Abstract: The sudden solar radiation heating can induce severe vibrations of spacecraft flexible appendages and negatively affect the proper functioning of a spacecraft. A spacecraft is a typical multibody system and the interactions among the components can greatly affect the spacecraft dynamic responses. Therefore, multibody dynamics models are necessary in the analyses of thermally induced vibrations of a spacecraft. This paper presents a thermal-structural coupled circular tube element with radiation heat transfer boundary conditions in flexible multibody system dynamics. The temperature variations can lead to both axial and lateral deformations of the tube. Moreover, the tube thermal boundary conditions are affected by the tube rotations and deformations when subjected to radiation heat flux from specified directions. The two-way thermal-structural coupling effects can be analyzed with the tube element, the rigid body and other flexible elements in multibody systems. The current approach is used to analyze the thermally induced vibration of the simplified model of the Hubble Space Telescope solar array, and the results agree well with the available results in the literature. This paper also analyzes the thermally induced vibrations of a spacecraft formed by a rigid hub, a flywheel, a flexible boom and a tip mass. The results showed that the interaction among the spacecraft components greatly affect the spacecraft thermomechanical responses.