Stochastic launcher-satellite coupled dynamic analysis

The design and verification of spacecrafts such as satellites is supported by the results of coupled loads analyses. Herein the finite element models of the launcher and the spacecraft are typically substructured and reduced, for example, with the Craig-Bampton method, and then coupled and analyzed under various load cases occurring during launch. Inherent random uncertainties, affecting virtually all facets of the model, are traditionally dealt with by means of safety factors, with the drawback that the degree of conservatism remains unquantified. The present paper reports on a systematic, full-scale uncertainty analysis of the spacecraft-launcher assembly. Because of its versatility and its insensitivity on the number of uncertain parameters, direct Monte Carlo-simulation has been used. Uncertainties in the launcher, in the spacecraft, and in the loading environment are considered separately. This allows for conclusions on the relative impact of the uncertainties on the response. The results encompass a transient load case (liftoff) and a frequency response load case (end-of-booster oscillation) and reveal that the response is particularly sensitive to uncertainties in the launcher properties, whereas the uncertainties in the loading have almost negligible impact.