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I want to know the pros and cons of hand held rail guns versus coil guns. They will be given to infantry who can easily lift the weapons. If need be they could have twice the strength of a normal human via cybernetic enhancements. What would be the various pros and cons, especially in rough terrain?

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    $\begingroup$ I've had the same question myself and ended up going with coil guns. Jim2B gave a good answer summing up my reasons. However, if you want to be realistic, you need to come up with a small, portable, hugely powerful power source for the gun. Both guns require huge amounts of electricity to fire. To fire at a typical machine gun rate (600 RPMs), you are going to need that huge power source multiplied by 600. Also note if such a power source existed, there are many, many other weapons and devices we could have. $\endgroup$ – DrZ214 Oct 16 '15 at 5:11
  • $\begingroup$ what about using either of them as a sniper rifle style system to produce a long distance shot wth out the light produced from a normal gun $\endgroup$ – madokk Mar 9 '17 at 19:01
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In short (links to follow as I find time to put them in).

Coil guns (aka Gauss guns)

Have a higher max projectile velocity. Powerful switches alternate the electromagnetic poles in the drive coils as the projectile passes through the coils. This requires high voltage, high amperage, high speed electrical switches. Researchers have been trying to build these for decades with only moderate success.

is a type of projectile accelerator consisting of one or more coils used as electromagnets in the configuration of a linear motor that accelerate a ferromagnetic or conducting projectile to high velocity.1 In almost all coilgun configurations, the coils and the gun barrel are arranged on a common axis.

Coilguns generally consist of one or more coils arranged along a barrel, so the path of the accelerating projectile lies along the central axis of the coils. The coils are switched on and off in a precisely timed sequence, causing the projectile to be accelerated quickly along the barrel via magnetic forces. Coilguns are distinct from railguns, as the direction of acceleration in a railgun is at right angles to the central axis of the current loop formed by the conducting rails. In addition, railguns usually require the use of sliding contacts to pass a large current through the projectile or sabot but coilguns do not necessarily require sliding contacts.2 Whilst some simple coilgun concepts can use ferromagnetic projectiles or even permanent magnet projectiles, most designs for high velocities actually incorporate a coupled coil as part of the projectile.

The force the projectile leaves on the weapon is it attempts to compress the coils (you'd get recoil similar to a normal weapon).

Magnetic fields are not inherently dangerous to people as long as they don't have magnetic metals on their person. Other than the difficulties with switches, a coil gun is much more suitable for use by unprotected humans (e.g. infantry):

Video at link: Man portable coil / gauss gun

Railguns

Are much easier to build from a technological perspective. Current runs down one "rail" through the conductive base of the projectile and back up the other rail. This is the brute force method of electromagnetic projectiles.

A railgun is an electrically powered electromagnetic projectile launcher based on similar principles to the homopolar motor. A railgun comprises a pair of parallel conducting rails, along which a sliding armature is accelerated by the electromagnetic effects of a current that flows down one rail, into the armature and then back along the other rail.

The forces applied to the railgun try to rip the rails apart. The recoil from the projectile also supplies a recoil like a chemical slug thrower.

Each rail conducts high voltage and amperage current. Touching or getting close to one of the rails would be exceedingly dangerous. This weapon is probably not suitable for infantry use.

Video at the links:
Artillery equivalent railgun
Man portable railgun

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    $\begingroup$ An infantry railgun would have the rail system enclosed. The big problem with them is the ferocious wear on the rails (not just from friction but from high current erosion as well) which makes them require frequent maintenance and given to sudden decreases in performance is the maintenance is not done. They would also kick because you can't beat the conservation of momentum. $\endgroup$ – dmckee Oct 16 '15 at 1:13
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    $\begingroup$ Coilgun rounds also have the problem that they must have certain magnetic properties (if you don't use sliding contacts). Railgun shells need only be conductive, as the current flow itself creates the necessary magnetic relationships. $\endgroup$ – Sean Boddy Oct 16 '15 at 7:44
  • $\begingroup$ Well could the infantry carry around extra rails? They would replace them after a few shots or so and continue use. Or with a covered rail system is that entirely unfeasible. $\endgroup$ – Sunspear25 Oct 16 '15 at 11:55
  • $\begingroup$ @SeanBoddy one of the article states that some designs use projectiles with an opposing electromagnetic. Alternatively the projectile only requires a shell of ferromagnetic materials. Railguns only require a base of conductive material AND it's ok if that base vaporizes during the shot. $\endgroup$ – Jim2B Oct 16 '15 at 12:58
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    $\begingroup$ @dmckee - For the same projectile weight and muzzle velocity, coilguns and railguns will have the same recoil. $\endgroup$ – WhatRoughBeast Mar 9 '17 at 19:39
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One advantage of a rail gun would be if you ran out of loads but still had power you could just jam the rails against and enemy and pull the trigger. The impedance would be higher, causing the voltage between the rails to be higher.

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  • $\begingroup$ lol, what an idea XD That would work too . . . $\endgroup$ – veryRandomMe Oct 16 '15 at 2:00
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While using rail or coil guns as infantry small arms is problematic (due to the various issues already discussed), there may be a place for railguns as a man portable anti tank weapon.

