A Flexible, Self-Regulating PTC Heater for Extreme Environments

Thin-film resistive heaters are widely used for maintaining optimal temperature ranges for critical components within satellites and other spaceborne systems. Propellant tanks and lines, active mechanisms such as valves and deployment features, as well as sensitive electronics including batteries benefit from integration with these units. Their widespread use stems from their high reliability in extreme temperature and radiation environments, relatively low cost, and lightweight, flexible construction, which allows installation on sharply-curved or irregular surfaces. These heaters are typically paired with redundant temperature sensors and onboard controllers to actively maintain thermal circuits. While this approach is effective, use of active controllers requiring feedback and onboard computation increases complexity of integration. Passively self-regulating heaters, requiring no active control, are available commercially and are used in various land-based industries; however, these units are packaged within stiff and bulky cables, highly unsuitable for the needs of the aerospace industry. In this context, a particular need has emerged for passively self-regulating heaters that have a thin form factor and are flexible, reliable, and tolerant of conditions found in space. To meet this challenge, Creare proposes collaborating with the University of Southern California (USC) to develop the first thin-film positive temperature coefficient (PTC) heaters qualified for use in extreme environments.In Phase I, we will select, develop, and evaluate a test matrix of thin-film heaters based on earlier demonstrated prototypes, aimed at providing increased resistance to extreme environmental conditions. Although the baseline geometry and materials may be robust to the relatively small temperature range of interest (-40şC to 70şC) and have limited cross-section to gamma radiation, tests in Phase I will establish performance characteristics and will inform the need for further design changes. In parallel, we will carry out testing of samples to evaluate susceptibility of these initial prototypes to ionizing radiation (up to 1 Mrad) and thermal cycling. Finally, with the most suitable candidate heater identified, we will conduct a demonstration involving one or more self-regulating heaters attached to a simulated propellant tank with outflow lines, to evaluate the overall approach in representative conditions. In Phase II, we will conduct additional manufacturing process optimization and refinement with USC, work towards scale-up of production with manufacturing partners, and carry out field testing of the developed flexible heaters for advanced aerospace applications with integrators.