The Principle Research And Prototype Development Of Micro-newton Field Emssion Electric Propulsion

In recent years,high-precision space missions in China represented by space gravitational wave detection are in the stage of rapid development.Drag-free control system is an indispensable part of the space gravitational wave detection task.As the actuator of the dragfree control system,the micro-newton thruster plays an irreplaceable role.Field emission electric propulsion(FEEP)is a new type of electric thruster,which has the advantages of small mass,high specific impulse,fast response time,and low thrust noise.It is a potential micro propulsion scheme.At present,the research on FEEP thruster abroad has been more in-depth,but the on-orbit verification applied to the space gravitational wave detection task has not been realized.There is still a certain gap between domestic and foreign research on FEEP,and further research is needed in terms of working mechanism,emitter preparation process and field emission stability.In this paper,the principle exploration and prototype development of FEEP thruster are carried out for these problems.Aiming at the problem of FEEP working mechanism,this paper investigates the characteristics and working fluids of needle,narrow slit and capillary FEEP.Based on the difficulty of implementation and the mature level of technology,the needle In-FEEP is selected as the research object.In view of the conventional working mode of single-needle FEEP,according to the theoretical model and the demand of space gravitational wave detection,the design index of FEEP experimental prototype is proposed: the power supply voltage range is 0-10000 V,the voltage resolution is 10 V,the tip radius of the emitter is 2-5?m,and the distance between the emitter tip and the extraction plate is 1-4mm.In view of the preparation process of emitter,this paper focuses on the electrochemical corrosion processing method of tungsten emitter.Combined with the corrosion processing theory and control variable contrast experiment,the influence of various factors on corrosion and roughening processing was analyzed.The optimal parameters of corrosion processing under laboratory conditions were determined as follows: the solution concentration was 4mol/L,the processing voltage was 5V,the depth of the emitter tip immersed in the solution was 3mm,and the optimal parameters of roughening processing were AC voltage peak 3V,frequency 50 Hz,and power-on time 2min.Finally,tungsten emitters with vertex radius of 2-5?m and good working fluid fluidity were successfully prepared by ultrasonic cleaning and infiltration of working fluids in atmosphere and vacuum.In order to solve the problem of field emission stability,the main structure of FEEP is designed and processed in this paper,and the high voltage loading function of 10000 V level is realized.The electrical insulation of each part of FEEP is realized by using ceramic and PTFE structure.At the same time,PID feedback control technology is used to control the temperature of FEEP at 220 ± 0.2 °C,so that the working fluid is supplied stably and the field emission stability of FEEP is ensured.Subsequently,the field emission experiment in the atmosphere was carried out,and the stable ignition phenomenon was observed.Through the comparison experiment,the optimal geometric parameters of FEEP were obtained as follows: the inner aperture of the extraction pole was 10 mm,and the distance between the emission needle tip and the extraction pole was 1 mm.Finally,thrust of the prototype is 0.1-2?N,which provides experimental preparation for the subsequent FEEP development.