Water Impact Simulation Of Spacecraft Capsule And The Analysis Of Its Factors Influence

As the last step of manned space activity, the return process of spacecraft is the final mark of the success of the mission. There will be a great impact force in the process of water landing, which will do harm to the cabin, the crew and related equipment. So the study on the water impact response of spacecraft capsule is of great importance.Foreign studies on water impact problems have lasted for many years, but the FEM application in the water impact simulating of spacecraft capsule was never seen in domestic literatures. In this paper, a FEM model for water impact including capsule, water and air was developed, based on study on the FSI (Fluid structure interaction) and ALE (Arbitrary Lagrangian Eulerian) algorithm in the FEM software of Ls-Dyna. After analyzing on the parameters in the algorithms which may influence the results, the appropriate values were selected, and a series of data including water impact maximum acceleration of capsule was obtained in simulation calculation. The simulating results agreed well on different vertical impact velocities with both experimental and empirical formula results, so the model effectiveness was verified, which meaned this model could be taken as the reference for later experiments and capsule design.In this paper, it also analyzed the five conditional factors of water impact response, which were the vertical impact velocity, the horizontal impact velocity, the pitch angle, the heeling angle and the rolling angle. After three sets of perpendicular experiments, it can be concluded that only the vertical velocity was significant and their F-values sequence was obtained. If the vertical velocity and the rolling angle were fixed to constant, the pitch angle, the heeling angle and their interactive effect were significant. The rolling angle was not significant in additional experiments which were used to analyze the influence of rolling angle only.In order to get the more clear and intuitive characteristics of water impact response, two sets of full implementational experiments were carried out. The corresponding single-factor respone characteristics of the vertical velocity, the pitch angle, and the heeling angle were got, and the velocity response surface and angular response surface were drawn, from which the qualitative estimates of the maximum impact acceleration could be given. In addition, using the experimental data some regression equations were found, which could be used to quantify the estimated value of the maximum water impact acceleration.