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Basically, I want the aesthetics of "EPS conduits" without the soft-sci-fi handwaving of actual Star-Trekian EPS conduits. Is there some system for distributing large amounts of power around a spaceship from a central reactor that isn't "big honkin' electical cables" and which actually makes sense when electrical technology is also available?

There are a few real-world examples of something similar that I know of, but they're not quite all the way there:

  1. Hydronic heating. We transfer heat through buildings from a central boiler by pumping steam directly into room radiators. But, that seems to be very limited in application. Could you do more than just heating rooms with steam pipes?
  2. Compressed air. Lots of tools run on compressed air, and for some applications the pneumatic versions can be simpler than electromechanical equivalents. But how many watts can you actually transfer that way?
  3. Power-over-fiber is a thing, transmitting energy as light rather than electricity, but I don't what the practical power limits for that are. Efficiency isn't bad--if you used fiber optics to trasnmit infrared radiation directly from a hot reactor to devices with photovoltaic cells, you can get over 60% thermal efficiency, which is comparable to electromechanical turbines.
  4. Plenty of home appliances still run on propane / natural gas--power delivered through a pipe!--because it is still easier to deliver large wattages that way than via electrical connections. This isn't particularly relevant to a spaceship, because you won't be manufacturing chemical fuel in your engine, but...
  5. Some designs for nuclear-powered rockets involve using lithium or sodium vapor to transfer heat from the reactor core to the reaction-mass heat exchanger, rather than passing reaction mass directly through the reactor. This is probably the closest analog to Star Trek's "plasma conduits" transporting energy from the reactor core to the engine nacelles, and then supplying excess energy to the "Electro-Plasma System grid". But is pumping lithium vapor around a ship actually useful for anything other than supply thermal thrusters?
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    $\begingroup$ The only large-scale non-electrical power distribution networks are the central heating networks popular in Europe; their entire purpose it to use the waste heat of thermoelectric power plants. Historically, some cities used to have compressed-air power distribution networks; for example, the compressed-air power distribution network of Paris had a total capacity of about 20 MW at the end of the 19th century. Unfortunately, compressed air is horrible as a power distribution medium, and that network was of course eventually abandoned. $\endgroup$
    – AlexP
    Mar 31 at 19:10
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    $\begingroup$ Can't you just say superconductor wiring is being used? $\endgroup$
    – DKNguyen
    Mar 31 at 21:13
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    $\begingroup$ First rule of electronics/electricity. Don't let the smoke out of the circuit. $\endgroup$
    – Justin Thyme the Second
    Mar 31 at 22:41
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    $\begingroup$ Small-scale nuclear reactors. They would be distributed when they were installed. Why run large cables all over the ship when each section can have its own power? $\endgroup$
    – shawnhcorey
    Apr 2 at 14:06
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    $\begingroup$ while it's very heavy hydraulic power distribution was used from 1883 to 1977 & as well there were 8 other cities that had hydraulic power networks, there were relatively little loses associated with it the problem being it was very very difficult to build infrastructure for it followed by the decline of the london docklands killing the biggest network. $\endgroup$
    – OT-64 SKOT
    Apr 14 at 10:06

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If you're talking a spaceship, then you want to talk "power per cross-section" or "power per foot per weight." If you do that, then you aren't going to be able to get better than superconductors.

The definition of a superconductor is that it transmits energy along its entire mass at the speed of light, without resistance loss. This isn't just electricity.

One of my favorite near-zero-kelvin experiments involves a flask of liquid helium. When you spin a flask of superconducting liquid, it immediately distributes the rotational energy across the entire mass. The problem is that, for solids, the outer edge of a disk will have more energy than the center. The helium winds up creating sub-vortices when the rotational momentum differential exceeds the transmission threshold so that the edge isn't as far away.

Since your ship has plenty of vacuum to insulate its conduits, they may very well just use liquid hydrogen coolant to keep their superconductors at a low enough temperature to stay that way. You could transmit gigawatts of power across a thin thread.

You should avoid anything that suggests you're going to use a gas to transfer energy. Gasses give off heat when you compress them, and release heat when you decompress them. Also, they transmit energy very, very slowly compared to electricity. It isn't a bad power storage mechanism, but it's rotten at transmission.

