8 ms·

Better superconductors means better magnets, which means cheaper fusion. Some modest improvements in high temperature superconductors from MIT is allowing Comm

by px43 2y ago

Better superconductors means better magnets, which means cheaper fusion. Some modest improvements in high temperature superconductors from MIT is allowing Commonwealth Fusion Systems to scale down ITER from being a 65 billion dollar five story behemoth, to something slightly taller than the average human. With a few more iterations, it becomes very feasible to imagine fusion reactors the size of a rice maker to power homes and vehicles, or even smaller to just have personal, wearable fusion reactors that can provide near infinite power to any gadgets we want to carry with us. Also I really enjoy the idea of reducing giant MRI machines down to the form factor of a hula hoop. If anyone could get highly detailed MRI scans whenever they wanted, a huge amount of disease could be prevented.

moffkalast 2y ago
What amazes me about MRI machines is that the magnetic field is "free" in terms of energy cost. It takes some power to start up but then the current just runs in a circle without losses, so you only have to maintain the cooling so the coils remain superconductive. Room temperature superconductors that wouldn't require any cooling would also make lots of use cases for strong magnets obsolete, increasing power and lowering mass for e.g. EV motors, generators, etc.
credit_guy 2y ago
> which means cheaper fusion. It does not mean cheaper fusion. Fusion via magnets is a lie. For 70 years the fusion scientists have been telling us the same story: we are nearly there. We did the math, and if we can just increase the power of the tokamak/stellerator/z-pinch/whatever by a factor of 10, we'll get ignition. The problem is that plasma shows all sorts of instabilities. All these projections need to come with an asterisk: "we did the math, and assuming there's no new instability that will show up this time, then ...". But each time there is a new instability. ITER will get built one day (maybe) and they'll figure out that there's yet another issue that requires a few more tens of billions (or maybe hundreds). They will not get the money this time. ITER did not start as a genuine quest for getting fusion. It was a political project designed to make the US and the USSR cooperate on something that both could perceive as helping humanity in general. Once the USSR disappeared, the impetus was gone, and a third of a century later it remains something that will be finished in the distant future.
- Retric 2y ago
  At the end of the day Fusion has been treated as a very expensive science project not some critical technology we really need to get working. Thus delays which have nothing to do with feasibility or even cost just politics. Joint European Torus (JET) built in 1983! eventually hit a plasma heating Q of 0.67. Scaling that up isn’t some big leap of faith. ITER was started as an agreement between Regan in Gorbachev in 1985, but didn’t begin construction until 2013! based on a significantly scaled down and very conservative design from 2001, with an expected completion date of 2025-2030. It’s terrible, but under funded multinational projects don’t move quickly. That’s why nothing got done with fusion, you need experiments to make progress running computer simulator and toy machines isn’t enough. Further, you can start site prep and building the facilities well before a design is finished. So much of these delays were completely political in nature not technical, we could start site prep for DEMO today but expect site selection and prep to add a few years of completely avoidable delay to that project as well. Of course being able to build a working device is only part of the story, it also needs to make economic sense. But that’s a different matter from why things have taken so long.
  - pfdietz 2y ago
    I agree that fusion has been treated as a science project, but I take a different implication from that. The importance of the science has been overstated, when more mundane engineering considerations are likely more important. There's this pervasive idea that once the science is done, that once the plasma is contained well, we're golden and fusion will be a sure thing. This is very far from the truth. Lawrence Lidsky pointed out back in the 1980s that there are serious arguments against DT fusion, even if you assume the physics isn't a problem at all. Just assuming you have a magic black box that can make DT go and you still need to capture the neutrons, and this simple sounding engineering problem makes DT fusion unattractive compared to alternatives, with volumetric power density at least an order of magnitude worse than fission reactors. Subsequent experience bears this out. Even supposedly compact designs like ARC will still be a factor of 40 worse than PWRs by this