Post Flight Simulation of Dynamic Responses at the Satellite Interface of a Typical Launch Vehicle During Solid Motor Ignition 2024-26-0461

Launch vehicle structures in course of its flight will be subjected to dynamic forces over a range of frequencies up to 2000 Hz. These loads can be steady, transient or random in nature. The dynamic excitations like aerodynamic gust, motor oscillations and transients, sudden application of control force are capable of exciting the low frequency structural modes and cause significant responses at the interface of launch vehicle and satellite. The satellite interface responses to these low frequency excitations are estimated through Coupled Load Analysis (CLA). The analysis plays a crucial role in mission as the satellite design loads and Sine vibration test levels are defined based on this. The perquisite of CLA is to predict the responses with considerable accuracy so that the design loads are not exceeded in the flight. CLA validation is possible by simulating the flight experienced responses through the analysis. In the present study, the satellite interface responses are validated for a launch vehicle with solid motors. The source of dynamic force in solid motor is mainly the motor ignition transient. Transient response analysis is carried out using the Finite Element models of launch vehicle coupled with the satellite to simulate the responses during solid motor ignition. The required excitation is generated from the motor ignition transients measured in the flight. The criticality in the simulation is to define and model the forcing function appropriately. The responses estimated from the analysis are compared with the responses measured in the flight and observed to be in good match in both time and frequency domain. The study confirmed that the forcing functions developed from the flight measured data are adequate. The post flight simulation studies helps to improve the prediction methodology for future missions.