Electrochromic Thermal Stabilization of Large Deployable Structures

Solar sails use a thin reflecting membrane to deflect sunlight, converting the momentum of solar photons striking the sail to a means of spacecraft propulsion. The trajectory of the sail-powered spacecraft may be controlled by through a mechanical arrangement or through the use of an electrochromic material that changes reflectivity or transmittance in response to the application of an electric potential. In Phase I of this effort, Eclipse Energy Systems, Inc. has demonstrated both reflective and transparent all-solid-state electrochromic membranes (EMs) built on 100cm2 flexible PET films. The reflective EMs demonstrated acceptable performance after cyclic potentiostatic tests in vacuum. The Phase II program concentrates on the development of 100cm2 VEMs built on 7 to 10 micron polymer films that can achieve a reflectance/transmittance modulation ranging from 10 to 75 %. Scale-up to fabrication of reflective EMs having 900cm2 (1? x 1?) active area will be also demonstrated in the Phase II program. EMs will be subjected to cyclic potentiostatic tests in vacuum as well as long-term exposure to ultraviolet radiation in order to demonstrate feasibility of use in orbit-to-space missions.