Verification of Practical Use of an Inflatable Structure in Space

Abstract

An extendible mast of a space-inflatable structure was used as a scientific probe onboard the sounding rocket S-520-23 launched in September 2007. The inflatable structure extended successfully and worked well as a scientific instrument. This was Japan's first space verification of a space-inflatable structure, and the world's first use of an inflatable structure as a practical antenna. The extendible mast as an inflatable structure is called “SPINAR” (SPace INflation Actuated Rod), and it consists of an extendible rod and inflatable extension mechanisms. The rod, which is an open section tubular member, can be stored around a spool and has the advantage of structural rigidity when extended. The principle of SPINAR is similar to that of STEM (Storable Tubular Extendible Member); however, relatively reduced weight and enlarged rigidity can be achieved in SPINAR if light and rigid composite materials replace the metallic STEM rod. In addition, an inflatable thin film tube is used as the extension actuator instead of an electrical motor for weight reduction, the extension mechanisms are simplified, and the storage and drive mechanism box are downsized. The inflatable tube does not have to be rigidized because of the virtual structural rigidization concept of the outer shell structure of the rod.