XPost: sci.physics   
   From: Use-Author-Supplied-Address-Header@[127.1]   
      
   Ed Green wrote:   
      
   |> Erik Max Francis  wrote in message news:<400   
   B424.8A636BC1@alcyone.com>...   
   |>   
   |> > I'm looking for general ways of calculating estimates of stationkeeping   
   |> > deltavee requirements (e.g., m/(s y)) for satellites/stations in various   
   |> > orbits (low, medium, high, and apostationary if relevnat) around   
   |> > arbitrary bodies, and at each of the five Lagrange points between each   
   |> > (sensible) combination of bodies.   
   |>   
   |> For the benefit of groundlings, would you mind explicating exactly   
   |> what "station keeping" and delta v means in this context?   
   |>   
   |> In nautical terms, station keeping can be expressed as remaining   
   |> stationary in the rest frame of the body on which you are keeping   
   |> station.  I assume this definition works in space, too, with   
   |> complication added by the fact that station keeping on a body in free   
   |> fall will in general _not_ place you in free fall: you will drift away   
   |> without constant course correction. True at sea also, even if the   
   |> physics is different!   
      
   For L points it is the energy cost of remaining within a given distance   
   (i.e., tolerance) of the particular point.  For example, Earth-Sun L1 is   
   not an equilibrium point, but the energy cost of staying there is low   
   enough that you can put a satellite there for several years.   
      
   |> Ok?  Then what does "deltavee requirements" mean as a term of art?   
      
   "station keeping" is the act of staying at the point   
      
   "delta vee" is the energy cost, usually in terms of a single maneuver,   
   but in this case you have to take into account the necessary frequency   
   of maneuvers   
      
   The calculations Erik is asking for are not simple and I'm not sure   
   there is a simple scaling with masses and orbital parameters, because it   
   would also depend on the nature of the perturbations making station   
   keeping more (or less) necessary from case to case.   
      
   |> e-folding time:   
      
   in the context he is using, it is the growth time of an instability,   
   following a simple linear equation like dy/dt = gamma y, where the   
   e-folding time is 1/gamma   
      
   --   
   cu,   
   Bruce   
      
   drift wave turbulence:  http://www.rzg.mpg.de/~bds/   
      
   --- SoupGate-Win32 v1.05   
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