Research On Performance And Life Of Two-stage Ion Thruster Grid System

Ion thrusters are one of the most important applications in electric propulsion technology.Its working principle is to accelerate the rare gas that is ionized into plasma by high potential difference,and finally form the thrust by electron neutralization ions^[1].The advantage of an ion thruster compared to other thrusters is that the principle of operation is relatively simple.The disadvantage is that due to its own inherent defects,the voltage of its gate system cannot be arbitrarily increased.And this could cause the magnitude of its thrust to be limited.In order to enhance the ability of deep space exploration,the improvement of traditional ion thrusters is an urgent task.The multi-stage accelerating optical system envisioned by Fearn,which is applied to the ion engine,can well solve the shortcomings of the ion propeller.This new model is capable of applying a large voltage difference across the gate system to achieve the desired thrust.However,due to the relatively new model,its research is still insufficient,especially the research on the focusing performance and life of its grid system.This paper studies the focusing performance and lifetime of the two-stage grid system.The three-dimensional model based on IFE-PIC algorithm is established to simulate the extraction process of the ion thruster gate system,and the focusing performance of the gate system is studied.The program is mainly composed of two major blocks:PIC and IFE.The difference between the traditional ion thruster and the two stages is embodied in the PIC module.The PIC algorithm calculates the motion of each particle in the calculation area and updates the motion of the particle until the simulation area is stable.The IFE algorithm calculates the magnitude of the potential on each grid node in the simulation region during each iteration,and obtains the magnitude of the electric field force received by the particles.Since the specific parameters of the two-stage grid system model have not been disclosed,this paper bases on the model of the existing two-stage ion thruster grid system,and simultaneously refers to the parameters of the optical system of the QinetiQt6 traditional ion thruster,and determines the basic parameters of the grid system in two stages through calculation.After obtaining the parameters of the two-stage gate system,the two-stage gate system is simulated based on the IFE-PIC method and the working condition graph is obtained.Since the two-stage ion thruster has a lower ion density upstream,the acceleration gate impact is severe compared to conventional ion thrusters.According to the design process,the parameter selection of the model is improved by adjusting the size of the extraction gate aperture and the acceleration gate aperture in the two-stage gate system.The advantage of the two-stage is that the gate system can apply a large voltage difference to obtain the desired thrust.However,in the current practice,the power supply of the propeller is solar energy,and the voltage difference is not reached for the time being.In the low power case,the two-stage focusing performance will be researched and analyzed in this paper.Finally,considering the two-stage model under high power conditions,the corrosion of the gate will be very serious,which will affect the life of the ion thruster.Therefore,in order to push up the life of the two-stage model,this paper will also study the corrosion process and degree of the improved two-stage grid system.