metric. Note that better superconductors than the HTSs in ARC would not help, since the mass of ARC is dominated by the structural material needed to keep the magnets from flying apart. Any stronger magnetic field is ruled out by practical considerations of strength of this structure. Maybe the limits can be relaxed somewhat if the reactor has thick liquid lithium as the first wall, so power/area can be increased (the liquid would be exposed directly to vacuum; at sufficiently modest temperature the vapor pressure of liquid lithium can be very low). Zap uses that approach, but notably Zap doesn't use external magnets (superconducting or otherwise); the magnetic field is generated by current flowing in the plasma. Zap doesn't cover all 4 pi steradians around the plasma with flowing metal though, so neutron load on exposed components may still limit their power density.
tambourine_man 2y ago
> fusion reactors the size of a rice maker Mr Fusion is almost 10 years late, according to Back to the Future. I’m still waiting for my hoverboard.
- 1992spacemovie 2y ago
  Ah that movie brings back good childhood memories for me. According to my mom I was addicted to watching Back to The Future when I was like 4-5.
  - tambourine_man 2y ago
    I believe in your mom
- ithkuil 2y ago
  Well, perhaps somebody fiddled with the timeline and destroyed the future we deserved and stranded us in this shit. They probably made a lot of money in the process. A new reason to hate the billionaires
jl6 2y ago
Lockheed Martin's Compact Fusion Reactor was announced in 2013. It's still up on their website[0] but the project seems to have been cancelled a few years ago, without any concluding remarks. [0]https://www.lockheedmartin.com/en-us/products/compact-fusion.htm https://www.lockheedmartin.com/en-us/products/compact-fusion...
sushibowl 2y ago
> Better superconductors means better magnets, which means cheaper fusion. Notably, what is required for this is superconductors with a higher critical field strength. A higher critical temperature eases cooling requirements somewhat but does not in itself make fusion easier. Also, quite a few other advances are required before home appliance-sized fusion reactors become feasible. After all, the largest part of most fission plants has to do with generating power from steam, not so much the nuclear reaction itself. > If anyone could get highly detailed MRI scans whenever they wanted, a huge amount of disease could be prevented. I think this is oversold. Regular MRI screening without any indication is generally regarded as unproductive not because of the cost of the scan, but because of the high number of false positives. Any normal human body is bound to contain some number of benign growths.
- rowanG077 2y ago
  Isn't the high number of false positives not just a symptom of us using it almost always on sick people? I would imagine if everyone got their monthly MRI we would learn far more about healthy bodies and the false positive rate would drop.
  - deleted 2y ago
    [deleted]
  - drowsspa 2y ago
    If you scan everyone, the prior probability is the rate of occurrence within your population. So the test has to be more sensitive than that. For things that have an occurrence of less than 1%...
- ijustlovemath 2y ago
  Not to mention that MRIs represent a significant portion of a person's yearly allowable radiation dose. Not worth it to irradiate people without having a reason. There's also a recent trend in some medical diagnostics of having a lighter touch, instead of running all the tests and potentially drawing the wrong conclusion from heaps of data.
bananapub 2y ago
> Better superconductors means better magnets, which means cheaper fusion. obviously that's untrue, since fusion for power use at the moment isn't "too expensive", it's "too hard". literally hundreds of billions of dollars have been spent and we're still not close. I can't tell why there are so many uninformed posters on this topic on HN. is astroturfing by the nuclear/fossil fuel industry to delay doing the hard work to eliminate fossil fuel use? is it just that people read too much scifi as a kid and then didn't read any real science on the topic for thirty years?
- barfbagginus 2y ago
  ITER will have 10x more volume and 6.6x greater thermal efficiency (Q factor) than any previous reactor. It fires in 2025. The reactor will use around 600mw of electricity to generated 500mw of heat, in 10 minute runs. Not break even by any means, but getting much closer than ever before. ITER uses - I'm estimating - about 5 billion dollars of cryogenic superconductors - 10,000 tons of superconducting tape. These require let's guess an extra 3 billion dollars in cooling capacity and cryonics. Cooling these magnets costs around 150mw of energy, reducing reactor efficiency significantly. We also use much bigger magnets than theoretically necessary, because cryogenic superconductors quench - instantly lose superconductivity - if they take too much power. Now imagine we have some 10x cheaper room temp superconductor that is 10x to 100x harder to quench: + Magnet mass drops 10-100x (to 1000 tons or 100 tons) + Magnet cost drops 100x-1000x (to 50 million or 5 million) + Cryonics system is 1.5 billion cheaper + We cut the reactor's electricity budget by 150mw, to 450mw Overall we saved over 6 billion dollars, thanks to a non-fusion innovation. Keep in mind these numbers are guesses and wishful thinking. But it suggests that a miracle superconductor could push ITER like devices closer to break even, perhaps even achieving it.
