7 ms·

Exactly the opposite: their task, assigned by Congress, is weapons work. Period. But pretending to work on "carbon-free energy" is good for funding, just now.

• jboy55 4y ago
  At least ITER has a plausible, in a sci-fi story sense, way of creating a sustainable fusion reaction to which more fuel could be given. The fact the neutrons produced, if it did reach the high Q ratios, would irradiate and break down everything involved, is probably 2070's scientists and engineers problems to solve.
  • moloch-hai 4y ago
    In that paradise of abundant cheap solar and wind power, only weapons people will be interested in fusion. They will probably be trying to come up with zero-fallout things they can use tactically.
    • zbobet2012 4y ago
      Solar and wind power are not sufficient for spacecraft, and many other applications. Fusion power still has very interesting applications.
      • moloch-hai 4y ago
        Most likely, spacecraft will rely on power delivered via laser. If anybody succeeds in working out D-3He fusion, that could work in a spacecraft. (D-T, no.) We could probably scare up enough 3He to use for that, if there weren't too many.
        • PaulHoule 4y ago
          If anybody in the universe is doing interstellar travel I think they would have developed D-D fusion which is somewhat more difficult than D-³He or D-T fusion but probably possible with the a scaled up version of the same machine. Outside the frost line there is a lot of water and a higher percentage of D relative to H so it seems possible to "live off the land" between the stars without being dependent on starshine. A D-D reactor would produce ³He and T, a lot of those products would burn up in the reactor because the reaction rates are high but it would probably be possible to separate some of those out and use it as a breeder reactor that makes fuel for D-³He and D-T reactors elsewhere. I could picture the big D-D reactor running on a large comet or dwarf planet like Pluto producing D-³He for smaller reactors on spacecraft. (D-T not only produces a lot of neutrons but the T has a half life of 12 or so years and won't last for long journies.) My guess is that interstellar travelers would develop a lifestyle that works around the frost line, where generic bodies above a certain size have liquid water inside. If they were grabby they might consume Ceres or Pluto but might not really care about dry, idiosyncratic worlds like the Earth and Mars.
          • moloch-hai 4y ago
            Anybody doing interstellar travel should hang their collective head-analog in shame if they haven't mastered aneutronic p-11B fusion yet. (They will need to have figured out how to reflect xrays.) Having got used to spending interminable ages out in the infinite chill void, they probably have come to prefer being there, so have no desire to roast deep in a stellar gravity well. Their equipment might not even work if warmed too much.
      • rini17 4y ago
        Solar is completely sufficient for 99% of applications.
        • iso1631 4y ago
          How do you power a moon base with solar? 14 days of battery? Fine. How do you power a Europa base with Solar? A Neptune probe?
          • rini17 4y ago
            Since we're talking in present tense that's the remaining 1%. Moon base can be fine with power beamed from a satellite or plain mirrors in orbit, no atmosphere in the way. Might end up being still cheaper than hauling nuclear reactor there plus all the infra to reliably dump waste heat from it.
            • iso1631 4y ago
              "Solar and wind power are not sufficient for spacecraft" I guess you're right that solar is useful for 99% of spacecraft -- in that they use it currently. Not a very useful observation "and many other applications" Power in polar regions. How well does Solar work in Antarctica? Or Alaska for that matter?
              • moloch-hai 4y ago
                It works super-great, collected in the tropics and shipped in chemical form. Before you object to depending on imported liquid fuel, consider that most of the world does already. The main difference is that literally anybody can make it, not just "oil exporting countries" and "fuel refiners". And, will. And export excess production when local tankage is full.
                • iso1631 4y ago
                  Last I looked, round-tripping solar via liquid fuel and back to electricity was under 2% before transport costs
    • aussieshibe 4y ago
      Why won't fusion still be a worthwhile goal even if we do have abundant solar/wind? Abundant and cheap are relative terms. Solar and wind could be abundant in a "powers everything we have now and for the foreseeable future of population growth" sense, but maybe not in a "gigantic power-hungry megaprojects which aren't remotely possible today" sense?
      • courgette 4y ago
        Also, is solar truly renewable ? Don’t we need some rare earth component to manufacture them. What happen when we run out of that ?
        • moloch-hai 4y ago
          Solar needs nothing that can be run out of. Likewise, storage. There are plenty of lies repeated, about that and about missing "breakthroughs".
          • courgette 4y ago
            Never heard about space and that sound outright silly. We do parking and we have space for that crap. The other was deeply ingrained in my understanding. That’s good news. I need to do my own research, like the crackpots are saying.
