From: Rodneykelp605@hotmail.com   
      
   What ever the hell lights up the tiles.   
   >   
   > Umm, what friction fire?   
   >   
   >   
   >>   
   >> "Andrew Nowicki"  wrote in message   
   >> news:41D4107D.4CF53E44@medianet.pl...   
   >> > Tommy wrote:   
   >> >   
   >> >> a better question is why didn't they make the shuttle out of titanium   
   >> >> rather than aluminium.   
   >> >   
   >> > Paul Hovnanian P.E. wrote:   
   >> >   
   >> >> Because the ceramic tiles also provide excellent insulation to protect   
   >> >> the interior systems and structures of the shuttle. While titanium   
   > might   
   >> >> withstand the temperatures of reentry, it would still conduct a   
   >> >> significant amount of heat. Some sort of insulation layer would still   
   > be   
   >> >> required.   
   >> >   
   >> > The ceramic tiles are very lightweight and very efficient   
   >> > insulators, but they are extremely brittle. I believe   
   >> > that the best solution is regenerative cooling (plumbing   
   >> > circulating cold water) in the leading edges of the shuttle.   
   >> > There are probably structural pipes in the leading edges   
   >> > already, so using the existing pipes would not add much   
   >> > weight. The regenerative cooling would be a backup system --   
   >> > when a spot in the leading edge becomes too hot, a safety   
   >> > valve melts down and water begins to circulate to cool down   
   >> > the hot spot.   
   >>   
   >>   
   >   
      
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