1990-07-01

Hermes Thermal Control Subsystem-Design Concepts 901365

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. During the various phases the space radiators, the Water Evaporator and the Ammonia Boiler are alternatively operated for this purpose.
The PTCS (Passive Thermal Control Section) is designed such as to limit temperature excursions and heat fluxes entering or leaving the various parts of the spacecraft. It will include thermal insulations, utilized for global control of enclosures or dedicated to individual items and equipment. The proposed technical solutions will be based on foam or fibrous materials, configured as single or multilayer insulation blankets. Thermo-optical tapes and coatings will be tailored to local needs. A system of temperature sensors and heaters will provide additional thermal control of interfaces during cold cases.
The analysis and design techniques adopted for HERMES are strongly oriented to the minimization of mass and power budgets, which makes the definition of the technical baseline a challenging objective.

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