在轨建造中的关键力学问题
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摘要
在轨建造是指在空间轨道或者地外天体上就地取材或者利用携带的材料、组件通过加工、组装形成航天器及其部组件的过程.由于无需经历发射段苛刻的力学环境,不受运载火箭整流罩空间的限制,因此,在轨建造能够有效降低航天器结构的重量,实现百米甚至千米级空间设施的建设.本文首先分析了在轨建造的技术优势和航天领域的工程需求.其次,分析了空间微重力、高真空和极端温度环境下加工过程中材料的受力和运动行为,以及对制件特性的影响;再次,分析了空间超大型结构在轨建造全过程的激励和扰动源、动力学分析与控制的力学问题;最后,梳理了面向在轨建造的空间大型结构设计的力学约束,给出多级空间桁架结构在轨建造的优化设计模型.
On-orbit construction is an space mission to construct spacecraft and modules on spatial orbits or objects outside the Earth, which would be manufactured and assembled with the local or carry-on materials. Since it is not necessary to undergo the severe mechanical environment during the rocket launching and not constrained by the limit room in rocket dome, on-orbit construction can reduce the weight of the spacecraft effectively and complete the construction of ultralarge space facility in hundreds or even thousands meters. It shows the tremendous potential for human space exploration. However, some challenging mechanical factors need to be considered for this exciting plan. In this paper some key mechanical problems were discussed about the concept and process of on-orbit construction with the complete concept on demand, material requirements, space environment, dynamics, and mechanical constrains. The technical advantages and the practical demand are introduced for the on-orbit construction in the aerospace engineering. And the methodology on material processing were proposed. Some unique chareacteristics of space enviroment were considered,e.g. microgravity, high vacuum and extrame temperature conditions, along with the change on physical properties. The material property is fundamental and challenging for the construction. Furthermore, the dynamic analysis and control strategy were analyzed in all fabricating process for ultra-lage structures. The possilbe exciters and source of fluctuation were discussed. At last, the mechanical constrains were clarified for large space sturcture in on-obrit construction. And a two steps optimization model was defined for structure topology and construction path. Some suggestions were given on the key mechanical problems in the field of on-orbit construction.
On-orbit construction is an space mission to construct spacecraft and modules on spatial orbits or objects outside the Earth, which would be manufactured and assembled with the local or carry-on materials. Since it is not necessary to undergo the severe mechanical environment during the rocket launching and not constrained by the limit room in rocket dome, on-orbit construction can reduce the weight of the spacecraft effectively and complete the construction of ultralarge space facility in hundreds or even thousands meters. It shows the tremendous potential for human space exploration. However, some challenging mechanical factors need to be considered for this exciting plan. In this paper some key mechanical problems were discussed about the concept and process of on-orbit construction with the complete concept on demand, material requirements, space environment, dynamics, and mechanical constrains. The technical advantages and the practical demand are introduced for the on-orbit construction in the aerospace engineering. And the methodology on material processing were proposed. Some unique chareacteristics of space enviroment were considered,e.g. microgravity, high vacuum and extrame temperature conditions, along with the change on physical properties. The material property is fundamental and challenging for the construction. Furthermore, the dynamic analysis and control strategy were analyzed in all fabricating process for ultra-lage structures. The possilbe exciters and source of fluctuation were discussed. At last, the mechanical constrains were clarified for large space sturcture in on-obrit construction. And a two steps optimization model was defined for structure topology and construction path. Some suggestions were given on the key mechanical problems in the field of on-orbit construction.
