Probabilistic Analysis Methodology for Thermal Protection System during Conceptual Design

This paper presents a probabilistic analysis methodology for a nonablative thermal protection system (TPS) of spacecraft at the conceptual design stage. The probabilistic analysis focuses on uncertainty characterization and uncertainty in failure prediction. TPS selection and sizing using sequential quadratic programming design optimization are first performed to provide the nominal values of the distribution parameters for uncertainty parameters such as the allowable temperature limits and thickness of TPS materials. Multi-input and multi-output support vector machines are utilized to approximate the thermal responses when failure modes are constructed, which dramatically reduces computational effort. Generalized subset simulation is used to estimate the failure probabilities at all nodes with a single simulation run, which further reduces the computational burden. The proposed methodology is applied to a lifting body vehicle model and a spacecraft model for conceptual design. Difficulties encountered and the performance of the method are investigated.