Optimized Gore/Seam Cable Actuated Shape Control of Gossamer Membrane Reflectors

This investigation explores the feasibility of using an active gore/seam cable-based control system to reduce global root mean square figure errors due to thermal loading and inflation effects (W error) in large, gossamer, inflatable membrane reflectors. Analysis is performed on an inflated spherical membrane with polyvinylidene-fluorideactuated radial cables, for which the cable lengths and attachment points are designed via genetic algorithm optimization. It is found that through proper tailoring of the cable lengths, significant global root mean square figure-error reduction is achieved. Specifically, root mean square errors due to on-orbit thermal loading were reduced by approximately 75% with a 104-cable active gore/seam cable-control system that has a mass equal to 15% the original reflector. Similarly, W errors were reduced by approximately 95% with a 104-gore/seam cable-control system with a mass ratio of 12 %. Finally, to deal with simultaneous W error and thermal loading with uncertain relative magnitudes, a hybrid gore/seam cable-control configuration based on a combination of independently optimized thermal and W-error cable patterns is considered. By adjusting the weights of a hybrid objective function, the gore/ seam cable-control system demonstrated robust shape-control performance for combined loading conditions. Because of the relatively lightweight designs and shape-control effectiveness, the gore/seam cable-shape-control concept seems promising for future gossamer reflector applications.