Analysis And Optimization Of Response Characteristics Of Alpha Magnetic Spectrometer Thermal Control System In Orbit

With the development of space technology in recent years,the space explorations and experiments have become an international frontier and hotspot.The International Space Station(ISS)is an ideal platform for space explorations and experiments because of its stable operation and large scale.As the first large-scale international scientific experiment performed on ISS,the Alpha Magnetic Spectrometer(AMS)aims to get a better understanding on the unknown and origin of the universe by detecting the high-energy cosmic rays.Influenced by the complex and harsh space environment and the ISS operation itself,the thermal control system(TCS)of AMS which installed outside of the ISS main truss is always faced with great challenges.Therefore,the study on the response characteristics of AMS TCS in orbit is the key to ensure the long-term safe operation of AMS,and provides an important reference for the TCS design of other station borne equipment.In this paper,the AMS TCS is taken as the research object,the dynamic characteristics of the thermal environment and the temperature response,the occurrence of the temperature anomaly and the corresponding optimization method under the ISS operations are systematically investigated by theoretical analysis and numerical simulation on the basis of the on-orbit experimental data,the main investigation work and the related results are as follows:1.The conductive and radiative heat transfer processes of AMS in orbit are theoretically analyzed,and the heat balance and the external heat flux of AMS are derived.On that basis,the theoretical analyses of the influences of three types of ISS operations on the thermal environment of AMS are carried out:the shielding effect of locking ISS solar arrays on the external heat flux of AMS is most significant in the ?ranges of(-75°,-21°)and(+57°,+75°);the mathematical model of the AMS external heat flux variation with the rotation of the ISS starboard main radiator is derived;based on the spherical coordinate system and the three angle control variables of ISS flight attitude,the dynamic mathematical model of the external heat flux of AMS under the ISS flight attitude adjustment is established,which can realize the accurate calculation of the external heat flux of the AMS specific surface under the ISS flight attitude adjustment.2.Based on the experimental data of AMS operating in orbit for nearly nine years,the variations and impact factors of AMS temperatures under all ISS conditions and all ? angles are analyzed,and the occurrence positions of temperature anomaly on AMS are determined.Based on the recording data of the ISS operation conditions,the temperature response characteristics of AMS under the ISS operation conditions with high frequency are comparatively analyzed,and the influence degrees of different ISS operations on AMS temperature are obtained.Based on the temperature recording data,the temperature anomaly occurrences and the corresponding existing thermal control measures are studied.The results of data analysis show that most of the AMS component temperatures under all ISS conditions are within the allowable ranges,except for the TRD gas system and Tracker Plane 1,where the low-temperature anomalies can occur.Under the same situation,the different types of ISS operations have various or even opposite effects on AMS temperatures.which proves the temperature compensation effects of the ISS operations on AMS between each other.The low-temperature anomalies of the AMS Tracker Plane 1 mainly occur at its central area without multi-layer insulation and concentrate in the ? angle range of(-75°,-65°).which can be effectively suppressed by activating the adjacent heater because of their limited overtemperature ranges.The low-temperature anomalies of the AMS TRD gas system maily occur in the P ranges of(-65°,-28°),(-25°,+28°)and(+44°,+75°),which is mainly caused by the ISS operations and AMS cold conditions.The insulation blanket can completely avoid the low-temperature anomalies in the ?angle range of(-60°,+60°),but may aggravate the low-temperature anomalies in the ?angle ranges of(-75°,-60°)and(+60°,+75°),in response,activating the adjacent heater,rotating the ISS starboard radiator and unlocking the ISS solar arrays can be implemented timely.3.The system-level thermal network model of AMS installed on ISS is established based on the commercial thermal analysis programs Thermal Desktop and SINDA/FLUINT,and its validity is verified by a variety of data comparison methods.The thermal environments and the temperature response characteristics of the AMS TCS key components are simulated by using thermal network method,and the thermal influences of the ISS operations on AMS TCS key components and the occurrence regularities of the corresponding temperature anomalies are mainly studied.The numerical simulation results show that the variations of the external heat flux of AMS TCS are mainly determined by the solar radiation.The three types of ISS operations can have a significant impact on the external heat flux of AMS TCS,making it decreases firstly and then increases with ? angle increasing and reach the maximum at extreme ? angles which can be 383.6 W/m2.The ISS flight attitude adjustment has a relatively larger impact on AMS TCS key components,and may even cause temperature anomalies.The temperature anomalies only have the possibility to occur when changing the flight attitude to flying in+Y and+Z directions with the occurring time ranging form 6235 s to 73897 s after the ISS operation,and they are most likely to occur in the right and bottom areas of the two main radiators of AMS TCS,with the most serious impact on the equipment hardware.4.In order to reveal the influence mechanism of different ISS operations on the AMS TCS temperature response characteristics,the linear correlation between the external heat flux and the temperature variations of AMS TCS under ISS opertions is numerically analyzed by using the established thermal model of AMS installed on ISS.According to the influence mechanism of rotating the ISS starboard main radiator on the AMS TCS temperatures and its temperature compensation effect,aiming at impressing the possible temperature anomalies of AMS TCS key components caused by the ISS flight attitude adjustment,two thermal control optimization methods based on the ISS starboard main radiator rotation are proposed,and their thermal control performances are comparatively analyzed.Results show that the AMS temperature response under the ISS flight attitude adjustment is mainly determined by its influence on external heat flux variation,while that under locking the ISS solar arrays and rotating the ISS starboard main radiator is jointly determined by the variations of the external heat flux and the radiative heat dissipation to space of AMS TCS.For the thermal control optimization methods based on the principles of "minimum heat flux"and "minimum temperature",they can delay the occurrence time of temperature anomaly by 2.0%?28.1%and 2.0%?42.7%respectively,and even completely avoid its occurrence under the specific conditions,showing a good thermal control performance.