Deployable structures : concepts and analysis

 S.D. Guest

Abstract:

Deployable structures are structures which can fold, either for transportation or for storage. The main application of deployable structures is for use in space. Launch vehicles are limited in size, while large structures are required for many current and proposed uses of space. Because of the high cost of failures, however, the space industry is conservative in its use of deployable structures. This dissertation is an attempt to inject new ideas into the field of deployable structures.

Three concepts for deployable structures are presented. Two of the concepts are new, a generic class of foldable cylinders, and a new solid surface deployable reflector. The third concept is an old idea for folding a membrane, which has been re-analysed and extended. Some analysis is done for each of these concepts to prove their viability.

Foldable cylinders are triangulated cylinders which fold axially into a compact stack of plates. The concept of foldable cylinders is introduced, and a geometric approach to their folding is pursued. This provides valuable insights into the folding process. Folding is also modelled computationally, which explains the behaviour observed during experiments. A number of these cylinders have been manufactured and tested.

Folding a membrane by wrapping it around a central hub was first proposed in the 1960s. Most recently it has been suggested as a method of folding a space-sail. Previous work on this concept is reviewed, and a new analysis of the fold pattern is presented. This corrects a number of errors in previous work, and suggests ways in which the concept can be extended.

A solid surface deployable antenna is presented. This is a new method of folding an antenna, suggested by the wrapping fold pattern. It improves on previous concepts. as it both shows a large reduction in size when folded, and requires no complex mechanical components. The folding of the antenna is modelled with a new technique, using dual quaternions to represent rigid body displacements. This analysis is used to optimise the design of the antenna to minimise deformation during folding. A simple proof of concept model of the antenna has been manufactured and tested.

Keywords: Deployable structure, Deployable antenna, Folding, Membrane Folding, Finite Displacements, Finite rotations, Quaternions.