[HN Gopher] Wendelstein 7-X: Gigajoule energy turnover generated...
___________________________________________________________________
Wendelstein 7-X: Gigajoule energy turnover generated for eight
minutes
Author : greesil
Score : 490 points
Date : 2023-08-11 18:36 UTC (1 days ago)
(HTM) web link (www.ipp.mpg.de)
(TXT) w3m dump (www.ipp.mpg.de)
| YossarianFrPrez wrote:
| If I understand things correctly, the problem with magnetic
| confinement (e.g. Tokomaks, Stellarators) is that once you have
| heated a plasma such that it is "fusing," how do you get the
| power out with out cooling the very plasma you've just spent a
| lot of energy heating up?
|
| Helion, a fusion startup, claims to have solved this problem via
| capturing an induced current from colliding two hot plasmas
| together. I'd be curious if there is any way the Wendelstein can
| produce electricity.
| Tuna-Fish wrote:
| Most fusion power systems assume they are doing that as
| neutrons. D-T fusion conveniently has the proportion of energy
| that gets lost from the plasma as KE of neutrons be pretty
| close to the amount of energy that a conveniently sized fusion
| reactor can afford to remove from the plasma.
|
| Then you trap the neutrons with, for example, a lithium
| blanket, use them to breed more tritium, and produce energy
| with a turbine from the heating of the blanket.
| YossarianFrPrez wrote:
| Ah, got ya. Thanks for the information.
| marsven_422 wrote:
| [dead]
| Roark66 wrote:
| >new record for discharge time on Wendelstein 7-X: the hot plasma
| could be maintained for eight minutes.
|
| This is of course a milestone, but note they're currently testing
| the heating system. It doesn't mean there was any fusion
| happening.
| karmajunkie wrote:
| This is perhaps an obvious question to some, but I'll ask it
| anyway: How is the power generated here converted into usable
| electricity?
|
| I know for conventional fission reactors the heat of fission is
| basically used to run a steam turbine. Given the extreme heat of
| the plasma, and that it must be magnetically suspended so that it
| doesn't even touch the sides of the containment, how is that heat
| transferred to some other medium to generate electricity?
| mdprock wrote:
| here there is no power generated as it's not working with
| deuterium-tritium. most of the heating will heat the plasma and
| a fraction of this will reach the cooling system. To make a
| comparison ITER is expected to have 50 MW heating for 400
| seconds approx. = 20 GJoule. Using a DT mix will result though
| in 500 MW Fusion Power
| peteradio wrote:
| You still get heat transfer from uncharged elements I guess.
| Etheryte wrote:
| I'm not sure if it's the case for this specific reactor, but
| the common answer to this question is that you need cooling in
| the surrounding walls and the coolant that runs through the
| walls transfers the heat out where it can be used to do useful
| work.
| WJW wrote:
| Given that the plasma is several million degrees, it will
| radiate a lot of energy and heat up the walls even if it does
| not directly touch them. Just cooling the walls can heat up the
| cooling fluid enough to later produce steam with. AFAIK the
| Wendelstein machine is not configured for electricity
| production though, so the cooling is just cooling atm.
| jeffbee wrote:
| > Given that the plasma is several million degrees, it will
| radiate a lot of energy
|
| That doesn't entirely follow. 2 particles whizzing past each
| other at relativistic speeds have extreme temperatures but
| don't offer much energy. Mass is in this equation.
| willis936 wrote:
| What if you have 10^20 particles? Each charged particle
| emits photons with energy/frequency proportional to their
| speed (Bremsstrahlung). This is mostly from electrons
| because they are much lighter and so are much
| hotter/faster. Plasmas are quasineutral though so you'll
| have those electrons present. There is a long line of
| research trying to get away from that constraint with
| little luck so far (but it should continue to be worked
| on!).
|
| Jumpjng back up the stack: photon radiation is mostly
| considered a loss since it transfers energy out of
| confinement and does not impart it on other fuel. You
| nominally extract your heat via neutrons: same as fission
| reactors. Some designs (Helion) aim for reactions with
| charged byproducts. The reaction produces a current that
| can be coupled by a surrounding coil, much like a
| transformer but powered by current induced by plasma rather
| than another copper wire.
| fizigura wrote:
| They currently run a bad-ass heatsink (which is one of the main
| challenges of this project, i.e., how to cool it), but
| eventually you will use that heat to convert it into
| electricity, yes.
|
| For the German-speaking crowd here, the Alternativlos podcast
| guys were there twice and had lengtly conversations with the
| researchers there. Like, between nerds. Really cool, if you
| understand the language.
|
| https://alternativlos.org/36/ (from 2016)
|
| https://alternativlos.org/51/ (most recent, from may 2023)
| drannex wrote:
| Omega Tau also visited and talked with some of the
| researchers and has a great podcast episode on it (and truth
| be told, all of their episodes are great).
|
| https://omegataupodcast.net/312-the-
| wendelstein-7-x-fusion-e... (from 2019, 3Hrs, English)
| tsimionescu wrote:
| Most of the answers are missing the actual (proposed)
| mechanism.
|
| The energy of the reaction is mostly carried away as high-
| energy neutrons. So, the way to get energy back is to "capture"
| those neutrons. Since neutrons are not electrically charged,
| you can't use them to directly create electricity, so all
| you're left with is using them for heat.
|
| Unfortunately, since they are electrically neutral, they're
| also relatively hard to catch. You need a dense material where
| they will have a good chance to hit some nucleus. The proposed
| designs are typically some kind of liquid metal blanket being
| circulated around the reactor and onto a place where it can
| boil water to produce steam to spin a turbine. Lithium is the
| metal most proposed for this, since it also has the advantage
| that it can produce tritium when bombarded with neutrons
| (tritium being the super rare half of the fuel that goes into
| the reaction).
| lambdatronics wrote:
| Just to amplify on your point about lithium: the tritium
| production function is critical. Every fusion neutron needs
| to produce more than one tritium atom on average, so that the
| reactor is sustainable (there are inevitable losses & tritium
| also decays radioactively) or even making excess tritium (to
| bootstrap other reactors). This is challenging b/c even in
| the best case each neutron can produce maybe 2 tritium atoms,
| so there's not much margin. The lithium needs to comprise
| most of the material surrounding the plasma, limiting the
| fraction that's available for other functions (structural
| supports, heat shielding, cooling, plasma control & heating
| systems, sensors, etc).
| stouset wrote:
| What eventually happens to the excess neutron "waste"? Surely
| there's some negative consequence to producing an enormous
| number of neutrons, no?
| tsimionescu wrote:
| All the neutrons that don't get caught by the blanket will
| usually be caught by the support structure of the reactor,
| damaging it and making it radioactive. This puts a cap on
| the maximum lifetime of this type of fusion reactor until
| significant parts of the structure need to be dismantled
| and replaced, and stored as highly radioactive waste. As
| far as I know, current estimates suggest something like a
| decade - one of the biggest problems with the economics of
| fusion power plants.
| quickthrower2 wrote:
| What is happening in a star to emit useful radiation? I feel
| I should know that, I probably did but forgot.
| tsimionescu wrote:
| Stars rely on gravitation to confine the plasma instead of
| magnetic fields, and they can reach the energy densities
| needed for other fusion reactions, typically D+D, which
| produces less neutrons. Also, there are hundreds of
| thousands of kilometers between the center of the sun and
| its outermost layers - neutrons produced in the core will
| have plenty of time to be absorbed by something else on
| their way out.
| nerdponx wrote:
| It's always fascinating to me that, no matter how many
| interesting new ways to release lots of energy we develop, we
| are still stuck with the same method for converting it to
| electricity: release the energy as heat, use heat to make
| steam, use steam to drive generator.
| rocqua wrote:
| Steam turbines are actually quite a bad method, because
| pure heat is a difficult energy source. It's just also a
| very available energy source.
|
| The 90% efficiency quoted in the comments is 90% of
| theoretical maximum efficiency. This theoretical maximum is
| about 50% for the best systems.
| jessriedel wrote:
| The reason just that this is a simple process for which a
| steam turbine can achieves 90% of the thermodynamic
| optimum. To my knowledge, the only reason people consider
| alternatives is to reduce capital costs. You're still
| capped by thermodynamics though.
| nerdponx wrote:
| That's what I was wondering: if heat -> steam -> turbine
| is close enough to the theoretical upper limit and you
| get diminishing returns by other means.
|
| Still, it seems very indirect. Like generating solar
| power by using a parabolic mirror to heat water instead
| of photovoltaic panels... but of course I just found an
| example of doing that too:
| https://en.wikipedia.org/wiki/Parabolic_trough
| Iulioh wrote:
| There are multiple solutions of that sort but all failed
| due to high maintenance costs
|
| Usually the liquid is some sort of oil that csn reach
| higher temperature and then the oil is used to heat water
|
| Another design uses hundreds of mirror centered around a
| high tower with molten salts as the heat medium
|
| The really good part of this design is that the molted
| salts can produce energy for 3-4h after the sun is set.
| sambapa wrote:
| It's because we're in local maximum - steam turbines are
| just so developed
| tsimionescu wrote:
| Well, we do have some other strategies. Hydro and wind just
| turn the turbine mechanically, they don't heat up water to
| make steam. And photovoltaics create electricity directly
| using an effect that won Einstein the Nobel prize and began
| the age of quantum mechanics, so that's about as advanced
| as they come.
| NateEag wrote:
| Helion is planning to use induction to generate electricity
| from the fusion reaction's generated magnetic field, IIUC:
|
| https://www.helionenergy.com/faq/
|
| (See "How does Helion generate electricity from fusion?"
| question)
| MichaelZuo wrote:
| Which doesn't make sense for power generation since there
| will always be some percentage of neutrons produced by
| any type of fusion reaction that can only be useful for
| generating steam.
|
| To entirely skip the steam cycle portion is to
| intentionally make a much less efficient design.
|
| For space-constrained, high-value, applications where
| economics don't matter that much, such as a submarine,
| that would make sense, but otherwise...
| jessriedel wrote:
| You could always add the liquid metal blanket if you want
| to eke out the extra 10% (or if you want to generate
| tritium). But it's not worth the complication in an early
| prototype.
| DennisP wrote:
| Helion's fuel mix produces just 6% of its energy as
| neutron radiation, and if you harvest it you'll lose a
| third of that. As long as you have enough net energy,
| collecting that 4% might not make financial sense.
|
| With fuel costs insignificant, your cost per kWh is
| mainly capital cost. Let's say it's all capital just to
| keep it simple. I don't know how much the input energy
| will be but if your choice is between, say, generating
| net energy of 50MW without a turbine or 54MW with a
| turbine, then you would skip the turbine if it adds more
| than 8% to the capital cost. I suspect Helion has done
| this calculation in detail.
| MichaelZuo wrote:
| It does seem to hinge on the cost of fuel, I have some
| doubts about whether they can secure a fuel supply so
| cheap as to skip out on that extra 4 MW, even after
| factoring in the cost of a small steam turbine
| installation.
| DennisP wrote:
| Deuterium costs several thousand dollars/kilogram. But
| even though it is just one part in several thousand of
| the hydrogen in water, there's enough deuterium in your
| morning shower to provide all your energy needs for a
| year.[1] Cost of deuterium is definitely insignificant.
|
| Helion's other fuel is helium-3 which they'll make
| themselves by fusing deuterium. So the helium-3 cost will
| directly depend on the capital cost of the reactor
| producing it.
