Belief reliability modeling and analysis for TPS considering physical principles, degradation mechanism and epistemic uncertainties

Thermal Protection System (TPS) with thick tiles, low thermal conductivity, and a short re-entry stage stands as a critical element within reusable aircraft, whose reliability is related to the function and changes with their physical properties, external conditions, and degradation. Meanwhile, due to the limitation of testing resources, epistemic uncertainties stemming from the small samples are present in TPS reliability modeling. However, current TPS reliability modeling methods face challenges in characterizing the relationships among reliability and physical properties, external conditions, degradation, and epistemic uncertainties. Therefore, under the framework of belief reliability theory, a TPS reliability model is constructed, which takes into account the physical principle, external conditions, performance degradation, and epistemic uncertainties. A reliability simulation algorithm is proposed to calculate TPS reliability. Through a case study and comparison analysis, the proposed method is validated as more effective than the existing method. Additionally, reliability sensitivity analysis is conducted to identify the sensitive factors of reliability under the condition of small samples, through which suggestions are provided for TPS functional design and improvement.