What are some of the key differences in how they function and what that means in practical applications?
In: Technology
A coilgun have a coil wrapped around the barrel creating an electromagnet. When you pull the trigger you activate this electromagnet which attracts the projectile to it. When the projectile is moving past the electromagnet you turn it off so that you do not pull it back again. A railgun on the other hand only have two rails going along the barrel. The projectile creates a short circuit between these rails. If you apply a current through the projectile you are essentially creating a coil with only one turn which acts as an electromagnet. But as you activate an electromagnet there are forces pushing it outwards. This is often the source of the buzzing sound you hear in transformers. But since nothing is holding the projectile in place it will just accelerate forward until it loses contact with the rails.
Coilguns are very attractive at first compared to railguns. All the wires are insulated so there is no risk of shock or short circuits. There are much less friction and currents are lower so less heating of the components. You also do not have to worry so much about the projectile losing contact with the rails as it travels down them. However a coilgun requires a lot of precise components to open and close the circuit at the exact right time. For something small like a BB gun this is a nice little challenge. However for much larger projects there just is not components that are both large and precise enough. On the other hand the issues with railguns does not grow as the size of the gun is increased. In fact if you get enough energy some of the problems resolve themselves, such as heating the projectile enough that it contacts the rails much better. And there is no active electronics involved, just capacitors, two rails and a switch. This is why we are actively researching railguns to possibly be used in future warfare while coilguns are more of a novelty concept for small devices.
Railguns have two conducting rails as the name implies and the projectile forms a bridge between them and slides down the rails and shoots out the end. Railguns require huge currents and the rails take a lot of damage from the projectile sliding down them at high speed, the electric current arcing to the projectile, and the insane repelling force between the two rails. This is why railguns have tons of bolts running down their length, they want to rip apart. Any projectile will work, if its not conductive then you put it on a conductive sled that drops off after launch.
Coilguns use a coil of wire to create a magnetic field to push the projectile out. In the non-weaponized sense we generally call these solenoids and they’re used all over the place, its just a small coil that causes a little metal pin to pop out. Now if you take that coil, make it bigger, put a lot more power through it, and let the pin shoot out you’ve got yourself a coilgun! Coilguns don’t need super high levels of current as you can use more voltage and more windings to generate the higher magnetic field rather than just moar current like a railgun which has no windings. Coilguns do require magnetic projectiles (or something that can have magnetism induced in it) which limits the options, but they also have the advantage of not trying to rip themselves apart or wearing significantly with each shot.
At the end of the day, making a strong/efficient railgun just requires a big ass capacitor bank, two conductive rails held together nicely, and a conductive projectile. A coilgun is a fair bit more challenging to make an efficient coilgun and you start needing staged coils and careful timing to sync up and get your projectile to high speed. DARPA made a 45 stage coilgun mortar and only managed to pull 22% efficiency out of it meanwhile the Navy’s Railgun is around 50% making it a much better use of power
Coilguns fire magnetic bullets. It requires the projectile to be a permanent magnet.
Railguns push a projectile with a conductive sled between two high current rails. The projectile can be made of anything.
Coil guns use magnetic coils to accelerate a magnetic bullet, then they shut the coil off so the bullet doesn’t get attracted back when it leaves the gun
A rail gun uses two electrically conductive rails to pass an enormous amount of current though a metal sort of shell thing that holds the bullet, the current that flows generates a magnetic field that launches the projectile
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