From: henry@spsystems.net   
      
   In article <770039be.0406290540.4ab5e794@posting.google.com>,   
     wrote:   
   >...NH3 gas decomposes endothermically and should be a   
   >good coolant for a low pressure (Pc about 1-2 atm.) engine made of   
   >electroformed nickel.   
      
   A small caution:  NH3 decomposition involves transient formation of atomic   
   hydrogen, which makes decomposing ammonia quite corrosive to some   
   materials.  (The early-60s nuclear-rocket guys discovered that running   
   ammonia through a graphite-core reactor was going to require really good   
   protective coatings for the graphite.)  I would guess that nickel would   
   be okay, but it's an issue to watch out for.   
   --   
   "Think outside the box -- the box isn't our friend."    |   Henry Spencer   
                                   -- George Herbert       | henry@spsystems.net   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)