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In my setting, magical civilizations have physical aversion to metals and moving metals have nasty distruptive effect to magic, so these civilizations development went completely different way from ours.

Eventually, after centuries of primitive protomagic, they discovered process to transform magic crystals(magic fuel, non-quark based matter) to magic cores, which could be endowed with spells/concepts(that still require magic crystals to run).

One of these are concepts of repelling or attracting something. This became a massive game changer, as it allowed to build them hovering ships, ships capable of flight up to hundreds of metres above water or ground (repelling solids and liquids). These ships are built similarly to normal ship (because they consume fuel to fly, they are usually in water for docking and can be sent by waterway to go cheap on fuel).

At first, they used side sails, sails to extend from sides of the ship, but later, they came up with idea of using air attraction core to propel the ship. My question is, how should such engine work? I myself came up with a rather simple but a crude design, but I feel that this design leaves a lot to be desired. I am not an engineer, and my few experiences are not even enough for me to call myself a dabbler.

So my question is: How would an engine that would be designed with use of magic of attraction (or repulsion) work? And is this kind of engine even worth it?

To set the technical restrictions: The cores require at least 0.25 second to turn on and off, so they can't use really short cycles of intake and expulsion. However, strength of their output can be controlled. The best the attractor core can reach is about 10 atmospheres stable pressure, the best the repellant core can do is 0.1 atmosphere.

My own idea was to use attraction cores to attract air - increase pressure in a wooden chamber, then block intake and turn the attractor core off, which pushes air into the only possible route of escape - thruster. However, with such technical constraints, I feel that my idea might produce only laughable thrust.

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  • $\begingroup$ the majoirity of the periodic table is metals, you are going to have a hard time creating technology without metal. the calcium in your bones is a metal. 2/3rds of the atoms in water are metals. $\endgroup$ – John Oct 30 at 2:05
  • $\begingroup$ I am currently handwaving it with 'metal has to be in its pure form', although I am aware that is not really good enough. I plan to look a little bit more at it. I wanted to restrict it a bit to only work with transitional metals, but to be honest, it feels completely artificial and I have bad time justifying this artificial decision. That being said, hydrogen is not a metal. As for what remains even after my restriction "metal has to be pure", I plan to leave that as everpresent background interference. $\endgroup$ – Failus Maximus Oct 30 at 7:17
  • $\begingroup$ Uhh... Did John just categorically state that hydrogen was a metal... Like, I'm pretty certain it's genuinely agreed to be relatively ambiguous in terms of its 'metalness'. $\endgroup$ – DoublyNegative Nov 2 at 22:37
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Well, this makes maglev style trains very easy.

For propulsion, have an open tube with a number of these "repulsion engines" (REs) inside it angled toward one end. That would cause air to be pushed out the "back" end and sucked in the front end. You now have jet propulsion. If you turn on of off some of the REs or can increase of decrease the repulsion effect, you can throttle the jet.

This tube would work in air and water.

You could also make a turbo prop out of this but I wouldn't unless they've had this tech for a very long time.

Note that if the RE is powerful enough, it would make a very good machine gun too.

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A jet engine has four components: the intake, the compressor, the combustion chamber, and the turbine. Your magic attraction and repulsion cores are capable of reproducing the first two stages of the engine: sucking air into the engine, and then compressing it to increase its pressure while decreasing its volume.

If they can make magical heating elements, they could reproduce the effects of the ignition chamber, assuming that they don’t want to just use mundane fuel oils and a crystal-lined combustion chamber to do the job.

Then comes the turbine, which turns a portion of the engine’s thrust output into the rotational power needed to run the engine; strictly speaking, your magic engine wouldn’t need this since it’d be entirely solid-state, without rotating components, though maybe if it’s possible to generate magical energy by rotating a wheel you might be able to produce something analogous by building some sort of wooden turbine.

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  • $\begingroup$ It's not possible to get magic by rotating a turbine, but perhaps I could use some device to harness the mechanical energy for the system to use to close the intake/thruster on its own. $\endgroup$ – Failus Maximus Nov 1 at 4:10
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There's an even better way of using these kinds of magical attractions / repelling engines. And that is the legendary Zero Mass Drive. Theoretically, using negative matter, you could have a drive which has a net mass of zero, and propel itself. Hence the name, Zero Mass Drive (technically, it's called a Reactionless Drive, whatever, Zero Mass Drive is a cooler name).

Now, you specify that the crystals are non-quark based matter, but you haven't done the same for cores, which means that they are quark-based - and thus real matter - and thus you can build cores that can attract and repel the material that cores are made of. So what you do is simple. You build a core which attracts cores, and a core which repels core. Then you line up the cores. The first core repels, the second attracts. And now is when the drive takes effect. The second is attracted to the first, and the first is repelled, sending both cores forward along the line. Then, all you do is mount the cores (when they aren't on, of course) to your ship, then simply activate them.

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  • $\begingroup$ I am really sorry but I have to correct you. I might not be an engineer, but I'm a sci-fi enthusiast. Key point of zero mass drive is, it requires one of cores have negative mass. We're not talking about gravitational mass, but negative innertial mass. Object with negative innertial mass is weird - if you push it, it starts accelerating towards you, if you pull it, it starts moving away from you. Cores and crystals, while both non quark matter do have both positive innertial mass. So sadly, that's not possible. $\endgroup$ – Failus Maximus Oct 30 at 18:14
  • $\begingroup$ I'm not saying you can do a zero mass drive. I'm saying you can do a facsimile of a zero mass drive. It won't actually be zero mass, but the drive itself, as long as you have the twin cores in place, will just accelerate forward once you turn them on. $\endgroup$ – Halfthawed Oct 30 at 18:25

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