/compact-fusion.htm... the concept is very good that' why lockheed
people are very serious
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neptunium
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seems like a commercial video professionally made but NO details on the construction, design, how they want to achieve their goals? there is no
science on that page ! or did I missed the link that explains how they do it ?
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careysub
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| Quote: Originally posted by neptunium | | seems like a commercial video professionally made but NO details on the construction, design, how they want to achieve their goals? there is no
science on that page ! or did I missed the link that explains how they do it ? |
Quite so. Lockheed Martin has not given anyone any reason to believe they have something real here.
http://www.technologyreview.com/news/531836/does-lockheed-ma...
There is a long history of similar fusion vapor-tech project announcements, and here we are decades later still with nothing but tokamaks as plausible
systems 50 years after their invention.
As the Technology Review article points out, L-M isn't even the only current purveyor of press-release fusion systems, it just has a bigger name and
better PR.
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neptunium
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my thought exactly
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