From: henry@spsystems.net   
      
   In article <1122296198.011021.158930@z14g2000cwz.googlegroups.com>,   
   Cray74@gmail.com  wrote:   
   >Different re-entry profiles can help, too. The original civilian   
   >designs for the US space shuttle used metallic heat shields. When the   
   >USAF signed on, it had requirements for the shuttle that included more   
   >demanding re-entries...   
      
   It wasn't quite that simple.  The original ideas for metallic thermal   
   protection were complicated, and nobody was really all that sure that they   
   could be made to work.  They required very thin layers of exotic metals   
   that were difficult to work with and tended to be brittle; it wasn't clear   
   that they were going to be very durable.  They certainly looked like   
   they'd be heavy.  And one big snag was that the metals required protection   
   against oxidation, and the coatings needed for that were poorly developed.   
   People had been *talking* about metallic heatshields for a long time, but   
   the reality wasn't so rosy.   
      
   Ceramic tiles -- lightweight, inherently oxidation-resistant, and good   
   insulators -- looked like a huge improvement in many ways.   
   --   
   "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)