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Considering that integrated testing of the TCS and ECLSS of the Attached Pressurised Module (APM) of the Columbus Orbital Facility (COF) is limited in scope and planned late in the programme in line with the Proto-Flight Model (PFM) approach, it is pivotal to make the system-level analysis of the interaction between the two subsystems as comprehensive as possible. The paper presents analysis with the Integrated Overall Thermal Mathematical Model (IOTMM) that is used by Alenia Aerospazio to determine the operational envelope of the combined TCS and ECLSS. It describes the model architecture and a number of the analysis cases that were selected to represent the wide range of COF APM operational modes. The analysis cases include both steady-state cases and transient cases simulating transitions between different heat load configurations. Based on the results of the IOTMM analysis, the paper discusses improvements to the COF APM TCS and ECLSS design.

The Columbus Attached Pressurized Module (APM), part of the International Space Station (ISS), will support scientific, technological and commercial activities in a low earth orbit micro-gravity environment. Basic and applied research, technology development and demonstration will be accomplished in areas such as material sciences, life sciences and fluid physics. The APM, now in the detailed design C/D phase, will provide location for ten International Standard Payload Racks (ISPRs) and three storage racks, in an atmospheric pressure “shirt-sleeve” environment. The maintaining of habitable conditions and the provision of essential thermal-environmental services to payloads will be ensured by the APM Environmental Control System (ECS), as defined on the Columbus Payload Accommodation Handbook, Appendix C. The ECS will control cabin air pressure, composition, temperature and humidity and module surface temperatures, to ensure suitable environmental conditions for crew and ISPRs.

The Columbus Attached Pressurised Module (APM) is intended to support a shirt-sleeve environment for crew activities. Top level requirements therefore define a cabin air temperature and humidity range (the so-called “Comfort Box”), extreme air velocities for ventilation in the centra aisle, maximum mean radiant temperature of the cabin walls. Air temperature selectability has to be ensured with adequate accuracy across the whole range. The APM environmental control system, in particular the Temperature and Humidity Control (THC) system, is designed and verified against these parameters. Cabin thermal conditions can be evaluated by the APM Integrated Overall Thermal Mathematical Model (IOTMM), representing the general thermal behaviour of the APM, including the THC system. Heat loads due to APM subsystem equipment and payloads, solar flux and the crew itself have been considered in the analyses.

As a consequence of the reduced funding by the ESA Member States contributing to the Columbus and Manned Transportation Programmes, the Columbus Project has undergone two major cost reduction exercises since 1993. An important cost reduction was achieved in mid '93 by downsizing the Attached Pressurized Module (APM) from 8 to 5 Double Racks equivalent length. To reduce the costs further, in 1994 the European space industry took the opportunity of exploiting specific features of the APM common with those of other projects, potential candidates being the Mini Pressurized Logistic Module (MPLM), developed by the Italian Space Agency (ASI) for NASA, or the European developed Russian Data Management System (DMS-R). In addition simplifications in System Function and in the Verification approach and maximum use of Off-the-Shelf and Commercial/Aviation/Military (CAM) hardware were investigated.

This paper describes the main changes affecting the APM Environmental Control System (ECS) as a consequence of the Space Station Freedom (SSF) restructuring and Columbus APM overall reconfiguration. The main purposes of this reconfiguration are: minimize the number and complexity of the interfaces with Space Station Freedom (SSF) centralize avionics command and monitoring tasks revisit the failure tolerance concept of some ECS functions unify/standardize similar functions in the two subsystem adjust lifetime requirements and simplify maintenance concept of equipment. The APM ECS consists of the following functions: active thermal control (ATCS) passive thermal control (PTCS) atmosphere pressure and composition control air revitalization and cabin ventilation temperature and humidity control vacuum and venting nitrogen supply fire detection and suppression. The new ATCS configuration provides a cooling capability for a reduced number of P/L racks by means of its moderate loop.

Manned Space Systems are usually designed to support the crew atmospheric conditions equivalent to those at sea level. In phases with frequent Extra Vehicular Activities (EVA), a reduced pressure environment is preferable to facilitate the EVA suit prebreathing procedures. The Columbus Attached Pressurised Module (APM) will face both pressure scenarios during its life. Operation at different pressure levels primarily affects the performance of the Environmental Control System (ECS) of the pressurised elements. A lower air density results in reduced heat exchange, adversely affecting both the crew comfort and the electronics air cooling. This paper reports the results of a study performed to identify the constraints and the numerous potential problem areas related to APM operations at reduced pressure. Effects of the reduced pressure on the environmental parameters have been investigated.

The Thermal/Environmental Control System (T/ECS) of the Columbus Attached Pressurised Module (APM) requires extensive modelling to assess the overall system performance and interfaces compatibility, and to verify the design capability of the specific functions of the Thermal Control System (TCS) and Environmental Control and Life Support System (ECLSS). The thermal/environmental design of APM relies on TCS active (Water Loop) and passive thermal control functions, while ECLSS provides racks air cooling and cabin temperature and humidity control. The selected modelling approach uses an Integrated Overall Thermal Mathematical Model together with a set of additional TMM's for detailed tasks. The Overall TMM (up to 900 nodes, written in ESATAN to exploit its special modularity features) allows the element thermal balance verification and the provision of the sink and interface temperatures for the equipment thermal design.

This paper gives an overview of the Vacuum and Venting Subsystem architecture of COLUMBUS Pressurised Modules, summarises the Subsystem's requirements and discusses the baseline design solutions at loop and component level. The Vacuum and Venting Subsystem architecture mainly consists of: Module internal loops collecting waste gases evacuated from directly interfacing Payloads (P/Ls) Space Station Freedom (SSF) based waste gas bus, providing removal and disposal of docked element vacuum loop waste gases Dumping nozzles to exhaust the collected gases towards deep space without generation of dynamic actions Loop control and monitoring functions provided by on/off valves and pressure sensors interfacing with an intelligent control unit Heaters and temperature sensors for thermal control of dumping nozzles in order to limit heat leaks.