|
| (This may be the same reactor, both generating
| electricity and breeding He3. Or they may use dedicated
| He3 breeders, and minimize the D-D reactions in the
| generators.)
|
| [1] https://dothemath.ucsd.edu/2012/01/nuclear-fusion/
| gus_massa wrote:
| They plan to use 2D + 3He -> 4He + 1H, so no neutrons htt
| ps://en.wikipedia.org/wiki/Aneutronic_fusion#Candidate_re
| ...
|
| (I'm still not convinced of their explanations, but a
| fast proton may be easy to catch by the magnetic field
| and create the effect they want.)
| fastneutron wrote:
| Nitpick: You're always going to get some parasitic D+D
| reactions because it's reaction cross section is
| appreciably higher than D + 3He below 50 keV, and non-
| negligible even after the crossover point.
| skykooler wrote:
| Doesn't D+D just yield 4He (and no neutrons) though?
| philipkglass wrote:
| It yields 3He plus a 2.45 MeV neutron at least part of
| the time.
|
| See the diagram here: https://undsci.berkeley.edu/teach-
| resources/products-of-deut...
| tsimionescu wrote:
| Helion is planning to use a different fusion reaction,
| one where the bulk of the energy will be coming out as
| charged particles, not neutrons.
|
| However, D+T fusion is the only type of fusion that we
| have been able to sustain for any significant amount of
| time with reasonable energy inputs. What Helion is
| planning to do is completely unexplored and requires some
| major scientific advances.
| 2-718-281-828 wrote:
| probably boiling water and the steam drives turbines whose
| coils and rotating magnets produce electricity.
| idiotsecant wrote:
| Yes, the boring and actually feasible answer is steam.
|
| But it sure is fun to dream!
|
| https://en.wikipedia.org/wiki/Direct_energy_conversion
| midasuni wrote:
| Isn't one of the problems with nuclear that it increases
| water temperature in rivers
| calfuris wrote:
| That's a problem associated with a particular cooling
| system design, so it's more of a thermal power problem than
| a nuclear power problem.
| midasuni wrote:
| Ok so wouldn't it be a problem with a fusion/thermal
| system too?
| jtriangle wrote:
| Same way most electricity is made, you use the energy created
| to heat up water into high pressure steam, high pressure steam
| turns a turbine(s) which turn gensets that produce 3 phase AC
| current.
|
| This one in particular isn't setup to do that, and as far as I
| know, none are yet. It's a pretty simple engineering problem,
| and, until we can maintain fusion for months at a time, it's
| not really something that needs to be built.
|
| There is, however, one fusion concept that shows some promise
| that doesn't require all that that helion energy is developing
| (helionenergy.com) they're yet to create net-power, but, their
| idea has some promise, and avoids the common problems with
| other forms of fusion power. I don't really see it as the be-
| all to end-all in the space, but from what I can tell they very
| well might be the stopgap that is needed between large scale
| stellerators and fission.
| gregfjohnson wrote:
| Question for this knowledgeable group of people: Which fusion
| start-ups look promising? How does inertial confinement look? Any
| thoughts on the newly funded start-up Blue Laser Fusion? Any
| thoughts on one of the older players, TAE? How about
| Commonwealth? Helion? Others?
| audunw wrote:
| I think Helion is most promising for two reasons. 1. Even if
| the more traditional fusion power plants manage to generate the
| plasma itself in a device that's not too expensive (big if) it
| seems that just the heat exchange mechanism itself would be
| extremely complicated and expensive. And since they're thermal
| power plants you're limited in where you can put them and how
| big they must be to be economical.
|
| 2. As CO2 emissions come down, I think there will be some focus
| on thermal power plants contribution to global warming. Helion
| will still be adding heat to the planet that wasn't there
| before, but there will be less heat for a given amount of
| electric energy. It's also not going to rely on dumping all
| that heat in a river. I don't know if Helion is feasible. But
| it feels like it's the only technology that could be feasible.
| greesil wrote:
| Zap Energy. They're at least thinking about co-opting existing
| infrastructure.
|
| https://www.neimagazine.com/news/newszap-energy-considers-re...
|
| Also their concept is just so weird, I love it. Worst case it
| works in space as a nuclear fusion drive :)
|
| My guess is that they're all going to tank without government
| money, unless by some miracle they have truly found some
| special low-cost of operation on the first try that beats the
| current heavily optimized solutions for power generation.
| cyberax wrote:
| Sorry, but this is bullshit. A steam turbine and a generator
| will be a _minor_ detail in the overall list of expenses
| building a fusion generator.
|
| It's like saying: "We should build an airport here in the
| desert, because we'll be able to save on cutting the grass!"
| onlyrealcuzzo wrote:
| I feel like it's more like saying, we should build an
| airport here, because it's near a city and in a good
| location, and the land is cheap because no one else wants
| it for a number of reasons and this is the only thing that
| practically makes sense to go there.
|
| It's not going to save a meaningful amount of money. But
| that doesn't mean it's a bad idea.
| cyberax wrote:
| Sure. But even in your example the site selection won't
| help you much to build the airport, you still need to do
| that, and it's still going to be massively expensive.
|
| I'm also in general skeptical about conversions of coal
| power plants into nuclear even for fission. Typical
| nuclear plants produce much milder steam temperatures and
| pressures than coal power plants, so their steam turbines
| are optimized for different conditions.
| greesil wrote:
| How would you know?
| cyberax wrote:
| I worked in the nuclear energy area. I also invested
| personal money into several fusion startups.
| greesil wrote:
| Well that'll teach me
| cyberax wrote:
| I invested a non-trivial amount of my personal money into TAE
| (Tri-Alpha Energy). They periodically raise more funds, so it's
| not hard to get in.
|
| From the overall perspective, Tokamak Energy also looks
| promising and I'm planning to invest.
| mjfl wrote:
| The Stellarator is theoretically a superior design over the
| Tokamak, designed to neutralize the JxB force, where J is the
| current through the plasma and B is the magnetic field guiding
| the plasma around the device. By twisting the plasma into a shape
| where the curl of B (proportional to J) is parallel to B, i.e. a
| helix, the cross product is 0, and thus there are no net
| magnetohydrodynamic forces on the plasma.
| juujian wrote:
| 'Theoretically' is the right word for sure. iirc, the
| predecessor of the Wendelstein led to the bankruptcy of the
| engineering firms building the parts, because tolerances were
| so tight and they failed multiple times to land within the
| constraints.
| mjfl wrote:
| true. but on the other hand, the 'theoretical' is being
| turned into practice as evidenced by this 8 minute
| containment. the best a tokamak can do is half a second.
| krasin wrote:
| Tokamak record time for plasma confinement is 403 seconds
| as of April 2023, see https://english.cas.cn/newsroom/mutim
| edia_news/202304/t20230...
|
| 403s is about 7 minutes, so less than Wendelstein 7-X.
| posterboy wrote:
| They could go longer. 7-8 mins is an arbitrary cut off
| out of fear that something might break ( _quench_ ),
| knowing that enough data has been gathered for the time
| being.
| posterboy wrote:
| The first Alternativlos Podcast of two conducted with the
| leader of the Wendelstein X project relates how certain
| magnetic coils were purpose made by a kind of emeritus
| engineer in Swiss. Which seems corollary to the common wisdom
| about EMI, it's magic, so the manufacturer must be a wizard.
|
| On the other hand it is reminiscent of a Georgian I met who
| used to be occupied with winding regular tire sized coils by
| hand, for over land transmission lines. This is _chirurgical
| precision_ , literally hand-craft.
|
| We do a lot of thinking with our hands. It stands to reason,
| metaphorically speaking, that Wendelstein is an experiment to
| gain hands on experience. Therein lies the difference to
| megalomanic projects that exceed initial estimates, eg. BER
| airport, which are a running gag by now.
|
| Insolvency means the investment returned no profits so
| investors on those projects stopped paying. It likely doesn't
| mean that the cheques bounced on liabilities. And it
| obviously doesn't mean that investment in this space had to
| stop.
| codethief wrote:
| > It likely doesn't mean that the cheques bounced on
| liabilities.
|
| But that's exactly what it means:
|
| https://dejure.org/gesetze/InsO/17.html
| nielsbot wrote:
| W7-X is a new stellarator design. It's magnet arrangement was
| optimized using a lot of compute time and is designed to
| overcome the faults of previous more naive designs.
| nielsbot wrote:
| *its. ugh.
| moffkalast wrote:
| The last time it was in the news I think naysayers listed the
| main caveat with stellerators as something along the lines of
| very low plasma density compared to tokamaks, which makes them
| unable to get anywhere close to the energy break even point.
| cyberax wrote:
| The main problem with stellerators is their murderous
| complexity. You need to manufacture several thousand
| different parts with complicated 3D geometry, micron-level
| precision, and from unobtanium-class materials.
|
| All while not being able to properly simulate the outcome on
| a computer.
|
| Stellarators are superior to tokamaks, so an energy-positive
| stellerator will be about 2 times smaller than a tokamak. But
| we're still talking about a building-sized vacuum chamber.
|
| That's why for ITER it makes sense to go with a simpler
| design to de-risk the main objective: building a burning
| plasma laboratory.
| willis936 wrote:
| Doesn't really track. Stellarators can operate above the
| Greenwald density limit. They just have shorter confinement
| times for a given field strength and major radius.
|
| http://fusionwiki.ciemat.es/wiki/Greenwald_limit
| expertentipp wrote:
| With gas cut off from pipeline terminated in Greifswald, how will
| they power now this bottomless energy pit? They still have some
| money, but a finite amount.
| TaylorAlexander wrote:
| Speaking of fusion does anyone know what is going on with SPARC
| at Commonwealth Fusion Systems? I have been very excited about
| their system but they are understandably in a deep development
| and construction cycle after a $2B investment, so all their news
| page has for the last year are updated business deals and awards.
| I would love to hear how reactor construction is going.
| cmplxconjugate wrote:
| My best friend works for them in diagnostic sub-systems
| development. The product is still a long way off delivery with
| many systems being actively designed and refined. Basically
| it's busy but will still be quite a while (3-5+ years at
| least).
| TaylorAlexander wrote:
| Makes sense. I would love to see a blog post with some
| progress pics, but I understand that building a fusion
| reactor is simply a slow process!
| howenterprisey wrote:
| Their progress pics are on Instagram and TikTok
| (unfortunately): https://www.instagram.com/cfs.energy/
| TaylorAlexander wrote:
| Gotcha that is helpful thank you!
| QuantumG wrote:
| I expect they'd happily give access to anyone who wanted to
| cover it. Say, if someone wanted to do quarterly update
| videos, and had the appropriate skills, they'd only have to
| find the right person to ask, on the academic side. Hint.
| TaylorAlexander wrote:
| Thanks. I do have the appropriate skills but I live in
| California and I'm busy with my own world changing
| projects that need videos produced about them! I just
| want to read blog posts about what's happening.
| QuantumG wrote:
| Thanks for the update. I was taking no news as good news and
| didn't expect to hear anything until 2025 anyway.
| [deleted]
| aidenn0 wrote:
| What is "energy turnover" in this usage?
|
| [edit]
|
| Found it: "Energy turnover is defined as the amount of heat
| multiplied by the duration of the discharge[1]." By "amount of
| heat" I assume they mean "heating power delivered to the plasma"
| b/c the the only way to multiply by time and get Joules is to
| start with power.
