hobscoop
hobscoop on Hacker News
Do you have the manual? It might be possible to configure a non-beeping mode. (I recently learned this was the case with my Panasonic model, to great delight.)
This cannot work: the power balance doesn't close for a 25 MWe tokamak. Otherwise people would have made plans to build one already. Tokamaks want to be big for physics reasons, way before economics reasons. This is part of why DEMO is so big. If ARC could be any smaller it would be.
Rubi is great. When I'm stuck on an integral in Mathematica with the builtin Integrate, I load up Rubi and sometimes it can find a solution.
Are they able to adjust the color and brightness simultaneously? Or would brightness be controlled with PWM?
This would eliminate the failure mode of my grayscale attempts. I would appreciate knowing the configuration steps.
Plasma physicist here. While this is an idea worthy of study, the answer to the (spaceweatherarchive.com) title question is "no". The researcher's article makes simple errors in what they call " undergraduate physics" (electricity and magnetism), in basic plasma physics, and in basic algebra.
As one straightforward example, their estimate of the (change in) Debye length ignores that their equations (2 and 3) are in terms of the square of the Debye length, so the purported change should be only sqrt as large.
As another example, it's not clear why the author focuses on aluminium in the upper atmosphere, or worries about small particles of aluminium shielding the earth's magnetic field from space. While a conductive shell can shield a changing magnetic field, it needs to have long-range conductive paths. A mesh has this property, but a mesh is not the same as a suspended dispersed powder, even if the individual powder particles are conductive on the nano-scale.
Actually, I think the strength of modern steels is a limiting factor for fusion magnets. Plasma "beta"s are only a few %, so for a few atmospheres of plasma pressure your magnetic cage needs to be like a pressure vessel that contains hundreds of atmospheres. And with large holes poked through it for access. If you look at CFS's magnet test from last summer, there's a huge amount of steel.
I thought they were ultimately limited by problems of corrosion at the electrodes?
Helion's scheme to turn fusion heat into pushing E&M fields back through their magnet to generate electricity is pretty different from a standard MHD generator.
Yes. We're currently living through a golden age of stellarator design powered by new algorithms and optimization techniques.
It'll ultimately be dissipated by infrared radiation into space. Earth receives something like 173,000 terawatts of radiation from the sun; this is equal to the amount radiated out as infrared, except for the "radiative forcing" which is the amount by which the world is heating. Radiative forcing is currently something like 1000 TW. All of human civilization is powered by something like 20 TW.
If we want to stop global heating we need to use a fraction of those 20 TW to "turn the ship" of size 1000 TW.
It sounds like they're trying to build a device with a distribution of ions in velocity space which is very far from the equilibrium Gaussian-type distribution ('Maxwellian'). This is difficult because there will be about a million collisions for every fusion reaction that happens, and collisions tend to redistribute velocities toward the equilibrium. Collisions between unlike particles (different species of ions, or ions vs electrons) will also cause diffusion in physical space. This could cause ions to leave the chamber much more quickly.
It's pretty different. This is pulsed; LM's was going to be steady state. LM's design had magnets internal to the plasma which has significant difficulties.
The proposed fuels are different.
As far as I can tell LM's fusion project has stopped.
For a long time fusion was funding constrained: there were many more ideas than could be tested and examined under government budgets. In the US nearly all funding went to one concept, the tokamak. While the tokamak has achieved the best performance thus far, there's now sufficient interest in fusion that less-well-developed ideas are being tried, in order to not put all the eggs in one basket.
It's not plausible that even fusion power plants would make energy 'basically free'.
1) Fusion plants still require site infrastructure, power conversion technology, waste heat removal, and (though not for this particular concept) steam generators (or other fluid cycle generators). These have significant capital costs but finite lifetimes. You're right that the variable cost of energy is pretty low, probably comparable to current fission plants, but that's still more expensive than the variable cost of electricity from solar and wind.
2) The price of electrical transmission and distribution starts to become important (I forget what the typical cost of that today is, but it's a few cents/kWh.) This doesn't matter if you can put a small power plant at your local industrial park though.
3) There's a big difference between $0.05/kWh, $0.02/kWh, $0.01/kWh, and $0.005/kWh, and then a huge difference to 'true zero'. This is because there's probably lots of industrial processes that we might like to do if electricity and heat were cheaper than it is today, each becoming reasonable at a certain price. There could be a large market at each price floor 'step'.
4) Yeah, the fuel is abundant, which is good, but fuel costs are not significant drivers of the cost of fission.
While not free, I'd like to think that fusion will help make a world with energy much cheaper than the world without fusion.
There are more plausible and less plausible concepts/companies out there.
Helion in particular was founded by respectable scientists who have a background in plasma physics, and they've developed their idea pretty quietly for the last 10 years, only de-stealthing this summer (presumably after reaching a key milestone). What they're trying to do is difficult, but I wouldn't say it's snake oil.
There's some interesting arguments in favor of the combination of magnetic and interial approaches. This is broadly known as 'magneto-inertial fusion', and there's a continuum of ideas between 'mostly inertial' and 'mostly magnetic'. I'd put Helion's approach far toward the magnetic side.
