Study of Correlation Criteria for Spacecraft-Launch Vehicle Coupled Loads Analysis

In spacecraft structural verification, Coupled Loads Analyses (CLAs) use Finite Element Models (FEMs) of the spacecraft and launch vehicle to predict flight loads. It is therefore essential that the spacecraft FEMs to be used in these CLAs are first validated through comparison with test measured data. This study has been conducted in order to assess the metrics/criteria used to quantify the level of correlation between the analytical model and physical spacecraft test structure. To explore this, both baseline spacecraft FEM and altered versions (generated by introducing errors to the baseline) have been subjected to the same loading scenarios. Differences in response between the baseline and ‘perturbed’ models have been observed. Various correlation criteria, such as modal assurance criteria and cross-orthogonality checks, and a lesser-known comparison of base forces, have been applied to quantify the level of correlation between each altered model and its corresponding baseline FEM. The results indicate that the more popular modal vector correlation methods may not be the most effective at predicting the level of error in peak displacement responses, and that the base force criteria, known as BFAC, may be more sensitive to changes in these responses.