No abstract

No abstract

The Alpha Magnetic Spectrometer AMS-2, planned for a five years mission as attached payload on the International Space Station ISS, is an international experiment searching for anti-matter, dark matter, and missing matter. AMS-2, an improved version of AMS-1 flown on STS 91, consists of various particle detector systems, one of these being the (Silicon) Tracker. The trade-off based choice and the experimental feasibility demonstration of a mechanically pumped two-phase CO 2 cooling loop for the Tracker is discussed in detail. Ongoing and planned development activities are indicated.

The Alpha Magnetic Spectrometer AMS-2 is planned for a five years mission as attached payload on ISS, the International Space Station. It is an international experiment searching for anti-matter, dark matter, and missing matter. AMS-2, an improved version of AMS-1 flown on STS 91, consists of various particle detector systems, one of these being the (Silicon) Tracker. The trade-off based choice and the experimental feasibility demonstration of a mechanically pumped two-phase CO 2 cooling loop for the Tracker is discussed in detail. The current status and ongoing and planned development activities are discussed.

No abstract

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.

It is assessed to what extent the results of two-phase two-component flow and heat transfer research can be usefully applied to support research on the flow and heat transfer in two-phase single-component systems. The latter singlecomponent two-phase systems, envisaged for spacecraft thermal control applications, are Mechanically Pumped and Vapour Pressure Driven Loops, Capillary Pumped Loops, and Loop Heat Pipes. In these single-component systems the working fluid is a mixture of a liquid (for example ammonia, carbon dioxide, ethanol, or other refrigerants, etc.) and its saturated vapour. The two-component systems considered consist of liquid-gas mixtures, e.g. water-air. Various aspects are discussed qualitatively and quantitatively to determine commonality and difference between two physically looking similar and close, but essentially different systems. It is focused on the different pressure gradient constituents and total pressure gradients, on flow regime mapping (including evaporating and condensing flow trajectories in the flow pattern maps), on adiabatic flow and the impact of flashing, and on thermal-gravitational scaling issues. It is elucidated that, though there is a certain degree of commonality, the differences are appreciable. The conclusion is that one shall be very careful in interpreting two-component outcomes to develop single-component two-phase thermal control systems.

Results are presented of the development and tests of a 1 m long ammonia ramified loop heat pipe, with two cylindrical evaporators (24 mm in diameter with an active zone length of 150 mm) and two condensers (length 200 mm, diameter 24 mm), made as pipe-in-pipe heat exchangers. Tests of the device at different orientations in 1-g have shown that it can efficiently operate at symmetrical and non-symmetrical heat load distributions between the evaporators, and also at different temperatures of the condensers cooling. The maximum total transport capacity is 1100-1400 W. Shutting down the active cooling of one condenser results in an abrupt decrease in the maximum transport capability of the device.