From: root@mauve.demon.co.uk   
      
   Henry Spencer  wrote:   
   > In article <20040505223253.03209.00000957@mb-m28.aol.com>,   
   > Allen Meece  wrote:   
   >>Yes, I'm sure we can do a better reentry model than nasa  uses. It would   
   >>involve a softer slower penetration of the atmosphere.   
   >   
   > If there *were* some way to do that, it would certainly be nice.   
   >   
   >>    If compressed air at the front of the craft imparts heat, then that heat   
   >>can also be transmitted back into the darn air by heat exchangers at the back   
   >>of the craft.   
   >   
   > Unfortunately, there's nothing that magically makes the air at the back   
   > significantly cooler than the air at the front.  It's *all* very hot; the   
   > back end is just exposed to less of it.   
      
   > You can, in principle, transfer forward-surface heat to the aft surface   
   > and *radiate* it away.  That idea has been around for a long time.  Alas,   
   > the engineering is difficult -- to get rid of a lot of heat that way, the   
   > radiator temperature has to be very high -- and it has never looked like   
   > it was worth the trouble.   
      
   The only case in which it's easy is if you have a thin section   
   that can transfer the heat directly.   
   It does mean strong, refractory light surfaces though.   
      
   Something like a metal shield that extends out past the edge of the vehicle   
   to lower the average areal density, and hence reduce heat soak into the   
   main vehicle.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)