A Novel Cross-strip Flexural Mounting-design For Large Rectangular Space-borne Mirror

Space-borne optical remote sensors have played an important role in the fields of resource monitoring,military reconnaissance,weather forecasting and space exploration,and have become a symbol of national economic and technological comprehensive strength.In order to meet people needs,high resolution,large field of view and light weight have become the inevitable development trends of space optical remote sensors.Mirrors are more sensitive to structural stress,thermal stress,etc.,so designing a more reasonable mirror lightweight structure and seeking a flexible support with better performance have become the current technical difficulties.This paper is of great significance to the design and research of the lightweight structure of the reflector and the flexible support of the new cross-strip.The large rectangular space mirror is the main component of an off-axis threemirror（TMA）optical system,and the surface figure accuracy of the long space mirror assembly is the main factor affecting the imaging quality of the space optical remote sensor.The large-size long space mirror assembly in this paper should meet the following requirements: the mass of the mirror is less than 28 kg,the first-order natural frequency of the mirror assembly is greater than 150 Hz,the surface figure of the mirror assembly under gravity,and temperature rise of 5°C should be.In X,Y,Z three directions RMS≤λ/50（λ=632.8nm）.In this paper,the domestic and foreign current status of large reflector and flexible support is briefly introduced first,and the development trend of flexible support and the significance of research topics are summarized;The commonly used optimization methods are expounded surface figure evaluation criterion.Secondly,in order to solve the problem of the material and configuration of the large-scale long mirror,the specific stiffness,density and thermal stability of the material are described in detail,and finally RB-Si C is selected as the mirror material;by comparing the mirrors with different structures,semi-closed and three-point support is chosen as the initial structure of the mirror;Hyper Study is used to perform multiobjective optimization of the mirror,and finally the lightweight structure of the mirror is determined,with a lightweight rate of 86%.Then,a new type of cross-strip flexural mounting structure is proposed,and the second Castigliano theorem is used as a design method to study it,its axial stiffness and rotational stiffness are deduced,and the key dimensions of the cross-strip flexible support are determined;The maximum error between the theoretical value,simulation value and experimental value is 8.6%,which verifies the feasibility of this method and the cause of the error are analyzed.Finally,the opto-mechanical integration analysis and dynamic test of the large rectangular space mirror are carried out.The analysis shows that the first natural frequency of the large rectangular space mirror is greater than 150 Hz,and the RMS of the mirror under 1G gravity in the X and Y directions is 4.49 nm and 10 nm,better thanλ/50（λ=632.8nm）.The maximum deviation between the dynamic test results and the finite element analysis results is within 10%,which verifies the accuracy of the finite element analysis,and verifies that the large rectangular space mirror has good structural dynamic performance and reasonable structural design.