tsimionescu 2y ago
> With a few more iterations, it becomes very feasible to imagine fusion reactors the size of a rice maker to power homes and vehicles, or even smaller to just have personal, wearable fusion reactors that can provide near infinite power to any gadgets we want to carry with us. No, because fusion reactors (of any currently realistic design) produce extremely harmful radiation in the form of neutrons. Since neutrons are neutral, they can only be stopped by a large shielding mass when they directly collide with atoms in that mass. The mass itself then turns highly radioactive (with a half-life of a hundred years or so, so much more radioactive than spent fission fuel). Plus, if the magnets fail while the fusion reaction is happening, then the superheated plasma will violently explode in all directions, killing anyone nearby, and spreading the radioactive remnants of the vessel all around. Finally, these fusion reactors need some quantity of tritium, which is an extremely rare and extremely radioactive form of hydrogen (half life of only a few years) , that is never going to be easily available to sell on a consumer market.
- XorNot 2y ago
  > Plus, if the magnets fail while the fusion reaction is happening, then the superheated plasma will violently explode in all directions, killing anyone nearby, and spreading the radioactive remnants of the vessel all around. No. Just...no. This is entirely wrong. The density of any proposed fusion plasma is 250,000 times less then the earth's atmosphere[1]. Fusion plasma would be crushed the surrounding air rushing in, not "explode". Fusion plasma's are incredibly light, and incredibly thin. In the event of a full magnet quench, the only significant damage would be from magnetic quench boil off of coolant...which is a designed for failure mode, and would vent either liquid nitrogen (in HTS designs) or liquid helium in LTS designs like ITER. [1] https://www.ipp.mpg.de/15144/zuendbedingungen https://www.ipp.mpg.de/15144/zuendbedingungen
  - sandworm101 2y ago
    People always think that the heart of a big machine will be some massive block of dense metal. The heart of these machines is, for failure mode purposes, an empty void. Be more afraid of the associated refrigeration plant. That is the bit more likely to explode.
wolfram74 2y ago
Daily reminder that the sun is incredibly bad at making power core power volumentric density: 276 w/m^3 core density: 150000 kg/m^3 alternative units: 1.8 mw/kg .276 w/L hello practical says a typical powered push mower might have about 1.7 KW and might weigh ball park 30 kilos, so ~60 W/kg or tens of thousands more power dense than the sun's core useful fusion is hard because we're not trying to recreate our sun, we're trying to recreate fusion environments so intense I suspect they don't show up outside of supernovas or shortly after the big bang.
amluto 2y ago
Even a hypothetical superduperconductor (flexible like copper wire, infinite current capacity, zero resistance, easy to splice, works up to 200 degrees C, smells like flowers, costs nothing, etc) wouldn’t make all this magic happen. Magnetic fields store energy, and a failure in an electromagnet (even a superduperconducting one) will dissipate that energy quickly (limited only by how high the kickback voltage can get before non-superconducting parts, arcing, etc carry the current). Also, an electric current (even a superduperconducting one) experiences a force inside a magnetic field — a lot of the material of a high-field magnet is the structure needed to keep the magnet from flying apart under its own Lorentz forces. Also, that MRI machine would appreciate a uniform magnetic field, and everything else in the room would appreciate a rapid fall-off outside the machine, and a hula hoop won’t achieve either one.
nothercastle 2y ago
I don’t understand the draw of fusion. Even if the fusion reactor itself was free, the cost of harvesting the heat and transforming into electricity is quite expensive and complicated to the point that it’s its very non competitive with solar or other renewables. It also has the same ramp up and down problems of nuclear. Besides being a cool physics problem is not actually an economically viable source of electricity.

