Numerical simulation of fragment generation from satellite breakup

A numerical method for simulating fragment generation from satellite breakup is proposed and the impact case relevant with the test is simulated.Currently HVI numerical simu-lation technique is mainly used in spacecraft protective structure analysis.And the most widely used method is SPH.In this paper,the complete disintegration of spacecraft will not occur be-cause of the small size of the impactor.Protective structure HVI simulation focuses on the pene-tration limit of the shield while the individual fragment characteristics in the secondary debris cloud are not concerned much about,such as:amount of fragments,size and mass of each frag-ment,etc.In contrast,the purpose of spacecraft breakup model is to provide the characteristics of individual fragment,which are also supposed to be the output of breakup dynamics simulation. Finite element reconstruction method is a hybrid of finite element method and the smoothed par-ticle hydrodynamics method.The characteristics of the individual fragments can be obtained from the simulation.The confidence individual fragment can be identified by reconstructing finite ele-ments from the smoothed particles.The size,velocity vector,and mass can be computed with the fragment statistics method based on graph theory.The fragment distribution can be obtained from the individual fragment data.The good agreement of simulated output and the test shows the feasibility of this method.The main difference between NASA model output and test data lies in the smaller size range.The possible reason might be the test for building NASA model is dif-ferent from the test of CARDC.The main data source for small fragment part in NASA model is SOCITE4 breakup test.The target used in the test is OSCAR satellite which has a more compact internal structure.It indicates that the material and internal structure do affect the distribution of breakup fragments,and it is necessary to analyze the fragment based on the impact dynamics.Finite el-ement reconstruction approach can model the spacecraft and the impactor in details including the shape,internal structure,material feature,impact velocity magnitude and direction,and also im-pact location.The simulation can provide the total number of fragments and the mass,size,ve-locity vectors of each fragment.With high resolution simulation model,the approach can output characteristics of small fragments.Further work aims at two aspects.First,the effect of the im-pact location to the breakup fragments distribution will be analyzed with the simulation approach,especially for large impactors.Different impact locations in the target will result in various debris characteristics,for example:the velocity direction,and then the orbit,of fragments.Second, the simulation approach will be applied to historical on-orbit breakup events.SSN data of frag-ments larger than 10cm could be used as a reference to verify the approach and to calibrate the true impact location which can not be observed.The disintegration process reproduced with the simulation and fragments smaller than 10cm can also be analyzed.The fragment output of FER can be directly imported into an orbit propagator to analyze the orbit distribution and lifetime of each fragment and so on.