From: lwcamp@gmail.com   
      
   On Friday, December 7, 2018 at 12:07:22 PM UTC-8, David Ellis wrote:   
      
   > 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?    
      
   You can build coilguns to work based on induction rather than pushing on a   
   permanent magnet.  Surround the payload with something highly conductive   
   (copper, say, or graphene or superconductors or whatever your tech assumptions   
   allow).  The fields in the    
   coilgun barrel induce eddy currents in the conductive sheath which turn the   
   sheath into an electromagnet for the coilgun fields to push on.     
      
   This is the same principle behind modern asynchronous electric motors.    
   Basically, any coilgun can be considered a rotory motor unrolled into a   
   straight line, making it a linear electric motor, so the same design   
   principles apply to both.   
      
   As to whether induction is more practical than a permanent magnet, I'll leave   
   that to the engineers.   
       
   >    
   > 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?     
      
   Wrap the electronics in something highly conductive (like the aforementioned   
   copper or graphene or superconductors).  This will act like a Faraday cage to   
   protect the electronics from external electric fields.  You will need to take   
   special care wherever    
   you have wires or cables going outside of the shielded space (such as inputs   
   from cameras or outputs to guidance rockets or power cords for the computer) -   
   there are ways to engineer such couplings that limit the amount of external   
   linkage, but it is    
   something you need to pay attention to.   
      
   Luke   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)