def stage_sep_range(v_ss, f_ss=0.02):
    """Estimate the downrange distance at stage separation.

    Arguments:
        v_ss (positive scalar): Velocity at stage separation [units: meter second**-1].
        f_ss (positive scalar): Stage separation downrange distance model coefficient
            [units: meter**-1 second**2].
    Returns:
        scalar: downrange distance at stage separation [units: meter].
    """
    return f_ss * v_ss**2