Room Temperature Super-Conductors

[PaperJack]

I know that a superconductor is something able to transmit electricity without any resistance and that creating a room-temperature one would be the biggest scientific discovery of the century, but why ?
What are the applications of room temperature superconductors that make them so special ?

[Zixinus]

Saving a lot on transmitting electricity from the power station to the consumer?

Better maglev-trains?

Ability to fire up space ships without booster rockets?

High-capacity batteries?

[dragon]

MRI use superconductors, so with room temp ones they one be able to eliminate the large expensive cooling unit.

Without having the spend loads of money on keeping them cool would allow far more every day uses.

The quest for room temperature superconductivity has gripped physics researchers since they saw the possibility more than two decades ago. Materials that could potentially transport electricity with zero loss (resistance) at room temperature hold vast potential; some of the possible applications include a magnetically levitated superfast train, efficient magnetic resonance imaging (MRI), lossless power generators, transformers, and transmission lines, powerful supercomputers, etc.

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[PaperJack]

Ability to fire up space ships without booster rockets?

do you mean with a gauss or rail gun of some kind ?

[Sea Skimmer]

A superconductor has zero resistance to the passage of electrical current, which means you don’t need to create high voltages to push a current past the resistance, and you don’t have waste heat. So all the huge transformers and cooling gear we need on electronics go and energy use goes way way down. The only thing that would matter is the voltage to push past the actual load on the circuit, and if the load object (like an electric motor) is also built of the superconductors then you basically could have zero voltage circuit that was absurdly efficient.

What’s more, the actual wires themselves can become orders of magnitude less massive, allowing everything we make that uses electricity to get much more compact. This would also go a long way towards extending the world supply of materials like copper/gold/sliver we currently need as conductors in quite large masses.

Just about anything that uses electricity could gain something from a room temperature superconductors. But the reality is even if we ever do find a room temperature superconductor it may be made out of such expensive, rare or difficult to manufacture materials that it won’t see use any outside of the limited areas able to use supercooled superconductors today.

[Isolder74]

Not only that the amount of wire required to generate a certain amount of Magnetic flux goes way down as you no longer have to take into account the energy losses of the resistance in the wires. This makes all superconductive electromagnets instantly smaller by default. More efficient electromagnets make things like MRI machines smaller and more able to function well.

[PaperJack]

so basically every electrical appliance gets smaller and more efficient ?

[Eleas]

so basically every electrical appliance gets smaller and more efficient ?

That's just the tip of the iceberg. Imagine, for instance, that way back in the late 19th century we'd never been able to crack the principle behind transistor-like technologies, and that technologies with similar characteristics were likewise difficult to miniaturize, expensive to use, etc. My point is, what if there had never been a way to create fast data-processing devices in an economical manner?

Well, we wouldn't just be bereft of the computer. We'd be without all the things that computers provide. Consider what our modern industry would have been like if everything had to be done through simple mechanics or under human supervision. Then consider that this is one field among many that the computer has transformed.

If we were to discover useful and plentiful superconducting materials, this might well inspire shit we couldn't even have imagined before. In other words, the influence of any revolutionary technology can be difficult to predict, particularly if there is a synergy effect.

[Gil Hamilton]

Room temperature superconductors would make alot of instruments much smaller. Like an NMR instrument isn't currently really flight ready for space probes, because the magnet and the cooling system. Get us room temp superconductors and you can make powerful NMRs that are handheld.

[Korvan]

One problem with (cheap) room temperature superconductors, is they can become small, very powerful bombs. Just take a continuous coil of superconducting wire and charge it up via induction for a good amount of time. Then to set it off, all you have to do is short circuit the coil.

The power of the explosion is only limited by how long you charge it for and the upper limit of current that the superconductor can handle (exceeding this current causes the superconductor to superconduct no more which will result in a premature boom). Room temperature superconductors with a really large current limit would likely have to be restricted.

[aerius]

It all depends on the current density of the superconductor, if it's really high then we can get rid of a bunch of transformers and make a lot of things smaller & more efficient. If the current density turns out to be around that of copper or other metals used in our wires, then the changes aren't nearly as drastic. We'll still need transformer stations or else those long distance transmission cables will exceed their current limits and stop superconducting, and when that happens there'll be a nice meltdown. We could make motors & so forth more efficient & powerful, but it'll be more of an incremental improvement than a revolutionary leap forward.

[Lord of the Abyss]

Another use for them I've heard of would be frictionless, levitation based replacements for bearings, and for various other types of direct physical contact in machines. Instead of, for example a rotating shaft being held in place with bearings, you simply use superconductor and magnets to levitate it. Doing that means less wear on the machinery, and less energy loss due to friction. This is actually possible to do now with computer controlled electromagnets; with room temperature superconductors though you can ditch all the added complexity of electromagnets, computers and so on, and replace it with a simpler, smaller, passive arrangement of superconductor and unpowered magnets.

[Junghalli]

Here's what I'm wondering: how plausible is it that a room temperature superconductor could be created someday?

