From: henry@spsystems.net   
      
   In article <20040601213440.13897.00000172@mb-m24.aol.com>,   
   Allen Meece  wrote:   
   >    Lift here is not aerodynamic lift but is rather, positive buoyancy. So it   
   >makes the L/D ratio irrelevant. The ship is weightless at 200K feet and needs   
   >little aerodynamic lift. As the velocity increases, so does centripetal force,   
   >helping to "lift" the craft.   
      
   Unfortunately, at Space Access they said (if memory serves) that it's at   
   nearly double that altitude at only about Mach 5, still too slow for   
   centrifugal lift to be very significant.   
      
   (A centripetal force by definition pushes *toward* the center of rotation;   
   the proper word here is indeed centrifugal.)   
      
   More generally, the apparent shortfall in L/D is much too large to be made   
   up that way.  Centrifugal force rises with the square of velocity, so you   
   have to be at 70% of orbital velocity to get half your lift that way, i.e.   
   to relax the required L/D by a mere factor of 2.   
      
   Buoyancy lift may be an important part of the picture, but centrifugal   
   lift almost certainly isn't.   
   --   
   "Think outside the box -- the box isn't our friend."    |   Henry Spencer   
                                   -- George Herbert       | henry@spsystems.net   
      
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