code: public double horizontalScope(double T, double d, double s)
      {
          double Fw = T / w;
          return (Fw - d) * Math.log((s + Fw) / (Fw - d));
      }
docs: Horizontal scope (length in plan view from fairlead to touchdown point)
  @param T Fairlead tension
  @param d Depth
  @param s Chain length
  @return