Space Transfer-Vehicle Concept for Deploying Solar-Power Satellites

A 200-kW-class solar-electric orbital transfer-vehicle concept, Swarm, for deploying elements of future, very large solar-power satellites, has been developed. Swarm is preintegrated with its payload on the ground and delivered into low Earth orbit aboard a reusable launch vehicle. The total mass initially deployed to an equatorial low Earth orbit is assumed to be 40 metric tons (mt)-divided roughly evenly between the transfer vehicle and its payload. The Swarm vehicle ferries the payload to geostationary orbit (GEO) in approximately 116 days using low-thrust Krypton thrusters powered by six large solar arrays. Once at GEO, the Swarm vehicle is disassembled to provide thrusters and propellant tanks for solar-power satellite station keeping. At an estimated mass of 20,000 mt per solar-power satellite and a nominal deployment rate of one satellite per year, over 1,000 one-way Swarm flights per year are required. Preliminary mass estimates for the Swarm transfer vehicle have been developed. A cost-estimating methodology suggests that further improvements are needed to achieve an acceptable cost for in-space transportation.