|
| 1:
| https://gigazine.net/gsc_news/en/20230227-wendelstein-7-x-en...
| snarkconjecture wrote:
| Yes, it's a little buried but the article says
|
| > The energy turnover results from the coupled heating power
| multiplied by the duration of the discharge
|
| The numbers:
|
| > The energy turnover of 1.3 gigajoule was achieved with an
| average heating power of 2.7 megawatts, whereby the discharge
| lasted 480 seconds
|
| Also:
|
| > Within a few years, the plan is to increase the energy
| turnover at Wendelstein 7-X to 18 gigajoules, with the plasma
| then being kept stable for half an hour
|
| i.e. 10 megawatts for 30 minutes
| [deleted]
| magicalhippo wrote:
| How long does it take to restart after losing stability?
|
| Ie, would it be feasible in a power plant scenario to settle
| for 30-60 minutes of stability, and just restart?
| amelius wrote:
| Isn't this similar to the monetary meaning of the word
| turnover? Like turnover : profit <==> energy turnover : net
| energy output?
| runako wrote:
| Possibly the poster is from a country like America where
| "turnover" is not a preferred term to refer to gross receipts
| of a business. (Americans typically use "revenue" instead.)
| aidenn0 wrote:
| I am indeed from the US and had never heard "turnover" to
| mean gross receipts.
| segfaltnh wrote:
| I'm also from the US and recently had an apple turnover.
| It was delicious.
|
| I lost money on the endeavor, though.
| alkonaut wrote:
| So when this had a turnover of 1.3 GJ (361 kWh), was that
| with a net loss in the end? How much electricity did they put
| in?
| aidenn0 wrote:
| My layman's understanding:
|
| There has never been a net-positive-energy magnetic
| confinement fusion experiment. Inertial confinement fusion
| has had 2 events that were "more energy out of the fuel
| than delivered to the fuel." But is still about a factor of
| 100 away from what is needed for "more electricity in than
| out"
| [deleted]
| vilhelm_s wrote:
| The 1.3 GJ is how much electricity they put in. There is no
| fusion reaction or energy production, it's just an
| experimental device to study plasma containment.
| fefe23 wrote:
| FYI: This milestone was in February.
| ChuckMcM wrote:
| I love these guys, they are just knocking down the engineering
| challenges in their plan to completely characterize and control a
| fusion stream. Sometimes they feel like the Tortoise in the race
| to a working fusion power plant but they are answering questions
| (managing wall temps and hold fusion in streams[1]) that the
| Tokamak folks have yet to solve. My bias though is I'm way more
| on the "D" side of the R&D spectrum and following ITER often
| feels like pure "R."
|
| [1] https://www.iter.org/of-interest/1188
| aquafox wrote:
| Interesting fact: Nuclear fusion, even if we'll make it work,
| won't stop global warming, because the heat it creates heats up
| the earth enough to bring us outside the Paris agreement:
| https://twitter.com/rahmstorf/status/1605967891928596481
| RivieraKid wrote:
| One immediately apparent flaw of this argument is the
| assumption of energy use growing by 10x over a century. But in
| developed countries, energy use per capita has been roughly
| stable for decades. The 2 main drivers of energy growth will
| weaken over time (population growth + countries becoming
| developed).
|
| Also, if energy use does increase by 10x, the solution is
| simple, build giant refrigerators powered by fusion energy to
| cool the atmosphere. (joke)
| MichaelZuo wrote:
| I could see a plausible 10x growth if literally the entire
| world achieved within the ballpark of 2023 US levels of per
| capita wealth.
| onlyrealcuzzo wrote:
| I don't understand the conclusion.
|
| According to the article, we currently emit 2.1w/sqm in
| greenhouse gasses.
|
| If we had 10x energy and it was all fusion - it would be
| 0.4w/sqm.
|
| This sounds like a massive improvement.
|
| Additionally, I'm highly skeptical we'll be using 10x the
| energy in 100 years - when there's likely to be significantly
| less people, and everything is getting more efficient.
|
| Sounds like the same argument that China is going to continue
| growing 10% per year for the next hundred years, because it did
| for the last 30 years. No. China's workforce is going to
| decline massively. It will be so much harder for them to grow
| at the same rate, it would take a real miracle to keep growing
| at that rate.
| andbberger wrote:
| this is a basic consequence of thermodynamics and true for all
| power generation. the only thing to be done to minimize waste
| heat is to to increase temperature of the hot side of the heat
| engine, with ie advanced fission reactors.
|
| and fusion never had any advantage over fission anyways, other
| than that people aren't scared of it yet.
| aquafox wrote:
| Why the down votes? What is factually wrong with that
| statement?
| constantcrying wrote:
| The threat of the earth heating up by 0.3 degrees due to
| energy production is irrelevant or at least absolutely worth
| it as a tradeoff for working fusion.
|
| The dangers of climate change is not that the earth heats up
| by some small amount, the earth can easily cope with that. It
| is that continued greenhouse gas emissons are causing a ever
| increasing heatup due to trapped solar energy.
|
| (It is also extremely strage that he argues for geothermal in
| his comments. Does he not realize what that is? Literally
| heating up the surface of the earth with energy from below.)
| coolspot wrote:
| Didn't downvote you, but having unlimited energy source is
| worth it and can allow us to remove heat from earth. Human-
| caused CO2 alone contributes 2.1W/sqm while all current human
| energy production is 0.04W/sqm . Removing extra CO2 alone
| would offset 50x energy production growth. Then you can do
| things like placing reflective satellites between earth and
| sun.
| pfdietz wrote:
| Because the argument involves unlimited future growth in
| energy use. Compared to the current energy use, fusion
| (assuming it could be made to work practically) would indeed
| solve global warming.
| EVa5I7bHFq9mnYK wrote:
| The burning of 1 kg of coal heats the earth in two ways:
|
| A) the energy that is produced immediately (about 24MJ)
|
| B) the excess energy absorbed from the Sun over many
| subsequent years, caused by CO2 emitted burning that coal.
|
| The B is much larger than A. The fusion only produces A, but
| not B.
| slashdev wrote:
| Assuming I trust the math, that's plotting exponential growth
| in energy usage out for 80 years, and assuming a fully nuclear
| grid. Neither of those is likely. Lastly the Paris accord is a
| pipe dream that will never happen. A target to aim for, and
| miss. Nothing more.
| lhoff wrote:
| Related recommendation for the german-speaking crowd here:
|
| The Podcast Alternativlos by Felix Von Leitner and Frank Rieger
| were twice in Greifswald to interview some of the people behind
| the Wendelstein. In the first episode
| (http://alternativlos.org/36 from 2016) they mainly focused on
| the development and build process and the history. The second one
| is from this year and they talk about the achievements and the
| future of Fusion (http://alternativlos.org/51/)
| dumdumchan wrote:
| > The energy turnover of 1.3 gigajoule was achieved with an
| average heating power of 2.7 megawatts, whereby the discharge
| lasted 480 seconds.
|
| Can a physicist/thermal engineer explain what this means?
| danbruc wrote:
| They heated the plasma with a power of 2.7 MW for 480 s which
| in total deposited 2.7 MW x 480 s = 1296 MJ, i.e. 1.3 GJ, of
| energy into the plasma heating it up. That is the energy of 310
| kg of TNT (4.184 MJ/kg) or burning 38 l of gasoline (34.2
| MJ/l). Keep in mind that this energy was deposited into the
| plasma which has a mass of only about 10 mg.
| anonuser123456 wrote:
| I don't get it; who cares? We know the equations to burn plasma;
| that's the easy part.
|
| The hard part is building a machine that can burn plasma and
| breed tritium at appreciable rates.
|
| Why even bother with these machines that can never be built
| economically?
| constantcrying wrote:
| >Why even bother with these machines that can never be built
| economically?
|
| If you can not build a research reactor which functions well,
| then "building a machine that can burn plasma and breed tritium
| at appreciable rates." is more than impossible.
| afterburner wrote:
| Progress is built by iteration. Did you think the world sprung
| into its current form in one step?
| fizigura wrote:
| We know the equations for flight. Why didn't they just build a
| 787 in the 40s already?
|
| Oh, is it because the technology didn't exist and first had to
| be developed, in incremental refinements? Initial airplanes
| didn't even fly and half the people trying them died? Oh...
| pfdietz wrote:
| The basic equations of aerodynamics led people (like von
| Karman) to conclude that lighter than air craft would not be
| competitive. And so it proved.
|
| The basic physics of DT fusion reactors led Lidsky to
| conclude that any DT reactor would have poor power density.
| And so it has proved.
|
| Sometimes knowledge lets one rule out whole branches of the
| technology search tree.
| munchler wrote:
| Maintaining a controlled fusion reaction for eight freaking
| minutes seems like a pretty worthwhile accomplishment in and of
| itself. The only other place this is known to occur is in the
| center of a star. Doing it here on Earth is pretty mind-blowing
| IMHO.
| rurban wrote:
| Major unit errors, I assume:
|
| > In individual areas, temperatures of up to 600 degrees Celsius
| are reached (red areas). The divertor tiles can withstand
| temperatures of up to 1200 degrees Celsius.
|
| How many 0's are missing there?
| danbruc wrote:
| None.
|
| _The picture does NOT show the plasma itself, but the
| temperature distribution at the water-cooled divertor baffles._
|
| It's about the temperature of parts of the vessel that get
| heated by leakage from the contained plasma.
| foolfoolz wrote:
| i've been following this project for 10 years. it's been
| successful. but how do projects like these move faster? the
| wendelstein 7x is never going to generate usable electricity.
| it's supposed to be the pre cursor to the producing reactor
| barbazoo wrote:
| > the wendelstein 7x is never going to generate usable
| electricity
|
| What's the reason for that?
| AnimalMuppet wrote:
| It's a research reactor, not a production reactor. Generating
| useful electricity was never the design goal. The goal was to
| learn _how_ to build a reactor that could generate useful
| electricity.
| ethbr0 wrote:
| tl;dr - Output nuclear fusion power, plasma volume, and
| magnetic field strength scale differently with reactor size
| increases
|
| In detail, I'll let someone smarter than me in nuclear
| physics explain: https://physics.stackexchange.com/questions/
| 175830/nuclear-f...
| KyleBerezin wrote:
| We are researching fusion technology. It would take a reactor
| many times larger to get more energy out of the facility than
| you put in. The technology still needs to mature before a
| reactor that size would be financially responsible.
| aeyes wrote:
| In the German Alternativlos podcast the Wendelstein team
| (Prof. Dr. Thomas Klinger, Dr. Adrian von Stechow) recently
| stated that it is already feasible, they estimate a cost of
| ~EUR20B and a 5 year construction time for a commercial
| fusion power plant if we started now.
|
| https://alternativlos.org/51/
| KyleBerezin wrote:
| Yea, but compare the financial burden of that compared to
| a solar farm of the same output. Not to mention the
| technical risk.
| fizigura wrote:
| Solar farms on farmland? That won't scale to the energy
| needs of 8bn+ people if we still want to keep feeding
| them. Especially a non-vegetarian diet.
| KyleBerezin wrote:
| I'm just saying the money doesn't back the idea yet. I'm
| not anti-fusion.
| pfdietz wrote:
| Where did he say on farmland?
| bmicraft wrote:
| No, solar farms in the desert with a HVDC lines
| obviously.
