From: henry@spsystems.net   
      
   In article ,   
   Tom Kent   wrote:   
   >> The 400-series Atlas V Centaur can only perform two-burns,   
   >> so it cannot do insertion burns at transfer orbit apogee.   
   >> (500-series Atlas V Centaurs do have a three-burn option.)   
   >   
   >So in the three burn circumstance, any third burn would be a   
   >cirrcularization burn?   
      
   Or part of one, anyway.  Maybe it couldn't get the perigee all the way   
   up, but it could drain its tanks doing as much as it could.   
      
   >...In that case (without case   
   >of doing the inclination transfer) you'd just want to go to a typical GTO,   
   >because you WOULD burn the tanks dry?   
      
   .probably.  The one small reservation is that until its tanks go dry,   
   you're still pushing the extra dry mass of the Centaur, so it's not quite   
   as good as having the satellite doing the work.  On the other hand, the   
   Centaur has a higher Isp than the satellite's maneuvering engines...   
      
   Stir in the inclination change, and I'd want to run the numbers before   
   deciding which of the three options was optimal.  (1. Burn Centaur dry   
   achieving highest possible supersynchronous transfer orbit.  2. Use   
   regular GTO and burn Centaur dry doing as much as possible of the apogee   
   burn.  3. Do small second burn into mildly elliptical orbit, and big third   
   burn at apogee to convert that into the perigee of a high-perigee GTO.)   
   --   
   "Think outside the box -- the box isn't our friend."    |   Henry Spencer   
                                   -- George Herbert       | henry@spsystems.net   
      
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