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longbyte1

Why do coilguns have to have a straight barrel?

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Why can't we make the projectile go faster and faster in a toroidal or helix-shaped barrel and then release the projectile once it is going Very Fast?

I wish I could show a picture but I don't have any program that would do a decent job of illustrating my concept.

I was thinking if a helical coilgun fit my description, but not quite sure.

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Because centrifugal acceleration will fling any potential round to the outside, and thus tear up the barrel

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How do you direct the bullet to where you want it to go if it is going in such a barrel? Wouldn't there be a chance it will just tumble and completely miss the mark, or even destroy the gun?

Quite curious about this.

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Coilguns require a straight barrel due to the physics involved: It's most efficient to a linear accelerator. I'm sure that, with enough power and a powerful enough set of coils, you could do a curved barrel, but for the same amount of resources, you could build a far more powerful linear design that would provide more energy on-target with a single shot than the helical could with multiple shots and a time-on-target firing trajectory.

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Search for Circular Magnetic Satellite Launch System

Launch_ring.jpg

The idea behind, is to have a more convenient package for something like a 20 kilometer long railgun That accellerate at something like 1G for humans travel launch ^^

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One of my crazy ideas in my teen years for a futuristic 'minigun' was something like this. A handheld particle accelerator in the shape of a tightly-bound helix with an opening at the end. Yeah. A million years from now.

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This would work. But only with a lot of magnets and very strong materials.

As long as you put the barrel in the right configuration, it'll shoot straight.

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The problem with these is that the projectile has to withstand pi times the acceleration that it would experience from launch along the radius of the same circle. If you have magrail that can withstand it, a linear accelerator is actually easier to build. And if you aren't using a magrail, friction will probably tear things apart.

That's before we even get to topic of air resistance, which is irrelevant to OP's question.

Generally, linear accelerators make more sense. The only real exception are cyclotron accelerators, where a mag field is used to steer the beam, while RF in cavities is used to accelerate it.

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The idea behind, is to have a more convenient package for something like a 20 kilometer long railgun That accellerate at something like 1G for humans travel launch ^^

Not very good idea. If we accept acceleration of 50 m/s (5g) and velocity is 10 km/s radius of the ring must be v^2/a = 2000 km. Radius of Earth is about 6400 km.

Radius will be impractical even with highest imaginable accelerations and most of energy and mechanical force would get spent to bend the trajectory of projectile. There are good reasons why barrels of guns are straight and railguns are not exceptions.

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With a circular accelerator the forces involved end up about the same as with a linear one. The potential advantage is a lower power requirement. I can't see that being applicable to a small relatively low-speed coilgun, but if your projectile is either large or superfast then a circular design may have promise. After all, the extreme example of "superfast" is the LHC and that's a circle.

(To keep the projectile moving in the circle requires theoretically no energy. Of course there will be efficiency losses, but if they can be minimised things look promising.)

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Not very good idea. If we accept acceleration of 50 m/s (5g) and velocity is 10 km/s radius of the ring must be v^2/a = 2000 km. Radius of Earth is about 6400 km.

I think the idea is that the payload makes multiple laps in the ring before being shot out. Thus, instead of having a 2000 km long railgun you get a 20 km long railgun that the payload travels through 100 times.

It probably still isn't a very good idea, though, for the reasons you mention in the rest of your post.

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With a circular accelerator the forces involved end up about the same as with a linear one. The potential advantage is a lower power requirement. I can't see that being applicable to a small relatively low-speed coilgun, but if your projectile is either large or superfast then a circular design may have promise. After all, the extreme example of "superfast" is the LHC and that's a circle.

Mass of typical projectiles in LHC is 1,6E-27 kg and radius is 4,2 km. Costs was billions of euros. If you scale the mass to ton size you need probably much larger planet than Earth to fit the ring. And I think that it is easier requirement. There are large exoplanets in our galaxy but such amount of money would not fit inside the visible universe.

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Particles in the LHC are also accelerated to 99.999991% the speed of light, earth escape velocity is 0.003% of light speed, that probably reduces costs by a somewhat significant margin as well ;) .

The LHC is doing something completely different from putting payloads in orbit and should not be considered one way or another for the plausibility of circular coil guns.

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Wouldn't a linear accelerator, if spanned at anything longer than a few dozen km, be under the influence of the Coriolis effect?

When I think of a coilgun, I think of something handheld, or a cannon of sorts, so the projectile would ideally be just a few grams.

What if the minor radius of the toroidal barrel is large enough to have the projectile be kept exactly in the middle by the magnets surrounding the barrel?

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You could theoretically do this, but it's hard to see what you'd hope to gain from it. If you wanted to accelerate a projectile in a circle, you'd have to apply a very strong force on the projectile towards the center of the loop to keep it moving in a circle, and the force required for this would get very large for small loops. For something like that launch track someone posted earlier in the thread, it could be practical, but for the case of remotely-portable weapons or anything where size is a particular concern, you'll be much more efficient to concentrate all of your energy into a high linear acceleration than to try to do anything fancy with circular stuff - you'll waste too much just keeping the projectile going in a circle, which won't be free.

And practically speaking, coilguns already have enough problems accelerating things to significant speeds; I don't imagine adding a need for centripetal magnets will make things any easier.

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