Two-dimensional deployable truss structures for space applications

Two types of two-dimensional deployable truss structures are introduced: 1) a variable-length diagonal member (VLD) truss that can be folded by elongation for some members and 2) a sliding-hinge double-fold (SHDF) truss that can be folded by sliding some hinge assemblies. These concepts are compared to existing concepts of folding by the elongation of some members (Vought double fold or VDF) or by sliding some hinge assemblies (Vought biaxial double fold or BADF). The number of mechanisms to be actuated and locked at the deployment of VLD and SHDF is approximately half that of VDF and BADF, respectively. The packaging efficiency of the newly introduced truss is almost the same as that of BADF and is superior to VDF in the case of the basic configuration. Necessary conditions for the trusses to be folded/deployed are formulated and the design flexibility of each concept in forming a globally curved surface is investigated. VDF and VLD are shown to have relatively large flexibility, while SHDF has the least flexibility of the four concepts. However, a numerical example demonstrates that SHDF still has sufficient design flexibility to form a parabolic surface of acceptable accuracy. Functional models of the new concepts are fabricated for trial and deploy/retract tests demonstrate the practicality of the concepts.