28th International Conference on Adaptive Structures and Technologies, Krakow, Poland, 8 - 11 October 2017, pp.1-14
Spacecraft having extended configurations must be stowed compactly for launch, with final stiffness adequate to maintain shape and stability under dynamic disturbances. This research focuses on deployable towers, one-dimensional beam-like structures comprising a lightweight, structurally-efficient assemblage of finer-scale structural members. In particular, tensegrity structures are considered for their potential to provide a new kind of deployable boom for space applications. Tensegrity structures (or "tensegrities") comprise a self-equilibrating assemblage of 1-D compression members (strut) and tension members (tendons or cables) connected via frictionless ball joints at member ends (nodes). Tensegrities can also carry external loads efficiently. In a classical tensegrity structure, struts are connected only to cables; however, in a generalization of the concept, struts can meet at nodes, and can be classified based on the maximum number of struts connected at a single node. A primary concern regarding the use of classical "Class-" tensegrity structures for space applications is inferior stiffness, due mainly to the small cross sectional areas of tendons. Structural stiffness can be increased by allowing strut-to-strut connections, but this decreases packaging efficiency. We investigate a deployment concept for a cylindrical tensegrity tower that culminates in a Class-2 tensegrity having higher stiffness. Deployment of a representative Class-2 tensegrity tower comprising pairs of mirror-image triplex configurations is illustrated, and compared to that of an analogous Class-1 tower. Strut lengths are fixed and deployment is achieved via active actuation of cable lengths. For the same strut lengths, a Class-1 tower exhibits a lower minimum height, while the Class-2 tower exhibits a higher maximum height, along with higher stiffness. We generalize the approach to n-strut cylindrical tensegrity towers. Such deployable tensegrity towers which exhibit both high packaging efficiency and high deployed stiffness have great potential for use in space structures and other applications.