Ultra-lightweight Mirror Research Articles

Ultra-lightweight mirrors with high solar reflectivity and high infrared emissivity for sun-facing radiative thermal management in space.

We report the design, fabrication, and characterization of ultralight coatings that employ Salisbury screen principles and the unique nature of ITO to achieve frequency selective broadband emissivity. Our coating comprises 60 nm SiO2, 10 nm ITO, 2.3 µm NeXolv LaRC CP1 polyimide and 300 nm Ag, and achieves an aerial mass of 4.07 gm-2. It has a calculated and measured visible spectrum reflectivity of R = 0.893 and R = 0.896 respectively when weighted against AM0 from 300 nm to 1800nm; and a calculated and measured IR spectrum emissivity of e = 0.574 and e = 0.554 weighted against a 300 K blackbody respectively. This simple coating design, fabricated on the centimeter scale, achieves broadband frequency selectivity, with the highest reported thermal performance for an ultralight sun-facing radiative energy management structure.

Surface Figuring of Large Carbon Fiber Reinforced Polymer Antenna Reflector with A Dual-robots Fabrication System

Carbon Fiber Reinforced Polymer (CFRP) has excellent physical and chemical properties which make it a promising material in making large space borne components, especially in making antenna reflectors and ultra-lightweight space mirrors. These components are usually in large scale to achieve the application requirements. In this research, a dual-robots fabrication system was in-house developed to meet the requirement for figuring a large off-axis parabolic CFRP antenna reflector with the size of 2.4m×4.58m. To make sure that whole surface of the antenna reflector could be covered by the fabrication system, the surface was divided into six regions to accomplish the fabrication. In addition, a special designed tool was utilized to adapt to the curvature variation of the surface. The final surface form accuracies obtained for areas ≤φ1750mm, ≤φ2400mm and the whole surface of the antenna reflector were 13.5μm RMS, 23.4μm RMS and 45.8μm RMS, respectively. Feasibility and surface figuring accuracy of the dual-robots system in fabricating large scale components were verified.

Optimizing design and manufacturability of reduced-weight mirrors for astronomy and space applications

The following are the most important phases in the development and optimization of ultralightweight mirrors: materials selection, determination of the type of cells to be used in the weight-reduction structure, and determining the parameters of these cells. Optimizing the mirror design via a calculation using the finite-element method enables us to optimize the parameters of the cells used in the weight-reduction structure in order to achieve maximum structural rigidity at minimum mass. The variable parameters are as follows: Thickness of working surface, size and shape of cells in the weight-reduction structure, and rib thickness.

超轻量化SiC反射镜的制备及性能

超轻量化SiC反射镜的制备及性能

Development of Silicon Carbide Substrates for Aerospace Applications

ABSTRACTPayload and high-tech are important characteristics when the goals are aerospace applications. The development of the technologies associated to these applications has interests that transcend national boundaries and are of strategic importance to the nations. Ultra lightweight mirrors, supports and structures for optical systems are important part of this subject. This paper reports the development of SiC substrates, obtained by pressing, to be applied on embedded precision reflective optics. Different SiC granulometries, having YAG as sintering additive, were processed by: ball milling, drying and deagglomeration, sift, uniaxial and isostatic pressing, and, finally, argon atmosphere sintering at 1900°C. Different porosities were obtained according to the amount of organic material added. Into one side of the samples pellets of organic material were introduced to generate voids to reduce the weight of samples as a whole. The substrates were grinding and polished, looking for a SiC surface having low porosity, as porosity is directly related to light scattering that should be avoided on optical surfaces. Laser surface treatments were applied (using or not SiC barbotine) as a method to improve the surface quality. The samples were characterized by optical and laser confocal microscopy, roughness measurements and mechanical tests. The results are very promissory for future applications.

Φ510 mm SiC超轻量化反射镜的设计与有限元分析

To develop a Φ510 mm SiC ultra-lightweight mirror,this paper proposes an ultra-lightweight structure with a section in ship form,an internal structure in regular-triangle,and a face plate reinforced with regular-hexagon.When the design weight is 1.85 kg,the structure performance is compared with those of other two lightweight structures with the same weight by adjusting all structure parameters.It is shown that in the same 6 point supportings on mirror backs,this ultra-lightweight structure owns absolute advantages in the gravitational deformation of mirror surface(RMS) as comparing with other two structures when the optical axis is pointed to the zenith.Furthermore,Patran\Nastran finite element software is used to simulate and calculate the gravitational deformation of the mirror surface when the axis is pointed to the horizon,and its thermodynamic and dynamical characteristics are analyzed.The results present that all performance indexes of this ultra-lightweight mirror meet requirements of applications.Finally,according to the design,a mirror blank with a weight about 2.2 kg and surface density about 10.8 kg/m2 is fabricated.With excellent performance, it has been up to the today's advanced level in the SiC ultra-lightweight mirror field.

