Thin Film, Variable Reflectance Materials for Solar Sail Control

Physical Sciences Inc. proposes to develop electrochromic devices which controllably and reversibly change their solar reflectance for applications as solar sail control surfaces. The devices will be very thin, and consume power only during reflectance change. They will be deposited directly onto the thin solar sail material, typically alumiminized PET. The variable reflectance materials (VRMs) will be applied to a fraction (<20%) of the solar sail surface, on areas near corners or outer edges, so that sail attitude control torques are generated with small forces due to reflectance modulation. VRMs will only slightly increase solar sail mass, < 5% for a 5 g/m2 sail, while potentially eliminating greater mass associate with mechanical and thruster systems, and increasing reliability. In Phase I, we will design and fabricate VRMs on solar sail substrates and measure their reflectance modulation performance. We will conduct preliminary space compatibility tests, and with General Astronautics (Mr. Jerome Wright), evaluate the applicability of VRMs for solar sail spacecraft missions. In Phase II, a prototype large area sail with integrated VRMs and thin-film microelectronics will be developed for delivery to NASA. Phase III will involve flight validation of variable reflectance sails and commercial development of VRMs as thermal control films.