Space tethers: low cost future orbit transfer system for massive and frequent transportation with construction of solar power satellites

Abstract

Summary form only given. The global scale solar power satellite (SPS) is the most effective energy resource in future. However, the construction of global scale SPS requires the massive and frequent space transportation that we never experience and the possibility exists that vehicle propulsion systems will largely spend the resources of the propellant itself and the resources for producing the propellant. Additionally, the exhaust from propulsion systems may harm the terrestrial environment, so low propellant consumption will be required, both to conserve resources and to protect the terrestrial environment. This requirement will apply not only to launch systems, but also to near-Earth orbit transfer vehicle systems (OTV). The tethers are most attractive transportation systems in orbit because they can provide a large velocity increment to the payload without propellant. There are two types of tether to transfer payloads. One is the momentum tether and the other is the electrodynamic tether (EDT). A conceptual figure of the single-stage rotational momentum tether orbit transfer system is shown. The single-stage means that a payload is transported by one tether system on one orbit. A payload in low Earth orbit (LEO) is caught by the tether system in the elliptical orbit whose altitude is L km higher than LEO at perigee. The payload is released at the perigee in the next round and is thrown into a higher orbit, finally reaching geo-transfer orbit (GTO). After the payload is thrown into GTO its orbit is changed to geosynchronous Earth orbit (GEO) by an apogee kick motor. The EDT consists of a long conducting wire, a power generator, and two plasma contactors which are installed in both ends of the tether wire. If the current flows through the tether wire in a geomagnetic field the Lorentz force is induced by the interaction between the current and the geomagnetic field. Such a type of propulsion method can apply directly to the transportation of Sun tower type SPS by using the main power transmission cable as EDT.