From: snidely.too@gmail.com   
      
   JF Mezei asserted that:   
   > Sanity check:   
   >   
   > If there were no atmosphere/drag, a satellite at 163km that is going at   
   > 28,080kmh and reduces it speed by 1kmh, would simply drop in altitude   
   > and now be at a lower orbit, correct?   
   >   
   > Theoretically, it could progressively reduce its speed and drop in   
   > altitude and end up going 28,440km in a orbit 100m above surface. Correct?   
   >   
   >   
   > Now, let bring is a purely theoretical chinese boosters called CZ-5B   
   > that is uncontrolled in a 163*301km orbit and bring back atmosphere.   
   >   
   > With every perigee having a bit of drag how is the orbit changed? Is   
   > only Apogee loweree? Both are changed equally? or does Apogee lose more   
   > altitide than perigee with tendency to circularize?   
   >   
   > If it circularizes, is it correct to state that the length of time spent   
   > at/near perigee altitude (and thus getung drag) increases?   
   >   
   > Since in an elliptical orbit, the object goes faster than required at   
   > perigee (hence having enough "oumph" to climb back up to apogee), I am   
   > curious at how the object eventually comes to a point where  drag lasts   
   > long enough to bleed enough speed to turn off orbital mechanics and turn   
   > on ballustic re-entry.   
   >   
   > Is there a magic altitude below which atmpsphere is instantly much more   
   > dense, so the minute perigee drops below that altitude, it bleeds too   
   > much speed to climb out of altitude that has drag and it is sayonara?   
   >   
   > Or is re-entry much more subtle and gradual?   
      
   The rule of thumb is that to raise one extremum of the orbit, you do   
   the burn at the other extremum.  Atmospheric drag at perigee is the   
   equivalent of a retrograde burn, so I'd expect apogee to be lowered.   
      
   As for the speed, remember that drag increases with speed.  It's a nice   
   differential equation to figure out the relative, um, impacts of   
   short-fast drag events vs long-slow drag events.  You can probably do   
   it quickly in Wolfram, but I'm not a Wolfram user.   
      
   The CZ-58 booster's perigee is well below the orbit of the ISS, but   
   IIRC from shuttle days the apogee is still within the bounds of   
   measurable drag.   You might also consider the orbit of the Falcon 9   
   2nd stage recently retrieved near Seattle; I suspect it was a lower   
   apogee, especially since it was a Starlink launch.  Hmmm, I see shell 1   
   is being loaded at 550 km/340 mi, but I haven't yet found the 2nd stage   
   apogee; maybe I'll replay some of the launch videos and scan the   
   telemetry display.   
      
   /dps   
      
   --   
   "I am not given to exaggeration, and when I say a thing I mean it"   
      _Roughing It_, Mark Twain   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)