Variational Coupled Loads Analyses: Reducing Risk in Development of Space-Flight Hardware

摘要

Before space hardware can be launched, positive structural margins of safety must be demonstrated relative to the booster-supplied math model and forcing functions. To identify appropriate structural loads on which to base such margins, several iterations of coupled loads analyses are typically performed during hardware development. Such analyses are traditionally done with a single payload dynamic math model, derived from finite element models, which are combined to form a booster/payload system-level model. Uncertainty in such analyses, relative to both the hardware's final configuration and its modes of vibration, is most often addressed with uncertainty factors selected without any insight into actual loads sensitivity. With recent advances, the analysis process has been accelerated, allowing for variational coupled loads analyses. Such an analysis can account for possible variations in the final hardware configuration: for example, frequency, weight, presence of comanifested payloads, damping, etc. The results of such a variational analysis are presented. The results demonstrate that the use of uncertainty factors can greatly penalize much of the structure with overly conservative load criterion, while at the same time being unconservative for those structural elements most sensitive to the variations. The conclusion is that the utilization of variational coupled loads analyses can result in both reduced risk and more efficient structural designs.