From: snidely.too@gmail.com   
      
   On Thursday, Alain Fournier exclaimed wildly:   
   > On Mar/11/2021 at 14:32, JF Mezei wrote :   
   >> Another question:   
   >>   
   >> Say you have decided your expedition will land at the equivalent of   
   >> Greenwich on mars (0" longitude, 51° latitude N).   
   >>   
   >> How difficult is it to send multiple ships to that precise location so   
   >> they land within walking distance from each other?   
   >>   
   >> Since Mars rotates, and since we're talking about a direct entry from   
   >> your transit velocity vector doesn't that require that you arrive at   
   >> atmosphere entry at a time where your destination (Greenwich) has   
   >> rotated to be directly in your path?   
   >>   
   >> Is this accomplished with long term micro adjustements is speed for the   
   >> whole transit so you arrive at the right time, or is transit speed   
   >> pretty much precisely fixed due to orbital mechanics and you need to so   
   >> a more significan speed adjustment as you near Mars to let Mars rotate a   
   >> bit more or less so you have your target in your path ?   
   >>   
   >> Just curious on how much flexibility a fleet of Starships bringling   
   >> supplies would have in terms of departing Earth and landing all at the   
   >> same spot.   
   >   
   > Not a major issue. You make small adjustments when still far away from Mars   
   > to get at the right place at the right time. Even if you just want to reach   
   > Mars anywhere, you still do mid-course corrections because aiming for Mars   
   > from Earth would require to much precision without corrections.   
   >   
   > The fact that you want to adjust for the exact location (and therefore time   
   > of arrival) only slightly complicates the computations for your mid-course   
   > corrections.   
   >   
      
   And Perry was targeted pretty precisely, so the calculations are well   
   understood in practice as well as in theory.   
      
   /dps   
      
   --   
   "What do you think of my cart, Miss Morland? A neat one, is not it?   
   Well hung: curricle-hung in fact. Come sit by me and we'll test the   
   springs."   
   (Speculative fiction by H.Lacedaemonian.)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)