Deployable Tensegrity Structures for Space Applications

Abstract

This thesis deals with the development of deployable structures, based on the tensegrity / concept, for applications in space. / A state-of-the-art review of deployable masts and reflector antennas for space applications / is presented. A comparison is made between the various reflector antennas / in terms of deployed and stowed sizes, mass and accuracy. / The key step in the design of tensegrity structures is the form-finding analysis. / Several methods proposed for this step are scrutinised and classified into two groups, / kinematic and static methods, and the advantages and disadvantages of each method / are investigated. Two of the statical methods seems to be identical. It is concluded / that several form-finding methods are available, but no single method is suitable for / general tensegrities. The force method, for the analysis of the kinematic and static / properties of large bar frameworks, is presented. / The analysis and design of deployable tensegrity masts, with three struts per stage, / is described. A routine for the manufacturing of physical models is proposed and / evaluated. Different schemes for deployment are investigated. A way to deploy / the struts using self-deployable hinges is introduced and demonstrated by four- and / eight-stage mast models. Finally, the tensegrity mast is compared with an existing / deployable mast with respect to stiffness. The mast is relatively stiff in the axial / direction but very weak in bending. / The requirements for a deployable reflector antenna used on small satellites are / formulated. A concept, which uses a triangulated cable network to approximate / the reflecting surface, is adopted. The kinematically determinate triangulated cable / network is thoroughly analysed. The achievable surface accuracy of the net, / both to systematic errors arising from the triangular approximation of the surface / and random manufacturing errors, is evaluated. The underlying principles and the / statical and kinematical properties of the new concept are presented. A physical / model is built to analyse the feasibility of the concept and to test various deployment / schemes. The scheme using telescopic struts are identified as the most suitable / and a preliminary design an antenna, with a diameter of three metres, for a future / space mission is performed. Numerical computations show that the antenna is stiff / and extremely light.