Railguns

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	Please bear with us. Your ride's still a work in progress.

A railgun is a projectile weapon that uses high electric currents to push a projectile between two rails. The potential advantages of a railgun are high speed projectiles. Disadvantages include rail wear, the need to store large amounts of energy, and the equipment to produce pulses of extreme currents.

Working principles

An electric current creates a magnetic field that circulates around it. If you have two parallel conductors carrying current in opposite directions, they both produce a field that points in the same direction between them, amplifying the field in that direction (likewise, outside the two wires the fields point in opposite directions making the field weaker there and causing it to fall off faster than the field from a single wire).

A magnetic field exerts a force on any electric currents going through it. The force is in the a direction perpendicular to both the magnetic field and the current, and is proportional to both.

The magnetic field (magenta) circulating around a cross sectional plane perpendicular to the direction of an infinite line of current (green).	The magnetic field (magenta) circulating around a cross sectional plane perpendicular to the direction of two infinite line of current in the opposite directions (green).	The force on a current due to a magnetic field.

The basic idea for building a railgun is to take two parallel conductive rails. Short the two rails with a conductive projectile near the breach. Apply a pulse of very high current, that will run down one rail, through the projectile, and back up the other rail. The current-carrying parts of the rail make a high magnetic field between them. This field pushes on the current flowing through the projectile, which launches it down the rail. As long as the projectile shorts the two rails, it experiences the force and is accelerated faster.

A simplified diagram showing the workings of a railgun.