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The paper describes the pre-development of the compact turbo-inachinery forming the heart of a reverse- Brayton-cycle refrigeration unit for application in a microgravity-compatible freezer. The machine has been configured to provide refrigeration at -80°C in the face of continuous loads of 10 W and transient loads of up to 30 W without disturbing the microgravity environment. Other important requirements were: operational life-time without maintenance of at least 10 years, high coefficient of performance to minimise power consumption, low mass and small size. In the interests of reliability and microgravity compatibility, the compressor wheel and the expansion turbine have been mounted on the same shaft, driven by a brushless DC electric motor. This approach assures the most compact design, however, it gave rise to complex design iterations.

The scenarios of Environmental Control and Life Support Systems (ECLSS) which will be necessary within the next sixty years are outlined. From this the need for technologies are derived and condensed in a programme plan. Technologies necessary for the Columbus Initial Operating Configuration (IOC) are already under development. The status of this programme which includes the development of regenerative CO2-control, condensing heat exchanger, contamination control and monitoring and a low noise variable speed fan is described. The areas where the technological development should start immediately are discussed.