A Technology Demonstration Model (TDM) of a heat rejection system dedicated to advanced spacecraft and payload thermal control has been manufactured by AERITALIA under an European Space Agency (ESA) Contract. After survey and studies, AERITALIA has defined the characteristics and performances of a heat rejection system able to fulfil the requirements of some future spacecraft. The TDM is a model representative of this system in term of applicable software and hardware and has the main objective of demonstrating the performance and of validating the utilized hardware. The TDM consists of radiator panels (1.85×1.2 m),Spacelab type plumbing, fluid loop servicer with pump package, thermal control valves (by-pass and flow metering) and of an electronic control unit based on a microprocessor. The radiator panels, flow control valves and the control unit have been designed and developed for this application which serves as a prequalification programme. Their use for flight would required further qualification testing. This paper gives a brief summary of the basic studies (already described in SAE Technical Paper N.820845-Ref. 1) and is mainly centered on the TDM design and manufacturing processes.