| t0mas88 wrote:
| For less than 15 billion euro you could buy enough solar
| to power a country the size of the Netherlands. With 5
| billion to spend on batteries you might even make it
| through night time usage.
|
| Or in other words: Fusion is too expensive at this point
| to be useful.
| jahnu wrote:
| That seems amazingly cheap! Are we really down to that
| low level of cost?
| t0mas88 wrote:
| 1 euro per kW of capacity isn't that low, residential
| systems can get below that and it includes installation
| cost and an inverter which would both scale better for a
| bigger system.
| sp332 wrote:
| Grid-scale solar is $33/MWh (+)
| https://emp.lbl.gov/publications/utility-scale-
| solar-2022-ed... and the Netherlands uses 1,000,000,000
| MWh/year
| https://ourworldindata.org/energy/country/netherlands so
| it's only off by a factor of ~2.
|
| (+) These numbers are for the USA. I found a mention of a
| cheaper project in Chile
| https://about.bnef.com/blog/cost-of-new-renewables-
| temporari... but I don't know what the situation is in
| Europe. And wind might be even lower.
| aeyes wrote:
| Chile is an outlier, the plants are in remote locations
| in the Atacama desert where you have two compelling
| reasons to build solar plants: There is a lot of space
| where nobody lives and the sun is always shining. There
| are mountains but there are also lots of places which are
| flat for as far as the eye can see, an example would be
| the Cerro Dominador plant which probably didn't require
| any ground preparation.
|
| On http://generadoras.cl/tipos-energia/energia-solar
| scroll down to "Capacidad por region", Antofagasta and
| Atacama are the desert regions in the with over 90% of
| installed capacity.
|
| In Germany or the Netherlands it is a bit harder to find
| space for large solar plants.
| pfdietz wrote:
| Chile is cheaper, and in a solar-powered world energy
| intensive industries will move to such places. If (say)
| Sweden wants to try to preserve industries by building
| nuclear power plants, they'll find the expensive power
| from nukes competing against the dirt cheap power from
| Chilean (or Namibian, or Australian, or Saudi Arabian)
| solar.
| worik wrote:
| > in a solar-powered world energy intensive industries
| will move to such places.
|
| And to windy places. Happening already in Europe,
| building new industrial plant close to the huge and fast
| growing offshore North Sea wind power plants
| bbarnett wrote:
| The first plant is going to be more expensive, and the
| next gens after that will benefit from things learned.
|
| The first TVs were for the very rich, and had 4" bw
| screens. Now they're 80", thin, and insanely cheap.
| peteradio wrote:
| How exactly is that calculated?
| aeyes wrote:
| From listening to the episode I'd say that it isn't much
| more than a gut feeling derived from their experience
| building the experimental reactor, coming from the head
| of W7X I'd give it at least some credibility. Without
| sufficient political will this isn't feasible at all.
| fizigura wrote:
| The same was said 20 years ago about solar power.
|
| Then some countries stepped up the subsidies game and
| booom, prices fell dramatically since suddenly everybody
| wanted a piece of the cake. And competition drove this
| all down.
|
| All you need is for somebody to start. Or we just keep
| telling ourselves that it's too expensive, shrug, and
| move on.
|
| Also note how the goal posts changed. Until recently,
| everybody made fun of fusion by basically saying it's too
| hard, it's too far in the future. Now it's not too hard
| anymore, it's just too expensive. What's next? Too loud?
| Too big? Induces headaches with the esoterically minded?
| pfdietz wrote:
| And it was pointed out 40 years ago that DT fusion will
| be inherently expensive (specifically, more expensive
| than fission, which itself has demonstrated it cannot
| compete.)
|
| https://orcutt.net/weblog/wp-content/uploads/2015/08/The-
| Tro...
| sercand wrote:
| Solar has the advantage of scaling down. 1000 people can
| give 1M US dollar which can produce approximately 1GW of
| power on a thousand of power plant in a year. You can
| scale down as low as 400W of energy production and
| distribute the financial cost to many people.
| cyberax wrote:
| You'll freeze to death in winter, but that's a minor
| thing. Living is overrated.
| pfdietz wrote:
| Not with a properly design energy system. The conclusion
| of 100% RE research is that such a system will have costs
| similar to fossil fuels.
| cyberax wrote:
| No. Right now there is no reasonable way to have a 100%
| renewable and reliable grid in Northern Europe, excepting
| classic hydro.
|
| I specifically studied the German grid, and it needs
| about a MONTH of storage to compensate for a once-in-a-
| century Dunkelflaute (a period with little wind, no sun,
| and cold temperatures).
| cesarb wrote:
| > Right now there is no reasonable way to have a 100%
| renewable and reliable grid [...] and it needs about a
| MONTH of storage to compensate for a once-in-a-century
| Dunkelflaute
|
| If you accept slightly less than 100% renewables, you
| could use diesel or gas backup for these once-in-a-
| century events.
| the8472 wrote:
| That drives up costs because you have to maintain many
| gigawatts of backup capacity sitting idle most of the
| year. It's better to have more flexible solutions that
| provide value the whole year. That's either baseload
| (fission, fusion) or grid-scale, seasonal storage
| (unsolved problem).
| pfdietz wrote:
| The backup capacity is cheap (in capital cost) compared
| to nuclear providing the same output. Like, an order of
| magnitude cheaper. Combustion turbines are remarkably
| compact and inexpensive for their power output (this is
| why they power our aircraft). It's wonderful what happens
| to machinery when you can reduce the need to transfer
| heat across fluid-solid boundaries. Rocket engines are an
| even more extreme example of this.
| cyberax wrote:
| > Like, an order of magnitude cheaper.
|
| Rooppur Nuclear Power Plant cost $6 per Watt of installed
| capacity over the projected 50 years of lifetime. Simple
| natural gas turbines (not combined cycle) cost around $2
| per Watt over 50 years in just capital costs. This
| doesn't take into account the cost of the fuel, or the
| magic infrastructure to produce, store, and deliver
| hydrogen.
|
| I'm taking Rooppur Nuclear Power Plant as the base for
| comparison because it's an example of what you can do,
| when you have a "mass produced" design that you can just
| quickly build.
| pfdietz wrote:
| That's funded by a loan from the Russian government, not
| from private financial markets, so we can assume the rate
| is below market. The actual cost when real risk penalties
| are included (as they must be for an accurate cost) would
| be higher.
|
| I also doubt anyone is going to be buying Russian nuclear
| power plants in Europe anytime soon. The strategic risk
| and associated cost (as seen with importing natural gas
| from Russia) would be far too high.
| cyberax wrote:
| > That's funded by a loan from the Russian government,
| not from private financial markets, so we can assume the
| rate is below market. The actual cost when real risk
| penalties are included (as they must be for an accurate
| cost) would be higher.
|
| Not much higher, though. Russia makes money on these
| contracts. South Korea has
|
| > I also doubt anyone is going to be buying Russian
| nuclear power plants in Europe anytime soon. The
| strategic risk and associated cost (as seen with
| importing natural gas from Russia) would be far too high.
|
| Of course. I'm not suggesting that Russia should be
| relied upon for ANYTHING at this point. It should be as
| isolated economically as possible.
|
| I'm just using this as an example of what you can do with
| a streamlined construction pipeline for plain old PWRs.
| No fancy new technology, no breakthroughs, just regular
| old good project management.
| cyberax wrote:
| First, backup generation is expensive. Right now Germany
| needs about 200GW, and this value will go _up_ when
| Germany switches from natural gas to heat pumps for
| heating, and expands the EV fleet.
|
| That's a lot. Even cheap gas turbine power plants will
| cost around $100B to build.
|
| And while the one-month Dunkelflaute is exceptional, the
| shorter versions lasting a couple of days happen
| basically every year. As a result, you probably need
| about 2-3 weeks a year of various levels of backup
| utilization every year.
|
| This is how it looks in practice: https://energy-
| charts.info/charts/power/chart.htm?l=de&c=DE&... - look
| at the period from 18th Jan to 25th Jan. The renewable
| generation fell to around 8% of the nameplate capacity
| during that period.
|
| I have not seen any real plans to fix this. My prediction
| is that Germany will just continue to burn gas and coal
| well into 2030-s.
| pfdietz wrote:
| You're wrong about that. Back up with green hydrogen is
| quite plausible. Europe has enormous salt formations in
| which cavities can be solution mined for gas storage
| (this is one of the chief ways natural gas is stored).
| Storing hydrogen, the cost of these caverns per unit of
| storage capacity in these would be about $1/kWh. The
| total potential capacity there is in the petawatt hours,
| far more than would be needed.
|
| A combined cycle power plant costs about $1/W of capacity
| (and for rare events, simple cycle would be even
| cheaper), so one could back up the entire grid with these
| at a small capital cost compared to powering the grid
| with nuclear. For Europe, these would also be useful for
| seasonal leveling, allowing solar to provide a larger
| fraction of Europe's energy demand.
|
| Hydrogen is an example of "Power to X" (PtX), where
| excess power, when available, is used to make some very
| storable commodity. This review article talks about how
| important these are to reaching 100% RE.
|
| https://ieeexplore.ieee.org/document/9837910
|
| "With every iteration in the research and with every
| technological breakthrough in these areas, 100% RE
| systems become increasingly viable. Even former critics
| must admit that adding e-fuels through PtX makes 100% RE
| possible at costs similar to fossil fuels."
| cyberax wrote:
| > You're wrong about that. Back up with green hydrogen is
| quite plausible.
|
| I have not seen any real plan to achieve this. Right now,
| it's basically a giant asterisk with a footnote saying:
| "Magic happens here".
|
| One plan I've seen where authors went totally wild and
| actually tried to compute what's needed, required
| converting 80% of housing to district heating with molten
| salt storage, all kinds of energy storage, and 2x price
| electricity increase.
|
| I've seen estimates that simply building out hydrogen
| backup will cost on the order of $300B in power line and
| pipeline upgrades (because hydrogen can't just be piped
| through natural gas pipes). And it will still require
| expanding the renewable fleet.
|
| I'm not at all optimistic about that.
|
| FWIW, I think power-to-natural-gas has the biggest
| chance, because it can re-use the natural gas
| infrastructure. But it's still going to be too expensive.
| pfdietz wrote:
| Argument-from-ignorance is not an argument. If you
| haven't seen "any real plan" that just reflects your
| disinterest in seeing such a plan.
|
| There is nothing preventing this from being applied to
| Europe. All the technologies are available. It's just a
| matter of integrating existing capabilities, which is the
| surest kind of innovation.
|
| No pipeline upgrades are needed for hydrogen for grid
| storage, since there's no need to move hydrogen away from
| the storage caverns. It can be created and consumed
| there. It could be useful to build pipelines, of course,
| but it isn't necessary. I am NOT suggesting using
| hydrogen to replace natural gas in distributed
| applications.
|
| Power-to-natural-gas has the problem of where does the
| carbon come from. CO2 capture (either from the
| atmosphere, or from the exhaust of the CC plants) would
| add to cost, and then the CO2 needs to be stored also.
| And, the round trip efficiency will be considerably below
| that of hydrogen. Power-to-liquid fuels would make more
| sense; it doesn't cost that much more to turn CO2 + H2
| into such fuels instead of to methane. Liquid fuels
| (normally for air or ship transportation, for example)
| could also serve as a rare event backstop along with
| hydrogen, for once-in-a-century events, as long as the CC
| plants can burn both.
