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An approach to the creation of passive radiative cooling system ensuring temperature levels less than 220K for the optical sensor of scientific space equipment elements is considered. The system is intended for the arbitrary orientation-in-space function under solar radiation. Theoretical analysis of the application field of this system, using heat pipes with constant and variable thermal resistance in a range of solar constant variation (500…2700)W/m2 is given. Experimental results on system models, in which two engaged in parallel thermodiodes with freon-22 and ammonium were used, showed the possibility to attain device temperature levels less than 220 K at the solar constant magnitude 1400 W/m2 and device heat release under (1…2) W.

The approach of finite element method (FEM) for simulation of thermal state of space apparatus and heat pipes integrated is presented. The practical tool discussed is 2D finite software package “HEAT'90”. Questions dealing with modeling of 2D construction, accuracy of simplification of 3D objects to pseudo 3D are under consideration. Several practically used cases of heat pipes connections with surrounding are analyzed: heat pipes are installed onto surface of device, heat pipes are inset into honeycomb panels, heat pipe crossing. Samples of simulation of heat pipe network for honeycomb panels illustrate the range of possibilities to forecast the thermal state of complicated ramified systems by using non traditional numerical FEM analyzer.

Description of design principles of thermocontrol system for small subsatellites “Magion - 4, 5” is presented. Passive type of system is intended to support the temperature level (-10…50) °C in inner volume of equipment compartment at solar subsatellite orientation and in temporary Earth shadow. Heat energy balance of object at necessary temperature range is provided by utilization of radiating surfaces with defined areas, by thermal connection of hot and cold subsatellite parts and by adaptation of constructive subsatellite elements to solve thermal tasks. Stages of heat pipe design, its development and testing separately and installed into object, thermovacuum test of subsatellite are presented. Initial time range of flight operation of thermocontrol system is analyzed as well.