by px43 2y ago

moffkalast 2y ago

What amazes me about MRI machines is that the magnetic field is "free" in terms of energy cost. It takes some power to start up but then the current just runs in a circle without losses, so you only have to maintain the cooling so the coils remain superconductive. Room temperature superconductors that wouldn't require any cooling would also make lots of use cases for strong magnets obsolete, increasing power and lowering mass for e.g. EV motors, generators, etc.

credit_guy 2y ago

> which means cheaper fusion. It does not mean cheaper fusion. Fusion via magnets is a lie. For 70 years the fusion scientists have been telling us the same story: we are nearly there. We did the math, and if we can just increase the power of the tokamak/stellerator/z-pinch/whatever by a factor of 10, we'll get ignition. The problem is that plasma shows all sorts of instabilities. All these projections need to come with an asterisk: "we did the math, and assuming there's no new instability that will show up this time, then ...". But each time there is a new instability. ITER will get built one day (maybe) and they'll figure out that there's yet another issue that requires a few more tens of billions (or maybe hundreds). They will not get the money this time. ITER did not start as a genuine quest for getting fusion. It was a political project designed to make the US and the USSR cooperate on something that both could perceive as helping humanity in general. Once the USSR disappeared, the impetus was gone, and a third of a century later it remains something that will be finished in the distant future.

Retric 2y ago
At the end of the day Fusion has been treated as a very expensive science project not some critical technology we really need to get working. Thus delays which have nothing to do with feasibility or even cost just politics. Joint European Torus (JET) built in 1983! eventually hit a plasma heating Q of 0.67. Scaling that up isn’t some big leap of faith. ITER was started as an agreement between Regan in Gorbachev in 1985, but didn’t begin construction until 2013! based on a significantly scaled down and very conservative design from 2001, with an expected completion date of 2025-2030. It’s terrible, but under funded multinational projects don’t move quickly. That’s why nothing got done with fusion, you need experiments to make progress running computer simulator and toy machines isn’t enough. Further, you can start site prep and building the facilities well before a design is finished. So much of these delays were completely political in nature not technical, we could start site prep for DEMO today but expect site selection and prep to add a few years of completely avoidable delay to that project as well. Of course being able to build a working device is only part of the story, it also needs to make economic sense. But that’s a different matter from why things have taken so long.
- pfdietz 2y ago
  I agree that fusion has been treated as a science project, but I take a different implication from that. The importance of the science has been overstated, when more mundane engineering considerations are likely more important. There's this pervasive idea that once the science is done, that once the plasma is contained well, we're golden and fusion will be a sure thing. This is very far from the truth. Lawrence Lidsky pointed out back in the 1980s that there are serious arguments against DT fusion, even if you assume the physics isn't a problem at all. Just assuming you have a magic black box that can make DT go and you still need to capture the neutrons, and this simple sounding engineering problem makes DT fusion unattractive compared to alternatives, with volumetric power density at least an order of magnitude worse than fission reactors. Subsequent experience bears this out. Even supposedly compact designs like ARC will still be a factor of 40 worse than PWRs by this metric. Note that better superconductors than the HTSs in ARC would not help, since the mass of ARC is dominated by the structural material needed to keep the magnets from flying apart. Any stronger magnetic field is ruled out by practical considerations of strength of this structure. Maybe the limits can be relaxed somewhat if the reactor has thick liquid lithium as the first wall, so power/area can be increased (the liquid would be exposed directly to vacuum; at sufficiently modest temperature the vapor pressure of liquid lithium can be very low). Zap uses that approach, but notably Zap doesn't use external magnets (superconducting or otherwise); the magnetic field is generated by current flowing in the plasma. Zap doesn't cover all 4 pi steradians around the plasma with flowing metal though, so neutron load on exposed components may still limit their power density.

tambourine_man 2y ago

> fusion reactors the size of a rice maker Mr Fusion is almost 10 years late, according to Back to the Future. I’m still waiting for my hoverboard.