| cyberax wrote:
| > Argument-from-ignorance is not an argument.
|
| You're making it right now.
|
| > If you haven't seen "any real plan" that just reflects
| your disinterest in seeing such a plan.
|
| No. I did a full literature search and I read most of the
| articles in that area.
|
| > There is nothing preventing this from being applied to
| Europe. All the technologies are available. It's just a
| matter of integrating existing capabilities, which is the
| surest kind of innovation.
|
| What is "this"?
|
| > No pipeline upgrades are needed for hydrogen for grid
| storage, since there's no need to move hydrogen away from
| the storage caverns. It can be created and consumed
| there.
|
| The thing is, most of German storage is in the northern
| part (Rehden, Etzel, Epe, etc) due to geology. That's not
| where the consumers are, so you need to build a huge
| amount of power lines.
|
| To give you a perspective, a fairly typical natural gas
| pipeline can transfer around 1 Bcf of gas per day, which
| translates to about 12GW of power. This is the same as
| the largest ultra-high-voltage direct current (UHVDC)
| line in the world (in Brazil), built at the cost of
| around $2.5B for 2400 km.
|
| And you'll need many, many such lines to transfer power
| from the points of generation and consumption to the
| hydrogen hubs. This is in addition to already expensive
| hydrogen production and gas turbines.
|
| I don't see this ever becoming cost-competitive with
| plain old PWRs.
| jasonwatkinspdx wrote:
| You can't jump from idea to production power plant in one
| step. This is research about the fundamental science
| involved. What they're doing is incredibly difficult and
| complex. They have a plasma at millions of degrees mere
| centimeters from superconductors at near absolute zero. The
| field geometry and interactions are so complex it brings even
| current supercomputers to their knees. The device wasn't even
| possible to simulate until the late 90s using the biggest
| machines in the world.
|
| What they've already demonstrated is a tremendous
| accomplishment. But apparently if it doesn't go from idea to
| an option in door dash in 6 months flat that's not good
| enough for people here.
| demondemidi wrote:
| > idea to an option in door dash
|
| I hear ya. The attention span of a TikTok or less.
| constantcrying wrote:
| >What's the reason for that?
|
| It is about research. It generating usable electricity is
| absolutely irrelevant.
|
| You need research projects to figure out what works and what
| doesn't. The goal isn't to build a practical reactor.
| Eji1700 wrote:
| Mostly, they don't?
|
| There should be more funding in this area, but at some point
| you've got to build it, and that takes a ton of time.
| Regulations/bureaucracy could be better but at the end of the
| day you're not going to cut off a ton of time safely.
|
| Once you have a working model iteration gets much much faster,
| but we've simply been hitting walls for decades.
| hedora wrote:
| Is there a minimum viable size for a fusion reactor? If it
| scaled down ennough, they could just launch prototypes into
| space, and see if they explode.
| adhesive_wombat wrote:
| Fusion reactors are pretty non-explodey. Really all they
| can do is spring a leak, then fill with air and extinguish
| the plasma. Maybe if you quench the magnets hard enough you
| might get something dramatic like leaking a gram of
| tritium.
| b3orn wrote:
| I'm no expert on this, but a minimum viable size exists and
| it's much larger than what you could just launch into
| space. I watched a video on this years ago, I don't recall
| the exact relation to size but if I'm not remembering this
| completely wrong there's a minimum size you need for a
| fusion reactor to "ignite", ITER is huge for a reason.
| willis936 wrote:
| ITER is huge because it uses weak magnets.
| Eji1700 wrote:
| I'm honestly not sure if you're joking but in case you're
| not, the "minimum viable size" is hardly the largest issue
| with what you're proposing and it sounds like you're not
| getting what the key issues are.
|
| You're talking about taking a technology that's so finicky
| we've barely gotten it to work after almost 100 years and
| rocketing it into space? We're no where near good enough at
| this to get a test that would work after the extreme
| violence of an escape velocity launch.
|
| Further fusion reactors aren't like fission. "exploding"
| really isn't a problem . Keeping the reaction going in an
| efficient manner is.
|
| IF exploding was a problem, space is probably the worst
| place for it? Putting it way underground would be vastly
| easier and a hell of a lot safer because you won't have
| material possible falling back to earth/hitting satellites
| in orbit.
| sdwr wrote:
| That was not a real question, it was a subconscious plea
| for elon musk to take over and make it work.
|
| "Shooting it into space" is a reference to how SpaceX
| disrupted the rocket industry through a "fail fast"
| mentality, aggressive goals, and sheer force of will.
| flotwig wrote:
| Please don't "move fast and break things" with nuclear
| fusion :-)
| worik wrote:
| What is the worst that can happen?
|
| Seriously, I think I might know (a fire) but I do not.
|
| Is there any possibility these can go ban! and spread
| nasty stuff around the neighbourhood?
|
| I doubt they can go thermonuclear bang! but I am not a
| physicist.
|
| What is the worst than can happen?
| the8472 wrote:
| Well, neutron bombardment from fusion means you get some
| radioactive isotopes. It's not as bad as spent fuel but
| still something to avoid.
|
| But that doesn't really matter. This is expensive
| technology you don't want to blow up. Yes, more expensive
| than rockets.
| andrewflnr wrote:
| It's true that working on fusion is high on the list of
| better uses for $44B than buying an overpriced social
| media platform.
| Eji1700 wrote:
| This take is even more baffling to me than the original
| question.
| ladams wrote:
| Stellarators in particular suffer from very long development
| cycles. It takes years and years of research to develop the
| algorithms used to optimize the coil geometries, and then the
| production of the coils and assembly of the vacuum vessel
| within the coils is much more challenging than for a tokamak.
| The coils are hard to produce because they have highly
| irregular shapes, and tight tolerances. Assembling the vacuum
| vessel is hard because the coils cover much more of the
| "toroidal-ish" surface area than in a tokamak.
|
| The is a lot of interesting work going on in stellarator design
| optimization now, but it will likely be many years before that
| research is realized in another actual reactor.
| fizigura wrote:
| For a few billion USD you could build a real power plant of
| this type. Sounds expensive, but consider how much money
| nuclear fission did cost initially, and how much money we
| burn on other stuff, then it's not unthinkable to have
| somebody rich chip in and make it happen. (Germany just gave
| $10bn subsidies for a domestic Intel factory.)
| Guvante wrote:
| They managed to handle what a fission reactor outputs every
| second in this experiment.
|
| I don't think that points to a commercial reactor whenever
| someone spends a few billions.
| willis936 wrote:
| HSX beat them to the punch by over a decade. Small is easy.
| Unfortunately no machine worth making (power generator
| relevant) is small. Practice helps.
| stjohnswarts wrote:
| Can someone tell me why this won't produce commercial level
| fusion for 30 years so I can shut down my eternally optimistic
| "physics kid" portion of my brain for a while?
| bmicraft wrote:
| It will cost too much
| airgapstopgap wrote:
| This is an incredible achievement but there are strong reasons to
| suspect that stellarators are not and will never be plausible
| candidates for energy generation. For some more experimental or
| perhaps military tasks, it's viable.
| schainks wrote:
| Why do you think this? Also, suggesting only the military
| should use it suggests it is stellarators are well suited for
| energy weapons versus powering homes/industry, which is also
| curious, as energy weapons need huge impulse amounts of power,
| not power that is constantly available and ramps slowly by
| comparison.
| slashdev wrote:
| Says you, without mentioning any of the strong reasons.
| Dulat_Akan wrote:
| I am thinking why companies making so huge reactors, everything
| should be simple just for test to get energy
| sp332 wrote:
| It's a been a long time, but in a talk at Google, I think
| Bussard said that power output scales with the 5th power of the
| radius of the device. There's really no point making a small
| one.
| pfdietz wrote:
| Bussard's last reactor concept, polywell, didn't work.
| sp332 wrote:
| Oh right, I had WB-7 confused with Wendelstein 7.
| pfdietz wrote:
| I greet W7-X with a huge yawn. A reactor based on stellarators
| will still be very large and have very low volumetric power
| density. The beta is not good, so these would only work with DT,
| and suffer from the generic problems of all DT schemes.
| moffkalast wrote:
| What makes tokamaks so much better at power density? After all
| it's the exact same setup, just shaped differently and without
| the center coil?
| pfdietz wrote:
| I didn't say that. Both tokamaks and stellarators on DT will
| have lousy volumetric power density. Indeed, any DT scheme
| will suffer in that respect.
| greesil wrote:
| I submitted TFA, which is from February. How come you nerds
| didn't see this yet?
| nielsbot wrote:
| W7-X seems on track to meet their goal of 30 mins sustained
| plasma. I wish them all the best!
| KyleBerezin wrote:
| Ahh, Wendelstein is that stellerator reactor. The stellerator is
| really cool, and an alternative to a tokamak reactor. Tokamak is
| the doughnut shaped reactor, and it has a problem where the
| plasma near the outer circumference has less magnetic
| confinement. The stellerator is similar, but confines the plasma
| to a ribbon and folds it over on itself in a mobius-like
| arrangement.
|
| I used to be really interested in this, but forgot it existed
| over the years. Glad to see it works!
|
| https://en.wikipedia.org/wiki/Stellarator
| lostlogin wrote:
| Are you able to say more about what you do? Judging by your
| comments, you have some idea what you are talking about.
| Simon_O_Rourke wrote:
| Just curious as to why a Mobius strip type arrangement is
| better than a toroid? Is it anything to do with the turbulence
| in the plasma flow being easier to control?
| KyleBerezin wrote:
| These are great questions for someone more knowledgable, but
| as I understand it, If you follow a single point on the
| surface all the way around the loop, it will spend as much
| time in high confinement as it does in low confinement.
|
| That explains why folding is important, as for the mobius, I
| oversimplified a bit. The Wendelstein has 5 folds, making it
| a mobius, but I think I read about one in Spain that had only
| 4 folds. That would mean the mobius isn't imperitive, but I'm
| sure there is a good reason for it.
|
| Really a stellerator doesn't need 'folding' at all, they can
| be as simple as a twisted torroid. I didn't want to go into
| excruciating detail though, the more in detail I go the more
| likely I am to say something that is wrong lol.
|
| Edit: I looked it up, the one in spain is called "TJ-II"
| NovaDudely wrote:
| First thing that comes to mind is like twisted pairing on
| cables. Distributes the external/internal forces more
| equally. Is it anything like this?
| KyleBerezin wrote:
| No, twisted pair wires are really cool but different.
| When you push current down one wire you pull current down
| the other. The signal is passed through the differential
| of those 2 wires. If the wire is hit with EM
| interference, that change will be seen as a 'common mode
| voltage', that is, both wires will be 'pushed' or
| 'pulled' the same amount, and you won't see a
| differential.
|
| That effect works both ways too, where a single wire with
| a digital signal will spew out radio waves, 2 wires with
| opposing signal cancel each other out and emit no em
| waves.
|
| The effect with the stellarator is more like stirring a
| pot.
| Bjartr wrote:
| I think it's about ensuring the plasma heat/energy
| distribution is more uniform so you get fewer outlier
| particles with high enough energy to escape confinement and
| damage the interior of the reactor. Or something like that.
| cyberax wrote:
| It's actually really easy to explain.
|
| Draw a torus and then draw rectangular "bands" across it,
| they will represent the containment magnets.
