Dynamics of Variable-Length Tethered Formations near libration points

Abstract

The dynamics of multitethered satellite formations near libration points are presented. The system consists of a parent satellite and subsatellites, connected together in a hub-spoke configuration via variable-length tethers. Based on Hill's approximation, a new dynamical formulation for nonrotating or rotating tethered formations is developed. The equilibrium positions are determined, and linearized analysis is performed for the nonrotating system with constant-length tethers. Numerical simulations using the full nonlinear and time-varying motion equations are carried out for the stationkeeping and reconfiguration stages. For nonrotating systems, the motion of the parent satellite is less stable for larger initial equilibrium positions during stationkeeping, and the tether librations during deployment are more stable than those during retrieval. For rotating systems, the orbital amplitude, orbital direction, and mass ratio have some impact on the stability of the system, and the retrieval is more conducive to keeping the system in its planar configuration when compared with the deployment.