Deployment Dynamics of Foldable Thin Shell Space Structures

Abstract

This paper investigates the deployment behavior of lightweight flexible space structures consisting of thin shell components. An extensive and detailed study of a symmetrically folded structure that dynamically deploys by releasing its stored elastic energy is presented. The challenges involved with ground testing of this structure are discussed, and a suspension system that allows propagation of the elastic folds is proposed. The dynamics of two 1 m-scale structural prototypes was measured using high-speed Digital Image Correlation. It is shown that, for the tests considered, the elastic folds remain stationary and behave as elastic hinges, resulting in a symmetric and repeatable deployment. Deployment experiments in air and vacuum showed that air mass significantly affects the dynamics of the structure, slowing its deployment by 70 %. However, this effect becomes negligible if the deployable structure is not covered by a film. A finite element model of the deployment is presented. The effects of air are approximated by an added mass to the structure, calculated through simple geometric arguments. This model shows good agreement with experimental results without increasing the associated computational time.

Deployment Dynamics of Thin-Shell Space Structures

“…For the particular experiments presented in the paper, the elastic folds did not move along the longerons, behaving as nonlinear elastic hinges. In experiments with different initial locations for the elastic folds (very close to the center or to the ends of the strips), not presented in this paper but available in [10], the folds did move, although they were often constrained by the battens to remain within one bay of the structure.…”

“…The present study was motivated by the desire to develop accurate simulation models for the deployment dynamics of future deployable structures of this kind. These models have been successfully applied to deployment simulations of smallscale prototypes of a complete SSPP spacecraft [10].…”