Numerical Simulation And Experimental Study Of Dual-stage Grid System In Electric Thruster

This paper describes the advantages and disadvantages of electric propulsion technology compared to chemical propulsion,and summarizes the principle and basic composition of electric propulsion technology.As one of the most successful electric thrusters,the gridded ion thruster has been studied more and more extensively in recent decades.With the introduction of various new space tasks,the electric thruster system will develop toward high power and high specific impulse.Aiming at the problem of coupling between the acceleration and extraction processes in the traditional gridded ion thruster,the scholars have proposed the concept of dual-stage grid,which separates the extraction and acceleration processes of ions,and thus the specific impulse of the gridded ion thruster is greatly increased.As a new type of grid structure,the simulation analysis of dual-stage grid system is necessary.This paper summarizes the preliminary research and related basic theories of the dual-stage grid system at home and abroad,and carries out PIC/MCC simulation on the grid system.The PIC/MCC method is commonly used in plasma transport and electric propulsion,which is a numerical simulation method based on particle kinetic.It uses the concept of “macro particle” to describe the plasma transport process in a realistic way.In addition,for the problem that the PIC/MCC method has a large amount of calculation,this paper proposes a three-dimensional parallel algorithm for solving complex electric fields,which accelerates the electric field solving speed of each time step in the PIC method,thereby improving the calculation efficiency.After preliminary calculation of the plasma transport process in grid system,the structure of the high specific impulse dual-stage grid system with Xe as the propellant has been optimized,including the influence of grid aperture,thickness,spacing and voltage,which improves the thrust and specific impulse performance and reduces the divergence angle loss.In addition,the beam collimation is improved,and the ion number density at the axis of the grid hole is greatly reduced,which improves the problem of over-focusing.The transport properties of different propellants under the same grid structure are also analyzed.Based on the optimized grid structure,a complete dual-stage grid system was designed and fabricated,and an electron cyclotron resonance ion source was used as a plasma generating device to carry out related discharge experiments.The ionization chamber diameter is 40 mm,which is the same as the opening area of the grid plates.The operating frequency of the microwave source is 5.6 GHz.Under the condition of 90 V extraction voltage,the ion beam is well extracted,and the plume morphology under different screen voltage conditions is obtained.With the change of voltage,the focusing performance of the thruster is also changed.Using the Faraday probe to collect the ion current extracted from the thruster,the performance parameters of the dual-stage grid ion thruster are indirectly obtained.