A document proposes that light-weight, deployable, large- aperture, controllable curved mirrors made of reflectively coated thin electroactive-polymer (EAP) films be developed for use in spaceborne microwave and optical systems. In these mirrors, the EAP films would serve as both structures and actuators. EAPs that are potentially suit- able for such use include piezoelectric, electrostrictive, ferroelectric, and di-electric polymers. These materials exhibit strains proportional to the squares of applied electric fields. Utilizing this phenomenon, a curved mirror according to the proposal could be made from a flat film, upon which a nonuniform electrostatic potential (decreasing from the center toward the edge) would be imposed to obtain a required curvature. The effect would be analogous to that of an old-fashioned metalworking practice in which a flat metal sheet is made into a bowl by hammering it repeatedly, the frequency of hammer blows decreasing with distance from the center. In operation, the nonuniform electrostatic potential could be imposed by use of an electron gun. Calculations have shown that by use of a single-layer film made of a currently available EAP, it would be possible to control the focal length of a 2m-diameter mirror from infinity to 1.25 m.
This work was done by Xiaoqi Bao,Yoseph Bar-Cohen, and Stewart Sherrit of Caltech for NASA 's Jet Propulsion Laboratory. NPO-40275.
This Brief includes a Technical Support Package (TSP).
Controllable Curved Mirrors Made From Single-Layer EAP Films
(reference NPO40275) is currently available for download from the TSP library.
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Overview
The document is a Technical Support Package from NASA's Jet Propulsion Laboratory (JPL) detailing the development of controllable mirrors made from single-layer electroactive polymer (EAP) films. These thin-film mirrors are designed for large aperture, lightweight optical systems and microwave antennas, particularly for use in microgravity environments. The ability to control the surface shape of these deployable structures is crucial, as it must be refined to a precision of sub-microns for optical applications.
EAPs are highlighted as promising materials for creating these mirrors due to their unique properties. They can be produced in thin film form with electrodes on their surfaces, allowing for the potential to achieve mirror finishes depending on the reflectivity of the electrodes and the surface roughness of the polymer. The document proposes a controllable mirror design using a single-layer EAP, presenting an analytical solution for the voltage distribution required to form a parabolic mirror from a planar film. Calculations indicate that such a mirror can adjust its focus distance from infinity to 1.25 meters, demonstrating the versatility and capability of EAP materials in this application.
The research was conducted under a contract with NASA and the Defense Advanced Research Projects Agency (DARPA), emphasizing its significance in advancing aerospace technology. The document also references various studies and models related to the control and precision of mirrors, showcasing the collaborative efforts in this field.
In summary, the document outlines the innovative use of electroactive polymers in creating controllable mirrors for space applications, detailing the technical aspects of their design and functionality. It serves as a resource for understanding the potential of EAPs in aerospace technology and encourages further exploration of their applications in both scientific and commercial domains. For additional information, the document provides access to NASA's Scientific and Technical Information (STI) Program Office, highlighting the ongoing commitment to disseminating aerospace-related developments.
