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  Compute the fuel mass required to reach a burnout velocity (single-stage)

  The answer is found numerically using the Newton Rhapson method.

  IMPORTANT NOTE: The structural ratio input is defined as the boost stage
  structural mass divided by the total boost stage mass (structure plus
  fuel). It is completely independent of the payload mass.
  
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   Form:
   [mFUEL,n] = RocketFuelMass( VBO, Isp, T, mPLD, sR, g );
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   Inputs
   ------
   VBO        (1,1)    Burnout velocity (m/s)
   Isp        (1,1)    Specific impulse (s)
   T          (1,1)    Thrust (N=kg*m/s/s)
   mPLD       (1,1)    Mass of payload (kg)
   sR         (1,1)    Structural ratio of the stage: 
                        - structure mass of stage over total mass of stage 
                        - independent of payload.
   g          (1,1)    Acceleration due to gravity (m/s/s)

   -------
   Outputs
   -------
   mFUEL      (1,1)    Mass of fuel (kg)
   n          (1,1)    Number of iterations

   See also MissileDistance, MissileLambert
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