Optimal Design Algorithms for Bare Electrodynamic Tethers in the Active Mode

Abstract

Two algorithms aimed at the optimal design of bare electrodynamic tethers in the active mode, including reboost and stationkeeping scenarios in low Earth orbit, are presented. By assuming a quasi-circular orbit evolution with constant environmental values at each altitude, the algorithms construct figures of merit as a function of the tether dimensions and the input power and look for their optimum values while satisfying other mission constraints like duration and safety. In the case of reboost scenarios, the figures of merit are the tether system-to-satellite mass ratio and the reboost time. Two separate subcases are studied: a nonautonomous tether system that receives power from the satellite, and an autonomous case where the power source is part of the tether system. Regarding stationkeeping scenarios, the design algorithm minimizes the tether system-to-satellite mass ratio while ensuring that the thrust provided by the Lorentz force compensates for the aerodynamic drag. A map of performances of the tether system in the altitude–inclination plane is presented. The optimal tether sizing and power obtained with the two algorithms were used as input to run simulations with the BETsMA Version 2.0 software. They confirmed that, although based on some simplifying hypotheses, the algorithms provide acceptable values of the design parameters in a preliminary design phase. The extension of the algorithms to bare-photovoltaic tethers and low work-function tethers is briefly discussed.