PFM Thermal balance-thermal cycling test of the ExoMars Entry Descent and Landing Demonstrator Module
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The PFM thermal vacuum test of the Entry Descent and Landing Demonstrator Module (EDM) for the ExoMars 2016 mission was carried out in June-July 2015. This test, combining the thermal balance and thermal cycling verification of the module, was executed in the TAS testing facilities in Cannes, for a total duration of 32 days. Due to the peculiar characteristics of the ExoMars mission, the test profile and objectives went well beyond the standard thermal verification of satellites. The heterogeneous environments encountered during the mission, the extremely limited energy resources, the novelty of this design in the European scenario, the fact that no STM results were available, drove the decision to implement in the test also a realistic simulation of some of the most critical mission phases. The strong thermal insulation of the EDM bays, needed to survive in the harsh environment of the coasting phase and during on-Mars operations, made the time constants of the system quite large, with an additional challenge in terms of test schedule. To meet such goals, a very optimized profile was conceived, based on detailed numerical simulation of the entire test in transient conditions. Besides the standard thermal balance phases and thermal cycling plateaus, representative Thermal Boost and Coast phases were implemented, including the relevant functional operations. This PFM-level test of EDM was the first experimental verification of this design, based on extensive numerical simulation and elementary testing of the basic technologies/materials. Insulating materials/solutions for vacuum conditions and Mars atmosphere, heat capacitors based on phase-change materials, proper operational profiles and ablative TPS heat shields for the entry phase are the design cornerstones. This paper describes the test setup and plan, presents the main results with focus on key points and discusses the test evaluation campaign, including the thermal model correlation activity.