Research On The Opening Process Of Large Parachute System

The process of recovery and landing makes great demands on the safety andreliability of the spacecraft recovery system. As an important part of the recoverysystem, the parachute’s operational performance must be analyzed and evaluatedentirely in the design phase. The dissertation studies on the opening process of the largeparachute and the phenomenon of the pulled-out parachute pack chasing the parachutecontainer cover. The main contents and conclusions are listed as follows:According to the features of the videos from ground-based cameras, a modularimage processing method is proposed. The non-linear motion characteristics of thecanopy and the ropes are analyzed via the videos, and uncontrolled state of the canopyand the velocity difference between the pack and the spacecraft in deployment areshowed to be the principal cause of the canopy vent’s rapidly swing after deployment.By using the image processing method, the motion information of the canopy vent afterdeployment, the projection area of the canopy and the attitude of the parachute areacquired for the first time in our nation. The experimental data from the videos isnecessary for the large parachutes’ theoretical research and engineering designimprovement.Considering the features of the videos from on-board cameras, an image processingwhich is used to measure the canopy’s projection area via its contour in the video isproposed. The missing and occluded part of the contour could be identified and berepaired, and then the projection area could be calculated. By using this method, theprojection area of the canopy and the relative motion information between the canopyand the spacecraft are acquired. The results could make up for the traditionalmeasurement limitation.Based on the video analysis, the inflation process of the large parachutes is studiedintensively. Formula and algorithms for calculating the drag area and added mass aregiven. The changing characteristics of the main influencing factors of the opening forceare analyzed, and the relationship between mass ratio and opening shock are discussed.The research shows that the added mass has an important effect on the opening force,and the specific mass ratio is the major cause of double force pulse during disreefing.Comparison with the model in the literature indicates that the new method has higherprecision. The new model has been applied to the spacecraft recovery system simulationsoftware successfully.In terms of the lack of research on the phenomenon of the parachute pack chasingthe parachute container cover, a discrete analytical model is established, and thesimulation result could reproduce the chasing phenomenon observed in the tests, thenthe influence of the major design parameters are discussed. The study shows that the chasing phenomenon inevitably appears when the cover separation unit uses an elasticbelt connecting the cover and the pack. The research supplies the theoretical basis forthe mechanism analysis of the phenomenon.The dynamic model of a spatial rope is deduced. An approach for analyzing theshock wave reflection and transmission in a rope with discontinuity is provided andvalidated by numerical simulation of simple examples. The features of propagation ofshock wave in two connected ropes with different general wave impedance is analyzed.By taking the belt and the parachute pack as interconnected ropes, a continuous modelof the parachute pack pulling process is established. The results shows that the impactloading has no significant effect on the force and velocity during the parachute pack’spulling process for its low level.