Optimization design of an ultralight large-aperture space mirror

Abstract

The ultralight space mirror has long been a hot topic in the research field of space telescopes. In this paper, an ultralight mirror is designed by obtaining the structure and parameters of a mirror with an aperture of 2 m through experimental design and multiobjective integrated optimization. Specifically, the materials near the neutral surface were replaced with elliptical holes. The back of the mirror was supported at three points. Finite-element analysis shows that the mirror had a surface figure error of 10.4 nm under 1 g in the x direction (gravity direction), which is sufficiently high to be applied to visible light optical systems. Further, the eigenfrequencies of mirror components were obtained through finite-element analysis: 70 Hz in the x direction, 70 Hz in the y direction, and 90 Hz in the z direction. The results demonstrate the excellent dynamics performance of the designed mirror. Compared with test results, the relative error of eigenfrequencies was within 4%. Hence, our ultralight design outputs reliable optimization results and applies to the development of large-aperture ultralight space mirrors. Finally, the ultralight mirror was prepared from reaction-bonded silicon carbide. The mass and surface density of the prepared mirror were 105 kg and 34 k g / m 2 , respectively. The mirror mass was 50% lighter than that of the mirrors designed by traditional lightweight methods.

The Optimization Design of a Lightweight 2 m SiC Mirror for Ground-Based Telescopes

“…Space-based mirrors thus offer a higher lightweight rate owing to launch weight constraints. For instance, the areal density of the 3.5 m Herschel PM is 25 kg/m² [11] and that of the 2 m ultralight space mirror is 34 kg/m² [15]. By contrast, the areal densities of the 2 m and 4 m SiC PM produced by CIOMP for ground-based telescopes are 105 kg/m² and 120 kg/m², respectively [6,12].…”

“…Zhai et al conducted a lightweight design for a 2.02 m SiC mirror using parameter optimization, resulting in a model weight of 228 kg [14]. Wang et al employed structural and parametric optimization to develop a 2 m ultralight SiC mirror weighing only 105 kg with an areal density of 34 kg/m 2 [15]. Topology optimization seeks to attain the most optimal structural topology, while parameter optimization aims to determine the optimal dimensions of a given structure.…”