Active and Passive Cable Elements in Deployable/Retractable Masts

Abstract

This paper describes a new type of deployable masts for use in Space, based on the following elements. A deployable backbone, consisting of rods and/or plates, which can be folded or deployed freely. One or more active cable, following specially chosen routes along the mast, and running over small pulleys. The overall length of an active cable can vary between two extremes: a maximum length when the mast is fully folded; a minimum length when the mast is fully deployed. A set of passive cables joining pairs of points on the backbone. The passive cables are all slack when the backbone is partially folded and become taut when it is fully extended. A final, essential ingredient is structural prestress in the deployed state, so that all of the cables are in a state of pretension and therefore are able to carry any tensile or compressive force changes induced by external loads. An additional effect of this state of prestress is to remove backlash at the joints. Three deployable masts based on this approach are presented in the paper.