1992spacemovie 2y ago
Ah that movie brings back good childhood memories for me. According to my mom I was addicted to watching Back to The Future when I was like 4-5.
- tambourine_man 2y ago
  I believe in your mom
ithkuil 2y ago
Well, perhaps somebody fiddled with the timeline and destroyed the future we deserved and stranded us in this shit. They probably made a lot of money in the process. A new reason to hate the billionaires

jl6 2y ago

Lockheed Martin's Compact Fusion Reactor was announced in 2013. It's still up on their website[0] but the project seems to have been cancelled a few years ago, without any concluding remarks. [0]https://www.lockheedmartin.com/en-us/products/compact-fusion.htm https://www.lockheedmartin.com/en-us/products/compact-fusion...

sushibowl 2y ago

> Better superconductors means better magnets, which means cheaper fusion. Notably, what is required for this is superconductors with a higher critical field strength. A higher critical temperature eases cooling requirements somewhat but does not in itself make fusion easier. Also, quite a few other advances are required before home appliance-sized fusion reactors become feasible. After all, the largest part of most fission plants has to do with generating power from steam, not so much the nuclear reaction itself. > If anyone could get highly detailed MRI scans whenever they wanted, a huge amount of disease could be prevented. I think this is oversold. Regular MRI screening without any indication is generally regarded as unproductive not because of the cost of the scan, but because of the high number of false positives. Any normal human body is bound to contain some number of benign growths.

rowanG077 2y ago
Isn't the high number of false positives not just a symptom of us using it almost always on sick people? I would imagine if everyone got their monthly MRI we would learn far more about healthy bodies and the false positive rate would drop.
- deleted 2y ago
  [deleted]
- drowsspa 2y ago
  If you scan everyone, the prior probability is the rate of occurrence within your population. So the test has to be more sensitive than that. For things that have an occurrence of less than 1%...
ijustlovemath 2y ago
Not to mention that MRIs represent a significant portion of a person's yearly allowable radiation dose. Not worth it to irradiate people without having a reason. There's also a recent trend in some medical diagnostics of having a lighter touch, instead of running all the tests and potentially drawing the wrong conclusion from heaps of data.

bananapub 2y ago

> Better superconductors means better magnets, which means cheaper fusion. obviously that's untrue, since fusion for power use at the moment isn't "too expensive", it's "too hard". literally hundreds of billions of dollars have been spent and we're still not close. I can't tell why there are so many uninformed posters on this topic on HN. is astroturfing by the nuclear/fossil fuel industry to delay doing the hard work to eliminate fossil fuel use? is it just that people read too much scifi as a kid and then didn't read any real science on the topic for thirty years?

barfbagginus 2y ago
ITER will have 10x more volume and 6.6x greater thermal efficiency (Q factor) than any previous reactor. It fires in 2025. The reactor will use around 600mw of electricity to generated 500mw of heat, in 10 minute runs. Not break even by any means, but getting much closer than ever before. ITER uses - I'm estimating - about 5 billion dollars of cryogenic superconductors - 10,000 tons of superconducting tape. These require let's guess an extra 3 billion dollars in cooling capacity and cryonics. Cooling these magnets costs around 150mw of energy, reducing reactor efficiency significantly. We also use much bigger magnets than theoretically necessary, because cryogenic superconductors quench - instantly lose superconductivity - if they take too much power. Now imagine we have some 10x cheaper room temp superconductor that is 10x to 100x harder to quench: + Magnet mass drops 10-100x (to 1000 tons or 100 tons) + Magnet cost drops 100x-1000x (to 50 million or 5 million) + Cryonics system is 1.5 billion cheaper + We cut the reactor's electricity budget by 150mw, to 450mw Overall we saved over 6 billion dollars, thanks to a non-fusion innovation. Keep in mind these numbers are guesses and wishful thinking. But it suggests that a miracle superconductor could push ITER like devices closer to break even, perhaps even achieving it.

