-------------------------------------------------------------------------------
   Controlled airship simulation with autopilot and feedback control.
-------------------------------------------------------------------------------
   Form:
   p = AirshipControlSim( latLon, h0, v0, psi0, theta0, trajDes );
-------------------------------------------------------------------------------

   ------
   Inputs
   ------
   latLon       (1,2)  Initial latitude & longitude                    [deg]
                          - Or, you may supply the string name of a U.S. city.
                          - Type "help LatLon" for more information.
   h0            (1)   Initial altitude                                [km]
   v0            (1)   Initial velocity                                [m/s]
   psi0          (1)  Initial heading angle                            [deg]
   theta0        (1)  Initial flight-path angle                        [deg]
   trajDes       (.)   Data structure containing desired trajectory.
                       Has the following fields:  
         .vel   (1,N)     Time-history of desired velocity             [m/s]
         .psi   (1,N)     Time-history of desired heading angle        [deg]
         .theta (1,N)     Time-history of desired flight-path angle    [deg]
         .dT     (1)      Time-step used in desired trajectory         [sec]

   -------
   Outputs
   -------
   p             (.)   Structure with time-histories of recorded simulation data

-------------------------------------------------------------------------------