Zero-gravity Simulation for Ground Dynamic Testing of Deployable Space Structures

"Deployable (unfolding) structures will be essential to meet weight and performance goals for a number of large spacecraft types, in spite of the risks associated with on-orbit deployment. Knowledge of dynamic properties is essential for predictingon-orbit behavior, including during deployment. Deployables present special problems in the ground dynamic testing needed to determine or verify dynamic properties. Deployables are usually large, with natural flexural frequencies as low as a few Hz.Behavior of hinges and latches often varies depending on static preloading. Both considerations imply that behavior in ground testing can be affected by the means of supporting the structure. A means is needed for supporting the test article such that itsfree-free dynamics are not altered; it must "float" in the earth's gravity like it would in space.. This must be done both during and after deployment, even though the former involves large displacements and geometry changes. After deployment, staticweight-induced loads on hinges and latches must be minimized. The proposing organization has largely solved the zero-g simulation problem for small-displacement dynamic testing of fixed-geometry structures. An extension of the technology is proposed forthe more difficult problem of accurate zero-g simulation for deployable structures with hinges and latches. The proposed development will allow high-fidelity ground dynamic testing of deployable spa