引文
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1)Hoyt R, Cushing J, Slostad J. SpiderFab~(TM):Process for on-orbitconstruction of kilometer-scale apertures[EB/OL].[2016-12-01]. http://www.nasa.gov/directorates/spacetech/niac/2012_phase_I_fellows_hoyt_spiderfab.html#.VyBroyws8jA
2 Ma X F,Li Y,Xiao Y,et al.Development and tendency of large space deployable antenna reflector(in Chinese).Space Electron Tech,2018,2:16-26[马小飞,李洋,肖勇,等.大型空间可展开天线反射器研究现状与展望.空间电子技术,2018,2:16-26]
3 Xu H B,Han X Z,Chen Y,et al.Discussion on the on-orbit construction technology of space large load platform(in Chinese).Space Electron Tech,2018,2:42-48[许焕宾,韩修柱,陈燕,等.空间大型载荷平台在轨构建技术探讨.空间电子技术,2018,2:42-48]
4 Davis G L,Tanimoto R L.Mechanical development of antenna systems.In:Imbriale W A,ed.Spaceborne Antennas for Planetary Exploration.Hoboken:John Wiley&Sons,Inc.,2006.425-454
5 Wang G.Structure optimization design of large-scale space antenna deployable truss(in Chinese).Dissertation for Master Degree.Xi’an:Northwestern Polytechnical University,2006[王刚.大型空间天线伸展臂的结构优化设计.硕士学位论文.西安:西北工业大学,2006]
6 Yu C,Zhang C B,Chen Y P,et al.Spreading of droplet on a rough solid surface(in Chinese).J Eng Thermophys,2014,1:145-147[于程,张程宾,陈永平,等.液滴在粗糙固体表面上的铺展特性研究.工程热物理学报,2014,1:145-147]
7 Crockett R,Petersen D,Cooper K.Fused deposition modeling in microgravity.In:Proceedings of the 1999 Solid Freeform Fabrication Symposium,1999.671-678
8 Snyder M,Dunn J,Gonzalez E.Effects of microgravity on extrusion based additive manufacturing.In:AIAA SPACE 2013 Conference and Exposition,2013.AIAA 2013-5439
9 Taminger K M B,Hafley R A.Electron beam freeform fabrication:A rapid metal deposition process.In:Proceedings of the 3rd Annual Automotive Composites Conference,2003.9-10
10 Lin S Y,Hoffman E K.Modeling of distortion and residual stress control in unitized 2219 aluminum stiffened structure produced by electron beam free form fabrication.In:AeroMat Conference 2007,June 25-28,2007,Baltimore Convention Center,Baltimore,Maryland,USA
11 Hu H Y,Tian Q,Zhang W,et al.Nonlinear dynamics and control of large deployable space structures composed of trusses and meshes(in Chinese).Adv Mech,2013,43:390-414[胡海岩,田强,张伟,等.大型网架式可展开空间结构的非线性动力学与控制.力学进展,2013,43:390-414]
12 Hoyt R.SpiderFab:An architecture for self-fabricating space systems.In:AIAA SPACE 2013 Conference and Exposition,2013.AIAA 2013-5509
13 Rozvany G I N.A critical review of established methods of structural topology optimization.Struct Multidisc Optim,2009,37:217-237
14 Sigmund O,Maute K.Topology optimization approaches.Struct Multidisc Optim,2013,48:1031-1055
15 Deaton J D,Grandhi R V.A survey of structural and multidisciplinary continuum topology optimization:Post 2000.Struct Multidisc Optim,2014,49:1-38
16 Liu S,Li Q,Chen W,et al.An identification method for enclosed voids restriction in manufacturability design for additive manufacturing structures.Front Mech Eng,2015,10:126-137
17 Andrei N.Continuous Nonlinear Optimization for Engineering Applications in GAMS Technology.Cham:Springer,2017.415-435
18 Svanberg K.A class of globally convergent optimization methods based on conservative convex separable approximations.SIAM J Optim,2002,12:555-573
1)Hoyt R, Cushing J, Slostad J. SpiderFab~(TM):Process for on-orbitconstruction of kilometer-scale apertures[EB/OL].[2016-12-01]. http://www.nasa.gov/directorates/spacetech/niac/2012_phase_I_fellows_hoyt_spiderfab.html#.VyBroyws8jA