Study of the Effects of Materials Selection for the Closeout Structure on the Service Life of a Liquid Rocket Engine Thrust Chamber

The external structure of rocket engines thrust chambers for aerospace applications should be designed in order to provide adequate stiffness to the thrust chamber; however, it affects in a significant way the engine service life since it acts as a structural bound for the internal structure which is subjected to very high temperature values. The adoption of thin closeout structures allows to have lighter structures and to significantly increase the service life of the thrust chamber. The aim of the present work is to perform numerical investigations on the influence of the closeout geometry and materials on the number of cycles to failure of the thrust chamber. Furthermore, a study on the impact of creep phenomenon on the service life is illustrated. In particular, the present paper is focused on the thermomechanical study of the closeout structure, in terms of material choice, thickness, joining process with the inner liner, etc. Transient thermal and static structural nonlinear analyses are conducted by means of a commercial finite element code (ANSYS), in order to evaluate the number of cycles to failure for the investigated configurations. Viscoplastic models are adopted in order to simulate the highly nonlinear and rate-dependent phenomena occurring in the inner liner structure.