A novel method to correlate a rocket launcher finite element model using experimental modal test measurements and identification algorithms

Abstract

The structural dynamics of a launcher system used to guide the initial trajectory of target test missiles is considered. Launcher induced body rates alter the trajectories of target vehicles at egress which can detrimentally affect the successful execution of flight test missions. As a result, flight mission analysts must have the capability to accurately reproduce the dynamic response of the launcher system to evaluate its effect on launch vehicle egress. Accurately reproducing this response requires a high fidelity finite element model that is correlated to modal survey test data. An experimental modal survey of a modified Nike-Hercules launch system is conducted and modal parameters are determined using conventional and output-only methodologies. A model correlation procedure is proposed and utilized that incorporates these experimentally determined modal parameters in conjunction with a set of correlation criteria to improve the accuracy of a high-fidelity launcher finite element model. After several iterations of the model correlation procedure, the model is able to accurately reproduce the dominant dynamic behaviors observed in the modal survey tests, especially at the key location of the launcher tip. This approach provides a basis for future launcher simulation and modeling efforts.