def simpleplanet(armageddon):
    """
    This returns a simple planet with g=0, Cl=0, alpha=0, and with an exponential atmosphere. 
    This planet will be used to compare the solver against the analytical solution as well as solve_ivp (Scipy's solver).
    """
    return armageddon.Planet(atmos_func='exponential', Cd=1., Ch=0.1, Q=1e7, Cl=0, alpha=0, Rp=1e10, g=0, H=8000., rho0=1.2)