From: andrew.gray@dunelm.org.uk   
      
   Afternoon all.   
      
   The current foremost contender for the X-Prize is, of course, Scaled   
   Composites - expected to formally announce soon, I believe - which uses   
   a staged flight method, with horizontal takeoff and landing.   
      
   Other contenders use vertical takeoff and landing single-stage vehicles;   
   Mr Carmack's group, for example.   
      
   Have any groups studied - I don't recall hearing of any, so I suspect   
   no-one ran with it - an in-air refuelling system, or would this be   
   barred by the competition rules?   
      
   (IOW: Spacecraft takes off "light" from a runway, meets tanker at   
   altitude, fuels up, then makes a ballistic shot with this fuel, gliding   
   back and landing light)   
      
   I'm not sure why this just wandered into my head, but it would seem to   
   offer the potential for a system about as efficient as the White   
   Knight/SS1 concept, with two more steps added (second takeoff,   
   refuelling) and one removed (in-flight separation).   
      
   (As an aside, would it be possible, in theory, for SS1 to take off from   
   a runway by itself?)   
      
   I'm travelling at the moment and seem to be having trouble finding a   
   copy of the rules to examine, but it's quite possible they would   
   invalidate this due to it involving multiple launches/transfer - the   
   system as a whole, however, is reusable.   
      
   It is a little more complex, and building two aircraft is beyond the   
   reach of most groups, but I can't help but wonder what makes it   
   inefficient that I'm missing    
      
   --   
   -Andrew Gray   
    andrew.gray@dunelm.org.uk   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)