Dynamics Modelling of Ultra-light and Cable-Harnessed Space Structures: Theory and Experimental Validation

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The high costs to launch satellite systems have been a major motivation for much lighter space structures’ designs. In this regard, inflatable gossamer technology offers interesting designs for lightweight, stow-able satellites that can be compressed into folded stacks of a few inches of thickness during launch before deployed over hundreds of feet in space. This ultra-light technology can offer promising solution for placing large metrology systems in space with improved coverage while meeting the launch volume and mass goals. While prized for their light designs, the dynamic behaviour of inflatable structures can be significantly impacted due to additional components such as space flight cables. The cables to payload mass ratio can be up to 20% in a traditional space structure; this number will increase significantly for inflatable structures due to much smaller weights. Additionally, flight program tests have shown that the complexities in dynamic behaviour of space structures are magnified when structural elements are harnessed with signal and power cables. This problem has also been identified by the US Air Force Research Lab/VSSV to impose major issues in vibrations modeling and verification of the satellite systems and their ground-based pre-launch tests. On the other hand, high flexibility, small mass, and high bandwidth controllers required for inflatable space missions mandate the need for accurate models to predict higher-order dynamics of these structures. This is particularly important for larger structures, as they cannot be fully tested prior to launch. Therefore, a major objective of the proposed research pertains to studying the dynamic effects of space flight cables on inflatable rigidizable structures and their major components such as inflatable rigidizable composite booms. This research builds on the previous research by the applicant to develop novel analytical models based on homogenization techniques and combined dynamical systems approaches to better understand the dynamic interactions between the host structures and the harnessing cables. The research is also aimed at the development of reduced-order models with significantly smaller computational time and increased ability to incorporate low-order vibrations control algorithms. Characterization of damping through the development of distributed parameter models, nonlinearities in a structure’s dynamic response due to the addition of the space flight cables, investigation of possible frequency dependent dynamics of these structure and experimental model validations present some of the novel aspects and short/long-term goals of the proposed research program. Additionally, part of the proposed research will focus on a continuation of the research by the applicant on shape control of inflatable membrane structures to improve their surface accuracy for antenna applications.