TransFormers for lunar extreme environments: Large origami deployable solar reflectors

Abstract

The TransFormers for Lunar Extreme Environments Project is a NIAC study, whose purpose is to determine the design requirements for powering robotic exploration in Shackleton Crater's 70K, permanently shaded interior, using sunlight reflected from the crater's rim. An analysis of the optimum placement of two vertically collinear reflectors suggests that placement atop a 300m deployable support structure would be sufficient to provide year round illumination to points of interest in the crater below. In order to provide the 300W/m^2 of sunlight necessary for the robots to operate, each solar reflector must unfold to over 1000m^2 of reflective surface area, have over 95% long term directional reflectivity in the visible regime, and be flat within 1mm/m of deviation. Each reflector must also stow to less than 1m^3 in volume, have less than 100kg of mass, and be less than 1mm thick. Two classes of origami crease patterns have been developed that will allow a 25μm thick aluminized biaxially-oriented polyethylene terephthalate solar reflector with 95% visible reflectivity, to be stowed within a cylinder 1m tall, 1m in diameter, with a mass of 35kg, and with up to 0.71m^3 volume to spare in the center for other components. Each class of origami crease pattern can be deployed from their perimeter by an attached inflatable thermoplastic torus that heats up during deployment to maintain flexibility and cools to maintain rigidity afterward. The remainder of the 1m3^ volume will be allocated to the inflatable deployment mechanism, electronics, and the deployable support structure. In order to maintain flatness, carbon fiber fabric tapes would run along the load bearing paths opposite of the reflective surface. Simulations of an elliptic solar reflector under lunar gravity show that a single carbon fiber fabric tape 40cm wide that spans the length of the reflector is sufficient to maintain the required flatness. Future work includes simulating the deployment of the solar reflectors with their support structure, building and testing larger scale prototypes, and performing field tests in relevant environments.

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