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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.

This paper describes a novel mechanism for heat switch applications in space. The VARiable Effective Surface Radiator (VARES) is a heat switch based on the Oscillating Heat Pipe (OHP) principle. In general all power consuming space objects need radiator surface to radiate surplus of heat. However when switched off the power dissipating objects (electronics) will decrease to unacceptable low temperatures present in space. To overcome this design challenge, several solutions are available such as paraffin heat switches, thermal louvers, and loop heat pipes. Objective of all is to isolate the electronics from the radiator (low temperatures) when switched off. The work described in this paper is performed at NLR on the development of the VARES-radiator for application in spacecraft thermal control systems. The VARES makes use of the property of oscillating heat pipes whereby at low temperatures the oscillation process stops.

The AMS Tracker Thermal Control System (TTCS) is a two-phase cooling system developed by NIKHEF (The Netherlands), Geneva University (Suisse), INFN Perugia (Italy), Sun Yat Sen University Guangzhou (China) and NLR (The Netherlands). The TTCS is a mechanically pumped two-phase carbon dioxide cooling loop. Main objective is to provide accurate temperature control of AMS Tracker front-end electronics. Additional objective is to prove and qualify a two-phase pumped cooling in orbit and collect operational data in μ-g environment over a period of three years. The paper describes the concept selection, breadboard results and an outlook to the experiments in orbit.

This paper discusses the thermal modeling activities as a design and development tool for the Tracker Thermal Control System, the mechanically pumped, carbon dioxide thermal management system for the AMS-2 Silicon Tracker. Main modeling topics are: radiator sizing and condenser development, set-point control and pre-heating issues with respect to the spatial and temporal temperature gradient requirements of the Tracker.

Various aspects of different sensors and components, (being) developed or fine-tuned for aerospace thermal control and propellant systems, are discussed, i.e.: rotatable radial heat pipe joints, vapour quality sensors, controllable valves, condensers, flow metering assemblies and propellant gauges.