The rail gun is a type of projectile weapon that uses a propulsion system different than the common gunpowder devices.

The rail gun is thus named because of the twin rails that make its usage possible. There are four basic components of a rail gun. The power supply, the rails, the armature, and of course the projectile. The power supply sends a current down one rail which comes back through the other rail by going across the armature. The armature is a conductive bridge that is allowed to move freely on the rails and which also holds the projectile. Whenever a current travels over a wire, a magnetic field is generated. Each rail acts as an individual wire and each generates a force that spirals around it. The forces of the two rails form a vertical upward force between them.

Meanwhile, the armature and projectile experience a Lorentz force. This force runs perpendicular to both the magnetic field which runs vertically and the current which runs horizontally. The only other way to move is parallel to the rails. The projectile-carrying armature is pushed with the Lorentz force according to the equation F=i*L*B where F is the force, i is the current, L is the length of the rails, and B is the magnetic field.

Building extremely long rails can pose design challenges. Therefore, most rail guns use extremely high currents, usually up around one million amperes while the rails are usually around four to nine meters in length.

The most outstanding advantage the rail gun has over gunpowder weapons is its sheer power. A gunpowder weapon can only fire with a velocity around 4,000 fps. The rail gun smashes this record with velocities around 52,400 fps. The United States Navy rail guns currently have an accurate maximum range of around 12 miles. Rail guns can reach a target 250 miles away in approximately six minutes.

Other advantages are that gunpowder ammunition is volatile and requires more caution than rail gun ammo. Gunpowder ammunition includes the casing, powder, and bullet, making the round heavier than a similarly sized rail gun round.

Along with advantages naturally come obstacles. Some of the obstacles facing the rail gun are:

  • Power supply-Rail guns require very high amounts of power to operate. The capacitors used to store the necessary charges are several cubic meters in size.
  • Heating-Wherever there is resistance, there is heat. With the amount of current running through the rails, lots of heat is generated even though rails are made of very conductive materials. This along with the friction generated by the swift moving armature can damage rails.
  • Repulsion-Because one rail is the positive rail and the other is the negative rail, the rails repel each other very strongly when a current is sent through them. For this reason, rails usually do not last for more than a few firings before they must be replaced.

So until we find a way to generate massive amounts of electricity all at once, rail guns have yet to find common usage on the battlefield.