Thermal Analysis And Thermal Control Investigation Of Deployable Shape Memory Composite Truss Structure In Orbit

The shape-memory-composite-based space intelligent developable truss structure can effectively solve the contradiction between multifunction and large size requirements of space structure with the limited load volume.It can realize in-orbit controllable deploying action under the condition of a low impact load,which has shown a prospect of wide application in the fields of space communication,manned spaceflight,earth observation,deep space exploration and so on.The thermal control technology of deployable truss structure is to control the heat transfer between the truss structure and the space environment,which makes the truss structure operating temperature be within the suitable range.The reliability of the thermal control directly influences the implement of the on-orbit deploying action of the folded shape-memory-composite-based developable truss structure.The thermal analysis,thermal control hardware and thermal test are presented in this dissertation,and the main contents and results are summarized as followings:Firstly,the calculation of exchange factor and external heat flux are the keys for the deployable truss structure thermal analysis on-orbit.The view factors among the deployable truss structure internal surface elements,the deployable truss structure surface elements,solar and earth are calculated with the new method combining the integral method,Hemicube method and Nusselt Sphere method.Then,the exchange factors are calculated according to the relationship between the exchange factor and the view factor.At last,the external heat flux is calculated according to the relationship between the external heat flux and the exchange factor.The external heat flux are set as the radiation boundary condition to solve the temperature field equation of the deployable truss structure.Secondly,the analysis of finite volume method used in the numerical simulation of temperature distribution has been performed.The element gravity method is adopted in the heat conduction calculation with finite volume technology.The calculation points are established on the gravity points and centers of boundaries.For the steady temperature calculation,the iterative method is performed to calculate the discrete equations.The Conjugate Gradient method is adopted for the linear discrete equations and the Newton-Raphson method is adopted for the non-linear discrete equations.For the transient temperature distribution simulation,the Bi-Conjugate Gradient method is adopted with different differential methods.Thirdly,thermal performance analysis for multi-layer insulation material used in space has been performed.In the investigation of the heat transfer in multi-layer insulation material used in space,several reasonable assumptions and the thermal performance analysis model are established according to the energy balance theory.A thermal performance comparison between the result calculated with the thermal performance analysis model and the thermal test result from reference literature is performed.At last,the effects of geometric parameters(containing layer density and layer number),reflective screen surface characteristic(containing surface emissivity and perforation ratio)and spacecraft out-surface temperature on the thermal performance of multi-layer insulation material used in space are discussed.Fourthly,the primary thermal control design and thermal analysis have been performed for the shape-memory-composite-based space intelligent developable truss structure.According to the structural feature and operating characteristics of the deployable truss structure,the passive and active thermal control schemes are presented.Then,the effect of with/without thermal control measures on the deployable truss structure is studied,and the on-orbit temperature distribution of the deployable truss structure under different shape(containing deployed,half-deployed and folded)is obtained in this dissertation.At last,the dynamic thermal response characteristics in the process of deploying and folding have been investigated,and the heating time and cooling time of shape-memory-composite-based tube are presented.Fifthly,four on-ground thermal tests of shape-memory-composite-based tube have been performed.The shape-memory-composite-based tube is sensitive to the temperature,which implements the action of deploying and folding based on the self-temperature control.The temperature distributions of shape-memory-composite-based tube under low temperature condition and high temperature condition are presented in this dissertation.According to the temperature results,the equivalent thermal conductivity of multi-layer insulation material is calculated and compared with the result predicted with the thermal performance analysis model.The deploying process of the folded shape-memory-composite-based tube under low temperature condition is successfully carried out.The thermal test is conducted to verify whether the thermal performance of multi-layer insulation material changed after the folding process.The results of the thermal tests is of the positive engineering values for the utilization of shape-memory-composite-based material in aerospace field and the development of the novel intelligent deployable truss structure.At last,the contents and results of this dissertation are summarized,and the future work is presented.