Description: Current manned and unmanned spacecraft require sophisticated thermal control technologies to keep systems at temperatures within their proper operating ranges. Future manned and unmanned missions to the moon, mars, and other destinations will require new technologies to maintain spacecraft temperature near a set-point while under variable heat loads and thermal environments under increasingly stringent size, weight and power constraints. Passive components that can assist with this goal can greatly extend and expand NASA mission capabilities. Physical Sciences Inc. proposes to develop a passive thermal skin with set-point temperature control using phase-change-material nanofilms. Our innovation will allow for simultaneous control of the visible reflectivity and the infrared emissivity of the spacecraft, causing the craft to reflect sunlight and radiate heat when hot, and absorb sunlight and become non-emissive when cold. By simultaneously optimizing both the visible and infrared optical properties, a turn-down ratio (TDR) of 18:1 is ultimately achievable.

Benefits: The proposed passive skin can significantly reduce the SWaP of spacecraft thermal control systems. For manned missions, the set-point can be near room temperature to reduce the work required by active thermal management components, removing the need for dual-loop thermal control systems. For unmanned missions, the passive skin can be designed such that the temperature set-point is at either the high or low end of the operating range of the craft electronics, depending on the various requirements, heat loads and thermal environments of the mission. Our innovation directly addresses the need within NASA Technology Roadmap Area 14; specifically 14.2.3.7 (Variable Emissivity Radiator), which has been called out as a need for NASA's planned, crewed Asteroid Redirect Mission (ARM), and more generally, NASA's preparation to send a crewed spacecraft to Mars.

The passive set-point thermal control skin (TCS) has potential applications on commercial satellites. Satellites orbiting the earth, when in direct sunlight, have some of their surfaces receiving solar radiation, while the other surfaces only see deep space. As the satellite warms and heat is distributed throughout the satellite, more of the TCS enters its "emissive" state, improving the self-cooling ability of the satellite. PSI's TCS would maximize the passive cooling ability of these satellites, freeing up power for other satellite functionality.