Lightweight structure design of 2m large aperture primary mirror

With the continuous improvement of optical system imaging quality requirements in astronomy, aerospace engineering, laser technology and other fields, in order to capture lighter objects and improve image resolution, the size of the mirror is getting larger and larger. Therefore, to meet various usage scenarios and operational constraints, the lightweight design of large mirrors has become an important research focus. In this paper, the lightweight structure design of the primary mirror of the 2.0m large aperture mirror system is studied in terms of the lightweight form of the mirror back and the shape of the lightweight hole. With the increase in the size of the primary mirror, the traditional material will no longer be able to ensure a good surface shape, so high-strength, low-density silicon carbide (SiC) is used as the main mirror body material. To achieve a high lightweight rate and maintain high internal stiffness, the simulation examined triangular, fan-shaped, and rectangular lightweight holes on the back of the primary mirror to determine the most stable form. In addition, this paper also compares the full-open and semi-closed lightweight forms. Finally, the semi-closed triangular lightweight back structure was used, and the displacement deformation and mirror profile accuracy of the 2m large aperture mirror under X, Y and Z gravity conditions were checked by the finite element analysis software Hypermesh and Patran. The final mass of the 2m mirror main mirror structure is reduced by 78%, and the surface profile (RMS) achieves 𝜆/40.