宇宙望遠鏡用C/C複合材料軽量反射鏡の開発

宇宙望遠鏡用C/C複合材料軽量反射鏡の開発

Ultra-Lightweight Design and Analysis of a 1.25m SiC Segmented Mirror

In order to explore the feasibility of large ultra-lightweight deployable optical systems, a 1.25m SiC segmented mirror is investigated. According to analysis and comparison, the mirror's material, ultra-lightweight structure pattern and support location are determined respectively. By FEM, an ultra-lightweight structure with areal density of 40kg/m2 is gotten. The results show that the self-weight deformation is 4.8nm RMS/22.6nm PV under supports, and the ultra-lightweight mirror has the enough strength to bear the stress at launch. The study may provide a technical scheme to develop the large ultra-lightweight deployable optical system.

Ultra light-weight and high-resolution X-ray mirrors using DRIE and X-ray LIGA techniques for space X-ray telescopes

We are developing novel ultra light-weight and high-resolution X-ray micro pore optics for space X-ray telescopes. In our method, curvilinear micro pore structures are firstly fabricated by silicon deep reactive ion etching (DRIE) or X-ray LIGA processes. Secondly, side walls of the micro structures are smoothed by magnetic field assisted finishing and/or hydrogen annealing techniques for high reflectivity mirrors. Thirdly, to focus parallel X-ray lights from astronomical objects, these structures are elastically or plastically bent into a spherical shape. Fourthly, the bent structures are stacked to form a multi-stage X-ray telescope. In this paper, we report on fabrication and X-ray reflection tests of silicon and nickel X-ray mirrors using the DRIE and LIGA processes, respectively. For the first time, X-ray reflections were confirmed on both of the mirrors. Estimated rms roughnesses were 5 nm and 3 nm for the silicon and nickel mirrors, respectively.

Hybrid linear microactuators and their control models for mirror shape correction

Future space-based imaging systems demand ultra-lightweight mirrors, which would involve a large number of actuators to provide the needed surface correction. These lightweight actuators are required to be integrated with the mirrors to avoid a significant increase in overall areal mass density. This paper presents the fabrication and testing of a linear microactuator and the modeling of an actuated mirror composed of such lightweight actuators. The linear microactuator is driven by a combination of a piezoelectric actuator block and electrostatic comb drive units. A full nonlinear optimization model of a mirror lattice was developed to simulate a lightweight primary with embedded microactuators, which allows for an arbitrarily connected lattice with connector elements having an arbitrary stiffness and actuation response. The modeling yielded a high precision estimation of the mirror shape correction.

407 大型SiCミラーのELID研削(OS-12 ELID加工)

Silicon carbide (SiC) is the most advantageous as the material of various telescope mirrors, because SiC has high stiffness, high thermal conductivity, low thermal expansion and low density. Therefore, we developed the ultra lightweight mirror by ELID grinding method which can obtain the surfaces of very hard materials efficiently. If a mirror becomes large, shape of the mirror becomes complicated, and thickness of the mirror surface and a lib part becomes thin for lightweight. Accordingly, it is thought that surface roughness of the mirror deteriorates by influence of vibration. And then, to improve the precision of the surface roughness, we did the ELID grinding by cross cut that the axis of rotation and a progress direction of a grinding wheel were vertical.

Optical Fabrication of a Large Lightweight Mirror of Unusual Shape

A large, ultralightweight Cer-Vit mirror of oblong shape has been optically polished to a surface irregularity of 0.060 rms, where = 0.633 urn. Although its major dimension is 193 cm, its finished weight is only 97 kg. The nonconventional fabrication methods required by its light weight, unusual aperture shape, relatively steep curvature, and excep tionally large diameter-to-thickness ratio are described. A 64-point fluid piston mount employed to support the mirror both for optical fabrication and for interferometric test ing is also described. Techniques specially developed to produce both the mirror blank and the final optical surface demonstrate significant advances in the manufacture of large, very lightweight glassy mirrors of high optical quality.