From: daellis94@gmail.com   
      
   So, I'm doing a bit of technological world-building, and I'm trying to decide   
   on rail-guns or coil-guns for use on high-velocity anti-ship cannons on   
   exo-atmospheric battleships and cruisers*.     
      
   I'm thinking that these main guns will fire a projectile at a velocity of   
   around 8,000-12,000 meters per second relative to the firing platform, and I'm   
   settling more in the realm of 9 or 10,000.  I've come to understand that   
   coil-guns are more efficient    
   for higher velocities such as these, but I'm not confident that I know how   
   well a coil-gun would serve as a launch platform for the projectiles I'm   
   thinking of.     
      
   The projectiles are to have a mass of roughly 50 kilograms, where 15 percent   
   of this mass is reaction mass for a hybrid propulsion unit--that is, solid   
   fuel with liquid oxidizer--featuring thrusters not unlike those on the payload   
   of the Ground-Based    
   Interceptor or Standard Missile 3.     
      
   My concern is in the need to replace more of the mass of my projectiles with   
   magnetic materials.  As far as I can tell, a rail-gun armature simply has to   
   be conductive.  My idea was to include a portion of the rear of my projectiles   
   made from copper    
   alloy.  The applied current would flow through the copper segment, at which   
   point the solid alloy would likely be heated into a plasma, but this hybrid   
   armature would continue to conduct electricity, as plasma does quite well, and   
   accelerate the    
   projectile by pushing from behind.     
      
   As far as I know, this behavior would take place regardless of the mass of   
   this copper alloy segment, with the force exerted depending only on the   
   current flowing.  This isn't the case for a coil-gun, as I understand.    
   Wouldn't I need to make sure to    
   incorporate a larger mass of magnetic material in each projectile?     
      
   Also, each projectile would have electronic guidance components on-board.  I   
   can insulate these from electric current, yes, though possibly with some   
   difficulty.  Would it be feasible to prevent the formation of electromagnetic   
   fields from damaging the    
   shell's electronics and sensors?     
      
   *--As a note, for those interested in the choice of nomenclature, or those   
   otherwise eager to dissuade me from applying a World War One-esque approach to   
   space combat, my use of battleship and cruiser as terms would actually find   
   more appropriate    
   comparison with warships in the mid/late 19th century, in the days of the   
   protected cruiser and the pre-Dreadnought battleship.  In these circumstances,   
   one saw battleships taking over from ships-of-the-line as heavy ships meant   
   for pitched battles, and    
   cruisers serving as cheaper, more numerous warships with the range to make   
   long voyages from base to raid enemy commerce or protect friendly shipping, as   
   well as other roles.     
      
   My use of "battleship" and "cruiser" parallels these roles.  I'm not thinking   
   that their tactical use must exactly resemble the duels of gun-armed turret   
   ships.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)