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    $\begingroup$ Having power lines surrounded by cryogenic hydrogen does give you similar "don't poke a hole in the dangerous pipe!" vibes as EPS conduits.... $\endgroup$
    – Logan R. Kearsley
    Mar 31 at 19:56
  • $\begingroup$ Superconductors are subject to current saturation, but I can't find straightforward references on what the limits are for actual superconductors to validate the "gigawatts across a thin thread" estimate. $\endgroup$
    – Logan R. Kearsley
    Mar 31 at 19:59
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    $\begingroup$ @LoganR.Kearsley Not an expert or particularly well-read on the topic but to my knowledge, appropriate "backing materials" are what limits superconducting magnetic energy storage (SMES). SMES wants to blow itself apart from the insane magnetic fields (which is what stores the joules), and a high-tensile strength backing material is needed to prevent that. Current materials limit SMES to like 3 MJ/kg iirc. Theoretical limit being like 60 MJ/kg. $\endgroup$
    – BMF
    Mar 31 at 20:18
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    $\begingroup$ Yea, you don't want to store energy in your conduits, but you'll have the same EMF issues as with any other wire. $\endgroup$
    – Robert Rapplean
    Mar 31 at 21:38
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    $\begingroup$ @BMF current charges are balanced by the positive nuclei in the material, just like any other conductor, and linear currents produce magnetic effects which try to compress them, not explode them. It's the magnetic field that produces current limiting: too high a current results in exceeding the SC's ability to exclude magnetic fields, which destroys the superconductivity and dumps current energy into resistive heating. $\endgroup$
    – Logan R. Kearsley
    Apr 1 at 13:36
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Electricity but as a liquid.

Liquid metal batteries are a technology that already exists, so it isn't beyond the realm of possibilities for someone to invent a chemistry that would make the pumping of the "liquid electrodes" from the reactor to the load a lighter and more energy-dense solution than having cables as thick as a professional cyclist's thighs.

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Cathode rays distribution

It's still electricity but waaaay cooler - as a stream of free electrons in vacuum. The ray can have very high power (it's sometimes used in metalworking). It can easily be steered by magnetic/electric fields and focused or defocused.

On Earth keeping the vacuum required is problem, not so in space. Vacuum tubes that used cathode rays are old tech for us and we have moved on quickly to solid state devices but they could still have potential in the right setting. They are much more robust in radiation filled environment.

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Magnetic containment conduits for antimatter

What transmits power faster than an electrical cable? Hard to outdo a stream of antimatter. The engineers use strong magnetic fields to contain a thin thread of antimatter in the center of a larger evacuated pipe. This thread can be delivered from the central antimatter fuel tanks to anywhere in the ship that requires huge amounts of power, such as weapons or the warp drive. The antimatter will be reacted with matter at the destination to convert the energy into whatever forms are needed.

For truly vast amounts of power transmission it might make some sense, to avoid having superconducting cables the size of houses. (Note: superconductors do not transmit infinite current. They do transmit more current than copper wires, but they stop superconducting above a certain level of current.) Antimatter conduits could also make sense if the antimatter will be used directly at the destination, e.g. the antimatter is used directly to power a photon drive, or used to fill a missile warhead just before launch.

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In a space ship, power has to be distributed twice- source to use to radiator

Almost every component has power going in and waste heat going out. Power intensive stuff has to get rid of gigawatts of heat by carrying it to the radiators- this is managed by pipes of hot, fast moving plasma. Of course, these are alongside wires to carry power from the reactor to the component, but the plasma pipes are much more visually impressive and maintenance heavy.

On a real spaceship, the ISS, the waste-heat-moving pipes are full of ammonia, not plasma, but they are real and needed.

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Robotic autonomous gas bottles

There could be many independant stirling generators each powering a section of the spaceship.

The main reactor happens to produce methane, so next to it there's a filling station where empty robotic gas bottles on wheels can fill up before moving to the section they're meant to bring methane to.

Those could look like an army of r2d2s with a quick disconnect valve on top of them.

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