lower values of and of open surfaces make it possible to decrease the external heat exchange of the docking device in heating and cooling to several dozen watts. Extended elements of the docking mechanism experience the greatest heating and cooling. These elements are conductively weakly linked with the main structure and have the same small thermal capacity. Their external surfaces are fully or partially covered with solid lubricants and have high values of and (0.8-0.9); nonetheless in near-Earth orbits these elements usually are not cooled below . The temperature of the joint seal may vary over a wide range due to small heat capacity, thermal conductivity, and small values of and . To reduce the extreme temperatures of the seals their contact with the hull should be improved. To reduce heating and cooling, some elements of the docking mechanism which have large surface areas and which do not contain mechanisms are installed through thermal bridges. Mechanisms which are sensitive to low temperatures may be equipped with electric heaters, for example, the hydraulic fuel supply connectors. Docking is a special case of autonomous flight. The docking conditions may be known beforehand or even planned with a consideration of the desired temperature range. Docking in arbitrary conditions of autonomous flight require a consideration of extreme thermal fluxes; this approach is used, Tor example, for long-term orbital stations. To reduce the extreme temperatures the hulls of the docking devices of the Soyuz-Salyut complex are thermally stabilized by hydraulic circuits of the thermal regulation system. The moment of docking may be chosen with a consideration of illumination conditions, in particular, with a consideration of the thermal state of the docking device. This approach is used for projects whose flight program is determined beforehand, or may be corrected considering the requirement of the thermal condition of the structure. For example, the APDA of this craft and the docking device of the Apollo were planned in this way. The hulls of these assemblies were not protected by screen vacuum thermal insulation, and their surfaces had relatively large values of and . At the same time they could withstand close to 1. This structure radiates and absorbs substantially larger thermal fluxes (up to several hundred watts) and requires a careful consideration of the illumination conditions and precise analysis.
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