MSVRatio

--------------------------------------------------------------------------
   Compute the velocity ratio for a multi-stage rocket

   Call this function with no inputs and no outputs to show a plot of the
   velocity ratio as a function of payload ratio for different numbers of
   stages.

   The equations used to compute the velocity ratio neglect the effects of
   gravity and drag.

--------------------------------------------------------------------------
   Form:
   vRatio = MSVRatio( sR, pR, nStages );
--------------------------------------------------------------------------

   ------
   Inputs
   ------
   sR           (1,1)  Ratio of stage dry mass to stage wet mass
   pR           (1,M)  Ratio of total mass above the stage to total mass
                          of the stage
   nStages      (1,N)  Number of stages

   -------
   Outputs
   -------
   vRatio       (M,N)  Ratio of burnout velocity to exhaust velocity.

   See also: M2EP
--------------------------------------------------------------------------
   References:   Wiesel, W. E., Spaceflight Dynamics, 2nd Ed. McGraw-Hill, 
                 1995, p. 201.
--------------------------------------------------------------------------