Modeling And Simulation Research Of Mars Probe Parachute Deceleration Process

Parachute is used for aerodynamic deceleration after the Mars probe entering the Mars atmosphere.The parachute deceleration process is one of the most critical stages of the whole landing process.Because of the giant differences between Mars atmosphere and Earth atmosphere,the opening conditions of the parachute in Mars exploration mission are consist of supersonic velocity,low dynamic pressure and low density.The special parachute opening conditions result in the problems of parachute “linesail” phenomenon,flutter and respiration,infinite mass inflation,deceleration efficiency reduction and stability deterioration.Considering the research of parachute deceleration system of Chinese first Mars lander,this dissertation focuses on some problems existing in the parachute working process.These problems include the aerodynamic performance of parachute in Mars atmosphere,the ejection and deployment of one large parachute from the lander,the dynamics of the assembly constructed by lander and parachute,and the opening control scheme of parachute deployment for Mars lander.The main contents in this dissertation are summarized as follows:Firstly,the ejection and deployment process analysis of the Mars parachute was studied.According to some specific parachute opening conditions for Mars lander,such as supersonic speed,low atmosphere density,and low opening dynamic pressure,the whole dynamics simulation model of the parachute ejection and deployment process was built in this paper.The simulation model was divided into several stages which considers the lander,parachute pack and shell of parachute cartridge as rigid model while assuming the parachute,ropes and suspension lines as flexible cable model.Meanwhile,the wrapping and occlusion effects of multiple ropes pulled out from the parachute pack had been considered.By setting the different initial conditions of ejection separation speed,angle of attack,height and Mach number,multiple simulations were conducted and the deployment time,deployment position,suspension line stress and largest deviation distance had been analyzed.The conclusions provided a reference for the determination of ejection separation speed index in the conceptual design of parachute deceleration system for the first Mars exploration in China.Secondly,the inflation process and aerodynamic characteristic of the disk-gap-band parachute used for Mar exploration were researched.Through the parachute multiple nodes model,the FSI problem of the parachute’s fast and big deformation in the supersonic condition was solved and the aerodynamic performance data were acknowledged.Based on the ALE(Arbitrary Lagrange Euler)method,RADIOSS software was firstly used for FSI simulations and analyses of the Mars parachute aerodynamics through different Mach number.A reasonable simulation model and contact setting method of parachute were put forward in this paper as well.The simulation results were verified by comparing to the wind tunnel experiment results.Based on this,the simulations of the inflation process and aerodynamic performance of the parachute under the Mars condition were carried out.Thirdly,a dynamics study of the assembly constructed by lander and parachute of China mission was carried out in this dissertation.The whole dynamics simulation model was built including parachute model,lander model and the hanger between parachute and lander model.The added mass of the parachute,the stress of the suspension line and the connecting belt effect were concluded in the simulation model.Based on Monte Carlo method,the variance deviation analysis of the parachute deceleration was conducted,and the comprehensive statistical result was obtained.The result showed that deviation of the opening conditions would lead to the large deceleration time and height deviation while small landing velocity,dynamic pressure and attitude deviation.The conclusions provide a reference for the determination of the parachute opening conditions in the conceptual design of the first Mars exploration mission in China.Finally,the deployment control scheme of the Mars parachute was presented in this paper.According to the characteristics of Mars parachute,combined with China’s overall plan for Mars exploration mission,a various applicability analyses of deployment control scheme had been conducted,and the adaptive dynamic pressure control scheme and Mach number control scheme were suitable for the Mars mission.The deviation simulation of the two control schemes was carried out accordingly.The angle of attack control scheme was firstly added to the adaptive deployment control scheme and the hardware implementation approach was described in this dissertation.The conclusions obtained in this part provide a reference for the parachute deployment control scheme selection of the first Mars exploration mission in China.