| Tethered satellites,originating in Europe and America,recently innovated for space probe,have become a prominent tool in scientific studies of space.Tether is the key component of tethered satellite,so its research is of great significance to the study of tethered satellite.This dissertation engages in theoretical and experimental research on tether material and structure,and designs an electrodynamic tether with corrosion and impact resistance for tether satellites in LEO.In view of the conductor without plastic deformation,the maximum diameter of the tether was obtained under pure bending through theoretical analysis and calculation method.The geometry of the flexible conductor was explored to determine the tether conductor material.Three kinds of tether materials: UHMWPE,Kevlar and polyimide fiber were selected as candidate materials for the strength of the tether.The reactivities of the mechanical properties of these three materials under AO or UV radiation were explored through the ground-based simulation experiment for space environment.The experimental results show that both AO and UV radiation flaw the polymer materials,leading to the degradation of the mechanical properties of the polymer material.Among the three materials,the reactivity of UHMWPE to atomic oxygen was the largest.The maximum tensile load of UHMWPE decreased by 31.73% when it goes through 420 h equivalent space time;The moisture of Kevlar fiber is highest and this kind of material is not resistant to UV radiation.The maximum tensile load decreased by 9.39% after 420ESH;Polyimide fiber has the lowest reactivity to AO and a strong ability to resist UV radiation so that its mechanical properties remain stable after 420 ESH.The research put forward a design strategy of the tether structure including a metal conductor,an insulation layer,a fiber strength member and an outer protective sleeve.It investigated the bending rigidity of helical conductor structure and its maximum stress under pure bending.The tether structure were determined according to the result of mechanical properties tests and ground-based simulation experiment for space environment on tether material.Finally,the feasibility experiments of the tether were carried out for each member,including conductivity,tensile strength and protection on strength member from space environment.The results showed that the tether structure proposed by this paper can meet the basic requirements on conductivity,mechanical properties and environmental stress for tether satellites in LEO. |
