Research On Transient Response Analysis Methods Of Satellite Structure Under Pyrotechnic Shock

There are commonly many different types of pyrotechnic devices in the satellite structure for the separation of structure subsystems, the deblocking of extension pieces, and the start on certain working parts, and it is also in the satellite-launcher separation that they are used. When the pyrotechnic devices work, they can produce severe pyrotechnic shock load, which causes the failure of many flight hardware, even a catastrophic failure. The common failure which is caused by the pyrotechnic shock includes the hard faults due to design factors or process defects, the flutter of relay switch, deformation of small and lightweight structure, and the short circuit caused by a conductive pollution ion in chamber that the pollution particles’ shift in parts leads to. On the other hand, it is rare that the main structure’s deformation or damage caused by explosion shock, unless in the area close to the shock source a structure’s damage may be produced. For this reason, it is necessary for satellite structure to analyze the transient response under the pyrotechnic shock in the process of developing a satellite, and to estimate correctly the shock environment’s influence on key components, which will help us take the right measures for protection.The most two commonly methods used in transient response analysis in the time domain are the Direct Integration Method and Modal Superposition Method. In this paper, the main work is to built the finite element model of satellite structure based on the Hypermesh platform and to convert the shock response spectrum(SRS) in the frequency domain in engineering using inverse discrete Fourier transformation(DFT) into an acceleration-time signal that can be input as an effect load in transient response analysis, and to calculate and draw acceleration-time response curves and acceleration-frequency response spectrum curves with the MSC Nastran solver using respectively by Direct Integration Method and Modal Superposition Method. Then we could analyze the advantages and disadvantages of two methods through comparing calculation results and analyze the possible factors influencing the results of the two computing methods.Comparing the Direct Integration Method and Modal Superposition Method, we can conclude that the advantages of direct integral method are that it can solve numerical solutions directly on the discrete time domain without ignoring the high frequency signal; The disadvantage is that the large amount of calculation is evitable time-costing, and its poor reliability on calculating results after a long time solving. When enough stimulated high modes of system and proper truncated mode range are selected, Modal Superposition Method can shorten calculation time dramatically and save resources if we adjust appropriate time step, which can be used when we need to understand response for a long time. But the disadvantages of Modal Superposition Method are also apparent, system eigenvalue must be solved first before coordinate transformation, which tend to ignore high stimulated frequency mode. Thus, Modal Superposition Method applies only to a linear system while is difficult to the analysis of nonlinear dynamics problem. In conclusion, Direct Integration Method is relatively appropriate and more reliable for the multiple DOF satellite structure analyzed in this paper which contains transient response analysis of short-time duration, high frequency signal of explosion impact load.