Heliostat with Adjustable Flatness Control

grabcad

This mobile heliostat uses a spring-tempered stainless-steel sheet for its mirror.In the stored state, the mirror is rolled into a large diameter coil. This puts potential energy into the material. Cables connected to brake-motors hold this position. The generous large curvature of the coil allows the mirror and its structural “tape springs” to stay coiled while remaining well above the material yield points. Said another way, the "spring" free state of the mirror (which is extended and slightly concave) is maintained, and the amount of stress relaxation occurring during storage time is managed.The deployment of the mirror is a slow and controlled “un-furling” towards the mirror’s free state. Cables connected to rotary dampers, are let out by brake motors to provide this controlled motion. The free, or natural, state of the mirror is slightly concave, which ensures the cables are always in tension during and after deployment.When deployment is complete, the cable system provides control and fine-tuning of the mirror's "shape". The mirror can be made perfectly flat, or, it can be made slightly concave or convex which would allow focusing or dispersion of the reflected light if desired. After shape adjustments are made, spring-loaded brakes "lock in" the position of the cables and the brake-motors are powered off. This is for the sake of energy efficiency, ensuring that energy is no longer consumed after tuning is complete.This system provides many benefits over hinged panel and inflatable designs because it is simple, robust, and allows active control over the flatness of the entire mirror. Fabrication tolerances, stress relaxation, creep, thermal expansion, damage, etc., in hinged joint could render a heliostat system inoperable, because all panels would not be perfectly flat to each other. Similarly, inflatable designs risk losing gas pressure due to permeation through bulk material, imperfect seals, degradation caused by solar radiation, or damage from micrometeorites. Pressure loss in an inflatable structure would cause the system to “sag” and lose its shape which would render the entire system non-functional – patching and recharging with new compressed air is difficult in space. The proposed design manages environmental risks well because it is robust and adaptable, it can physically stand up to the large variety of hazards and abuse which it is likely to encounter in space.The structural support for the mirror is provided b...