From: schillin@spock.usc.edu   
      
   alexterrell@yahoo.com writes:   
      
   >Why is arcing more of a problem in a vacuum than on Earth. I assume   
   >vacuum tends to be a poor conductor.   
      
   A *perfect* vacuum is a poor conductor, but there is no such thing.   
   The sort of vacuums you find in space, depending on exactly where   
   in space you are, often have just enough free electrons or ions to   
   carry a modest current and nothing to slow them down.   
      
   And a modest current at high voltage, represents a high power.  A   
   high power that, with nothing to impede it, will concentrate at   
   whatever bit of your high-voltage circuit you expose to it.   
      
   At which point, you find that a high concentration of power on a   
   metal surface, boils off lots of electrons and ions.  Now see step   
   one...   
      
      
   >Is arcing a problem with a straightforwad voltage step up - transmit -   
   >voltage step down system?   
      
   Yes.  The high voltage parts have to be well and thoroughly insulated,   
   or you have to be real sure you're only going to operate in the parts   
   of outer space that have real good vacuums.   
      
   Unfortunately, most of our experience with high power systems in space   
   is with communications satellites, which necessarily operate in the   
   parts of outer space that have vacuums with a particularly high density   
   of stray electrons.   
      
      
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