FRotatingPlanet:

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   Sail orbit RHS in a planet-centered cylindrical rotating frame.
   The equations are nondimensionalized. 
   See also SphOrb and FOrb.

   Since version 7.
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   Form:
   xDot = FRotatingPlanet( t, x, theta, accel )
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   ------
   Inputs
   ------
   t                (1,1) Time
   x                (6,1) state [rho;theta;z;drho/dt;dtheta/dt;dz/dt]
   theta            (1,1) Sail control angle
   accel            (1,1) Sail acceleration

   -------
   Outputs
   -------
   xDot             (6,1) state derivative

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   Reference: Colin McInnes, Solar Sailing, Springer-Praxis 1999.
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