Technical Feasibility of a Novel Method for Station Keeping

Abstract

Long-term operation of large orbital structures, such as a solar power satellites (SPS), requires an efficient and replenishable station-keeping system. A novel station-keeping concept, recently awarded a US Patent, introduces an ablative propulsion method based on the slag produced by the processing of regolith. A refractory slag, composed primarily of calcia and magnesia, is the effluent of an isotope separation process. Solar cells, fabricated from silicon, aluminum, and phosphorus elements in lunar regolith, can be delivered to a geostationary orbit (GSO) inside ferrous payload canisters. Emplacement of square solar cells inside a spherical canister leaves space for six spherical sections of refractory slag. In this paper, the technical and economic feasibility are studied for the use of such slag targets to provide reaction mass for a laser ablation station-keeping system. Six degree of freedom torque and translation can be effected when slag targets are placed at extrema of an orbital structure, and pulsed by laser beams. A first order, first principles analysis is used to determine the mass production rate of refractories, the method of forming them into spherical sections for delivery from the moon to GSO, and their installation on a generic SPS. This simple model also includes analysis of the ablation process, characterization of the ejecta (direction, speed, and mass flow rate), and assesses the magnitude of the stationkeeping system vis-a-vis the orbital mechanics requirements for the SPS. This study provides key data needed to construct an overall systems-of-systems analysis of SPS based on lunar materials – an energy technology with significant potential to address baseload terrestrial energy needs.