ASSESSMENT OF THE PARAMETER VARIATION OF AN ELECTRODYNAMIC SPACE TETHER SYSTEM UNDER THERMAL ACTION

Анотація

This paper presents a refined model for determining the tether temperature variation in orbital motion, which is of importance to the operation of passive electrodynamic space tether systems (EDSTSs) with a thermoelectronic coating. It is shown that a thermoelectronic coating of a tether significantly increases the collection of currents by the system, thus considerably increasing the EDSTS operational efficiency in comparison with the absence of additional contactors. The effect of thermal conditions on the EDSTS parameters is studied. The EDSTS component temperature variation is studied using a thermal balance equation, which accounts for the direct solar heat flux, the Earth-reflected solar heat flux, the Earth’s intrinsic heat flux, the aerodynamic heating, the ohmic heating, the electron impact heating, the thermal radiation of the tether, and the tether hat conductivity. To calculate the electric currents in the EDSTS passive operation, use is made of models based on orbitally limited current models for the anode segment of the tether and the Richardson – Dushman theory for total emission from the cathode segment of the tether. It is shown that on of important issues in EDCTS designing and making is the choice of a tether material that would meet certain requirements for its characteristics. The material parameters to be accounted for are the heat capacity, the IR solar absorptance, and the IR emittance. These parameters are crucial in the calculation of the system temperature variation. The greater the heat capacity, the slower the processes of system component heating and cooling. It is shown that the extreme temperatures of the system components in the shadowed and the illuminated portion of the orbit depend significantly of the ratio of the tether IR solar absorptance to the tether IR emittance. This ratio is governed both by a specific material and by the presence of impurities therein and the roughness or mirror finish degree of its surface.

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