From: j.garry@chem.leidenuniv.nl   
      
   "Monte Davis" wrote in message   
   news:sttu31l7lsvepnl7kkldj6lfno2r2ukkse@4ax.com...   
   > Dumb question: If one were in circular LEO and crazy enough to want a   
   > 90-degree change of inclination, what's the cost in delta-v? Is it, as   
   > intuition is telling me, equivalent to throwing away all your ~9 kps   
   > and re-acquiring it all?   
   > (Assume a spherical Earth, homogeneous frictionless elephant, etc)   
      
   Yes, your intuition is spot on.   
      
   But you could save a little by either making the plane change elsewhere.   
   Recall, escape speed from a circular orbit is root 2 times the orbital   
   speed, so after a 2.8 km/s burn in your flight direction, you find yourself   
   with a very high apogeee :) after a while, *then* when suitably far from the   
   earth, perform the plane change for near zero delta-v cost, and then make a   
   de-orbit burn of another 2.8 km/s, leaving you in a nice polar orbit. It'll   
   take a bit longer than the brute-force powerered turn that you describe, and   
   would be far less theatrical, but would save around 1.5 km/s.   
   This option, for LEO to GEO is termed a super-syncrhonous plane change for   
   obvious reasons, and is not uncommon.   
      
   The other fun way is to deorbit and make the plane change in atmosphere. Use   
   aerodynamic lift to rotate your velocity vector, raise your apogee with a   
   burn and then circularize as normal. Much higher 'wow' factor but this is a   
   non-spherical cow solution as you'll be riding in a (sadly) non-existing   
   vehicle.   
      
   -James Garry   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)