tsimionescu 2y ago

> With a few more iterations, it becomes very feasible to imagine fusion reactors the size of a rice maker to power homes and vehicles, or even smaller to just have personal, wearable fusion reactors that can provide near infinite power to any gadgets we want to carry with us. No, because fusion reactors (of any currently realistic design) produce extremely harmful radiation in the form of neutrons. Since neutrons are neutral, they can only be stopped by a large shielding mass when they directly collide with atoms in that mass. The mass itself then turns highly radioactive (with a half-life of a hundred years or so, so much more radioactive than spent fission fuel). Plus, if the magnets fail while the fusion reaction is happening, then the superheated plasma will violently explode in all directions, killing anyone nearby, and spreading the radioactive remnants of the vessel all around. Finally, these fusion reactors need some quantity of tritium, which is an extremely rare and extremely radioactive form of hydrogen (half life of only a few years) , that is never going to be easily available to sell on a consumer market.

XorNot 2y ago
> Plus, if the magnets fail while the fusion reaction is happening, then the superheated plasma will violently explode in all directions, killing anyone nearby, and spreading the radioactive remnants of the vessel all around. No. Just...no. This is entirely wrong. The density of any proposed fusion plasma is 250,000 times less then the earth's atmosphere[1]. Fusion plasma would be crushed the surrounding air rushing in, not "explode". Fusion plasma's are incredibly light, and incredibly thin. In the event of a full magnet quench, the only significant damage would be from magnetic quench boil off of coolant...which is a designed for failure mode, and would vent either liquid nitrogen (in HTS designs) or liquid helium in LTS designs like ITER. [1] https://www.ipp.mpg.de/15144/zuendbedingungen https://www.ipp.mpg.de/15144/zuendbedingungen
- sandworm101 2y ago
  People always think that the heart of a big machine will be some massive block of dense metal. The heart of these machines is, for failure mode purposes, an empty void. Be more afraid of the associated refrigeration plant. That is the bit more likely to explode.

wolfram74 2y ago

Daily reminder that the sun is incredibly bad at making power core power volumentric density: 276 w/m^3 core density: 150000 kg/m^3 alternative units: 1.8 mw/kg .276 w/L hello practical says a typical powered push mower might have about 1.7 KW and might weigh ball park 30 kilos, so ~60 W/kg or tens of thousands more power dense than the sun's core useful fusion is hard because we're not trying to recreate our sun, we're trying to recreate fusion environments so intense I suspect they don't show up outside of supernovas or shortly after the big bang.

amluto 2y ago

Even a hypothetical superduperconductor (flexible like copper wire, infinite current capacity, zero resistance, easy to splice, works up to 200 degrees C, smells like flowers, costs nothing, etc) wouldn’t make all this magic happen. Magnetic fields store energy, and a failure in an electromagnet (even a superduperconducting one) will dissipate that energy quickly (limited only by how high the kickback voltage can get before non-superconducting parts, arcing, etc carry the current). Also, an electric current (even a superduperconducting one) experiences a force inside a magnetic field — a lot of the material of a high-field magnet is the structure needed to keep the magnet from flying apart under its own Lorentz forces. Also, that MRI machine would appreciate a uniform magnetic field, and everything else in the room would appreciate a rapid fall-off outside the machine, and a hula hoop won’t achieve either one.

nothercastle 2y ago

I don’t understand the draw of fusion. Even if the fusion reactor itself was free, the cost of harvesting the heat and transforming into electricity is quite expensive and complicated to the point that it’s its very non competitive with solar or other renewables. It also has the same ramp up and down problems of nuclear. Besides being a cool physics problem is not actually an economically viable source of electricity.