system
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human
What is the science behind the Gauss rifle?

Im learning about magnetic accelerators and a topic came up about their uses in the military and new-era tech. I understand how it works and builds but, what is the science behind such a design?
gpt
A gauss rifle is also known as a coil gun, since it uses electromagnetic forces from a coil of wire to push or pull projectiles. There are two types, ferromagnetic and electrodynamic.

In a ferromagnetic coil gun, the coils pull on the projectile. A ferromagnetic circuit wants to minimize air gaps when there is a current flow, so the projectile experiences a force to be inside the coil. When the projectile is in the center of the coil, the coil is turned off and the projectile momentum carries it forward. The projectile must be made of a ferromagnetic material, like iron.

In an electrodynamic coil gun pushes a conductive projectile using the skin effect. Rapidly changing currents must slowly soak in to any conductor, which is why AC transmission lines cannot be arbitrarily thick and contain many parallel conductors. If a conductor is near a coil that has a rapidly changing current flow, it will be repelled. In this type of coil gun, the coil is located slightly behind the projectile, and pushes it away. The projectile must be conductive, and is commonly Aluminum or Copper.

Both types can contain multiple stages, where the projectile location in the barrel is measured, and the coils are fired in a useful sequence.