RHSLaunchVehicle2D:

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   The right hand side of a 2D launch model with gravity turn.

   The states are vertical and horizontal position, velocity and flight
   path angle. The model assumes a flat Earth that isn't rotating. The
   model can handle multiple stages. The dry masses and exhaust velocities
   are entered using the data structure d. For each stage you add a fuel
   state to x. Thus a 3 stage vehicle will have 7 states and d.mStage,
   d.thrust, d.uE and d.cDA (the drag coefficient) will each have three
   entries. The data structure is the same as is used in LaunchVehicle3D.

   Any planet that is included in AtmDens1 can be simulated if entered by
   name. For Earth, the standard atmosphere is used below 80 km altitude.

   Since version 1.0
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   Form:
   xDot = RHSLaunchVehicle2D( x, t, d )
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   Inputs
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   x           (:,1)  [x h v gamma massFuel]'
                        x        Downrange distance (km)
                        h        Altitude (km)
                        v        Velocity (km/s)
                        gamma    Flight path angle (rad)
                        massFuel Fuel mass of each stage (kg)
   t           (1,1)  Time (not used)
   d            (.)   Sim RHS data structure
                      .fThrust (:)  Function handle for thrust model
                      .cDA    (1,:) Drag coefficient of each stage times area
                      .mu     (1,1) Gravitational constant
                      .Rp     (1,1) Planet radius (km)
                      .planet (1,:) Planet name, or empty for Earth
                      .drag     (.) Empty or 3D drag data structure
                      .rocket   (.) Rocket model data structure

   -------
   Outputs
   -------
   xDot        (:,1)  State derivatives

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	References:	Wiesel, W. E., Spaceflight Dynamics, McGraw-Hill, 1988,
               pp. 207-211.
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   See also MSThrustModel, StdAtm, RocketDatabase, LiftAndDragJonesSearsHaack
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Children:

LaunchVehicle: LVDatabase/RocketDatabase
LaunchVehicle: LaunchSim/LaunchRHSData
LaunchVehicle: LaunchSim/RocketDrag