[dragon]

Here's what I'm wondering: how plausible is it that a room temperature superconductor could be created someday?

Alot of scientist seem to think so as a lot of money, time and effort is being poured into the quest. However it looks like material science isn't quite there yet.

[Sarevok]

One problem with (cheap) room temperature superconductors, is they can become small, very powerful bombs. Just take a continuous coil of superconducting wire and charge it up via induction for a good amount of time. Then to set it off, all you have to do is short circuit the coil.

The power of the explosion is only limited by how long you charge it for and the upper limit of current that the superconductor can handle (exceeding this current causes the superconductor to superconduct no more which will result in a premature boom). Room temperature superconductors with a really large current limit would likely have to be restricted.

On the flip side cant you use this property for applications that need a very large amount of electric power for a short time? Like to store a high ampere current in a superconductor loop and discharge it only when you need to fire a high energy laser pulse ?

[Gil Hamilton]

One problem with (cheap) room temperature superconductors, is they can become small, very powerful bombs. Just take a continuous coil of superconducting wire and charge it up via induction for a good amount of time. Then to set it off, all you have to do is short circuit the coil.

The power of the explosion is only limited by how long you charge it for and the upper limit of current that the superconductor can handle (exceeding this current causes the superconductor to superconduct no more which will result in a premature boom). Room temperature superconductors with a really large current limit would likely have to be restricted.

Breaching a tank of fuel can suck pretty heavily too. Would preventing them from being a bomb come down to engineering them so that shorting them is really hard?

[Sea Skimmer]

One problem with (cheap) room temperature superconductors, is they can become small, very powerful bombs. Just take a continuous coil of superconducting wire and charge it up via induction for a good amount of time. Then to set it off, all you have to do is short circuit the coil.

The power of the explosion is only limited by how long you charge it for and the upper limit of current that the superconductor can handle (exceeding this current causes the superconductor to superconduct no more which will result in a premature boom). Room temperature superconductors with a really large current limit would likely have to be restricted.

You realize you could just go make a bomb like that with a freely bought capacitor right now don't you? The only limitation is cost, and I suspect nitromethane will always cheaper. An electrical arc from a wire however is never going to make all that effect of an explosion because of its limited reaction mass and the fact that it won't all vaporize in an instant. Anyway, you can make explosives out of a damn lot of common items and chemicals. The saving grace being that most terrorists are simply complete and utter idiots, which is why they think terrorist attacks have any chance of accomplishing anything in the first place. So I wouldn't worry much about it.

[Fingolfin_Noldor]

We may never get a room temperature superconductor. Maybe if research into superconductivity might yield something over the next 2 decades, and some interesting property is found, then we might get one. But I wouldn't place my bets.

[Korvan]

One problem with (cheap) room temperature superconductors, is they can become small, very powerful bombs. Just take a continuous coil of superconducting wire and charge it up via induction for a good amount of time. Then to set it off, all you have to do is short circuit the coil.

The power of the explosion is only limited by how long you charge it for and the upper limit of current that the superconductor can handle (exceeding this current causes the superconductor to superconduct no more which will result in a premature boom). Room temperature superconductors with a really large current limit would likely have to be restricted.

You realize you could just go make a bomb like that with a freely bought capacitor right now don't you? The only limitation is cost, and I suspect nitromethane will always cheaper. An electrical arc from a wire however is never going to make all that effect of an explosion because of its limited reaction mass and the fact that it won't all vaporize in an instant. Anyway, you can make explosives out of a damn lot of common items and chemicals. The saving grace being that most terrorists are simply complete and utter idiots, which is why they think terrorist attacks have any chance of accomplishing anything in the first place. So I wouldn't worry much about it.

Depending on the critical current density of the superconductor, the amount of energy that can be theoretically stored is surprisingly high. For a Niobium-Tin superconductor, I found that it can have a critical current density of 200,000 amps per square centimeter. Now this superconductor only works at 18 K and is too brittle to form into wire, but we are going to assume that a room temperature superconductor that can be worked with exists and has the same critical current density (big assumption, but I was concerned about the dangers of such high current density superconductors possibly existing).

If we take a single loop, 1 meter in radius with a wire thickness of 5cm in diameter (think of an oversize hula hoop), the inductance for this is about 4 henries. The cross sectional area of the wire is pi(2.5cm)^2 = 19.63 square centimetres. This gives us a maximum current of just under 4 million amps. The amount of energy that can be stored in this loop is E=1/2(L * I^2) where L is the inductance and I is the current. This gives us a stored energy of over 30 Terra Joules or the equivalent of over 7 kilotons of TNT.

That seems a bit nuts, but even looking at a much more modest critical current density of 400 amps per square centimeter (about the current density of copper), you can store the equivalent to 7 kilograms of TNT. But even if such high critical current density superconductors exist, a would-be terrorist with access to 1 mega-watt power supply would still need just about a year (356 days) of continuous charging to reach full power. Or 50 years for a garage based one.

