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The Multi-Purpose Logistics Module (MPLM) is the primary carrier for “pressurized” logistics to and from the International Space Station (ISS). The MPLM is transported in the payload bay of the Space Shuttle and is docked to the ISS for unloading, and reloading, of contents within the ISS shirt sleeve environment. Foil heaters, controlled originally with bi-metallic thermostats, are distributed across the outside of the MPLM structure and are utilized to provide energy to the structure to avoid exposure to cold temperatures and prevent condensation. The existing bi-metallic, fixed temperature set point thermostats have been replaced with Programmable Thermostats Modules (PTMs) in the Passive Thermal Control Subsystem (PTCS) 28Vdc shell heater circuits. The goal of using the PTM thermostat is to improve operational efficiency of the MPLM on-orbit shell heaters by providing better shell temperature control via feedback control capability.

During the Bridging Phase of the Columbus project, the Attached Pressurised Module has been subjected to a series of design changes to accommodate the new International Space Station interface requirements and to comply with the reduced budget allocated to the Columbus Orbiting Facility (COF) Programme. In parallel to the studies aimed to define the COF Configuration, tests have been performed on the Thermal Control Subsystem, in those areas not affected by redesign changes, to investigate some typical aspects in thermo-hydraulic mathematical simulation areas and in the passive design areas.

The redesign of Space Station Freedom (SSF) and the requirement of the Columbus programme board to reduce costs have led ESA to change the design and development strategy of the Attached Pressurised Module (APM). A revised APM reference design for integration with the SSF Alpha has been produced with sufficient flexibility to allow adaptation as part of a global space station or to permit operations as part of a European Free Flyer. The main objectives of the redesign have been to simplify the design, reduce the costs and provide increased autonomy from the SSF. The key groundrules for the redesign have been an AR5/ATV launch from the Centre Spatial Guyanais (CGS) into an orbit inclined at 51.6 degrees. The APM has a length equivalent to 5 double racks and a net launch mass of 1200 kg. It will be delivered to the SSF at an altitude of 407 km for a 10-year operational life. Safe disposal will be by ATV.

The COLUMBUS Attached Pressurized Module (APM) is the European orbiting laboratory which will be permanently attached to the International Space Station Freedom (SSF). It is designed to provide a range of laboratory facilities in a microgravity environment for payload experiments originating from the international payload-user community. The individual payloads will in general be mounted in payload racks which can be accommodated in fixed positions on the left and right hand sides of the laboratory and in the ceiling. International standard payload racks (ISPR) can be located in any of the SSF laboratory elements and find compatible interface conditions subject to agreements made between the international partners (NASA, NASDA and ESA). The APM design provides a water cooling capability by means of moderate temperature (MT) and low temperature (LT) pumped fluid loops. The cooling loops serve both the APM essential subsystem equipment as well as the payload users.

The Columbus Attached Pressurised Module (APM) Active Thermal Control System (ATCS) water loop collects the APM waste heat and transfers it to the Space Station Freedom (SSF) Central Thermal Bus (CTB). The interface between the APM water loop and the SSF ammonia loops is achieved with two ammonia/water interloop heat exchangers (IH/X), one being low temperature (LT) and the other moderate temperature (MT). The APM internal water loop provides cooling to payload and subsystem users which have varying temperature requirements at their heat rejection interfaces, and can be categorized as cold branch and warm branch users, (e.g. condensing heat exchanger (CHX) and refrigerator are cold branch users, while Avionic heat exchanger (AHX) and furnace payloads would be warm branch users.)

Columbus Pressurised Modules (APM permanently attached to Space Station Freedom and MTFF free flyer) will support the scientific experiments and commercial space exploitation requiring manned interaction and intervention (APM) or infrequent servicing/resupply by flight crew (MTFF) in a low gravity environment. This paper is based on the activities performed during the early stages of Columbus Phase C/D and presents: the Active Thermal Control design solutions including the architecture of the fluid loops, the fluid loops monitoring and control philosophy and the fluid loops components and design features; the Passive Thermal Control design solutions including MLI, anticondensation, heaters concept and thermo-optical properties selection.

This paper presents the active thermal control architecture of Columbus Pressurized Modules. APM (Attached Pressurized Module) and PM-MTFF (Pressurized Module, coupled to the Resource Modute to form the MTFF, Man Tended Free-Flyer). Active thermal control architecture consists of: module- internal water loops collecting heat from directly interfacing P/L's and S/S's, avionic and cabin air loops external freon loop (PM MTFF only) providing removal and transportation of water loop heat loads to the heat rejection system SS (Space Station) based thermal bus providing removal and rejection of docked element water loops heat loads loop control and monitoring functions provided by modulating pumps and valves, temperature, pressure sensors interfacing with an intelligent control unit. Aeritatia is involved as Prime Contractor for the APM and Element Contractor for the PM-MTFF and retains responsibility for the Thermal Control Subsystem of both elements.