In my latest article, we present a powerful direct approach to simplify complexly structured nonlinear systems with external periodic excitation via normal forms. This approach is liberated from special treatment of nonlinear systems such as ‘book-keeping’ parameters, detuning parameters etc. It does not mandate the system to be minimally excited and the system may possess constant coefficients or be parametrically excited. Inopportunely, comprehensive space systems dynamics often egender intricate analytical models that are generally intractable. Consequently, this approach will facilitate modelling, analysis and control of such unwieldy dynamical systems. This article is published in the Journal of Nonlinear Dynamics under the title, ‘A direct approach for simplifying nonlinear systems with external periodic excitation using normal forms‘ .