[Eleas]

But even if such high critical current density superconductors exist, a would-be terrorist with access to 1 mega-watt power supply would still need just about a year (356 days) of continuous charging to reach full power. Or 50 years for a garage based one.

Interesting. What are the other assumptions here, though? Are we talking at perfect efficiency? How does one add charge to such a coil while preventing it from releasing its energy; does it have to be done in a virtual instant, for instance? If so, aren't we looking at having to use intermediaries, further reducing efficiency, etc?

[Korvan]

But even if such high critical current density superconductors exist, a would-be terrorist with access to 1 mega-watt power supply would still need just about a year (356 days) of continuous charging to reach full power. Or 50 years for a garage based one.

Interesting. What are the other assumptions here, though? Are we talking at perfect efficiency? How does one add charge to such a coil while preventing it from releasing its energy; does it have to be done in a virtual instant, for instance? If so, aren't we looking at having to use intermediaries, further reducing efficiency, etc?

Just want to say that I'm far from an expert on superconductors but I'll see if I can elaborate a bit. We're charging (charging isn't a really good term as we are not adding charge to the hoop, just energy) the superconducting hoop via induction and the energy is being stored in the hoop as an ever increasing magnetic field. Now this is a bit out of my depth, but I'm guessing whatever you are using to charge the superconducting hoop will need to be able to overcome the hoops magnetic field if it wants to keep adding energy to it.

This magnetic field might not be too strong even at full strength as we are dealing with just one loop and an air core. I tend to go a little bit wibbly when I look too hard at magnetic field equations so if anyone actually knows this stuff, any insight would be appreciated.

[starslayer]

Along the axis of an infinitesimally thin ring of current of radius R, the field is given as

B(z) = μ0IR2/(2*(R2+z2)3/2)

One meter away from the loop, this gives a field of about .9 T, pretty strong, but not remotely unheard of; MRI machines use a 2-3 T field, which coincidentally is about what this gives in the center of the loop. I've no idea what the field would be at points not on the loops axis; I don't believe that is analytically solvable. Regardless, you would have to be very careful around such a field if you wanted to short the superconductor out, because it is going to attract anything metallic near it with great force, including the wire you want to short this thing out with.

However, I don't know that shorting out a superconductor is even possible. Electric current follows the path of least resistance; it will not decide to travel over a metal if it has a nice zero resistance path that it is already on. Obviously, this is not a perfect rule, and there will be some leakage, but it really won't be that much; certainly not enough to initiate an enormous, explosive discharge. If you were to snap the loop, you could get an enormous spark, but you would have to do so on a very short timescale to initiate a huge explosion. More likely, as the energy has to go somewhere, the instrument that did the cutting would melt or even vaporize, and there would be a large arc to ground through it; the effect could be reminiscent of a lightning strike, but probably nothing like a nuke.

[Korvan]

Just had a thought, once the hoop is powered up and are lo longer supplying power to it's energy should remain constant. In that case, a little rearranging of the energy equations shows that the current in the loop is inversely proportional to the square root of the inductance and the inductance is proportional to the radius of the loop. So if you reduce the radius somehow, the inductance falls as well and the current increases. If you were already close to the critical current value, this puts it over the edge and the loop stops being a superconductor and then I guess all the stored energy gets released at once.

[Sea Skimmer]

If we take a single loop, 1 meter in radius with a wire thickness of 5cm in diameter (think of an oversize hula hoop), the inductance for this is about 4 henries. The cross sectional area of the wire is pi(2.5cm)^2 = 19.63 square centimetres. This gives us a maximum current of just under 4 million amps. The amount of energy that can be stored in this loop is E=1/2(L * I^2) where L is the inductance and I is the current. This gives us a stored energy of over 30 Terra Joules or the equivalent of over 7 kilotons of TNT.

In energy terms it might be the same, but a giant electrical current will arc to ground as soon as you release it rather then exploding in an omnidirectional blast. That would tend to vaporize a path down into the ground like a lighting strike, but that's not going to be like a nuclear weapon went off. It might be like a truck bomb though.

That seems a bit nuts, but even looking at a much more modest critical current density of 400 amps per square centimeter (about the current density of copper), you can store the equivalent to 7 kilograms of TNT. But even if such high critical current density superconductors exist, a would-be terrorist with access to 1 mega-watt power supply would still need just about a year (356 days) of continuous charging to reach full power. Or 50 years for a garage based one.

So basically, simply monitoring home power consumption, exactly like the government does to catch people growing pot with lots of power hungry grow lights, would already be enough to counteract this risk in large part. Only terrorists who can afford to run a high power generator for months on end without being noticed could do anything.

[Korvan]

So basically, simply monitoring home power consumption, exactly like the government does to catch people growing pot with lots of power hungry grow lights, would already be enough to counteract this risk in large part. Only terrorists who can afford to run a high power generator for months on end without being noticed could do anything.

Even with grow-op type power (about 80,000 watts), you'd be looking at over 12 years to reach full power, so it looks like big superconductor bombs are strictly in the realm of wealthy supervillain types.