|
| Due to pure geometry, the area closer to the center will have
| a smaller distance between bars. This means that the magnetic
| field will be stronger near the center.
|
| This in turn means that particles will separate (depending on
| charge) and drift to the sides. It seriously interferes with
| the containment.
|
| You can fix that by changing the torus into something
| resembling "8", so that particles move to one side when they
| fly through the upper part, but then they'll move back as
| they fly through the lower part.
|
| Of course, you can't just do that in 2D because the part in
| the middle of "8" will have no magnetic field. You need
| something without self-intersections. You can try to move one
| side up and another down. But that doesn't quite work either
| because you will get another set of preferred directions.
|
| So instead you go with the gentle twisting, resulting in the
| Mobius-looking shape.
| MBCook wrote:
| How do Tokamaks solve the issue since they're still torus
| shaped?
| RedShift1 wrote:
| Brute force: just use stronger magnetic fields to contain
| the plasma.
| cyberax wrote:
| They don't. As a result, they have to be much larger, so
| that the difference in the field strength is low enough.
| extrapickles wrote:
| It primarily has to do with the physical construction of the
| magnets, in a toroid the inside of the toroid effectively has
| more windings per meter of circumference than the outside
| causing uneven containment.
|
| With mobius strip you regularly flip between inside and
| outside, so the plasma particles get more even force applied.
| dylan604 wrote:
| Even just reading "mobius" and I cannot not hear the line from
| Warf "There is this theory of the mobious. It twists in the
| fabric of space where time becomes a loop. Time becomes a loop.
| Time becomes a loop." Of course, I'm referencing the Orbital
| track
| mastersummoner wrote:
| I've listened to that song hundreds of times yet somehow
| never realized it was Worf.
| dylan604 wrote:
| I didn't either, since I spelled it Warf! I never watched
| Star Trek (probably get my HN privileges revoked for that),
| but I did know that much. And then the Reading Rainbow
| guy's "whatever happened will happen again". I know the
| character's name is Geordie or whatever, but he didn't have
| the right accent for him to be a Geordie, so he will
| forever be Reading Rainbow guy instead.
| yoz wrote:
| _> I know the character 's name is Geordie or whatever,
| but he didn't have the right accent for him to be a
| Geordie_
|
| it's a fair demand to make, given that his TV predecessor
| was called Scotty and DID have a Scottish accent
| downvotetruth wrote:
| Kunta Kinte is closer to his roots.
| noduerme wrote:
| Wow. A triple play.
| hinkley wrote:
| He could have been the Jeopardy guy too.
| TecoAndJix wrote:
| Ken J was a much better choice
| dylan604 wrote:
| But I didn't grow up watching him on Jeopardy, so no, he
| would never be that guy either.
| fastball wrote:
| Genuine question: why? That isn't even a song, it's just a
| vinyl record skipping for a minute and a half.
| dylan604 wrote:
| I think you're not considering the first album with an
| actual track called Mobius. You're thinking of the
| opening cut on Orbital II (the brown album). That one is
| the one where the "where time becomes a loop" becomes
| fun. The Mobius track is the one where "whatever happens,
| will happen again" is also included. Sorry, but I will
| have to deduct Orbital fanboi points, and you will lose
| your next turn
|
| https://www.youtube.com/watch?v=4PG5PCd284o
|
| Edit: But as to the why, it's fun. Just like the
| "input/output translation" trickery.
| egypturnash wrote:
| It's two copies of "...where time becomes a loop." One on
| the left, one on the right. One of them is _slightly_
| shorter than the other, so that as they repeat again and
| again, they slide in and out of phase. The track ends
| after they come back into phase.
|
| If you listen to this with headphones, or speakers with
| decent separation, paying attention to this feels
| interesting. It's similar to the way listening to
| "binaural beats" can do interesting things to your brain.
|
| Also if you are in the habit of putting an entire album
| on repeat and this is one of your favorite albums, then
| you've probably heard this a zillion times. If you have
| your music player set in "randomize by album" mode, then,
| well, it's the first track on this album, so every time
| it comes up you'll hear most of it unless you _instantly_
| decide you are not in the mood for Orbital 2, and even if
| you 're _not_ in that mood it may be _pleasant_ to let
| everything come back into phase before going to another
| album.
|
| ----
|
| The next track on the album starts up _entirely_ in the
| left ear, with a tinny, distant little loop, and the
| words "Even a stopped clock tells the right time twice a
| day". Once it brings in a deep bass, this bass is also
| doing some weird cross-ear phasing things.
|
| And then the _third_ track _also_ opens with "Even a
| stopped clock..."; a theme has been established at this
| point. Time is a loop, and a stopped clock is right twice
| a day. The opening of "where time becomes a loop" is also
| a bit of a joke; Orbital's musical craft is very much
| about making a bunch of short loops that work together,
| and bringing them in and out over each other for four to
| seven minutes. Occasionally as much as thirty minutes,
| the extended version of "The Box" is _glorious_. This is
| something that utterly dominates most electronic dance
| music now, but Orbital was one of the first notable acts
| to really go hard on this, and this is their second
| album; they are saying "yes it's just more loops, we
| think they're good loops, enjoy!".
|
| By the time you get to the last track, you've probably
| forgotten about Worf's repeated mantra. Especially if
| it's your first time listening to the whole thing and
| Halcyon + On + On just blew all the cobwebs out of your
| head. But Orbital returns to the idea, with two
| _different_ loops that are very close in sound and
| length, played on both channels: "Input
| Translation"/"Output Rotation". They begin in phase with
| each other, drift out, and come back together. And the
| album is over.
|
| Or, if you have the CD player on repeat (remember, this
| album is from a time when people bought CDs and probably
| stuck them into a one-disc player, _maybe_ a 3 or 5-disc
| player if they were lucky, and the whole album is built
| with an awareness of this), you 're back where you began,
| inputs translated and outputs rotated, and ready to be
| reminded of the Theory of the Moebius.
|
| Time has become a loop. Come out of the trance Orbital
| has put you in. Do you want to experience this loop
| again? Does it feel rude to jump to another album before
| Worf's come back into phase again? You may as well let
| him get you back in sync with the moment the album began
| before going back into normal time.
| dylan604 wrote:
| >remember, this album is from a time when people bought
| CDs and probably stuck them into a one-disc player
|
| You just describe the first time I every danced with
| Lucy. I went back and forth with this disc and The Orb's
| A Huge Ever Growing Pulsating Brain That Rules from the
| Centre of the Ultraworld.
| dr_dshiv wrote:
| Same!
| yoz wrote:
| BEST HN THREAD EVER (and WOW is that an essential
| explanation of the first two Orbital albums)
|
| is this where we talk about
|
| - the 39:59 mix of The Orb's "Blue Room" (which, like
| several other Orb singles, is better than the album
| version thanks to Jah Wobble providing a proper bassline)
|
| - the academically-verified lack of repetitiveness in
| Autechre's "Flutter"
|
| - and Orbital's "Criminal Justice Bill?" on the "Are We
| Here" CD single, which is four minutes of silence
| rolandog wrote:
| > The stellerator is really cool, and an alternative to a
| tokamak reactor.
|
| They should've gone with a catchier name like "forbidden
| cruller".
| tw061023 wrote:
| What's interesting is that stellarator actually is not just an
| alternative, but a wholly parallel branch of evolution - it's
| not like one was invented strictly after another, and the
| authors of both designs never knew about the other's work
| before they completed theirs.
|
| What's even more interesting is that the fusor - the simplest
| possible design for a thermonuclear reactor, so simple that
| anyone skilled in electrical engineering and having access to
| proper civilan equipment can build one with ease - seems to be
| invented _after_ both stellarator and tokamak.
|
| That said, I never particularly liked stellarator design. The
| very _complexity_ of it somehow feels subtly wrong, like
| doubling down in the wrong direction.
|
| However, this is one of the cases where I would absolutely love
| to be proven wrong. We are far past due big breakthroughs in
| the field.
| jcheng wrote:
| > The very _complexity_ of it somehow feels subtly wrong,
| like doubling down in the wrong direction.
|
| This made me think of modern jet fighters being designed to
| be aerodynamically unstable, making them all but impossible
| for human pilots to operate without flight computers.
| Apparently the maneuverability benefits make the added
| complexity more than worth it.
|
| https://en.wikipedia.org/wiki/General_Dynamics_F-16_Fighting.
| ..
| avar wrote:
| > The very _complexity_ of it > somehow feels subtly
| wrong.
|
| Why is in complex? Because it's not all square corners or a
| donut shape?
|
| I understand that it was hard to build, but isn't that just
| because it's a one-off?
|
| Any one part of the inside of it looks no more oddly shaped
| than the outside of any modern car, and we've managed to
| scale that.
| waterheater wrote:
| Compared to a tokamak, the stellarator bring engineering
| efficiency while matching performance. Though ideas for the
| tokamak and the stellarator may have emerged together, the
| main reason tokamaks were built first is because they COULD
| be built. Without computer-assisted magnet design,
| stellarators simply couldn't be properly built; the magnetic
| geometries are just too complex.
|
| In the long run, it's not known stellarators will be the
| eventual winner in the long race for a viable fusion reactor.
| The attributes in a winner will be net-positive operational
| efficiency and superior energy harvesting abilities. Perhaps
| multiple approaches will be viable.
| tw061023 wrote:
| I understand the theory. I just hope I will live long
| enough to see a winner in this race.
|
| To be honest, I've been interested in the domain for quite
| a time and I still want to build a fusor or a polywell at
| some point just to see it glow. Probably won't happen
| though.
| waterheater wrote:
| The most difficult parts to obtain will be the power
| supply and vacuum chamber. Still, there's nothing like
| garage fusion!
| fpoling wrote:
| The big plus of stellarator design is inherent absence of
| plasma instabilities affecting tokamaks. Notice that future
| upgrade of Wendelstein may allow to hold plasma for a hour
| compared with minutes at best with tokamaks. Many physicists
| for that reason believes stellarator is the only way to
| archive practical fusion.
| white_dragon88 wrote:
| You know enough to say more. Say more!
| waterheater wrote:
| I'm not that guy, but I can speak to what you're asking. I've
| followed Wendelstein 7-X for almost a decade.
|
| Nuclear fusion occurs at extremely-high temperatures. As you
| heat your fusion fuel to sufficiently-high temperatures to
| allow fusion, the matter transitions into a plasma, which is
| great: plasmas react to electromagnetic fields. As such, a
| major challenge with achieving viable nuclear fusion is
| making a vessel capable of holding the fusion reaction.
| Because we can't create on-demand gravity wells, the next
| best option for confinement is using electromagnetic fields
| to hold the plasma in the air.
|
| So, you now have an "electromagnetic bottle" capable of
| suspending a fusion reaction above the reactor's walls. Now,
| you have another issue: how do you ensure the fuel will
| sufficiently mix to sustain a fusion reaction? One approach
| is to move the plasma in a loop. The topologically-simplest
| method to accomplish this loop is the torus. Such a plasma-
| confinement device is called a tokamak. A tokamak uses two
| magnetic fields, torodial and polodial, to accomplish its
| task. The torodial field is driven through the plasma to push
| it forward, while the polodial field pulls the plasma in
| toward the center. Proper balance of these fields will allow
| the plasma to circuit the vessel following a helical path,
| achieving confinement.
