A good point. I haven’t read up on this since grade school, so I’m definitely speaking from a layman’s perspective.
Factor in the heavy insurance load and staggering decommissioning costs after several billion years, and they’re not that economical. /s
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I don’t know the underlying physics of it well enough to explain at all. The gist is that though - make elements fuse together by one means or another. We can do that much already, but it’s turned out to be extraordinarily difficult to do in a way that produces more energy than it consumes. That’s the big trick. The sun has the advantage of sheer mass on its side, giving it enough gravity to cause it naturally.
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They’re trying to create an environment that’s extremely hot and under extremely high pressure, so that hydrogen (though more likely deuterium) fuses with itself and creates helium and an extreme amount of energy. The theory is fine and stars exist so it works, no problem there. The problem is recreating the conditions that exist in the core of a star, and containing it. They’re doing this with lots of superconductors and magnetic fields, or at least trying, I don’t think anyone has actually sustained a reaction for more than a few seconds.
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As I understand it, the fuel (usually deuterium or tritium, isotopes of hydrogen) has to be in the form of a superheated plasma before fusion can occur. This plasma is really hard to keep hot (so costly to start any reaction) and is really hard to contain once the reaction starts (so big engineering challenges).
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Fusion tries to persuade two hydrogen nuclei too squeeze together and turn into a helium nucleus. The hydrogen nuclei are both positively charged and repel each other like magnets. To get them together you need to put in a lot of energy (heat) to crash them together, or squeeze them (pressure). The Sun does it by squeezing the weight of a giant ball of gas thousands of times bigger than the earth onto the nuclei in its core.
A particle accelerator can smash a limited number together by shooting them into a stationary target like a gun or shooting two streams together like two bullets hitting each other. This does not produce enough energy to be useful.
The reactors pictured are “tokamaks”. These move the hydrogen around in a circle like a doughnut, heat them and squeeze them with magnetic fields. The energy used to heat and generate the magnetic fields is often more than the energy generated by the reactor. When the energy used is the same, it is called the “break even point”. People get excited to reach that point. To be useful you need to produce more energy than you put in.
The “engineering problems” that come after this is that they put so much energy into the doughnut that the nuclei want to shoot out of it. The nuclei get so hot that no material can hold it without melting so only the magnetic fields can contain them. After nuclei get smashed together, neutrons spit out, go right through the magnetic field, hit whatever the tokamak is made and slowly changes the metal so that it becomes brittle and starts falling apart. The material the reactor is made of then becomes radioactive but not as bad as fission power reactor.
There are other types of reactor. One involves lasers that smush and heat pellets of hydrogen. Another pinches the hydrogen instead of making it run around in a doughnut shape. The tokamak doughnut ones seem most successful so far.
People mention deuterium and tritium fuel. Normal hydrogen is just a proton as a nucleolus and an electron going around it. Deuterium has a neutron and proton as a nucleolus and tritium has two neutrons and a proton. They are all hydrogen (chemically). The extra neutrons make the atoms heavier and better at smashing together. The “plasma” is just a gas of a bunch of nuclei with no electrons. Without electrons they are charged and can be controlled with electrical fields. Neutrons have no charge and can go right through the fields, that is why they em-brittle the containers.
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Well at last, with unlimited free energy, we will enter an era of peace and plenty for all. Right?
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The party we throw when we get fusion power is gonna be EPIC!
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Totally get you on the perpetual 10 years away thing, though i do think its tantalizingly close. I think 10 years is reasonable based on my very casual following of fusion advancements, but i think that’s deceptive at the same time. It doesn’t mean it’d have mass use by 10 years. I would give it 20-30 years out for mass use because commercial/industrial use of new tech brings up problems that werent apparent during the R&D. Still its a safe bet that in our lifetime we’ll see fusion be adopted in some form at the least, widespread adoption could take a while depending on the complexity of the end result. As is the reactors that are being tested are very very complex even as they improve the efficiencies, until they can make a robust version its going to be a hard thing to implement.
A similar issue is quantum computing, it’s a thing that currently exists and mostly works but its not robust and efficient enough for anyone to start using. That’s also similarly 10-20 years away and will massively move forward whats possible.
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Yes, I’m enamored with General Fusion too. Their piston/liquid metal system just seems properly industrial to function in an actual power plant, as opposed to a lab setting. I love the thought of taking one of these reactors and fitting it into an old coal fired power plant. Rather than burning coal to generate steam to spin a turbine, you use fusion to heat liquid metal to generate steam and spin the same turbine.
That said, Dennis Whyte really knows his stuff. I recommend seeking out some of his talks on YouTube.
I still worry that climate change will be society’s end, but this gives me some hope.
