| The space telescope is the most important and direct tool for human research and exploration of the universe.It is related to the speed and process of human research on the universe.It is an important scientific mehtod for human development and progress and understanding of the natural world.Compared with ground-based telescopes,it has a good observation environment and observation conditions and is favored by astronomers.The large-aperture space mirror is the most important component of space telescope,and it is also an important factor that restricts the development of space telescope.Carrying out research on the design and manufacture of large-aperture space telescopes can solve the major bottleneck problems of space telescopes and promote the development of cosmology.It is a very meaningful research work.China's space science and technology is blocked by Europe,America and other developed countries,and independent space science research can not be separated from independent space mirror design and manufacturing technology.In view of the urgent need for large-aperture space mirrors in the course of the development of space science and technology in China,this article relies on the major innovative project of Changchun Institute of Optics,Fine Mechanics and Physics in Chinese Academy of Sciences(CIOMP),"Design and Manufacturing Technology for Large-aperture Space Mirrors",Project Number:"CIOMPCX 2014 02".On the basis of fully investigating the research results of large-aperture mirrors at home and abroad,the goal is to master the design and manufacturing technology of large-aperture space mirrors on a full-chain and systematic basis.The design and optimization of the mirror assembly structure was carried out by means of parametric design optimization method under manual intervention with large tolerance composite three-point approximately spherical hinge support.The static and dynamic simulation models based on the computer are also used in the design and optimization.The 1.5 m space mirror based on SiC has been developed and tested.The various technical indicators meet the requirements of space telescope applications,and verifies the technology of design and manufacturing 1.5 m SiC space mirror systematically.This paper mainly completed the following five aspects of research work:(1)This paper combs the design constraints of the space mirror,analyzes the design requirements of the mirror under various conditions,establishes a mechanical principle model of the space mirror support structure.Through analyzing the support requirements and support principles of the mirror.The concept of large tolerance mirror composite three-point support structure is proposed,and the extremely approximate elastic spherical hinge substructure is designed.Based on these,a complete static model and dynamic model of the mirror assembly are established,the forces of the mirror are analyzed and determined,and simulation is carried out using nastran simulation software.The calculation results are consistent with the test data obtained by the 1.5 m SiC mirror.Therefore,the model has good guidance for design optimization and test prediction.(2)The optimization method of the mirror lightweight structure design under manual intervention is proposed,and the calculating software is compiled.The software for parametering the mirror structure and UG,UG and Nastran are automatically linked by the calculating software.The semi-automated optimization design from parametric structure model to finite element model is realized,which greatly improves the efficiency and accuracy of the lightweight structure design of the mirror,and lays a foundation for ensuring the development quality and cycle of the 1.5 m aperture mirror.Manual intervention makes the whole design optimization process perfect,solves the problem of pathological solution output,and eliminates the outputs of poor processing technology.This method and software were used to optimize the lightweight design of a 1.5 m SiC mirror under traditional process.After optimization,the weight of the mirror was 155.6 kg,the lightweight rate reached82.9%,and the areal density was 88.1 Kg/m~2.The lightweight mirror shows good stiffness and stability in the subsequent development and test.Each performance parameter meets the actual needs of the space telescope.The method and software were used to further optimize the lightweight design of the 1.5 m SiC mirror under the new process.The weight of the mirror was reduced from 155.6 kg to 56.1 kg,the lightweight rate was increased to 93.8%,and the areal density was 31.7 Kg/m~2.The mirror performance has reached the leading domestic and international advanced level.(3)Very similar to the design of elastic spherical hinge sub-structure,making the actual developed mirror very close to the physical model,the designed structure is as expected.This structure makes the space mirror has a strong immunity to thermal stress,assembly stress and other external stresses.Based on this structure,the stress and strain can not be transmitted to the mirror,and the surface precision of the mirror is better than 1/60?RMS(?=632.8 nm)before and after the assembly,which satisfies the requirements of the optical design.The application of the spherical hinge pair can realize the assembly work after the space mirror is coated,so it can further reduce the weight of the main support structure on the back of the mirror and increase the lightweight rate of the mirror assembly.At the same time,it also reduces the requirements of assembly accuracy and machining precision,so that the mirror can be developed quickly and efficiently,and the cost and cycle are reduced.(4)The 1.5m SiC space mirror was designed and developed,and the lightweight rate of the mirror was 82.9%,and the mass was 155.6 kg.The surface precision was better than0.016?RMS(?=632.8 nm),which can be reduced less than 0.002?due to the environment.The mirror assembly with an assembly error of 0.02 mm can also meet with the optical need,and the mirror assembly(including the main structure)has a first-order frequency of 101.3Hz.By testing,it is verified that its technical indexes meet the demand of space telescope.and the feasibility and task satisfaction of the technology was verified through the whole process development of the 1.5 m aperture SiC space mirror.which verified the effectiveness and feasibility of the technical solutions for the design and manufacture of large aperture space mirror.The following innovative results have been achieved:(1)This paper presented the parameterized design and optimization method for the lightweight structure of the mirror under artificial intervention,then developed a software,in which parametric structure model and finite element model are linked together,to achieve the semi-automated optimization design for space mirror.Artificial intervention made the whole design and optimization process perfect,solved the problem of pathological solution output,and eliminated the output results of poor processing technology.The parameterized design and optimization method greatly improved the efficiency and accuracy of the structure design of space mirror,which guaranteed the quality and development cycle of large aperture space mirror.(2)The concept of high tolerance mirror support structure was proposed.This concept greatly reduced the machining precision of the support structure of the mirror,therefore the requirements for structure assembly and the assistant equipment were reduced greatly.At the same time,the high tolerance support structure has a low sensitivity of the external strain and stress changes.Results and technical indicators show that,the surface accuracy of the 1.5 m SiC mirror is stable,and well adapt to force and heat.It meet the design expectations and the mission requirements of the space telescope.(3)The actual development results of extreme approximate elastic spherical hinge,is pretty close to the physical model.And the concept of high tolerance mirror support is achieved.This structure made the space mirror have strong immunity to thermal stress,assembly stress,and other external stresses.The application of the spherical hinge achieved the mechanical alignment after the space mirror is coated,and the carbon fiber which has high specific stiffness,can be used.Therefore,the weight of the main support structure can be further reduced,and the rate of assembly lightweight can be improved.At the same time,the application of the spherical hinge also reduces the requirements for assembly accuracy and machining precision,allowing the mirror to be rapidly and efficiently developed,then reduce the cost of development and shorten the developing cycle.(4)According to the existing technical level and industrial capability of China,the design and manufacturing technology of large aperture space mirror is explored systematically in a full-chain way.1.5 m diameter space mirror independent research and development capability is achieved.This technology is of reference to the development of larger aperture space telescope in China.It provides a priori experience for the future research of segmented mirror for deployable system.Meanwhile,this technology provides technical support for commercial remote sensing in China and has high commercial value. |
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