def atmDensPoly6th(ht, dens_co):
    """ Compute the atmosphere density using a 6th order polynomial. This is used in the ablation simulation
        for faster execution. 

    Arguments:
        ht: [float] Height above sea level (m).
        dens_co: [list] Coeffs of the 6th order polynomial.

    Return: 
        atm_dens: [float] Atmosphere neutral mass density in kg/m^3.
    """

    # Compute the density
    rho_a = 1000*(10**(dens_co[0] 
                     + dens_co[1]*(ht/1000)
                     + dens_co[2]*(ht/1000)**2 
                     + dens_co[3]*(ht/1000)**3 
                     + dens_co[4]*(ht/1000)**4 
                     + dens_co[5]*(ht/1000)**5))

    return rho_a