SPARC is very important, but it's a physics demonstration facility, not a reactor. Its not going to generate any electricity. CFS (SPARC's parent company) will use SPARC to demonstrate that their magnet technology and plasma physics can be scaled to a reactor -- I think they're aiming for 2030 or 2035 to 'put electrons on the grid' with their 'ARC' reactor. SPARC stands for 'smallest possible ARC'.
Compared to CFS's approach, Helion's approach is different in two or three key ways.
First, it's a different fusion reaction, which has important engineering consequences. The reaction that Helion wants to use generates fewer damaging neutrons, which makes the rest of the reactor easier to engineer and eliminates several tricky subsystems.
Second, it's a different geometry, which does not require huge powerful steady-state superconducting magnets. However, it does require very fast magnets.
It's a pulsed machine (they would fire several shots per second; each shot lasts on the order a milliseconds if I recall). So it requires more pulsed power systems and the components may need a different kind of high-repetition lifecycle testing.
Third, they want to use a 'direct energy conversion' scheme, which means eliminating the need for gas turbines (i.e. steam turbines) coupled to generators. This is important since the heat exchangers and turbines make up very roughly half the cost of a traditional power plant, so this would allow the electricity price to be lower by about a factor of two!
Helion's scheme would require a specific isotope of helium, of which there's not much of in current stockpiles. Assuming that you had some He-3, remember that since this is a reaction between nucleons, the typical energy scales are a million times higher than typical chemical energy scales. Therefore the amount of fuel (in kg) is a million times smaller. And so, there's a significantly larger margin for extracting and purifying the helium fuel from whatever source.
> Will the total output in electricity be greater than the inputs for this?
Yup, that's the goal!
> Extra: what happens if there’s too much expansion or things are too hot?
Fusion reactions are difficult enough that if it were physically possible to make them run 'hotter' or release energy faster, frankly we would already be doing so.
> Could this explode or implode? If so would it be a huge deal?
The radiation risks from fusion are orders of magnitude smaller than from nuclear fission power. We still need to think about them and make sure that plants are safe, but it should be significantly easier to manage.
No currently operating device is 'attempting' to achieve Q_total; they are all physics experiments, not simply searching for a magic combination of knobs that will ignite the plasma.
The Europeans are doing quite a bit of preliminary design scoping and engineering for DEMO, a 'demonstration' reactor which is supposed to come after ITER and generate net electricity, but there's not been a site selected, for example. Similarly, Chinese researchers are working on their CFETR, 'Chinese Fusion Engineering Test Reactor'.
SPARC is aiming for Q_plasma of about 10 in 2025, but not to generate energy at all: it doesn't have any of the required 'blanket' system for breeding tritium. SPARC is a physics test, to make sure our theories of burning plasma are correct and to test the stability of these high field tokamaks.
ITER is (among other things) supposed to be a physics test, but won't come until 2035. So SPARC's goal is to 'leapfrog' that by 10 years.
You're right that there's a lot of work to be done between Q_plasma = 10 and generating energy. A lot of this work on the materials side, to engineer materials that can last for years in a fusion reactor environment.
If only the US Forest Service knew about this, they could have properly answered Rep Louie Gohmert's questions!
ITER is planning to do its flagship D+T runs in 2035, not 2050.
While inertial confinement fusion facilities like NIF are also used for weapons work, the physics of magnetic confinement fusion plasmas are quite different from the physics needed for bombs. There's no chain reaction, and the 'hot neutron physics' is actually a very small part of the overall system. The neutrons essentially go in a straight line until they hit the wall; they don't interact with the plasma itself.
Most people in magnetic confinement fusion are studying magnetized plasma waves, instabilities, turbulence, and other collective behavior that are in a very different regime from bomb physics.
I don't understand the promise of lattice confinement fusion. While it is certain believable that they measured fusion events, the explanation they give involves several unlikely steps of one particle hitting another. Since each step is unlikely, the overall gain of the process is extremely low, like 10^(-6). It's not obvious how the gain might be improved to something technologically useful (over 1).
Try H3 mining of Uranus or Neptune rather than Jupiter! The gravity well is much smaller.
Say you shoot the deuterium and tritium ions at each other in beams. Making two ions fuse isn't quite the same as hitting a fixed bullseye. Typically, physicists consider a 'cross section' for a reaction between two particles as a function of their relative velocity: a notional area that allows one to compute the probability of a reaction occurring, which may be thousands of times larger or smaller than what we typically think of as the physical size of the particles.
The cross sections for fusion reactions are significantly less than 1000th those of elastically bouncing off, even at the optimal velocities. Fusion reactions release about 1000 times[2] the typical energy needed by the reactants in order to get close enough for there to be any significant probability of reaction. So a one-pass beam system is always going to lose out to elastic scattering.
[1] https://en.wikipedia.org/wiki/Nuclear_cross_section
[2] D + T releases 17.6 MeV of energy; typical fuel temperatures are 15 keV.
We would not be sun-transiting to them, at least at the moment: the current declination of Ross 128 happens to be less than 1 degree [1], meaning it's near the celestial equator rather than near the ecliptic. Since the ecliptic plane is at 23.5 degrees to the equator, they would see the Sol-Earth system tilted at that angle: much too large to be sun-transiting.
[1] https://en.wikipedia.org/wiki/Ross_128