|
| However, driving two separate magnetic fields is energy-
| intensive, and a successful fusion reactor will want to
| minimize its own power consumption to maximize the amount
| available for external usage. Enter the stellarator. The
| stellarator also drives the plasma around in a circle, it but
| uses a single magnetic field. How? It "tricks" the plasma
| into "thinking" there's only one magnetic field by using
| computer-optimized magnets with highly-complex geometries.
| This provides stellarators with a major engineering advantage
| over tokamaks and is a primary reason Wendelstein 7-X would
| have chosen it.
|
| With the confinement vessel topology largely identified, the
| next main step is to figure out how to build a vessel able to
| contain a sustained fusion reaction. For context, fusion
| experiments traditionally only operate on timescales of
| milliseconds to maybe a second. The reason? Fusion occurs at
| millions of degrees, and keeping the reaction vessel cool,
| ensuring a continuous supply of fuel, and dealing with
| reaction "exhaust" (e.g., alpha particles) and stray high-
| energy neutrons from the common deuterium-tritium reaction
| (which irradiate your reactor walls because neutrons don't
| react with electomagnetic fields) is a major, major
| engineering challenge. Any operational, net-positive fusion
| reactor must be able to operate for days, weeks, and months
| on end.
|
| What Wendelstein 7-X has been attempting to do for years is
| demonstrate that building such a vessel is even possible.
| Their overall goal is to sustain a fusion reaction for about
| 30 minutes. Such a timescale will show a proof-of-concept
| system which enables sustained fusion reactions to occur.
|
| Currently, the preferred fuel is deuterium-tritium because
| the fuel is generally available and has an attainable fusion
| temperature. The stray neutron issue can be mitigated by
| lining reactor walls with lithium to breed tritium fuel. Even
| better is to use the helium3-helium3 reaction, which
| completely annihilate to produce pure energy as the output
| (welcome to e=mc^2, enjoy your stay). The main holdups are:
| (1) the reaction occurs at much higher temperatures than
| deuterium-tritium, and (2) he(lium)3 is quite scarce on
| Earth. Once Wendelstein 7-X shows how to engineer a proper
| confinement vessel at a "lower" temperature, you can then
| work on the higher temperature levels required for he3-he3.
| Also, he3 is plentiful on the surface of the moon, so mining
| the surface of the moon will be performed to obtain the
| required fuel, which is the fundamental premise of the movie
| "Moon".
|
| Someone asked for information on electromagnetic plasma
| containment folding. I recommend reading up on
| magnetohydrodynamics (MHD). It's the mathematical and
| physical foundation of your interest.
| pschuegr wrote:
| great comment, thanks - this is why I read HN
| bombcar wrote:
| I'm going to assume the name "waterheater" is from a
| prosaic way of naming a nuclear reactor.
| KyleBerezin wrote:
| One guy asked why the mobius aspect is needed and I
| couldn't answer. I know a lot of stellarators aren't odd-
| period like Wendelstein, and the old designs didn't do
| folding at all. Do you know what improvements the mobius
| design has over something like TJ-II?
| waterheater wrote:
| The helical path creates a twist in the plasma which
| cancels out the drift forces. This is what I meant by
| "tricking" the plasma. User mjfl gives an even more
| technical explanation:
|
| > By twisting the plasma into a shape where the curl of B
| (proportional to J) is parallel to B, i.e. a helix, the
| cross product is 0, and thus there are no net
| magnetohydrodynamic forces on the plasma.
|
| Hope all that's a good answer for you.
|
| > Mobius aspect
|
| You might avoid using the word "Mobius" and instead use
| "helical." A Mobius strip is important because it has two
| faces which form a single surface. The surface aspect
| isn't relevant in this context, so a term which refers to
| the shape would likely dispel confusion in a reader.
|
| As far as I'm aware, each section of a stellarator is
| periodic in its own right, which means the end and start
| points of each section are the same. Though I'm not
| certain, the choice of four versus five is more likely an
| engineering factor rather than one of physics, whereas
| the distinction between a tokamak and stellarator is of
| physics and not just engineering.
| golem14 wrote:
| I suppose that any number of twists would be OK, but the
| more twists, the less efficient ?
|
| Is that what you are saying ? Or are there other
| constraints on the number of twists (e.g. must be odd,
| ...)
| KyleBerezin wrote:
| Yes I was referring to odd. But I've been reading some
| papers and I think even 4-fold had the mobius effect.
| I'll comment here again tomorrow when I have learned a
| bit more on the topic.
| KyleBerezin wrote:
| If a 'particle' (I don't know a better word) finds itself
| near one of the top divertors, at the same point in the
| next orbit it will find itself near the bottom divertor.
| That is a product of the "mobius-like" shape, so although
| it isn't really a 'ribbon' and isn't really a mobius, it
| helps explain the concept concisely. I just don't know
| WHY that shape helps lol. Maybe it doesn't and it was
| just a practical design change like you said.
|
| edit: changed language about the divertors.
| waterheater wrote:
| Did a little research to try and understand this better.
|
| The most precise term to describe the "twisted ribbon"
| flux tube in W7-X is "toroidal helix". The toroidal
| quality comes from the general torus shape of the
| stellarator, and the helix quality comes from the
| twisting of the magnetic field by magnets. (The torus
| shape is required only topologically; look up the
| knotatron to see what I mean.)
|
| The "ribbon" we're talking about is properly called the
| flux tube. The flux tube is the volume created by the
| flux surface, which is where the magnetic field lines
| lie. A given volume of plasma contained within a flux
| tube should remain inside it, causing magnetic
| confinement of the plasma.
|
| The optimality of the confinement of the flux tube is
| expressed with the term "omnigeneity". Conceptually, a
| flux tube has onmigeneity if ideally all of the non-
| colliding plasma inside the tube stays in the tube.
| W7-X's flux tube appears to be approaching omnigenity.
| (Another experiment which approaches omnigenity is HSX.
| Interestingly, HSX has one set of primary magnets,
| whereas W7-X has two. That's likely because HSX achieves
| omnigenity via quasisymmetry, whereas W7-X uses various
| stellarator optimization techniques.)
|
| With these points, we can call the W7-X "ribbon" a near-
| omnigenous toroidal helix flux tube, which sounds way
| cooler. So, all that said, why is a helical property
| desired? From what I've read, the twist in the flux
| surface reduces plasma drift inside the flux tube.
|
| I think it makes sense to analogize this stuff as a
| circular semi-permeable pipe filled with a high-pressure
| "magic fluid" flowing around-and-around inside. By semi-
| permeable, it means fluid will leak from the pipe if the
| internal pressure is too high (remember that this is
| magic fluid). Trying to understand the helical twist
| along this analogy, I think the effect is evening of
| internal pressure across the pipe surface to reduce fluid
| turbulence and permeation while maximizing laminar flow.
| At least, that's my best analogous interpretation of
| "why" the twist helps.
|
| The divertors are useful for long-term reactor operation
| but have no direct relevance to the magnetic field
| geometry. I'm guessing there's two divertors for
| engineering reasons (performance, redundancy, etc.) and
| not for reasons of basic physics.
| less_less wrote:
| > Even better is to use the helium3-helium3 reaction, which
| completely annihilate to produce pure energy as the output
| (welcome to e=mc^2, enjoy your stay).
|
| It doesn't completely annihilate to produce pure energy. It
| produces helium-4 and two protons. Or you can react
| helium-3 + deuterium to produce helium-4 and one proton.
| The point is that helium-4 and protons are easier to shield
| against than neutrons, don't turn your reactor radioactive,
| and at least in theory their energy can be extracted
| directly (eg through induction) instead of through heat.
|
| Edited to add: except helium-3 + deuterium still produces
| neutrons, because sometimes the deuterium will react with
| itself to produce helium-3 and a neutron.
| waterheater wrote:
| You're absolutely right, thank you for the correction.
| he3-he3 doesn't produce neutrons, which is the major
| advantage, in addition to the massive energy output.
|
| Here's an interesting link which lists various fusion
| reactions:
| https://en.wikipedia.org/wiki/Helium-3#Nuclear_fuel
| huribfobcf wrote:
| The terms (not specific to tokamaks) are "toroidal" and
| "poloidal". https://en.wikipedia.org/wiki/Toroidal_and_polo
| idal_coordina...
| waterheater wrote:
| Oops, my bad on the typos. Thanks for the correction.
| gabereiser wrote:
| Seconded. This is fascinating stuff and reminds me of some
| crazy rant some guy was telling me about anti-gravity and how
| electromagnetic "ribbons" could propel you. Obviously the guy
| _was_ nuts, right? How would one go about learning more about
| electromagnetic plasma containment folding?
| KyleBerezin wrote:
| Haha, no I am just some random guy who reads too many
| Wikipedia articles. "Electromagnetic plasma containment
| folding" does sound like something a crazy person at a bus
| station would rant about.
|
| My explanation was definitely over simplified, but I'm not
| knowledgable enough to go into detail on the topic. I can't
| even point you towards something to read on the topic since
| everything I read about it is like 15 years old at this
| point.
| tootie wrote:
| If a Hollywood screenwriter were naming a crazy science
| device, they would come up with something like
| Wendelstien 7-X
| tboughen wrote:
| My favourite fact about it comes from
| https://phys.org/news/2016-02-plasma-physicist-discusses-
| wen...
|
| "...the supporting structure can only withstand the
| forces if the interfaces between the ten individual
| segments of the central rings, which weighs several
| tonnes, are built with a level of precision of less than
| 100 millionths of a metre..." - and they found a small
| family business in the north of Italy capable of doing
| this!
| dale_glass wrote:
| Odd units.
|
| 1 meter = 100 cm = 1000mm.
|
| So 1 millionth of a meter = 1/1000th of 1mm.
|
| thus, 100 millionths of a meter = 0.1mm, or ~4 thou in
| American units. Easily achievable by hobbyists, let alone
| by serious, professional equipment.
|
| Sure, that is a pretty exacting specification for what I
| suppose is a big machine, but I'm pretty sure very normal
| things like say, car engines get made to far tighter
| tolerances.
| Retric wrote:
| You messed up at your last step 1 millionth = 1mm, 10
| millionth = 0.1mm, 100 millionth = 0.01mm
|
| 0.01mm is very difficult when you're talking large custom
| objects with complex shapes.
| dale_glass wrote:
| Oh, English fail on my part then. I had assumed that 100
| millionths of a metre == 100 * 1/1000000.
| eis wrote:
| The german site of the source speaks of 0.1mm so you were
| correct > bei Toleranzen von teilweise
| nur 0,1 Millimeter
|
| https://www.ipp.mpg.de/de/aktuelles/presse/pi/2020/01_20
| Retric wrote:
| No your correct, I just read it wrong. Really needed to
| pay attention to the s.
| starkrights wrote:
| I think the original commenter is right- correct me if I
| missed what you're getting at.
|
| Keeping it all in the same units until the end here:
|
| 1 millionth of 1 meter = (1 / 1,000,000)m = (1e-6m)
|
| 1 millionth * 100 = 100 millionths => (1e-6m) * 100 =
| (1e-4m) = 100 millionths
|
| (1e-4m) = .0001m | 1m = 1000mm => .0001m*1000 = .1mm
| [deleted]
| Retric wrote:
| Ops, 100 ( 1 millionths of a meter) is a much more
| reasonable tolerance here than 1 / (100 millionth) of a
| meter.
