Inflatable space structures are expected to be a promising candidate for future large scale space structures because of the lightness and compactness of the volume at the launch stage. In this paper plausibility of a inflation structure was examined utilizing the expansion force of foam materials for the inflation thrust. As a trial inflatable space structure, an sandwich-structured extension mast was chosen, i.e., made of foam materials covered with an aluminum sheet or a carbon fiber cloth, due to the simple extension mechanism. As the first report of the inflation structures, this paper describes forming behavior of urethane foam in a tube and mechanical properties of processed foam rods. The discussion was at first done with respect to the effect of tube geometry on the expansion behavior. Compressive modulus and strength were then examined. Various phenomena appearing in the forming process were pointed out and their influence to the compressive modulus and the strength were studied by use of Gibson and Ashby model.
