XPost: sci.space.policy   
   From: henry@spsystems.net   
      
   In article ,   
   Roger Stokes  wrote:   
   >Even at .7 ppb of  the Earth's atmosphere, I assume it must still be cheaper   
   >right now to refine it on Earth...   
      
   You don't get it from the atmosphere.  Rather, it's a product of tritium   
   decay.  Most modern nuclear weapons contain small amounts of tritium for   
   "boosting" fission yield (either of the whole bomb, or of the fission   
   trigger for a fusion bomb), and it must be repurified regularly because   
   He3 poisons the reaction.  So the US nuclear arsenal, in particular,   
   generates a steady trickle of He3 as a byproduct of bomb maintenance.   
      
   >and try some fusion experiments, rather than   
   >go to the moon to get it - what's the reason it hasn't been done?   
      
   We don't have a fusion reactor that works even for the D-T reaction, never   
   mind for one involving He3.  The basic physics of the He3 reactions have   
   been understood for a long time; it's the engineering details of the   
   fusion reactor that might, or might not, be able to overcome the problems.   
   We can't run meaningful experiments on that until we can build one.   
   --   
   MOST launched 30 June; science observations running     |   Henry Spencer   
   since Oct; first surprises seen; papers pending.        | henry@spsystems.net   
      
   --- SoupGate-Win32 v1.05   
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