J. van Es

Active CO2 two-phase loops for the AMS-02 tracker

The Alpha Magnetic Spectrometer AMS-02 [1]-[4] is an astro particle physics experiment running on the International Space Station (ISS; see Figure 1) since May 19, 2011. Its missions include the search for antimatter and the identification of the nature of dark matter. The AMS silicon tracker is the only subdetector inside the AMS permanent magnet that can detect the charge of a moving particle to distinguish an anti-particle from particle (see Table 1 for nomenclature).

The control electronics of the silicon tracker cooling system of the AMS-02 experiment

AMS-02 is a space experiment that will perform cosmic ray observations on board of the International Space Station starting from July 2009. This presentation describes the control electronics for the silicon tracker cooling system in the AMS-02 apparatus. It also contains a brief description of the tracker detector and its cooling system necessary for the description of the electronics. The tracker cooling system includes a set of various sensors and actuators which are necessary for bringing the tracker detector to a uniform temperature at which it can operate correctly. The sensors include: Pt1000 thermistors, semiconductor thermal sensors, differential and absolute pressure sensors, and pump rotational speed sensors. The actuators are: resistive heaters, peltier heat pumps, and liquid pumps. The electronics process the sensor signals, control the actuators, and perform automatic safeguard actions so that the system is capable of operating in a stand-alone mode, i.e. without operator intervention. The electronic system also sends relevant operational data to ground. This paper will describe the design, construction and space qualification of these control electronics.

Development of a Mechanically Pumped Fluid Loop for 3 to 6 kW Payload Cooling

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 SinglePhase 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 purpose of the project was to design, develop and qualify an European manufactured single-phase cooling loop components such as pumps, valves, an accumulator and coolant fluid that can be used as high performance heat transfer device for extended payload power ranges between 3 and 6kW. The main requirements for MPFL were: operational temperature range of -20C to +90C, non operational -100C to +100C, 3 KW heat transportation, 15 years. As the temperature, reliability and lifetime requirements are severe, this put highly challenging requirements to the coolant (temperature range), pump (bearings, motor) and accumulator design. The selected and (space) qualified fluid was Galden Zt85 (manufactured by Solvay Solexis) which gives the best overall performance. The baseline selected MPFL pump is a design with a demonstrated accelerated life test for 10 years. The pump provides for an almost constant fluid flow through the Payload Heat Exchanger (PHX) branch whereas the By-pass Valve regulates the flow through the Radiator Heat Exchanger (RHX) branch. The accumulator compensates for fluid expansion over the operation and non-operational temperature range. A modular design which can be used for applications within a 3 to 6 kW payload range and compatibility with a variety of coolants was the result of this approach. Hence the qualified equipment for MPFL is suitable for multiple applications.

Investigation of Carbon Dioxide Explosive Boiling in Single Evaporator of a Two-Phase Mechanically-Pumped Thermal Control Loop

We investigated experimentally the start-up characteristics of a mechanically pumped two-phase loop (MPTCL), with CO2 as working fluid, and a single evaporator that consists of a bent inner ring and an outer ring constructed by stainless tubes with hydraulic diameter of 2.6 mm and length of 9 m, along which totally 54 pieces of heating element are distributed. Experiments were performed in the following conditions: mass flow rates of 1.1, 2.1, and 3.3g/s; heat loads ranged from 50 to 300W, with the heat-load ratios of the inner ring to the outer ring 2.2:1, 1:1, and 1:2.2 at the operational temperature of −15°C, respectively. During the start-up cases, we detected a reverse flow accompanying with pressure spike, which can be understood as explosive boiling, and a subsequent temporal dry-out phenomenon at the outlet of the evaporator, as a result of explosive boiling. The back flow together with the pressure spike is helpful to set up a two-phase flow all along the evaporator, though it may have negative effect on the loop, especially, when coincident explosive boiling happens. However, such a pressure spike that depends on initial superheating should be controlled to avoid possible harm to the loop.© 2010 ASME

The electronic ground support equipment for the silicon tracker cooling system of the AMS-02 experiment

AMS-02 is a space experiment that will perform cosmic ray studies on board of the international space station starting from July 2009. This paper describes the design and production of electronic ground support equipment (EGSE) that emulates the silicon tracker cooling system in the AMS-02 apparatus. This emulator is needed in order to test the control electronics of the cooling system without the cooling system itself. The cooling system will be assembled and integrated separately and with a different schedule. Using the EGSE, with a proper emulation software, it will also be possible to simulate the behavior of the cooling system in space. The tracker cooling system includes a set of different sensors and actuators which are necessary for bringing the tracker detector to a uniform temperature at which it can operate properly. The sensors include: Pt1000 thermistors, semiconductor thermal sensors, differential and absolute pressure sensors, and pump rotational speed sensors. The actuators are: resistive heaters, Peltier heat pumps and liquid pumps. The EGSE should simulate the behavior of all these sensors and actuators. This means that it must generate the same signals from the electrical point of view but also its global behavior, namely the response to any internal and external condition change should be the same as the actual tracker cooling system. In order to achieve this performance appropriate software that includes the simulated response of the tracker cooling system will be developed. The EGSE has been developed in three phases: in phase 1 we emulated the electrical behavior of each sensor or actuator as a single unit, in phase 2 we integrated those sensors in a single unit and we added a USB computer interface and basic control software. In phase 3 we will develop software emulating the behaviour of the entire tracker cooling system.

Modelling of the Transient Environmental Heat Load on the ALADIN Instrument in an Arbitrary ISS-related Orbit

3 INTRODUCTION 3 SIMULATION ENVIRONMENT 3 LIPAS SIMULATOR 3 THERMAL MODULE 4 OBJECTIVE 4 APPROACH 4 LAYOUT 4 PROCESSING 5 Sun heat load calculation 5 Planet heat load calculation 5 View factor calculation 5 Albedo load calculation 6 Dynamic instrument temperature calculation 6 RESULTS AND EVALUATION 6 HEAT LOAD CALCULATIONS 7 Solar heat load 7 Planetary heat load 7 Albedo heat load 8 Transient temperature prediction 8 RESULTS EVALUATION 9