Re: railgun parts

A railgun is a device used for launching a projectile using an 
electromagnetic force. It has applications in weaponry, nuclear physics, 
and perhaps as a means of launching an object into space.

The best way to think of a railgun is as a linear direct current motor with 
an armature that is free to leave the end of the track.  Linear motors, and 
railguns, both have similar parts.

First you need an armature, which becomes the projectile that you hope to 
launch.  The armature must be electrically conductive, since the force to 
propel it is generated by the combination of the current through it and the 
magnetic field surrounding it.  In the nuclear physics version, a gas 
plasma is used.  In the simplist version, a penny, ball bearing, or other 
metal object is used.  As long as the current going through the armature is 
perpendicular to the magnetic field of the rail, a force is produced which 
propels the armature along the rail.

The rail itself is a pair of long conductive, parallel bars.  The rail 
serves several purposes.  It provides a track to guide the armature.  It 
forms the magnetic field around the armature due to the current in the 
rails.  Finally, it supplies current to the armature as the armature moves 
along the rail.

Finally, you need a supply of electrical current.  This can be as simple as 
a battery or charged capacitor feeding the rails, with the armature closing 
the circuit.  Due to the low resistance of the rails and armature, high 
currents are generated.  This creates sparks similar to what happens when 
you have a short circuit in your home or car. If you want to re-use the 
railgun, a more complicated power source is required. (See University of 
Texas at Austin web site.)

Although the above is all that is needed, other parts can be added to the 
rail gun.  You might add controls or sensors to the power source to prevent 
the armature from welding itself to the rail due to the tremendous currents 
produced.  A means of lubricating the armature to avoid wear of the rail 
and armature might be added.  All of these would be used to make the 
railgun more useful, reliable, or allow repeated use.

To get an overall view of how they work and what they are used for, see the 
web sites below.

http://www.perpetual.net/kyle/railgun.html

http://www.wpi.edu/~seraphim/railgun.htm

http://www3.hmc.edu/~jengel/rail.html

http://www.utexas.edu/research/cem/rd/rd02/02.html

http://www.sover.net/~geoffk/railgun.html