From: henry@spsystems.net   
      
   In article ,   
   Cameron Dorrough  wrote:   
   >> But ablative heatshields don't work very well if you start insisting that   
   >> the vehicle has to have *wings*...   
   >   
   >Henry, having said that.. what are your thoughts on something along the   
   >lines of Rutans' SpaceShipOne "shuttlecock" design?  That has wings but   
   >would reenter quicker than a conventional airframe shape.   
      
   I don't know quite enough about its reentry profile to confidently compare   
   it.  The impression I have is that it's a pure drag device, non-lifting,   
   until it swings its tail back down.  That's actually *too* drastic for an   
   orbital reentry, or even a higher suborbital, where you want a little bit   
   of lift to reduce the G-loads.  Unless you get quite a bit of lift,   
   though, its reentry is still in the "sharp and short" category where   
   ablators etc. do well.   
      
   >Would something like that (but with an Apollo-style ablative shield on the   
   >belly) offer any advantages?   
      
   I would worry about ablators on aerodynamic surfaces, because of concern   
   that uneven ablation would change the shape or leave a rough surface.   
   There are also a lot of surfaces needing protection -- the belly is worst   
   but it's not the only concern -- which is going to run up the ablator mass.   
      
   That aside, there is a lot of advantage in variable geometry, or more   
   generally, in being able to change vehicle modes to deal with the changing   
   environment.  The more you can separate the problems of reentry from those   
   of landing -- for example, by using different vehicle configurations --   
   the easier the problems are to solve, because you don't have to satisfy   
   several sets of constraints simultaneously.   
   --   
   MOST launched 30 June; science observations running     |   Henry Spencer   
   since Oct; first surprises seen; papers pending.        | henry@spsystems.net   
      
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