Mission Analysis of Spinning Systems for Transfers from Low Orbits to Geostationary

Abstract. An analysis of the use of space-borne spinning tethers for a reusable system to transfer payloads with a mass up to 4000 kg from low orbits to geostationary is presented. Results indicate that a two-stage system is lighter than a single-stage tethered system with present-day tether materials. A Žfirst stage in low orbit and a second stage in medium Earth orbit provide the required velocity increments for injecting the payload into geotransfer orbit with the Ž final orbit circularization provided by the satellite kick motor. The orbits of the stages are resonant in order to provide periodic encounters and are optimized with the goal of reducing the overall system mass. The close-approach dynamics between the second stage and the payload released from the Ž first stage is simulated to demonstrate the salient features of the rendezvous process. A total of 10 transfers over two years of operation without refueling is adopted for computing the propellant needed to reboost the stages. A preliminary analysis leads to the conclusion that a two-stage tethered system is more competitive, on a mass basis, than a chemical upper stage after two transfers.