@staticmethod
def thermal_conductivity(T):
    """Method defined in the US Standard Atmosphere 1976 for calculating
        thermal conductivity of air as a function of `T` only. 
        
        .. math::
            k_g = \\frac{2.64638\\times10^{-3}T^{1.5}}
            {T + 245.4\\cdot 10^{-12./T}}
    
        Parameters
        ----------
        T : float
            Temperature, [K]

        Returns
        -------
        kg : float
            Thermal conductivity, [W/m/K]
        """
    return 0.00264638 * T ** 1.5 / (T + 245.4 * 10 ** (-12.0 / T))
