Search Results

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.

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.

Against the manufacturing requirement for both lower lead time and reduced machining time for titanium components, a new concept was conceived assembling sheet material and other stock into semi finished parts by (explosive) impact welding. It is believed that this concept (which we named SLAM) could be especially beneficial for titanium alloy and nickel alloy. The present investigation centered on the feasibility of this technology for the widely used Ti6Al4V alloy. Impact process parameters were established and mechanical properties were investigated. In general, static properties were good. Fatigue strength reduced however, although much less so for notched specimens compared to un-notched material. Fatigue crack initiation could be linked to complex features within the (wavy) weld interface associated with the ‘first generation’ impact welding parameters. Next steps are foreseen to improve the fatigue performance.

Two-phase heat transport systems are currently considered for the thermal management of future large power spacecraft. The monitoring of the quality, being the relative vapour mass content, of the two-phase mixture at various locations in the system, is valuable - possibly indispensable - for the proper operation of such a system. This paper reviews concepts for quality monitoring. Only a few concepts turn out to be suitable for spacecraft applications. Promising concepts are based on the capacitance, sonic velocity and index of refraction. These concepts are described and quantitatively analyzed. Applicability, advantages, restrictions and some hardware aspects are discussed.

The described thermal model is part of the Lidar Performance Analysis Simulator (LIPAS), a simulator of the Atmospheric Laser Doppler Instrument ALADIN. The developed model calculates the transient environmental heat load on ALADIN and gives an overall instrument temperature prediction. The heat load model accounts for the fact that the ISS orbit is a non-fixed one, and is therefore essentially based on the actual position of the spacecraft, rather than on orbit parameters. In order to verify the validity of the model developed, results are compared with results from other heat load programs.

This paper presents selected results of four experiments into air traffic control (ATC) aspects of free flight (FF). The first two examined basic human performance implications of FF, in terms of workload and ability to monitor traffic. The third explored the potential for improved ATC displays to benefit controllers under FF traffic patterns. The fourth experiment examined methods for accommodating mixed equipage, such as during a transitional FF era in which both FF capable and FF incapable aircraft would be expected to share the same airspace. The first three experiments involved controllers operating in “open-loop” simulations, with computer-generated traffic and simulated pilot responses. In the final experiment, pilots and controllers were linked in real-time sessions.

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 CO2 cooling loop for the Tracker is discussed in detail. The current status and ongoing and planned development activities are discussed.

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).

As it is not possible to directly use commercial liquid flow meters in spacecraft fluid loops, a study was carried out for the European Space Agency to adapt commercial flow meter assemblies for space applications. The various activities (described in detail) eventually led to the selection of two commercial units, which were redesigned/adapted to be used in spacecraft single-phase (water) and two-phase (ammonia) thermal control loops. These flow meter assemblies were tested according to an agreed test programme, that included performance and calibration tests in a test bench (developed during the study), vibration testing and EMC/EMI testing. The results are discussed in order to assess to what extent the study objectives were met. Recommendations for future work are given also.

Free Flight (FF) would permit aircraft to fly preferred routes, and self-separate, with minimal ATC intervention. The controller would be expected to intervene tactically only as necessary to ensure separation. Based on the results of earlier experiments at the NLR, an enhanced ATC display was developed that incorporated airborne-derived conflict detection and resolution information. Trials with controllers demonstrated benefits in terms of monitoring time and performance, as well as in general acceptance. Two important issues were identified for future work: (1) FF training needs and (2) controller responses to abnormal system modes.