Test Analysis of Three Dimensional Folds in Tape Springs for Space Applications

There is a requirement in the current space industry (due to recent technological advances) for small satellite, area deployment devices. Such devices are used to deploy antennae and solar arrays, and demand the usual requirements of low mass, low cost and high reliability that are needed for space missions. Due to the mass reduction of small satellite missions, new systems are required to achieve these deployed areas. Scaled down versions of existing larger mechanisms would not achieve the required performance. Therefore, these systems are specifically designed and optimised for missions with a very low total mass. There has been significant research performed into using tape springs (thin metallic strips with a curved cross section) folded to form simple but effective hinges, in such deployment systems. The advantages of tape springs are clear. They have low mass, do not require lubrication and automatically locks in the deployed configuration. The past research has focused on analysing and modelling tape springs folded in two dimensions. Applications of using tape springs folded in three dimensions have now been envisaged initiating this study which focuses on analysing the dynamics of tape springs folded in this way, using both experimental and theoretical methods. A test rig has been constructed to measure both the bending and twisting moments induced by the presence of such a fold in a tape spring. This test rig is initially used to verify the moments created from a two-dimensional fold and compare these results with existing theories. The results of the three dimensional experimental tests are then presented and compared with theoretical models. The paper is concluded by discussing the future steps and advancements required to model the deployment of an array which incorporates tape springs folded in three dimensions.