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   Non dimensional reentry dynamics model.
   The time derivative is with respect to non-dimensional time. Includes
   the Earth rotation terms (if d.omega is not zero)
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   Form:
   xDot = Reentry( x, t, d )
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   Inputs
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   x           (:,1)  [r;theta;phi;v;gamma;psi;massFuel]
   t           (1,1)  Normalized time (not used)
   d           (1,1)  Data structure
                      .thrust  (1,1) Thrust (N)
                      .uE      (1,:) Exhaust velocity engine (m/s)
                      .g       (1,1) Gravity (km/s^2)
                      .rPlanet (1,1) Planet radius (km)
                      .omega   (1,1) Planet rate (rad/s)
                      .planet  (1,:) Planet name
                      .mDry    (1,1) Dry mass
                      .atmData (1,1) Data for atmosphere
                      .l       (1,1) Characteristic length
                      .cDP     (1,1) Parasitic drag coefficient
                      .sRef    (1,1) Reference area for lift and drag
                      .alpha   (1,1) Angle of attack
                      .sigma   (1,1) Bank angle

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   Outputs
   -------
   xDot        (:,1)  Stage structural ratios

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