Sun Shields for the Next Generation Space Telescope

A report discusses the design of inflatable Sun shields proposed for use in keeping the primary mirror of the Next generation Space Telescope (NGST) at a temperature "d60 K. The report summarizes a paper presented at the 33rd Intersociety Energy Conversion Engineering Conference in August 1998 at Colorado Springs, Colorado. The proposed shields would include six parallel layers of thin aluminized polyimide film separated by gaps wide enough to ensure against contact. The layers would be radiatively isolated from each other. The proposed shields would weigh 247 kg less than those of an older proposed design involving multilayer insulation with 10 inner layers, or 388 kg less than those of another older proposed design involving multilayer insulation with 18 inner layers. Relative to the shields of both older designs, the proposed shields would also offer advantages of simplification of packaging, simplification of mechanical structure, and less dependence of telescope temperature on a poorly adherent thermal coating on the Sun side of the outer shield layer.