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The Mini-Pressurized Logistics Module (MPLM), shown in Figure 1, is the primary vehicle for the transportation of equipment, scientific payloads, and supplies for use inside of the International Space Station, hence the importance of the MPLM environmental control system design. Agenzia Spaziale Italian (ASI), an International Space Station Partner (IP), will supply three MPLMs, currently being designed and fabricated by Alenia Aerospazio, Divisione Spazio, to the Space Station Program. Design oversight for this activity is being performed by NASA's Marshall Space Flight Center (MSFC).

The MPLM (Mini Pressurized Logistic Module) is one of the Elements constituting the ISSA (International Space Station Alpha). With respect to the other Elements, the MPLM is not permanently attached to the ISSA, but it is transported by the Orbiter several times from/to the Earth, since its primary use is to resupply and return cargos. The MPLM capability to support the logistic flights is guaranteed during several mission phases (ground, Orbiter transportation, on-orbit docked to the Station). Since the installed cargo can be passive or active, the required MPLM functions are based on the actual flight. This paper presents an overview of the activities performed in Alenia Spazio to identify the criticality and peculiarity of the MPLM mission scenarios from the thermal point of view. The best technical solutions, foreseen up to now, have been implemented in the design to guarantee the reliability requested by such an important and unique Space Station Element.

The Mini Pressurised Logistics Module (MPLM), a cooperative project between NASA and ASI that will be designed, developed, produced, integrated and delivered by Alenia, is a pressurised volume devoted to the resupply and return of Space Station (SS)containerized cargo requiringapressurised environment, via the National Space Transportation System (NSTS). As a servicer for the SS, the MPLM will have to accomplish several trips between Earth and SS in support of logistic needs. Since the active payloads launched with MPLM (freezers and refrigerators) require resources during the transportation phase inside the NSTS, the MPLM has the peculiar capacity to exchange power, data and fluids with the Orbiter before docking to SS. Once docked to SS, the MPLM will be required to provide its full performance, making use of the resources available from the SS Node; nevertheless, in this phase some of the MPLM functions are demanded from the SS.

The Mini Pressurized Logistic Module (MPLM) is designed to transport supplies and return cargo requiring a pressurized environment to and from the Space Station Freedom (SSF) via the National Space Transportation System (NSTS) Shuttle. The MPLM provides accommodation for a number of cargo racks, including two Freezer/Refrigerators (F/Rs) and one subsystem rack. The maintenance of the habitable conditions for the crew and the control of the MPLM thermal environment are carried out by the Environmental Control and Life Support System (ECLSS) and the Thermal Control System (TCS). The ECLSS and TCS functional concepts are tailored to the peculiarities of the MPLM design, based on mass and volume minimization, maximum simplification and exploitation of the resources available at the SSF interface.

Air cooling of the avionics units (Subsystem equipment and Payloads) of the Columbus Pressurised Modules (PM) is performed via avionics loops, providing heat collection from dedicated racks and rejecting the collected heat load by means of an avionics heat exchanger (AHX). An overview of possible rack architectures, air loop accommodations and control solutions which are candidates for the Columbus PMs is presented. The system requirements have been assessed as a starting point, in order to define the requested capabilities and the constraints that the design of the rack and the loop has to fulfil. In particular, the architectures of the European single and double rack and of the U.S. double rack in Space Station Freedom (SSF) have been compared and the relevant options of accommodation in the avionics loops and functional interfaces have been investigated.