-------------------------------------------------------------------------------
   Computes the thrust and fuel consumed for thrusters. 
   The thrust is dependent on the pressure of the propellant. The exhaust
   velocity is dependent on the pulsewidth, it increases from a minimum to a
   maximum.

   The data structyre and default values of the properties can be found from
      p = DeviceProperties( 'hydrazine thruster' )

-------------------------------------------------------------------------------
   Form:
   [thrust, dF, impulse, iSP] = HydrazineThruster( d, pressure, pulsewidth, dT )
-------------------------------------------------------------------------------

   ------
   Inputs
   ------
   d               (:)    Thruster model data structure
   pressure        (:)    Pressure, can also be a scalar
   pulsewidth      (:)    Pulsewidth (sec)
   dT              (:)    Simulation timestep, for scaling (optional)

   -------
   Outputs
   -------
   thrust          (:)    Thrust
   iSp             (:)    Specific impulse
   dF              (:)    Fuel consumed
   impulse         (:)    Total impulse per thruster

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