As previously mentioned in my post Carb Loading for Superheroes, Superheroes are really the stuff of fantasy more than science fiction--though some superheroes come close to obeying the laws of Physics (I used Batman and Spiderman as examples), they still don't really account for all the energy required to perform their amazing feats of strength and prowess.
But just as a huge increase in food intake could go a long way to explaining the how Spiderman leaps from building to building, a generous use of superconductors could make an Iron Man-type suit much more realistic.
Superconductors transmit electricity down a wire with no loss due to electrical resistance. So it's possible to loop a superconductor, put a charge of DC current into it, and the current will go around and around the loop, effectively making a battery of near-perfect efficiency. The amount of current the wire can hold is mainly a function of its length, though current flowing in a loop will create a magnetic field that has a tendency to crash the property of superconductivity, so there is a limit to how much electrically-generative magnetism the circuit will support. A Wikipedia article on Superconducting magnetic energy storage includes (under "technical challenges") the estimate that it would take about 100 miles of wire to hold a gigawatt of power (of course, actual energy storage would vary according to the type of wire and the arrangement of the system).
Current superconductors have to be kept very cold, so any storage of electricity requires bulky refrigeration…and running the refrigeration system also burns power. But imagine a superhero of the Tony-Stark-inventor-type, who invents a superconductor that requires no refrigeration, is ductile (easy to make into wire), and is resistant to collapse from high magnetic fields. This guy could make huge money selling this wire to the world if it were cheap to produce (or even if it were relatively expensive), but let’s imagine as a story idea that this wire is far more expensive than platinum—hey, platinum could be one the wire components for story purposes. So our hero has enough money for to use this for himself, but not for the whole world…so naturally he makes a superhero suit, powered by coiled superconducting wire.
The suit would have to be made of something resistant to magnetic fields, or the metal would get warped out of place immediately—a composite carbon material probably would do…and you’d have the problem of all metal objects outside of the suit flying at your superhero worse than taking metal into an MRI…really to make this work, the suit probably would have to be very large, so the magnetic field would remain mostly inside the suit.
A large powered suit (say, at least 20 feet tall) would be a lot different from the iron man suit—it’d be more like something from Gundam. Still, a powered suit, if there were only one of them, would be more like a superhero scenario than a Japanese-imagined future filled with massive combat robots…
A small version of the suit could possibly work if the superconducting material were in the shape of a toroid (so the suit would have a ring on the back, like a bigger, rounder version of the disc on the back of suits in Tron). A small suit probably could never get a hundred miles of wire in a coil, but depending on the thickness of the wire, it doesn’t seem unrealistic to think you could fit a mile’s worth of superconducting wire in there.
So, using the figure from the Wikipedia article of 1 gigawatt for 100 miles of wire, 1 mile would hold 10 megawatts of instantly-available power. How much would that move the suit? Consider that 1 watt equals 1 joule per second. One joule equals the force of 1 newton through one meter—10 newtons are approximately enough to move an object of one kilogram upward one meter against Earth’s gravity.
So, assuming I understand the units of force correctly, the maximum power of 10 megawatts can be considered the same as 10 million joules, which is enough power to lift something weighing one kilogram against Earth’s gravity a million meters, or around 620 miles—straight up into the sky—easily into Earth orbit. That’s some shot put, right?
Of course, mechanically speaking, it would probably be impossible to harness all the power of a major superconductor in a single throw…but it does illustrate that really good superconducting power system would store a lot of power, enough to qualify for superhero status—though this isn’t quite as awesome as it might first seem. To illustrate, let me translate this into what it would take to hop around in this suit:
To be conservative (and to give a simple calculation), let’s assume even a relatively small suit with human passenger included would be pretty heavy—1,000 kilograms. So doing the math, a 1,000 kilo suit would be able to thrust itself straight up into the air about one kilometer in a single leap. This is assuming perfectly efficient motors and very strong materials and a number of other things that aren’t realistic, but let’s ignore all of that for the moment, since very efficient motors are at least possible and materials could be stronger than we expect—plus, we’re trying to identify the limitations of available power here.
In shorter hops, a 2.5 meter accelerating jump at a 45% degree angle would yield significantly more distance in fall and would be a lot more efficient than a straight vertical leap. I offer a rough order of magnitude estimation that such an upward leap would cover 10 meters distance horizontally. So that would mean the suit would have enough power for a series of impressively high and fast jumps (ten meters is over 30 feet at a shot), but for only about 4 kilometers total distance—only a few miles.
So the system could yield enough power for a very impressive performance, superhuman leaps and jumps, punches, and running at an amazing speed…but only for around five minutes or less, depending on exactly what the hero was doing. Please note, though, that many fights are finished in less than five minutes…
Superconductors would allow for some other interesting superpowers—the magnetic force of a coil could be focused to a degree, not as much as Magneto does without a sweat, but there are things you could do with it—for a limited time. For an essentially unlimited time, superconductors in the feet would allow someone to suspend a supersuit over a strong magnetic field. And a superconducting rail gun could hurl bee bees or ball bearings at dangerously high speeds, much faster than a rifle bullet.
So there are lots of variations for scientifically-plausible superheroes who have suits powered by superconductors. But it would seem that one feature all of them would share in common—their special kryptonite—would be the extreme limited time such a suit would have at its highest performance level. Imagine the inventor-genius superhero staging suits for rapid change as each one powers out…or changing the toroid on the back…while any villain, of course, would seek to sabotage these essential pre-staged pieces of superhero tech…or catch the hero while he was low on power…