This paper addresses the challenge of accurately predicting the strongly coupled orbital and structural dynamics of tethered space systems, such as momentum exchange tethers and tethered spacecraft formation flying. Conventional modeling approaches typically rely on artificial rigid-flexible partitioning between spacecraft and tethers, complex interface constraints, and non-physical coordinate transformations, which hinder their ability to simultaneously capture elastic tether deformation, spacecraft structural dynamics, orbital motion, and environmental disturbances within a unified framework. To overcome these limitations, a high-fidelity unified elastic dynamic modeling approach based on the Nodal Position Finite Element Method (NPFEM) is proposed. By expressing all kinetic and potential (gravitational and elastic) energies exclusively in terms of finite element nodal positions, the proposed framework preserves elasticity in both the spacecraft and tether while eliminating explicit separation of rigid-body variables and complex interface constraints. Orbital disturbance effects are directly and consistently incorporated at the element level with nodal position information, allowing the governing equations to be assembled directly from individual contributions. Rigid-body motion and elastic deformation of spacecraft and tethers are subsequently reconstructed algorithmically from the nodal state for physical interpretation. The proposed modeling framework is validated through three representative tether mission scenarios, including a tether system in its local vertical, a momentum exchange tether and a hub-spoke tether formation. The results demonstrate robust capability in capturing strongly coupled orbital–structural interactions and critical transient responses in large-scale tethered systems, thereby enabling higher-fidelity analysis and supporting design automation for applications such as momentum exchange, formation flying, and space debris removal.
Zhang et al. (Wed,) studied this question.