From: sylvia@email.invalid   
      
   On 13-Feb-21 6:29 am, JF Mezei wrote:   
   >   
   > Say we had a repeat of Columbia.   
   >   
   > If Columbia is at a 300km circular orbit, and fires its engines to reach   
   > 400km elliptical orbit. Would its perigee remain at 300km by definition   
   > or is there a way to sacrifice perigee energy to boost apogee?   
      
   Your intuition is correct - firing engines at perigee cannot alter the   
   perigee, only the apogee.   
      
   >   
   > I know Columbia had not even close to enough fuel to change its orbit   
   > and gently dock to ISS.  So not debating this at all.   
      
   It would have to fire its engines near apogee to circularise its orbit.   
   >   
   >   
   > BUT...   
   > And I ask this conceptually, forget safety rules for a second.   
   >   
   > Could Columbia have positioned itself such that it would cross equator   
   > on descening node at same time and longitude as ISS, and fire its   
   > engines to get elliptical orbit that would reach apogee matching ISS   
   > altitude while crossing equator on descending node, and then upon   
   > approaching equator, fire engines sideways to temporarily match   
   > trajectory of ISS (at equantor, is it fair to state that direction of   
   > travel isn't that different?   
      
      
   A spacecraft can put itself anywhere at any velocity, provided it has   
   enough fuel.   
      
   Sylvia.   
      
   --- SoupGate-Win32 v1.05   
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