Propagation of Elastic Folds in the Deployment of 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.