From: henry@spsystems.net   
      
   In article <20040212005330.11576.00001803@mb-m12.aol.com>,   
   Allen Meece  wrote:   
   ><solved only when Harvey Allen realized that a reentering spacecraft was   
   >*NOT* an aircraft and should not be designed like an aircraft.>>   
   >   
   >   Bless Harvey Allen but some would say that  the reentry problem  has yet to   
   >be solved. We  invented better thermal insulation and called it a reentry   
   >solution but it's an unsatisfactory way of descending from orbit, as we   
   >witnessed with Columbia.   
      
   Some would say that the reentry problem was solved quite satisfactorily,   
   until the aircraft nuts got their foot in the door and started insisting   
   that spaceships had to look and act like aircraft.  The Apollo heatshield   
   had tremendous safety margins, and a little bash from falling debris   
   wouldn't have bothered it in the slightest (not least because the really   
   crucial part of it wasn't exposed during launch).   
      
   But ablative heatshields don't work very well if you start insisting that   
   the vehicle has to have *wings*.  That's what killed Columbia:  the long,   
   slow, reentry of a winged vehicle gives it a prolonged roasting rather   
   than a quick blowtorching, requiring thermal protection that radiates heat   
   away rather than soaking it up... and thus needs exotic high-temperature   
   materials, which typically involve compromises in areas like physical   
   durability.   
      
   >   It's  premature to say airplanes can't reenter.   
      
   Nearly half a century ago, we already understood that an airplane shape   
   was not the best choice for reentry.   
   --   
   MOST launched 30 June; science observations running     |   Henry Spencer   
   since Oct; first surprises seen; papers pending.        | henry@spsystems.net   
      
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