Design and efficiency assessment of hybrid thermal protection structures for return capsule reentry

Charring ablators are widely used for the thermal protection structure (TPS) of return capsules. However, adopting only a single type of ablator limits the structural efficiency of the TPS due to the thermal protection and insulation requirement conflicts. Here, we report on different types of hybrid TPSs to improve the heat-shielding performance. An ablative-thermal-structural analysis model was first established based on the finite element method, and optimization analyses were performed to determine the sizes of the hybrid structures. Meanwhile, an evaluation indicator to characterize the weight and ablation resistance performance of the TPS was defined. Finally, comparison studies on the heat transfer characteristics and structural efficiency of the hybrid and traditional TPSs were carried out. The results suggest that the heat-shielding performance of all the proposed hybrid structures is superior to the traditional one, and the structural efficiency of the hybrid TPS can be up to 2.73 times greater than that of the traditional structure. The combination of the flexible insulative material and the phase change material can improve the thermal insulation performance of hybrid structures, thus offering a promising route for the design of thermal protection structures for reentry capsules.