Experimental Investigations to Support a Multi-Layer Deployable Membrane Structure for Space Antennae

Abstract

This paper presents an investigation into the properties of membrane structures for space-based antenna applications. Various experimental activities that have been undertaken at the early phase of development of a multi-layer, deployable membrane structure are outlined. The membranes described here are prototypes for the development of a possible on-orbit flight experiment in thin structure deployment, where such an experiment addresses necessary questions related to the use of this technology for membrane synthetic aperture radar. The shape of the membrane surface in its deployed state was selected based on optimized equations that determined which planar membrane shape would distribute the tension of the structural boundary evenly throughout the deployed surface. A campaign to measure the variations in membrane flatness in response to thermal input was carried out for a single membrane layer. The results of these flatness experiments contained significant temporal variation, which prompted an investigation of material creep in the membrane material. Concurrently, the microplasticity of the membrane material was also investigated experimentally, in order to be able to better predict the flatness variations which would result from the stowage of the structure prior to deployment. Two types of thin material film were considered for the membrane structure, due to significant differences in their dielectric properties and the reaction of the materials to atomic oxygen. Experimental results are reported for structures made of each of these materials whenever possible. It is expected that the stowage and deployment method, as well as the tensioning system for the multi-layer membrane once deployed, will depend on the results of these investigations of fundamental properties.