|
| I am to used to people saying 100 millionth of a meter to
| mean 10 nm or 0.01 um which would have looked insane if I
| had written that.
|
| Aka 100 millionth vs 100 millionths
| kortex wrote:
| What usually matters more than absolute tolerances is
| relative tolerance, aka ppm. 100 micron / 4 thou
| tolerance can be achieved with hand tools and a bit of
| patience on the benchtop scale, say a 4" part. That's
| about 1000 ppm, or 0.1%. If I gave you a meter stick, you
| could probably eyeball marking something +/- 1mm.
|
| Getting the same finish on a 120"/3m coil is 33 ppm. 100
| ppm / 0.01% for any operation or process tends to be
| where things start to get really challenging. Deflection
| goes up by the length _cubed_ , so increasing the size of
| all the tooling relative to the tolerance gets really
| challenging really fast.
| dekhn wrote:
| millionths of a meter are known as micron so most people
| would call this '100 micron' (or '100 micrometers') which
| is indeed close to 4 thou, as you calculated, and is the
| level of accuracy of my ~$500 3d printer.
|
| 1 thou was achievable in routine shops in the 1940s and a
| tenth of a thou (2.54 micron) is a common accuracy to
| target these days. Obviously it depends on the context
| and the size of the object, at some point you move away
| from cutting to using grinding and lapping to achieve
| your results, which is ultra-timeconsuming.
| dylan604 wrote:
| >"Electromagnetic plasma containment folding" does sound
| like something a crazy person at a bus station would rant
| about.
|
| Or the very person that someone with a show like Art Bell
| would have as a guest.
| StackOverlord wrote:
| > Dr. Ning Li of Huntsville, AL passed peacefully away on
| July 27, 2021. She was 79 years old. One of the world's
| leading scientists in super-conductivity anti-gravity. Dr.
| Li had constructed first 12" HTSD of the world in late 90s.
|
| https://www.berryhillfh.com/obituary/ning-
| li?lud=4CF765EE88E...
| gabereiser wrote:
| I just read a bunch of stuff about her from her son.
| About how he took care of her in her advanced years and
| her alzheimer's disease. Sad but also peculiar about her
| DoD work and how she "never talked about it". I wonder
| what it was? trying to get an alien craft working again?
| developing anti-gravity weapon? a ship? a hoverboard?
| please say it was a hoverboard.
|
| Her claim that "You can take a bowling ball and place it
| and it will stay." is fascinating. I would love to see
| footage/video of this. Small electro marbles and globes
| are one thing, a bowling ball or other large non-magnetic
| object!? man oh man!
| themagician wrote:
| I find the geometry of things like this fascinating. We
| typically think in such simple shapes. I feel like my brain can
| do triangle, rectangle and maybe hexagons and that's about it.
| I remember when I finally understood radians enough to really
| understand circles and waveforms--I felt so enlightened. Like I
| actually remember the moment when it clicked. For years I was
| just "doing the work" without actually understanding what I was
| doing, but once I was able to understand it... it's like
| something changed in my brain.
|
| I want to be able to think in mobius, but my brain is currently
| like, "No thanks."
| sdwr wrote:
| I'll argue that "thinking in mobius" is simpler than thinking
| in circles, and more true to life than thinking in basic
| shapes.
|
| The core concepts in mobius-land are local curvature and
| global cumulative field.
| stjohnswarts wrote:
| Sorry those just aren't the way the average joe on the
| street thinks about things.
| KyleBerezin wrote:
| Yea they are kinda confusing, especially when you get into
| the 3D ones like klien bottles and roman surfaces. I also
| recently learned that if you make a mobius shaped
| transmission line (like a ladder line) and you send a pulse
| down it, that pulse will continue looping until it dissipates
| (or forever if it is a superconductor).
|
| https://www.microwavejournal.com/articles/21001-printed-
| reso...
|
| I have no idea if there are any advantages over a simple
| planar circular loop though.
| colordrops wrote:
| Are real life superconductors ideal, i.e. they truly would
| store a charge forever (at least until the material
| disintegrated)? Or is there some sort of loss, albeit much
| less than typical resistance?
| klodolph wrote:
| 1. Something "in a superconducting state" has zero
| resistance, but the transition to superconducting states
| is not sudden, and there are various things which disrupt
| that state like magnetic fields.
|
| 2. Alternating currents will dissipate even with zero
| resistance, because the circuit will emit EM waves.
| KyleBerezin wrote:
| Ladder lines are balanced transmission lines, so they do
| not emit EM radiation.
| klodolph wrote:
| Wouldn't that require kind of an idealized transmission
| line, not just a superconducting one?
| KyleBerezin wrote:
| Yes. I don't think super conduncting ressonators of any
| design are perfect.
| KyleBerezin wrote:
| So long as you do not exceed a certain current, they have
| zero resistance. There are other forms of parasitics
| though that can effect it.
|
| Those crazy electromagnets they use on these stellarator
| are simple superconducting loops that they 'charge' by
| inducing a current. That current is maintained so long as
| the superconductor stays below a certain temp. There is
| even something called a SMES (superconducting magnetic
| energy storage) that stores power this way, as I
| understand it they have a 0% self discharge rate.
| colordrops wrote:
| Is the charge static or in motion? If in motion, isn't
| this basically a perpetual motion machine? Electrons have
| mass right?
| KyleBerezin wrote:
| In motion. Yes it is perpetual motion. The same thing can
| be observed in superfluids.
| adrianN wrote:
| It is my understanding that electrons on a curved
| trajectory will lose energy to electromagnetic radiation.
| Is that not the with electrons in a superconductor?
| thibauts wrote:
| That is my understanding also. I would very much like an
| expert answer on this one !
| dekhn wrote:
| I can't really think in (visualize) 3d shapes, so I depend a
| lot on 3D geometry programs when I design things like for my
| microscope. A fair number of people I've talked to can
| visualize complex shapes in their head, rotate them around,
| do interference checking, etc.
| wizzwizz4 wrote:
| Aphantasia? https://en.wikipedia.org/wiki/Aphantasia
| dylan604 wrote:
| What about those tests where they say to fold a piece of
| paper X number of times, and then punch holes in specific
| places. You then have to pick the image of what the paper
| would look like unfolded. Do these types of visualizations
| give you the same issue? I have known several people that
| just could not visualize these tests, and I'm curious if
| these are related.
| willis936 wrote:
| They're actually quite simple geometries in the right
| (unintuitive and warped) coordinate system.
| hobs wrote:
| Just play Asteroids, congrats, add a twist between certain
| edges (which would manifest as a flip) and you now are in the
| mobius.
| dylan604 wrote:
| >I want to be able to think in mobius, but my brain is
| currently like, "No thanks."
|
| I spent a lot time staring at Escher images as a teen, so I
| think my brain says "yes please". I have no idea what to do
| with any of it, so it's not like it does me any good.
| eternityforest wrote:
| Doing CAD design is really interesting. A lot of stuff is
| just 2.5D, extrusions of 2D sketches sitting on other 2D
| sketches.
|
| Then you accidentally make something truly 3D by intersecting
| things and realize you have no idea what you're looking at,
| couldn't imagine it if you closed your eyes, couldn't
| replicate it if you had a picture of the result and didn't
| know the 2D inputs that made it... and then you realize there
| are probably people out there who can see that entire design
| in their head.
|
| To me it's like unicycling on a tightrope or skateboarding or
| realistic oil painting or playing piano well. I have no real
| concept or reference point for what that experience must be
| like.
| p1mrx wrote:
| Just drawing a 3D slanted plane to match the front of my
| printer made my head hurt:
| https://www.printables.com/model/526981-ender-3-s1-quad-z-
| br...
| nomel wrote:
| Coming from 3d sculpting to CAD was...eye opening. It
| really makes you realize how much of design constrained by
| the CAD tools, which are mostly constrained by
| manufacturability.
|
| If true 3d printing* ever gets cheap, it'll be interesting
| to see how much form will be able follow function, rather
| than manufacturing cost.
|
| * true 3d, as in overhang are allowed. Something like a
| cheap FDM is more 2.5d, since overhangs aren't allowed.
| rkagerer wrote:
| Well, there's SLS which is tolerant of overhangs and
| other exotic features. Formlabs has a machine in the 5
| digit price range, and I wouldn't be surprised to see
| competitors come out with a 4-digit one in the near
| future.
| eternityforest wrote:
| Overhangs up to 45 degrees work fine, and usually
| steeper. Bridges also work, most of the time, although I
| am having trouble with them at the moment.
|
| They're not quite unconstrained, and the layer adhesion
| strength makes some geometries not strong, but they're
| much more than 2.5D.
| dmm10 wrote:
| With powder bed printers overhangs and detached captured
| parts aren't a problem. Try making your own from an old
| inkjet printer.
| oefnak wrote:
| You can print with supports to print any shape.
| waldothedog wrote:
| Interesting. With a very strong reference for the
| experience of skateboarding, reading your sentence made me
| think about how hard it is to explain! I suppose when it's
| going well, it feels like body/mind flow, when it's going
| poorly it feels like physics :)
| eternityforest wrote:
| That kind of thing is super amazing! I've secretly
| suspected for a while that people who are able to
| skateboard or do similar things must live in 4 or 5
| dimensions.
|
| I can't figure out any kind of way someone could do that
| with anything resembling what I understand "thought" to
| be like, so I assume you must be able to process entire
| sequences and their alternate possibilities
| simultaneously?
| jkestner wrote:
| CAD is hard! I think about this a lot as I'm doing a
| makerspace at an elementary school and adults think it
| needs a 3D printer, but what are kids going to print on it?
|
| I think for me, the prerequisites for mastering CAD were 1)
| the practice I got visualizing 3D shapes so I could
| translate them into unambiguous mechanical drawings on
| paper (I swear, I'm not that old but my college was behind
| and we were the last class to actually do mechanical
| drawings with a pencil), and 2) having a procedural thought
| process from coding so that I could sequence the CAD
| operations to get where I want.
| eternityforest wrote:
| For me CAD is pretty much the opposite, I rely heavily on
| the apps, I spent about a week trying to learn to draw
| before deciding I didn't really want to spend months or
| years on it.
|
| I'm not a mechanical engineer, I mostly only do
| incidental CAD and hobby level work, so it's not really
| essential to have the deep understanding of space that
| real MEs need.
|
| I often don't know what sequence of operations I'll need
| until I actually open the app. Generally it's more of an
| "Oh I need a mounting hole, lets look around on the
| screen and see where one could go" thing, a lot of the
| thinking is in the app rather than in the mind.
|
| Of course you can't make nicely parametric things without
| a lot more thought so I will often wind up having to redo
| things that aren't one offs...
| RRWagner wrote:
| Try Blockscad3d.com
|
| It's a block language where you program the object rather
| than manipulate shapes. It works well for my brain. Ymmv
| pineaux wrote:
| Grasshopper for rhino is awesome too. It's actually
| really relevant for this topic. It's the only syste I
| know that integrates so well into a precise cad design
| system and also allows you to do complex stuff easily. I
| love it. Drawing a stellarator precisely is probably not
| that hard on it... Will see if I can throw something out
| quickly today.
| imtringued wrote:
| It not only works. It beats tokamak reactors by orders of
| magnitude to the point that it and ITER are the only fusion
| reactors that even matter, so saying that you forgot about one
| of the most important fusion reactors in history is highly
| condescending.
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