Research On Some Dynamic Problems Of Large Parachute Recovery System Of Manned Spacecraft

Recovery and landing system of manned spacecraft requires strict performance analysis and evaluations by thorough computational experiments for safety and reliability promotion. This thesis focused on some dynamic problems in the large parachute recovery process of'ShenZhou'manned spacecraft recovery and landing system. The main contents and conclusions are listed as following:The extrema of the peak values of parachutes'opening load in extreme conditions and the influencing factors'sensitivity, which are influnced by 21 factors, were discussed by utilizing the orthogonal experiment approach on the'SZ-7'hardware-in-loop simulation system. The extrema of the peak values of parachutes'opening load and the influencing factors'sensitivity were utilized in the evaluation of the'SZ-7'spacecraft recovery system.As the attitude data of parachutes and cabin are difficult to measure accurately in the flight tests, suspended body's attitude motion was classified systematically into several modes by means of simulation and analysis. Possible attitude modes of parachutes and cabin were retrieved by analysis and observing the flight tests'videos. And different phenomena which were observed in the flight videos were explained by using the classification, and which is helpful especially for the failure evaluation.The line-sail phenomenon's three-dimensional continuous mechanical models of pre-tension and pre-relaxation situations were established, which exist at the ending of large parachute's deployment process. The collocation method for solving the pre-relaxation problem was proposed, and the models and algorithm were validated by the static equilibrium problem of suspension line system. The line-sail phenomenon of manned spacecraft's parachute system was analyzed based on above mechanical models, and parameters'influence on the line-sail phenomenon were discussed by the evaluation indexes for two possible configures, noted as'line bowing'and'fish hooking'phenomena.Three-dimensional continuous dynamic model of tethers and finite difference method to solve equations of motion (EOM) were deduced and established to analyze the bullwhip phenomenon, which follows the parachute's deployment process. The methodology utilized here was validated by several examples and flight tests'data. The bullwhip phenomenon's mechanism was discussed based on the dynamic model, and the bending existing in tethers and the normanl velocity of the bending segment aroused by stress wave propagation were recognized as the direct causes of the swing or bullwhip phenomenon; the shock load of velocity difference between tethers'two ends and the unloading at the tethers'free end were recognized as one of the main causes of the large parachute's bullwhip phenomenon by phenomenon simulation of certain 'ShenZhou'spacecraft flight test, and the velocity of the end-point of canopy is consistent with the results of spring-damper discrete model and the results of analysis on flight tests'videos; the influence of the parameters and tether different bending configures on large parachute's bullwhip phenomenon was discussed with combination of the line-sail simulation results. As a first attempting to introduction the continuous model in the line-sail and bullwhip phenomena analysis of large parachute's deployment process, the preliminary investigation in the thesis could be considered valuable in both theory and applications.