In article ,   
   	henry@spsystems.net (Henry Spencer) writes:   
   > In article ,   
   > Tommy   wrote:   
   >>a better question is why didn't they make the shuttle out of titanium   
   >>rather than aluminium.   
   >   
   > NASA did in fact consider it, with the higher cost and greater weight of   
   > titanium structure almost completely balanced out by the ability to relax   
   > the requirements on the tiles a little.  The decision was ultimately made   
   > on secondary issues, notably the US's limited titanium supply.   
   >   
   > It would not have made any great difference to Columbia.  Titanium is not   
   > *that* much better; the conditions in Columbia's wing were far beyond the   
   > working limits of *any* reasonable structural metal.   
      
   Thanks for an answer to one of my pet post-Columbia questions.   
   Recognizing that a complete titanium rework was out of the question,   
   I was wondering about using titanium for just the leading structural   
   member. Comparing Al to Ti the melting points are 669C vs 1660C,   
   quite a bit different. I guess that says nothing of how much strength   
   either loses as they approach the melting point. How hot do they   
   estimate it was inside the leading edge?   
      
   The second part of my pet post-Columbia idea was to flow air through   
   the leading-edge space. Arrange some sort of exhaust port at the   
   wingtip to create some negative pressure. Open an airflow from the   
   leading-edge wing-root into the cargo bay. Open some sort of positive-   
   pressure inlet from the coldest (I know no point is really cold.)   
   exterior into the cargo bay. The net airflow would be from cold-side,   
   probably somewhere on top near the back, through the cargo bay, and   
   out the leading edges. The idea was to dilute hot leaks from the   
   leading edge, itself. For small leaks I suspect it might help, but   
   for one the size on Columbia, I don't know if anything could have.   
      
   Dale Pontius   
      
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