External Heat Flux Analysis And Temperature Control On Alpha Magnetic Spectrometer In Orbit

Alpha Magnetic Spectrometer(AMS)is an high energy physics detector.The measurement results of cosmic rays by the AMS support humanity to understand the Universe and the origin of the Universe.As an equipment installed on the International Space Station(ISS),the structure and thermal environment of the AMS are complex,and its thermal analysis is important for ensuring the long duration mission of the AMS in orbit.With the developing of space technology,more and more countries and organizations started projects of detecting cosmic rays,the thermal analysis and temperature control of the AMS can serve as guidelines for the design of those equipment.The AMS thermal expert system was built by applying the database management technology and hybrid inference strategy of based on cases and knowledge,which combines the flight data,experts' experience,technology files and research articles.The data processing and graphical functions of the expert system are used to evaluate the state of the AMS in orbit.Based on the analysis of temperature records,three requirements of the temperature control of the AMS were concluded: analysing of the effect of the ISS Starboard main radiator angle(STRRJ)operations on the AMS temperature,avoiding the low temperature warning on the Transition Radiation Detector Gas System(TRD Gas System),evaluating the effect of the ISS side flight operation on the AMS temperature.Among of these requirements,the AMS Ram main radiator,the AMS Wake main radiator and the TRD Gas System are the AMS main components.Based on the calculation of orbital mechanics formulas and simplified hexahedral model,the rule of the external heat flux density variation with orbit parameters in the low earth orbit and the rule of orbital solar flux density of the AMS thermal control areas are analysed.The calculation suggests that the ISS Port and Starboard sides have poor heat dissipation conditions,where are not suitable for arranging the heat dissipation components with the ISS normal flight attitude;the difference between the orbital solar flux density of the AMS top and the ISS top is the inclination of the AMS z-axis and the ISS z-axis.The AMS thermal model is built with Monte Carlo-Network method.The external heat flux of the AMS main components is calculated through the AMS thermal model.And the calculated results are used to be compared with the results of the orbital external heat flux,which indicates the effect of the ISS components and operations on the solar flux of the AMS main components.The analysing conclusion shows that the ISS components can change the external heat flux density of the AMS Wake main radiator and the TRD Gas System by shading or reflecting the Sun illumination to these components.Besides,there are following effects which also can affect the temperature of the AMS components:heat supplementaries of thermo-stats and heat dissipations of electronic crates for the AMS Ram main radiator,heat dissipations of electronic crates for the AMS Wake main radiator,and heat conductions with surrounding areas for the TRD Gas System.By using steady and transient numerical simulations,the following items are finished: evaluating the temperature effect of the STRRJ operations on the AMS adjoining and main components,projecting the temperature control plan for the TRD Gas System,analysing the effect of the ISS side flight operation on the AMS external heat flux,planning the AMS thermal control method for the ISS side flight operation.According to the simulations,STRRJ adjustments can marked cause the temperature changing of the TRD Gas System,which could improve or worsen temperatures of main elements in the TRD Gas System.Although when ?<-45?there is improvement on the TRD Gas System,this system still meets low temperature warning when-20?<?<+20?.Additional thermal blanket can increase the temperature of the TRD Gas system by blocking the infrared radiation,and the best solution for TRD Gas system is following: with the ISS normal flight attitude,keeping STRRJ at +25?,operating the ISS solar arrays as ‘Auto-Tracking sunlight mode',and installed the additional thermal blanket on the AMS Port side.The ISS side flight operation obeys the arrangement principle of the AMS heat dissipation,which could trigger temperature warnings or even alarms on the AMS components,the thermal safety condition is-30?<?<+15?for the ISS positive side flight operation,-15?<?<+30?for the ISS negative side flight operation.Through the above researches,we built the AMS thermal expert system;realized the quantitative analysis on the thermal effect of the ISS to the AMS;and finally designed and verified the temperature control plans.All of research findings were applied in the AMS running process.They are protecting the science mission of the AMS and can serve as guidelines for thermal analysis of similar equipments.