Performance Optimization Of Micro Hollow Cathode Thruster Based On Electron Magnetic Confinement

With the development of space technology,more and more attention has been paid to the ultra-low orbit micro satellite in recent years.To realize the long-time ultra-low orbit flight,the propulsion system with high efficiency and high specific impulse is needed for continuous thrust compensation.Micro hollow cathode thruster has the advantages of small volume,simple structure and low power,which is very suitable for the electric propulsion system of micro satellite.It is of great significance to optimize the micro hollow cathode thruster into a micro thruster with high efficiency and high specific impulse.In this paper,the full ionization method of working medium is studied.According to the mismatch between electron energy and neutral gas distribution in the old configuration,the idea of gas split is proposed.Based on the idea of gas split,two new configurations are proposed to change the mode of gas supply.The improvement of the ionization rate of the thruster with the new configuration is verified by measuring and calculating the ionization rate with Faraday probe.Through the numerical calculation model,the influence mechanism of gas split is analyzed,and it is found that the ionization rate is increased by increasing the ionization region at the edge of the channel.Secondly,the electronic current control method is studied.The main factors that affect the electron current are magnetic field and anode.The optimization of magnetic field is mainly to design multiple magnetic field configurations and determine the optimization scheme by changing the magnetic field intensity and measuring the discharge characteristics.To optimize the anode,the shape,inner surface area and position of the anode were compared and studied.It was determined that the anode shape was annular,the inner surface area was 50mm~2 and the distance from the magnet was 6mm.In order to determine the performance parameters of the micro hollow cathode thruster,the characteristics of the optimized cathode thruster were measured.Through the measurement of start-up characteristics,the impact characteristics of start-up mode are determined,and the start-up scheme to avoid the impact of start-up is proposed.Through the measurement of discharge fluctuation characteristics,the stable voltage range under different flow rates is determined,and the oscillation range can be avoided.Through the analysis of oscillation characteristics,it is found that there are two typical oscillation modes.The thrust and specific impulse of the thruster are higher than those of the early cathode thruster.Through the measurement of plasma parameters,it is found that the plume divergence angle of cathode thruster has a great correlation with the working conditions,and the divergence angle ranges from30 to 50 degrees.Finally,the stable discharge test of the hollow cathode thruster is carried out.Two kinds of experiments were carried out:100 h steady-state discharge and 400times switch detection.In the continuous steady-state test,the discharge state of the thruster is relatively stable,and the average anode current is increased due to the decrease of magnetic field strength.In the switch detection experiment,the start-up time increases first and then becomes stable.In the measurement after the experiment,the heating resistance increases.Combined with the model,the life of the heater is analyzed.According to the comprehensive analysis,the failure mode mainly lies in the emitter sputtering of the hollow cathode and the magnetic field demagnetization of the permanent magnet.