    • courgette 4y ago
      I do software for a living so that gives you my level of ignorance of the real world. I do have two question about solar - is it “drivable” / “pilotable” ? meaning reacting to surge in the grid? My understanding is that this feature is highly desirable for a grid. - can we actually build enough solar panel, physically ? Don’t we need some rare earth thingy that is not in sufficient quantity on our planet as far as we know ? ( follow up : if there is enough, will there be enough in 200 years ? )
      • moloch-hai 4y ago
        The "rare-earths thingy" is a common, transparent lie told frequently about both solar and wind. No rare-earths are used in any solar panel. Some wind turbine generators have used them, but not the big ones. And, "rare-earths" are not in fact rare. So, a double lie. Solar panels provide cheap power generation on a schedule. For dispatchability, you rely on storage. There are many different kinds of practical, efficient storage; which are used where will depend on local conditions. Which will be cheapest isn't clear, but probably not batteries. Batteries used won't need lithium, or rare-earths, either The lie most frequently repeated is that storage needs some sort of "breakthrough". Second is that the small amount built out means more than that there is not enough renewable power yet to charge it from; when there is will be time to build it. In the meantime, we fill in with NG burning. The third is that "pumped hydro", the most common used just now, needs "special geography". Hills are very common. The lie most frequently repeated about solar is that there is any shortage of places to put it. It is most efficiently floated on water reservoirs, where it cuts evaporation and biofouling, although efficiency is only one consideration. It shares nicely with pasture and even crop land, cutting water demand and heat stress without reducing yield. There will never be any shortage of wind or solar: need more, build more; materials needed are all abundant. Likewise storage. Costs are still falling as fast as ever, but are already lowest of any energy source ever known.
        • zardo 4y ago
          > And, "rare-earths" are not in fact rare. It's not a lie but is an unfortunate synonym. They are rare in the sense that they are rarified, spread thin everywhere not concentrated in ores.
  • rbanffy 4y ago
    > is probably 2070's scientists and engineers problems to solve. With some clever choices in building materials, we may be able to dismantle ITER and its successors to use them as fission fuels.
• xbmcuser 4y ago
  If they can get a continuous fusion reaction going converting the heat energy from that to electricity won't be a problem. Getting a contained fusion reaction that gives out more energy than input is the problem how to convert that into electricity is not going to be a problem.
  • jacquesm 4y ago
    > If they can get a continuous fusion reaction going converting the heat energy from that to electricity won't be a problem. Even accepting the qualification that's not just a mere matter of engineering, capturing that heat from a source that hot is not without trouble. A bit like how there is plenty of energy in a single lightning strike and yet we can't easily catch it even though in principle 'just build a large enough capacitor and connect it to a lightning rod' is a workable recipe. > Getting a contained fusion reaction that gives out more energy than input is the problem Not in the least because the container itself is a very hard problem to solve. > how to convert that into electricity is not going to be a problem. It is also a problem, albeit a lesser one. The better way to look at all of these fusion projects is a way to do an end run around arms control limitations with as a very unlikely by-product the possible future generation of energy. But I would not hold my breath for that. Meanwhile, I'm all for capturing more of the energy output by that other fusion reactor that we all have access to, and learning how to store it over longer periods. Preferably to start with a couple of days with something that doesn't degrade (think very high density super capacitor rather than a battery), but I'll take advanced battery technology if it can be done cheap enough per storage cycle. We're getting there.
    • dd36 4y ago
      There’s not plenty of energy in a lightning strike. https://engineering.mit.edu/engage/ask-an-engineer/is-there-a-way-to-harness-electricity-from-lightning/ https://engineering.mit.edu/engage/ask-an-engineer/is-there-...
      • HPsquared 4y ago
        Funnily enough it's about the same order of magnitude as the fusion event discussed in this TFA: about 1 MJ. Energy from one hohlraum ≈ energy from two lightning strikes
• elihu 4y ago
  > The fusion startups are spending down investors' money with zero possibility of payback (Helion conceivably excepted), because if they did get Q>1, they have no workable way to harness it. ITER will not even try to produce one watt-second of electricity. Its follow-on demo reactor won't start building until 2050, if not further delayed. You seem to be awfully certain of that. I'm not an expert in this area, but my understanding is that the MIT Arc reactor is planned to use FLiBe as a liquid coolant that absorbs heat/neutrons/etc from the fusion reaction and is pumped into heat exchangers to boil water to run turbines. I mean, maybe there's some details not worked out and maybe I'm misunderstanding how it works, but it seems like a plan to generate electricity to me. There's no plan to hook ITER up to a thermal plant because it's a research reactor not a power plant, but there's no conceptual reason they couldn't do it. (Not that ITER is a great example; the design is already antiquated before it's even finished.)
  • moloch-hai 4y ago
    "Some details"... Have you ever built anything? Driving steam turbines, even with other costs at zero, leaves you uncompetitive with renewables. But other costs would be very, very far from zero. Extracting the grams of tritium at PPB concentration dissolved in 1000 tons of FLiBe every day so you have fuel for tomorrow is an expensive job all by itself. Making a whole new reactor every year or two because it destroyed itself with neutron bombardment is another.
    • Dylan16807 4y ago
      > Driving steam turbines, even with other costs at zero, leaves you uncompetitive with renewables. Everything gets beaten by renewables when they're at high output. But renewables plus reliable storage costs a lot more, and there's no way it's cheaper than steam turbines attached to a bottomless source.
      • moloch-hai 4y ago
        You seem to forget that storage also has no operating expense. The cost of operating a steam turbine far exceeds the cost of the coal or uranium driving it. But the steam turbine would not be the only operating expense for fusion. We don't know exactly what it would cost to sieve a thousand tons of molten FLiBe every day to get out the tritium produced that day, because no one even knows any way to achieve it at all. But it would certainly be a huge daily expense, if achieved.