Fabrication of thin film concentrators for solar thermal propulsion applications

Development of Solar Powered Rocket Engine systems depends heavily on demonstrating the technology for lightweight space-deployable solar concentrators. Large elliptically-shaped thin film reflectors can be packaged with other solar-powered propulsion elements and deployed in low earth orbit. A significant step in demonstrating the feasibility of fabricating large lightweight deployable concentrators has been accomplished. Thin film casting and coating techniques for fabricating thin film concentrators have been demonstrated. These techniques have significant promise for extrapolation to large highly accurate concentrators. The concentrators achieve a low weight/area ratio and high concentration ratio by utilization of spin casting and subsequent creep and/or relaxation forming processes. These processes use newly developed polyimide materials supplied by Langley Research Center (LaRC). This paper will summarize continuing research to develop methods to fabricate parabolic thin film membranes. The research has included selecting candidate thin film materials through a materials testing and evaluation program. Reflector fabrication and forming techniques were evaluated. Analytical models to represent forming techniques were developed. Thin film polyimide membranes using the selected techniques were fabricated. The facilities and equipment for constructing the spin cast concentrators are also presented.