Solar Thermal Propulsion Investigation Activities in NAL

We successfully developed the ultra‐light single shell paraboloidal concentrators made of a sheet of aluminized or silvered polymer membrane, formed via plastic deformation due to stress relaxation under high temperature condition by means of Straight Formation Method. Furthermore, we improved the precision of the concentrators by taking the elastic deformation of residual stress into consideration, and obtained the best concentration performance equivalent to a highly precise paraboloidal glass mirror. In solar concentration, the diameter of solar focal image via the single shell polymer concentrator is almost equal to that via the glass mirror and they are twice as large as that of the theoretical. The ultra‐light single shell polymer concentrators are very useful for the concentrator in solar thermal propulsion system and solar power station in particular, and also promising item for beamed energy propulsion.