Study On Nozzle Plume-dust Ejective Characteristics And Passive Lunar Dust Surface Protection Technology During Soft Landing Of Spacecraft

The lunar exploration mission is a strategically significant project.Lunar exploration programs have been conducted both domestically and internationally.Previous soft landing processes on the lunar surface have revealed that engine exhaust can create significant lunar dust clouds.These clouds not only obstruct the view of the landing camera and cause deviations in landing area positioning but also deposit on lunar exploration equipment,resulting in functional degradation or even failure.These challenges significantly affect the safe execution of lunar exploration missions.Therefore,the identification and quantification of engine nozzle plume-lunar surface erosion can yield valuable quantitative data for lunar dust protection,ensuring the safe landing of future manned lunar missions.This thesis quantifies the dynamic process of engine plume erosion on the lunar surface,obtaining data on the characteristics of ejected lunar dust under specific conditions.Subsequently,a passive lunar dust protection method is proposed to mitigate the damage resulting from the deposition of lunar dust on solar cells caused by ejected dust.The primary research content and innovative achievements of this thesis are as follows:Firstly,in response to the accuracy issue in calculating the internal flow of the engine nozzle,a simulation method based on on-orbit dust lifting nozzle thrust in Chang’E missions and a verification method for thrust calculation verification are proposed.By establishing a 1:1 structural model of the engine nozzle identical to that used in Chang’E-5and Chang’E-4,combined with on-orbit telemetry data and landing trajectory analysis,the effective thrust of the dust lifting stage in the two missions is determined to be 2900 N and2200 N,respectively.Using the flow characteristics of exhaust flow under on-orbit effective dust lifting thrust as the inlet condition,the flow characteristics of exhaust plume flow in the engine nozzle and the parameters of the outlet flow are obtained,and the numerical simulation results are compared using three methods to verify the accuracy of the simulation model of exhaust flow in the nozzle under specific thrust.Secondly,a boundary-constrained simulation model based on key erosion parameters extracted from landing images is proposed to address the challenge of the inability to quantify the diffusion flow and physical erosion process of the plume on the lunar surface.This model solves the problem of unclear dynamic erosion mechanisms caused by the plume and the inability to quantitatively calculate erosion characteristics.Firstly,optical method is adopted to analyze the landing images of the Chang’E-5 and Chang’E-4 missions,and key parameters such as the distance between the engine and the lunar surface,landing time,and initial erosion position during the dust lifting phase are extracted.Then,the plume turbulent flow model in a vacuum environment is established and optimized using the flow parameters at the engine nozzle outlet and the extracted key erosion parameters as boundary conditions,which is able to quantify the lunar surface erosion characteristics.Based on it,the key erosion parameters such as erosion rate,erosion range,erosion area,and erosion mass during the soft landing process of the Chang’E-5 and Chang’E-4 missions are obtained.This provides a theoretical model support and quantitative analysis basis for the lunar dust erosion caused by subsequent lunar landing missions.Thirdly,this study addresses the challenge of the coupling between lunar dust particles and a non-uniform plume field in the lunar environment.To tackle this,an adaptive drag force calculation method is proposed specifically for lunar dust particles.Additionally,a self-programming method is used to establish a coupling model for the interaction between lunar dust particles and the plume flow field.Subsequently,the study obtains essential parameters,including dust lifting trajectories,elevation angles of lifted dust particles,and distribution maps of dust lifting velocities for different particle sizes.Furthermore,the study focuses on the local terrain within the landing area of the Chang’e-4 mission to analyze the impact of lunar surface slope angles on dust lifting characteristics.The analysis reveals that lunar dust is more prone to being lifted by plumes on the windward side.Finally,to address the ejected lunar dust deposition issue of performance degradation in solar cells,this study proposes and experimentally verifies a passive lunar dust protection method suitable for solar cell surfaces in the lunar environment.The sol-gel-dipping process is selected as the method for preparing the surface protection coating,and the optimal process parameters are determined.Microscopic adhesion force testing and macroscopic evaluation methods for dust-proof efficiency are designed to quantify the lunar dust protection effectiveness.Additionally,a space environment evaluation of the coating is conducted to verify its suitability and adaptability in the space environment.