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.
Some discrepancies, such as the different application of the air cooling standard, have been identified that make the interchangeability of racks on the SSF PMs difficult. Possible solutions to the problem and impacts on the design have been presented.