From: henry@spsystems.net   
      
   In article ,   
   Wallace Berry   wrote:   
   >> There's a limit to how large you can pour a solid-fuel stage.  Make it too   
   >> large, and the grain will crack from internal stresses...   
   >   
   >What experiments have been done to examine incorporating some sort of   
   >fiber reinforcement into the grain to prevent cracking? How about the   
   >obvious: carbon fiber?   
      
   Carbon fiber in particular is probably a bad choice, because it's quite a   
   good thermal conductor, and solid fuels want low thermal conductivity   
   (partly to insulate the outer case, partly to concentrate combustion heat   
   near the inner fuel surface to encourage the surface to boil off).   
      
   I think fiber reinforcement of solid fuels has been done, but the mass   
   penalty is substantial if you want good reinforcement.   
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