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With the fast growing demand for space based telecommunication capabilities in combination with application of high density electronics, the cooling requirements for future telecommunication satellites is steadily increasing, up to a point that conventional cooling technologies using (loop) heat pipes are no longer ennough to cope with in-orbit load and heat rejection variations, large number of thermal interfaces and testing constraints. To prepare for future high performance cooling requirements, the European Space Agency, ESA initiated the development of a Single-Phase Mechanically Pumped Fluid Loop (MPFL) which was one of the two heat transfer element options for the large Alphabus deployable radiator (see Figure 2).

The paper describes freezing and pressure tests required to develop a freeze-proof condenser for the Tracker Thermal Control System (TTCS). The TTCS is a mechanically pumped two-phase carbon-dioxide loop dedicated to control the temperature of the Tracker electronics. The TTCS is part of the Alpha Magnetic Spectrometer planned aboard the truss of the International Space Station (ISS). The TTCS collects the heat at two evaporators and rejects it at two radiators. In case of an accidental power-down of the AMS02 experiment, resulting in a loss of radiator heater control, the Tracker radiators and the connected TTCS-condensers may cool down as low as −120ºC, which is well below the CO2-freezing point (−56ºC@3MPa). During uncontrolled radiator heat-up and thawing of the solid CO2, liquid CO2 can be trapped in between solid parts resulting in high pressures. To withstand these high pressures, a high-pressure resistant condenser has been developed.