Physics-Based Modeling for Stage Separation Recontact

Abstract

Physics-based modeling for a stage separation recontact fault is presented. Numerical models and analytical estimations are applied to analyze the physics of the failure and reconstruct the following sequence of events: structural dynamics of the nozzle extension during impact, yielding and melting of the damaged nozzle under plume loadings during engine startup, reduction of the actual thrust and side loads in the steady burning regime, response of the thrust vector control system to the fault-induced torque, and rocket trajectory variations due to the fault. The obtained results are discussed in a context of engineering risk assessment and development of an onboard diagnostic and prognostic system for stage separation failure. Analysis using the models developed as part of this research shows that the damage results in three possible outcomes: actuator failure with resulting loss of control, loss of performance resulting in an inability to reach orbit, and effects that are sufficiently minor so that orbit is still attainable. In the case of crewed missions, abort triggers based on navigation and flight control data (as described in this paper) may be used to determine the need to abort immediately or to estimate the likelihood that orbit will be reachable.