Gravity unloading of a very large spaceborne monolithic SiC mirror

We formulated a gravity unloading strategy for a monolithic silicon carbide (SiC) mirror with a 403 m aperture in space. Employing the finite element analysis (FEA) technique, a rapid solution analytical approach for determining optimal support forces during gravity unloading is introduced. This method demonstrates enhanced efficiency and accuracy compared to conventional approaches. A quantitative evaluation methodology for the gravity release error, grounded in the minimum -energy mode, is delineated. The adverse impacts could be expeditiously computed by assessing the maximum deflection of minimum -energy modes generated by various errors. The analytical findings revealed that compliance with the stipulated gravity release error criterion of less than 6 nm (root -meansquare) necessitated the gravity unloading force error to fall within the range of +/- 0.1 N. Additionally, the gravity unloading support position error was required to be within 400.5 mm, and the measurement error pertaining to the rib thickness of the actual mirror blank had to be within +/- 0.02 mm. (c) 2024 Optica Publishing Group