Electro-thermo-mechanical modelling of micro solar sails of chip scale spacecraft in space

Abstract

This paper presents a novel design of micro solar sails for emerging lightweight chip scale spacecraft based on flexible electronic circuits. To acquire large deformation, the micro solar sails were designed to be bilayer beams that were able to be electro-thermally actuated by Joule heating. The concept design of the solar sail with high area-to-mass ratios allowed the solar sailing system, named as ChipSail, for efficient orbital transfer and attitude adjustment. The principle of solar sailing with ChipSail was illustrated, and the thickness of the two metals for the bilayer sails should be no more than 1 µm, so as to achieve the efficient solar sailing. Then, the fabrication and characterization of such bilayer microstructures for solar sails were introduced briefly. After that, the electro-thermal analysis of such solar sails deployed on the low earth orbit was carried out, and it was found that the balanced temperature of the sails under the effect of solar radiation and thermal reemission of the sails was 315.31 K, followed by electro-thermal modelling of the sails under the Joule heating. A nonlinear second order differential equation was derived, which allowed rapid prediction of the thermal distribution across the sail. Equivalence of the bilayer solar sail to a width-changing 980 µm long bilayer beam was proposed and validated by finite element analysis. Finally, the thermo-mechanical model on the bilayer sail was then established and solved numerically. Results showed that the maximum bending angle could reach to 94.05º by applying a voltage of 0.05 V across the sail. The electro-thermo-mechanical model laid a solid foundation for dynamic control of the configuration of the ChipSail for efficient orbital transfer and attitude adjustment in space.