Application efficiency analysis of anisotropic heat-shielding materials when executing trajectories with multiple entrance in the atmosphere

A significant increase in cargo turnover between the Moon and the Earth is expected in case of full implementation of recently announced programmes of exploration and development of the Moon (Luna, Artemis, Chang’e). A feature of the spacecraft trajectory when it returns from the Moon’s orbit is that the spacecraft speed at the entry into the Earth’s atmosphere is close to parabolic. Compared to orbital landing sections, those of lunar interplanetary spacecraft expose to more intensive radiation and heat flows, and due to it and the above circumstance, the problem of the design of thermal shield for these spacecraft becomes much more complicated. This paper considers two approaches, which help decrease heating of the thermal shield. The first one is the use of trajectory with multiple entrance in the atmosphere. This approach allows for reducing the heat flow intensity due to the gradual deceleration during the repeated re-entries. The second one is the use of anisotropic heat-shielding materials referring to the heat conductivity. This approach allows for reducing the surface temperature in the area of the maximum density of heat flow by redistribution of thermal energy in the thermal shield along the tangential direction. As follows from the analysis provided in the paper, the use of two approaches described herein provides the reduction of the temperature of the spacecraft surface either to the level not destroying the thermal shield or to that providing to reduce its destruction significantly. It allows for improving the spacecraft reliability and, in prospect, provides the multiple uses of it.