Numerical study on shock generation and propagation on satellite due to pyrotechnic devices

Abstract

Various kinds of pyrotechnic devices such as explosive bolts, jet cord, pin pushers etc. are used in aerospace structure during many space missions. During their operation, these devices generate pyrotechnic shock which have very strong acceleration level at high frequency and can fail the mission equipment installed on the structure. Therefore, the estimation of shock response induced by these pyrotechnic devices has become essential work for success of the corresponding space program. In the present study, a clamp band system with an explosive bolt that separates the satellite from the launch vehicle is considered. Numerical programs like Ansys-Explicit Dynamics and AUTODYN are jointly utilized to analyze the shock generation and Statistical Energy Analysis (SEA) along with Virtual Mode Synthesis (VMS) methods are applied to predict the shock propagation during satellite separation. Explicit Dynamics and AUTODYN are explicit code program for highly nonlinear dynamic problem which focuses on transient dynamic wave propagation like gases, liquid and solids and their interaction. SEA in the other hand employs a statistical description of the structural parameters in which frequency and spatial averaged frequency response functions are adopted and subsequently used for the input of VMS to calculate structural responses in time domain.

In this thesis, pressure type bolt which is used in clamp band system is modeled using Explicit Dynamics and AUTODYN is employed to perform the behavior analysis. Several gauge points are set in bolt and also in the part of clamp band to measure the acceleration time history and then the shock response spectrum (SRS). Results from experiment conducted previously by several researchers are used to validate the numerical analysis. Then, a satellite structure comprised of 24 subsystems is modeled in SEA with various assumed loss factor. The results obtained are evaluated and several conclusions are drawn.