Thermal protection of a lunar lander from multi-engine plumes using thin film cooling

During the descent and ascent of the lunar lander, the gas plume exhausted from its engine imposes a significant thermal load on the lander when it approaches the lunar surface. This challenge becomes more pronounced for multi-engine landers due to the intricate interactions between their plumes, making it difficult to ensure adequate thermal protection for the lander. In this study, a thermal protection method utilizing a supersonic cold gas film is proposed to shield the lander bottom from high-temperature backflow from the lunar surface. Unlike conventional film cooling that relies on the boundary layer flow, our approach is specifically designed to accommodate irregular surfaces of the lander bottom. The applicability of this heat protection method in vacuum or low-pressure environments is first confirmed. Subsequently, the effects of three key annular injector parameters, including total pressure, expansion ratio, and injection angle are investigated. Our findings reveal that increased coolant total pressure results in better protection, while the effects of the expansion ratio vary with different coolant total pressures. Under our conditions, an annular injector angle of 45 degrees is determined to be the optimal choice for enhancing cooling efficiency.