Based On The Structure Design Of The Expandable Space Telescope With Spring

The space camera is equipped to microsatellite to capture high-resolution images in space,which has important influence on social,economic,scientific research,military,and other fields.In recent years,the rapid development of microsatellites puts higher requirements on the weight and launch volume of space cameras.To solve this problem,the deployable space telescope with a compact size,light weight,high-resolution has become a research hotspot in the field of space in the world.Several deployable structures have been proposed at home and abroad to solve this problem.Space deployable telescope has been used extensively in the space field.Based on the theme of compact]size and light weight,the realization of a prototype deployable space telescope based on tape springs is finished in this paper.The deployable telescope is composed of primary mirror assembly,secondary mirror assembly,6 foldable tape springs to support the secondary mirror assembly,deployable baffle,aft optic components,and a set of lock-released devices based on shape memory alloy,etc.This kind of telescope can be folded during the launch phase to reduce the volume and the quality,and after entering the working track,it can be deployed to work.According to the requirements of Cassegrain's optical system and optical parameters,this paper has completed a structural design of a space deployable telescope based on foldable tape springs.The finite element analysis of the designed expandable telescope was carried out,and the ground experiment was performed on the fabricated telescope prototype,including the repetitive deployment precision test and modal test.First,the Cassegrain optical system and the optical parameters of the telescope were proposed,and the structural design of the telescope's secondary mirror deployable mechanism was introduced.The deployable mechanism with the spring secondary mirror can be deployed and folded,and the secondary mirror deployable mechanism can be locked and released by the lock-released device.The telescope can be folded during the launch phase.After arriving at a given working track,it will be deployed to allow the secondary mirror to reach a given position to work.The structure and function of each part of the secondary mirror deployable structure are introduced in detail;Based on the deployable hood with spring,two kinds of deployable hoods with different structures are proposed.According to the requirements of the optical parameters,the structure of the light blocking ring is calculated and designed so that the hood has a good ability to eliminate stray light.The software of stray light analysis was used to analyze the PST values of the two structures.A hood with good extinction ability was selected as the predetermined scheme.The quality of the structure was improved,and the shading cloth was used to instead of the sleeve to reduce the quality.The expandable telescope support and the connection to the camera are designed so that the telescope can be successfully connected and assembled as a single unit.It can be fixed to the electric turntable through the the support frame so as to facilitate ground-based experiments on the telescope.Secondly,using software of the finite element analysis to perform modal analysis on the deployable hood and the secondary mirror deployable mechanism,and analyze the dynamic performance of the structure to get the first six modes.Through the sixth-order modal map structure,the first six major mode shapes can be better reflected,and the theoretical modal analysis results provide a theoretical basis for experimental modal analysis to evaluate the structural characteristics better.Again,then the deployment errors of the secondary mirror are measured with three-coordinate measuring machine to examine the alignment accuracy between the primary mirror and the deployed secondary mirror.the maximum translation error is 0.097mm,and the maximum rotation error around x,y axes is 0.032°.The maximum rotation error around z axis is 0.057°.The impact of the deployable error on the telescope image is negligible;Perform modal experiments on deployable telescope prototype.The indentified first two frequencies are 95.41 Hz and 97.41 Hz.The experimental results were compared with the finite element analysis.The results were consistent.Finally,the research content and results of this paper are systematically summarized,and the shortcomings of this space deployable telescope and research directions of future are proposed.