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Comment by lumost | Hacker News Reader

I wouldn't rule out extremely high internal pressures in static materials as a future research direction. Prince Rupert drops reach a pressure of 700 Megapascals, roughly 2-3 orders of magnitude less than the required pressure for this experiment. I'd imagine that more advanced processes and materials can already manage internal pressures substantially greater than the Prince Rupert Drop.

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I can readily imagine some cross-discipline techniques achieving this. A little lithography, some selective dissolution like Gorilla glass, perhaps some tricks from the optical fiber industry, and bam, you have a fine coaxial filament which creates a region of 100's-of -MPa stress along the length of the fiber. Maybe even GPa, though that's tensile-strength-of-nanotubes territory.

Certainly it's years away but I dunno...This feels possible in an engineering sense.

>100's-of -MPa stress along the length of the fiber

It's all fine and dandy until it breaks open, along the length, and releases not just the stored mechanical energy, but also all the inductive energy from the flowing current of few million amperes.

I'd love someone smarter than me to do a back-of-the-napkin job on that. Are we talking a firecracker, a cherry bomb, a few kilos of TNT, or a MOBA?

1 meter of 1mm diameter wire with 1 million amperes amounts to 750kJ, or ~180g of TNT.

A superconductor blowing up across the length and distributing the energy doesn't seem as bad a whole transmission line's energy released at a point fault.

that also sounds like pretty ok risks for an under sea cable. though given one break you have to replace the entire cable might cancel it out.

You could break it into sections connected by liquid nitrogen superconductors, or maybe extremely heavy gauge copper ones.

Put two superconducting fibers next to each other with a thin insulating layer, or many fibers in a bundle.

Have the supercurrent in one direction matched by the same supercurrent in the other direction, alternations as closely spaced as possible.

The magnetic field will be confined, at least.

When the fiber breaks, join the entwined superconductors together (equivalently: have the insulator break down), and the current in the rest of the transmission line can continue flowing.

Coaxial variant also available.

Superconductors aren't magic. You can't just stuff a few million amps into a tiny wire. Just as there is a critical temperature, there's also a critical current density. While those two numbers are related, you'll need quite a bit more than "room temperature" superconductors to carry currents like that. And there's a temperature/current tradeoff: if the ambient temperature is close to the critical temperature, then a whisp of current can make it go normal.

http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/scbc2.html

Assuming superconductors replace existing wires, it won't be more power than the wires already carry, just in a smaller area.

My instincts tell me it would actually be much safer. Overheating wire would instantly lose superconductivity and vaporize into an open circuit. The same thing a fuse does.

Current wires have enough bulk to heat up and melt slowly. This is more opportunity to burn things and set stuff on fire. Vaporized plasma is low density which probably won't concentrate energy enough to light surrounding materials on fire. Plasma also disassociates quickly in air, again way less time for fires.

For mechanical stress, it may be sufficient to just ensure the stress is evenly distributed in all directions. This way the energy will be driven into shockwave and heat rather than motion. The wires might make a big bang but this isn't very harmful underground or high in the air on lines. Explosions are way less dangerous in open air than they are confined

It is hard to imagine a material strong enough to maintain residual stresses this high! Maybe in diamond? And what happens when it fractures and all comes apart? (unless it is contained in a very small volume so has bugger all potential energy)

Looks like some recent synthetic diamonds manage pressure in the TPa regime! 1 order of magnitude higher than that required for this experiment.

https://advances.sciencemag.org/content/2/7/e1600341

Materials do a little better under compression than tension. But yea, 267 GPa is a lot. The working stress for most high strength metals is about 1 GPa. With that being said under shock conditions for instance.

That said you can locally get huge stresses without out breaking the material.

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