From: henry@spsystems.net   
      
   In article <1122700717.589550.285630@z14g2000cwz.googlegroups.com>,   
   Cray74@gmail.com  wrote:   
   >> They required very thin layers of exotic metals   
   >> that were difficult to work with and tended to be brittle;   
   >   
   >Where's the requirement for "very thin" layers come from? Just weight   
   >requirements alone?   
      
   Correct.  The high-temperature metals, unfortunately, tend to be really   
   dense.  Things like niobium and molybdenum are nearly as dense as lead;   
   tantalum and tungsten are substantially *denser* than lead.  They have to   
   be kept thin or the weight just goes out of sight.   
   --   
   No, the devil isn't in the details.                     |   Henry Spencer   
   The devil is in the *assumptions*.                      | henry@spsystems.net   
      
   --- SoupGate-Win32 v1.05   
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