条带式太阳帆的结构动力学分析

依靠光压推进,太阳帆被认为是最可行的星际探测航天器,太阳帆结构总体方案主要有两类:桅杆式和旋转式,其中,帆膜被分割成窄条的条带式太阳帆在桅杆式太阳帆中具有较为理想的结构效率,如何准确计算条带式太阳帆的结构动力学特性值得研究.本文对条带式太阳帆结构的振动特性和结构稳定性进行研究,将太阳帆看作是由若干个桅杆–膜带组件依次连接而成的整体结构,桅杆–膜带组件由4根桅杆段和4条薄膜条带组成,分段轴压作用下的桅杆与薄膜条带耦合振动.考虑帆面薄膜条带与支撑桅杆之间的耦合振动,采用分布传递函数法建立了的条带式太阳帆的结构动力学模型,推导了条带式太阳帆结构自由振动和失稳载荷的求解方法.研究表明:条带式太阳帆构型有利于提高太阳帆结构的整体刚度和结构稳定性,随着帆面薄膜条带数目的增加,太阳帆结构的振动频率和失稳载荷增大;随着帆面薄膜预应力的增大,太阳帆结构振动的基频减小,稳定性变差;随着支撑桅杆刚度的提高,太阳帆结构整体的振动频率和失稳载荷增大.本文建立的解析求解方法具有求解效率快和精度高的特点,为条带式太阳帆的结构设计和姿态控制提供了有力的分析工具.

STRUCTURAL DYNAMIC AND STABILITY ANALYSIS OF A STRIPPED SOLAR SAIL

Propelled by solar pressure, solar sail is thought as the most promising interstellar exploration technology. Two kinds of solar sail architecture have been proposed: boom-supporting solar sails and rotating solar sails, among them, stripped solar sail whose membrane is divided into separate narrow membrane strips is the ideal architecture for boom-supporting solar sails. How to precisely calculate structural dynamic characteristics of a stripped sails is worth studying. In this paper, the dynamic characteristics and stability of a stripped solar sail is studied. The whole solar sail structure is regarded as an assembly consisting of several sequentially connected boom-strip components, and one boom-strip component includes four boom segments and four membrane strips. In the stripped solar sail, the booms are under multiple-step axial loads and their vibrations are coupled with the vibrations of stripped membranes. Considering the coupling effects between booms and membrane strips, a closed form vibration model of the stripped solar sail is established by the distributed transfer function method. Based on this model, vibration characteristics and buckling loads of the stripped solar sail can be determined accurately and efficiently. Numerical results indicate that stripped solar sail architecture benefits to enhancing structural stiffness and stability, the more membrane strips will provide the higher stiffness and buckling loads, increasing membrane pre-stress will decrease base frequency of the stripped solar sail and worsen the structural stability, free vibration frequencies and buckling loads will increase with stiffness of the supporting booms. This presented analytical method is more efficiency and accurate than the numerical methods, which provides an efficient analysis tool for structure design and attitude control of stripped solar sails.