Structural design and testing of carbon fiber composite primary-secondary mirror connecting cylinder for large-aperture coaxial space camera

In large-aperture coaxial space cameras, the relative positional accuracy between the primary and secondary mirrors is crucial for ensuring the imaging quality. Therefore, the design of the connecting structure between the primary and secondary mirrors is a key part of the camera's structural design. The space camera studied in this paper has an aperture of 1.6 meters. To meet the requirements of large aperture, high stability, and high lightweight performance of the camera, a thin-walled carbon fiber composite connecting cylinder for the primary and secondary mirrors was designed and developed. Several structural materials were compared, and Carbon Fiber Reinforced Polymer(CFRP) was chosen. Next, making full use of the designability of carbon fiber composite layering, the layering design of the connecting cylinder for the primary and secondary mirrors was carried out, and finite element analysis was conducted simultaneously.The finite element simulation results show that: The lateral fundamental frequency of the connecting cylinder is greater than 50Hz, and the axial fundamental frequency is greater than 100Hz; When the optical axis is horizontal, the displacement of the secondary mirror relative to the primary mirror caused by gravity is less than 0.05mm, and the tilt is less than 20 arcseconds; The axial CTE is 0.28×10⁻⁶ ℃⁻¹. Subsequently, the molding and manufacturing process of the thin-walled carbon fiber connecting cylinder was introduced. Finally, through the qualification-level mechanical tests of the camera, the rationality of the structural design of the connecting cylinder for the primary and secondary mirrors was verified.