Design And Experimental Study Of Iodine Propellant Electric Thruster Feed System For Small Satellites

The low cost and short development cycle of small satellites make t hem increasingly used in commercial spaceflight.Compared with traditional chemical propulsion,electric thrusters can provide high specific impulse power for small satellites and reduce the fuel mass carried by them.Compared with conventional xenon propellant,iodine propellant requires no high-pressure tanks,is cheap and has relatively high atomic mass.Therefore,it is of great significance to study the iodine propellant electric thruster.This paper first analyzes some key problems encountered in the des ign of feed systems in the world and puts forward the design objectives of storage and supply systems.Then,the power range of thruster is determined based on the actual demand of small satellite,and then the flow control range of feed system is determined.The key parameters of the system design are calculated by the theory of known flow range.And the qualitative analysis found that the temperature uniformity inside the iodine tank had a great influence on the flow stability.In the design of feed system,the solenoid valve guide tube should be corrosion resistant,deposit resistant and heat accumulation free.Because iodine tank and hot throttling tube are the key parts of flow control.In addition to the above requirements,the iodine tank structure is designed to make the iodine block uniformly heated,and the size of the throttling tube is determined by the calculated theoretical data.After the design of the system,the heat transfer analysis and thermal stress calculation are carried out.First,the performance indexes that meet the requirements of practical application are analyzed.Then,the system model is established,the boundary conditions of the system are analyzed,and the setting parameters are determined.By comparing and analyzing the calculation results of the two storage systems,it is found that some problems exist in the temperature distribution of the fin heating core storage system and the spring porous plate storage system,especially the hot throttling tube and iodine tank.The influence of thermal deformation on system performance is analyzed quantitatively.Combined with the design indicators,the optimization scheme is proposed to solve the problems one by one.After simulating the optimization,the system verifies the rationality of the optimization scheme.The variable ambient temperature caused by the sun's radiation on the yin-yang surface during the satellite's orbit around the earth is simulated and an improved scheme is proposed.The external dynamic environment of small satellite is complex in practical application,so the dynamic analysis of the system is carried out.According to the external dynamic environment of the small satellite,the dynamic e valuation index is established.The material selection and loading conditions of the sys tem are defined,and the vibration types of the system dynamics analysis are also determined.Modal analysis,response spectrum analysis and random vibration analysis were performed for the two systems respectively.The weak parts which are fragile and easily deformed are optimized.After the theoretical design of the system is completed,an experiment is carried out to verify the system performance.According to the requirements of the iodine propellant system,a test bench with corrosion resistance and iodine steam recovery ability was built.Xenon gas supply system is added to realize mixed gas supply.Thrusters and cathodes are selected according to the actual requirements of small satellites and existing experimental conditions.The system performance test found that the shape of the iodine block changed after the finned heating core iodine tank consumed certain iodine elements,and the heat transfer between the heat source and the iodine block weakened and the supply flow could not be stabilized.In terms of long-term performance,the spring porous plate storage system has better performance.Ignition tests show that the color of iodine working plume varies greatly in different discharge states.The ignition interval is narrow and unstable,but the iodine tank can discharge steadily for five minutes under the condition of heating 55? and 250 V voltage.