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Do we know it’s physically possible? It sounds almost like they’re saying “The sun does fusion so we should be able to make a small sun, it’s just engineering!”
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in simcity 2000 i put two of them in. my city really only needed one, but it was also shaped like a penis so for aesthetic reasons we built two.
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Totes true. Researchers regularly run experiments that are much much hotter than the sun on a regular basis so “making a small sun” is not all that alarming, it’s a matter of efficiencies. Right now it takes more energy to put in to keep it going than you get out though a lot of progress has been made on that front. I forget what the current efficiency % is for fusion experiments.
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Obligatory reference
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Just in time to power my flying fully autonomous car!
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Didn’t those experiments usually go by the term “H-Bomb tests”?
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Building a space elevator is just material science.
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Fusion happens naturally in the cores of stars. We can make fusion happen here on earth in a hydrogen bomb, by using an atomic bomb to compress and heat hydrogen to millions of degrees and millions of atmospheres. These examples should give an idea of the nature of the problem. In order to make fusion happen gently enough that we can extract energy from it instead of be killed by it, you need to somehow heat the hydrogen really fucking hot while compressing it really tightly, while at the same time not letting it do what hot compressed things want to do.
So far there are research reactors that can make fusion happen for short periods of time by expending far more energy than is generated. Tomahawk Tokamak reactors use magnetic fields to contain the hot compressed hydrogen. That the magnetic fields tend to leak is the main stumbling block with those. The physicists who invent H bombs for the US government have been mucking around with a design whose name I forget where you blast hydrogen with lots of very powerful lasers from all directions. The upside of that design is it lets them simulate an H bomb and thus continue to do weapons research without actually setting off bombs. The down side is that lasers are very inefficient, and making the hydrogen fuse for more than a few nanoseconds at a time without, you know, blowing up the place, is tricky.
Going a bit more into the tech details,. inside the sun and other stars, four normal hydrogen nuclei get merged in a series of steps into a single helium nuclei (with two protons getting turned into neutrons, with release of energy). Here on Earth, in H-bombs, we fuse heavy hydrogen (deuterium) and extra heavy hydrogen (tritium) atoms into a single helium atom (heavy hydrogen has one proton and one neutron, tritium has one proton and two neutrons). There’s still a release of energy because of subelementary particles – basically one helium has less glue holding its nucleus together than one deuterium plus one tritium.
Deuterium plus tritium gives you three neutrons and two protons, so there’s one extra neutron which goes zipping out until it hits some other atom, adding a neutron to its nucleus and making it radioactive. D+T fusion is the easiest kind of fusion, it happens at the lowest temperature and pressure.
(ETA: the radiation produced by neutron bombardment is pretty minor, the big problem is that the materials that get bombarded by neutrons transform to different elements, which means over time your pure strong alloys turn into impure and much weaker alloys, your superconducting wires stop superconducting, and so forth. Regular fission reactors have the same problems with alloys becoming brittle due to neutron poisoning, but it’s trivial compared to the problem of extremely high amounts of radiation from the fission products)
D+D fusion is harder but there’s no release of neutrons, hence no radioactivity whatsoever. - it takes higher temperatures and pressures, and since it generates a light helium atom (with only one neutron), it still gives off neutrons. The beauty of it is that it doesn’t use tritium, which has to be manufactured and which is radioactive. Ordinary water contains a small percentage of deuterium, refine it and you get “heavy water” with a much higher percentage of deuterium. So a D+D reactor can literally be fuelled with water.
Considering that we are having incredible trouble achieving sustained D+T fusion outside of a nuclear bomb, D+D is even more out of reach. Most fusion physicists consider Proton-Proton fusion (4 light hydrogen → 1 helium) impossible outside of the core of a star - the energy requirements are just too extreme.
ETA: Governments have been funding research fusion reactors for at least the past 50 years. Right from the start, they’ve been having the exact same problems as today – getting some hydrogen to fuse together in a safe and controlled manner is easy enough, but the energy required to make it happen by far exceeds the energy released. Getting enough fusion to happen that energy output exceeds energy input is as elusive today as it was in the 70’s.
eta2: I don’t want to say how many years I have been misreading Tokamak as Tomahawk. Fixed, and now I’m going to go wear my dunce cap for a while.
eta3: physics is complicated. Fixed explication of D+D vs D+T fusion.
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Sure, but there’s also a lot of research with lasers and reactors. The laser research is really cool though as it can also be used not just for extreme temperatures for also extreme pressures
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Lawrenceville Plasma Physics is close to net energy. LPPFusion.com
Their next series of experiments over the next 12-18 months will tell the tale.
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