Current ATGM's generally use shaped charge warheads to actually penetrate the armour (the rocket motor just gets it there), and various techniques have been developed since WWII to defeat these types of warheads, including spaced armour (such as the "cages" around modern tanks), explosive reactive armour (the brick like devices attached to the outside of most Russian tanks) and even counter missiles like the Russian "Arena" or Israeli "Trophy" systems. Hypervelocity "darts" (Armour Piercing Discarding Sabot Fin Stabilized; APDSFS) fired from tank cannon are much harder to defeat, and using current or near term technology the only practical means of defeating such rounds is plates of high strength and density armour.

A tank cannon is a huge piece of equipment, firing large 120mm rounds and having massive recoil, so you need the tank to carry it around and use it effectively.

A man portable railgun would resemble a recoilless cannon:

M-40 106mm Recoiless Rifle

The propellant charge would not be used to drive the round, but rather energize a MHD generator with the jet of high velocity gas exiting the venturi, while the long barrel will house the rails which actually drive the projectile. The actual projectile can be rather small and relatively light, since the damage is delivered in the form of kinetic energy. A small projectile moving fast enough could conceptually be able to engage helicopters and aircraft as well, although a very advanced sighting system and mount capable of rapid movement of the weapon will be needed.

The downside of this weapon will be much like regular recoilless cannon: the jet of the driving charge (in this case driving the MHD generator) will certainly alert any enemy of where you are, and you will need to leave immediately after firing.

Still, this would allow light infantry to be able to take on tanks on a more equal basis, as well as defeat most types of fortification (blasting through bunkers and buildings with relative ease), so something along these lines may be considered as the technology of railguns matures.

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  • $\begingroup$ Or maybe it would use a pair of electrolodes to create "ionic wind" to propel the projectile out of the barrel with less mechanical complexity. Like so:news.mit.edu/2013/ionic-thrusters-0403 I'm not sure how complex it would be however or wether the power to weight ratio would be high enough. $\endgroup$ – Efialtes Feb 11 at 13:51
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They both differ from conventional weapons in that they use electromagnetism to propel the projectile rather than using an explosive charge. Both of them need incredible amounts of energy, which is why they are not practical in an infantry weapon at the moment. The gun barrel and mechanisms do not need to be massively heavy, the problem is supplying the power.

The advantages of rail guns is that they are much simpler to build and operate than a coil gun. They are also more powerful as they have a direct contact between the projectile and the rails while the coil gun has a gap between them.

The advantage of a coil gun though is that the coils can be insulated from the outside world more easily, which could well make them more reliable in the long run. It will be harder for external conditions to interfere with the coils and the coils will take less wear and tear in use. Rail gun rails in particular are subject to a lot of wear even from normal use.

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  • $\begingroup$ They are most definitely not "essentially the same weapon". @Jim2B's answer explains it in more detail, but in essence: coil guns are way easier to build than a proper rail gun. Both can be insulated very easily, but you fail to mention to wear railguns experience. because of extreme currents? Downvoted. $\endgroup$ – Isaac Woods Oct 18 '15 at 19:51
  • $\begingroup$ @IsaacWoods They both use electromagnetism to propel the projectile, the difference is in how that force is applied. This means both have similar requirements in terms of energy, no need for propellant, etc. My final sentence also said "the coils will take less wear and tear in use". $\endgroup$ – Tim B Oct 19 '15 at 8:14
  • $\begingroup$ While they both use electromagnetism to propel the projection, the coilgun uses straightforward magnetic attraction to pull the projectile through the barrel (the fact that it's an electromagnet is actually almost irrelevant), whereas the railgun uses the Lorentz Force to propel the projectile along the barrel. Also, in a coilgun, the coils take no physical wear and tear, whereas a railgun can only take a few shots before you end up with something like this: princeton.edu/~romalis/PHYS210/railgun/DSC01190.jpg $\endgroup$ – Isaac Woods Oct 19 '15 at 19:43
  • $\begingroup$ @IsaacWoods I've re-worded it. Hopefully that's more to your liking. $\endgroup$ – Tim B Oct 19 '15 at 19:49
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Railgun for one they can fire faster because the rails do not need to be deactivated. Also, with a coilgun you need capacitors which can fry easy. So railgun is my preferred choice.

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    $\begingroup$ Do you not need capacitors for a railgun? All of the designs I've seen involve them. And what makes you say that railguns can fire faster? The coils in coilguns turn themselves off as the projectile goes through them, so what are you talking about? $\endgroup$ – Kevin Wells Mar 30 '17 at 19:48
  • $\begingroup$ You do not need them but it saves power to have them. $\endgroup$ – rubyrude.infinite Dec 5 '17 at 13:46
  • $\begingroup$ Then presumably you could also not use capacitors for a coil gun at the expense of power, which makes the point moot right? And either way, in what way does a railgun fire faster? As far as I understand both could be set up to fire quickly given enough energy, but the railgun would actually overheat far before a coil gun would $\endgroup$ – Kevin Wells Dec 5 '17 at 23:54
  • $\begingroup$ You could use flywheels as a safer alternative to capacitors. They are whats used on the EMALs to charge up the em catapult. en.wikipedia.org/wiki/Flywheel_energy_storage $\endgroup$ – Efialtes Feb 11 at 13:54

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