MODELING ISSUES RELATED TO RETRIEVAL OF FLEXIBLE TETHERED SATELLITE SYSTEMS

The retrieval dynamics of the tethered satellite system is simulated using Galerkin's method with and without the contribution of the lateral vibration to the strain and the bead model approach in which the tether is assumed to be a series of point masses connected to each other by massless springs and revolute joints. Simulation results show that all the methods produce significantly different responses. It is found that Galerkin's method without the lateral strain contribution does not reproduce the longitudinal bobbing motion due to lateral vibrations and does not show attenuation of lateral vibrations as the tether shortens. When the lateral contribution is included, convergence of the response is not achieved and sudden divergence is exhibited during retrieval as the number of modes used in the simulation is increased. The simulations using the bead model show the longitudinal bobbing motion as well as the skip-rope motion during the terminal phases of retrieval. In addition, a simple method for obtaining nonrecursive order-N computation for the bead model simulation is presented.