Thermoelastic Deflections of Thin-Shell Composite Space Structures

Abstract

As space structures become larger, lighter, and deployable, thermal deflections induced by sunlight become a significant source of structural inaccuracy and even spacecraft vibration. Studying these deflections is notoriously difficult: analytical solutions rapidly become intractable, experiments under vacuum and cooling are low-visibility and expensive, and multiphysics finite-element simulations are computationally demanding and usually don’t account for coupled thermo-structural analyses and/or changing radiation view factors.

This work demonstrates key improvements in experimental methods and thermo-structural simulation of these thermal deflections. First, simultaneous full-field measurements of structural temperatures and deflections are achieved by constructing and using a custom vacuum chamber and heating setup; significant thermal gradients and repeatable thermal deformations are measured and analyzed, forming a ground truth for succeeding simulations. Second, multiphysics models of the experimental chamber are created in COMSOL Multiphysics and characterized, even accounting for residual convection, and used to inform prototype improvements and more advanced simulations. Third, based off such predictions, the unit structure prototype composite is improved by adding a layer of graphitized polymer film, with further experimentation showing a dramatic reduction in deflections.

Finally, the accumulated knowledge is used to simulate a satellite slew maneuver with realistic orbital heating; a custom technique to couple thermal (Thermal Desktop) and structural (Abaqus) finite-element software via a MATLAB script allows for the recalculation of radiation view factors during simulations, a feat necessary for accurate heating calculations on deployable structures. These results have immediate applicability in predicting structural temperatures and deflections during the satellite maneuvers proposed for the Caltech Space Solar Power Project, as well as suggesting critical improvements to ensure reliability and mission success.