Would the discovery of a room temperature superconductor with a high critical current improve ion drives?

Question

I'm just an optimistic, uneducated bum, so if any of the terminology or ideas are wrong I apologize. So I understand that ion drives are very economical but very low thrust. Partly because powering them with anything stronger than solar panels and batteries is unfeasible right now, but also because they just fundamentally have a low T/W ratio. However, they are easy to make and easy to handle. Much moreso than a fusion rocket. So, lets say scientists make the discovery mentioned in the title. Would this allow for ion drives powerful enough for interplanetary travel, something like the VASIMR?

Answer 1

The real issue with things like VASIMR and other electromagnetic thrusters is not so much the rocket bit, but the amount of power it takes to operate the things. Unless you're visiting the inner solar system, you're probably going to want a nuclear reactor if you want a rocket that's powerful enough to generate thrusts that are science-fictionally "interesting" and compact lightweight multi-megawatt nuclear powerplants that work effectively in space aren't necessarily things that need superconductors to make them work. Fusion reactors (and rockets!) would probably benefit from better superconductors, but you have to get them to work at all first. Fission plants need a different kind of engineering though.

There are a bunch of things you can do with good superconductors that are hard to do without them, such as storing, discharging and switching very large amounts of energy without everything going boom. That's potentially useful for exotic rocket proposals like the MiniMag Orion which uses an electromagnetic z-pinch to trigger fission in a subcritical assembly of fissile material, but maybe that isn't the sort of rocket you were interested in (though remember, "easier than a fusion rocket" almost certainly includes the regular Project Orion nuclear propulsion system, that's probably doable with modern technology!)

I'd be looking at quite different flavors of propulsion technology, though. Rockets are always gonna be subject to the "tyranny of the rocket equation". I like things such as MagBeam which uses an electromagnetically focussed plasma beam to push against a spacecraft carrying a magentic sail. All things that benefit from cheap, light, capable superconductors and avoid a load of the usual torch-ship issues such as producing and carrying enough fuel and reaction mass, or dealing with heat, or miniaturizing nuclear reactors, and shielding everything, and all the rest.

Answer 2

Probably!

The really cool thing about superconductors is that they have exactly zero resistance - hence the superconducting properties they have. In an ion engine, you’re dumping kilowatts of power into a miniature particle accelerator to get charged ions up to speed and shoot them out the back of your rocket. For reference, the LHC uses superconducting electromagnets for beam guidance and acceleration extensively, and it works great (citation: the LHC works).

The issue with just slapping YBCO magnets in a regular ion engine is that they need to be kept extremely cold to work; the liquid nitrogen required to cool them adds mass, and the systems and radiators to keep the LN2 cold adds a lot more mass. Ultimately, using YBCO magnets on an ion engine ends up lowering the TWR so much that it becomes useless. Ion engines are used for stationkeeping for small satellites and sometimes propulsion - if you need to carry big liquid nitrogen tanks and cooling systems around with you, you might as well use liquid fuel rockets or nuclear thermal propulsion.

But the discovery of a room-temperature superconductor is awesome! Now you can cut the liquid nitrogen, the tanks to store the LN2, the systems to maintain those tanks, and most of the radiators, and you can still have an LHC-level acceleration system for your ion engine.

Will it be fast? No, no interplanetary travel is fast without torchships. But it will be very efficient! Ion engines are among the most efficient engines known to humanity, and require a very small amount of fuel to push a probe very far, and scaling up the engine to incorporate a bigger power source (perhaps a small fission reactor, or even a fusion reactor using the room-temp superconductors) would increase the thrust sufficiently to carry human payloads.

Answer 3

Why wait for 'room temperature' superconductors? The background temperature in space is about 2.7 Kelvin. If you shield from the sun, this is cool enough for most conventional superconductors.

Don't get misled by the 'endless current' in superconductors. It is only endless as long as nothing takes any energy out of it. It can provide a static magnetic field that could contain and focus an ion beam (this is what the LHC does) but it cannot of itself accelerate the ions. That would take energy from some power source. If you have a powerful source of high-energy charged particles, you probably also have a fair amount of waste heat and other forms of energy that may upset the state of your superconductor. Conventional magnetic lenses may be a better solution.

Ion drives output pretty narrow beams. It is possible that you could use a superconducting field to tweak the finesse of the beam a bit, but it won't provide a huge increase in efficiency.