Characteristic Analsis Of Water Impact Simulations Of Spacecraft Capsule

Dynamic loads are transient loads (≤500ms) which are most likely to occurduring launch, pad or launch abort, and landing. The impact force will have a greatereffect on the cabin, the crewmembers and related equipment. During spacefli ght,crewmembers and equipment are at risk of injury or damage due to poorly protection.Several extrinsic factors affect the risk of injury including: the structure of spacecraft,the design of the seat and restraint system, as well as the spacesuit and h elmet. Whilethe vehicle design is highly correlated with the landing field (sea landing field or landlanding field), the spacecraft that can land on landing field safely may suffer the riskof destruction in the water environment. Because of the restrict ion of spacecraft size,test condition of equipment and high testing cost, little test data can be collected,either ground experiment or simulation analysis is aimed for specific conditions,rarely used for statistical analysis. Therefore, the statistical analysis of water impactresponse characteristic for spacecraft capsule has important significance.Firstly, as using the commercial software of LS-DYNA, through studying thefluid-structure interaction algorithm, this paper established the finite element (FE)model of spacecraft capsule consisting of three parts: the capsule, a volume of air anda volume of water, analyzes the characteristic of water impact response and splashstate. Since the impact environment of spacecraft capsule is uncertainty, thi s paperused4parameters (horizontal velocity, longitudinal velocity, capsule pitch and waveslope) for simulation and selected three nodes of capsule mark as the seat of astronaut.After simulation the impact acceleration curve of the capsule, pressure w ave curveand other meaningful can be successfully obtained. The simulating results consistentwell with the empirical formula results in the maximum impact acceleration index, sothe effectiveness of the model was proved.Secondly, This paper analysis the effect of various parameters on the waterimpact acceleration. Through orthogonal test method, the effect of horizontal velocity,longitudinal velocity, especial for pitch angle and wave slope on the impactacceleration is studied. Then discussed the effects of wave slope and enter velocity onthe impact acceleration. Results reveal that due to the elastic deformation when thecapsule structure hits the water and perturbs the fluid, the peak acceleration of thepoint where capsule firstly contacts the water increases significantly. With theexpansion of the wet surface, peak point of the acceleration changes mainly occurred at the place where the jet flow generates. Also, this paper focus on studying theeffects of enter velocity pitch angle and wave slope on the impact acceleration. In thesame condition, the less the longitudinal velocity is the smaller the acceleration of thecapsule is and when the pitch angle is27degree the acceleration is the smallest.Finally, in order to get a clearer and more intuitive response characteristics ofcapsule impacting water, the impact acceleration is changed into the DRI Index(NASA emergency escape standard evaluation system) for statistical analysis. DRIcan effectively reflect the acceleration amplitude and the length of time. Hence it ismore reasonable and effective than using acceleration value to assess the rate ofhuman injury. The study points out that the vertical velocity and wave slope are moresensitive and have more significant influence on DRI values. Combined withstatistical, this paper also presents contour of the DRI(x) of d2crewmember, whichprovides a valid reference to assess the value of DRI for each impact environment.