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The aim of this paper is to present the Hermes Thermal Control Concept which constitutes the reference baseline for the phase 2 of the Hermes program. The technical solutions based on active and passive means, are dictated by a variety of requirements including temperature and heat flux limits, mass & power minimization, availability of space for accommodation of TCS devices. Furthermore thecomplex mission profile (including atmospheric flight and several modes of operation o002d;orbit) and the configuration of the space-vehicle, require the adoption of a particularly flexible thermal control. The ATCS (Active Thermal Control Section) is based on a dual loop concept, using both water and Freon R114 cooling loops for heat collection from the various sources, heat transportation and heat rejection through dedicated devices.

The requirements related to the thermal control of HERMES space-plane suggest the utilization of technical solutions based on active and passive techniques. The configuration of the space-vehicle with pressurized and unpressurized compartments presents a variety of different problems, which generally require dedicated solutions. The complex mission profile include atmospheric and orbital conditions, with several phases and modes of operation (free-flying and docked). The extremely wide range of environmental conditions, together with the timeline of internal power dissipations requires the adoption of a particularly flexible thermal control. The ATCS (Active Thermal Control Section) mainly relies on the capability of water and Freon 114 fluid cooling loops. They collect waste heat from the sources located inside the compartments and transport this power to the available rejection devices.