Study Of Rarefied Plasma Plume Sputtering Effect

With the unceasing steps of human space exploration, eletric propulsion technology is increasingly attracting interest from the world astronautic field. Unlike conventional chemical propulsion systems, electric propulsion devices do not rely on the internal energy stored within their propellent.Instead, an external electric power source is used to impart energy to the working fluid. As no inherent limitation due to the propellant exists, a high Isp and a precise thrust is attainable. Consequently, electric thrusters is an optimum subsititute for chemical propulsion which isn't capable for deep space exploration or micro-satelite station-keeping or orbit transfers missions.Hall thrusters is a kind of electric thrusters studied most in the world currently, it can be classified as electromagnetism thrusters. Equipped with various advantages such as high Isp, high reliability and light weight, however, hall thrusters has its limitations in extensive space application as people know little about the potential contamination of its plasma plume. These contamination effect include thermal effect, sputtering effect, additional force contamination, deposition effect and electromagnetic interference effect. Because of the ion velocity is far greater than neutral plume molecular velocity, investigating the sputtering effect induced by ion bombardment is of great importance.In order to study the sputtering effect between hall thrusterplasma plume and satellite solid surfaces, this paper used SPT-70 developed by Shanghai Aeronautic Bureau as the research object. Firstly, properties of rarefied plasma plume of SPT-70 are diagnosed by utilizing single Langmuir probe, double Langmuir probe, data acquistion systems and shift devices in the vacuum chamber. Electron density, electron temperature at different axial postions or angles are investigated and compared with the plume simulation result, the comparison validated the 2D plume flowfield model and the FORTRAN code. Then 2D DSMC/PIC methods and codes are extended to 3D, the 3D results is compared with previous 2D results. The simple sputtering model based on experiments is then added to DSMC/PIC FORTRAN code, sputtering on satellite solid surfaces caused by SPT-70 plume is simulated on a CUDA platform euipped with double GPUs through FORTRAN computation code. Simulation results of sputtering yield agreed with data from reported papers. The model developed in this paper can be applied to evaluation of sputtering contamination effect of all kinds of electromagnetic electric thrusters, and can provide a reference for reasonable distribution of satellite surface.For the purpose of providing researchers with a more user-friendly and convinient design tools, we established a visual contamination evaluation platform. The core computation code writen in FORTRAN language and the user-interface builded in VB.net of the platform is capable of displaying, draging, zooming and rotating the grid of a 3D physical model and the computation results by means of Open GL. Plume flowfield computation model, FORTRAN program and contamination evaluation model are coupled within this platform. All the parameters are inputted in an interation way, surface structures, sizes and locations of satellite are visualized in the geometry model function of the platform, the final computation results are also displayed directly through geometrical model.