Implementation of temperature dependant thermo-optical properties and complex 3D geometries in ESATAN-TMS

Abstract

Radiative heat transfer plays a major role in the thermal behavior of any space application compared to a typical Earth-based system. Space systems are known to operate in an environment characterized by a wide range of temperatures and heat loads, such as planetary and solar fluxes or deep space, planet and sun temperature. All these factors will critically impact upon the thermal design of spacecraft and special thermal coatings are generally used in thermal control. Many of these coatings present temperature dependent thermo-optical properties, which cannot be neglected in the design of space systems. However, in most thermal models, the temperature dependence is often reduced to the definition of two sets of properties, namely the IR and UV ranges. In addition, space systems usually present complex 3D geometries like antennas, optical devices or reflective baffles. For such components, the thermal behaviour is generally strongly coupled to their geometry, for instance the amount of rejected environmental radiation of a reflective baffle depends upon the shape of its reflective surfaces. It is therefore essential to model their surfaces with high accuracy. Unfortunately, complex shapes are often not fully implemented in thermal software. The objective of this paper is to present a general method to implement temperature dependant thermo-optical properties and to approximate complex 3D geometry using ESATAN-TMS, the European standard thermal analysis package. Practical applications for current space missions will be used to illustrate both methods and a comparison between different models will be presented to show the high inaccuracy that occurs when temperature dependencies are neglected.