Moon & Mars Orbiting Spinning Tether Transport - Tethers Unlimited

Commercial Tether Transport AIAA 2000-3842COMMERCIAL DEVELOPMENT OF ATETHER TRANSPORT SYSTEMRobert P. HoytTethers Unlimited, Inc., Seattle, Washingtonwww.tethers.comAbstractMomentum-Exchange/Electrodynamic-Reboost tether facilities can form the infrastructure for a fullyreusablelow-cost in-space transportation architecture. Several technical challenges must be met to enabletether transport systems to be fielded, including development of rapid AR&C capabilities and techniquesfor building and controlling the tether facilities. A tether transport system to carry frequent traffic betweenEarth, the Moon, and Mars can be developed in a modular, incremental fashion, in which each componentcan generate revenue to fund the development of the rest of the system, much as the first railroads were developed.The initial Tether Boost Facility would be sized for launch on a single large rocket vehicle, andwould be designed to immediately service traffic to GEO. The capacity of this facility could then be builtincrementally, and additional tether facilities deployed to handle Earth-to-Orbit Assist, LEOóLunar Surfaceround-trip travel, and deployment of manned Mars bases.IntroductionBy providing a fully reusable, zero-propellant infrastructurefor in-space transportation, momentumexchangetethers have the potential to reduce the costsof delivering payloads to GEO, the Moon, Mars, andother destinations by an order of magnitude or more.Under funding from NASAÕs Institute for AdvancedConcepts (NIAC), Tethers Unlimited, Inc. and the BoeingCompany are developing an architecture for a tethertransportation system. This system will utilize momentum-exchangetechniques and electrodynamic tetherpropulsion to transport multiple payloads with little orno propellant consumption. The tether transportationarchitecture is designed to be built incrementally, witheach component able to perform a useful revenuegeneratingmission to help fund the deployment of therest of the system. The first component of the systemwill be a Tether Boost Facility that will transfer satellitesand other payloads from low Earth orbit (LEO) togeostationary transfer orbit (GTO). This same facilitywill also be capable of boosting payloads to lunar transferorbit (LTO). Later components will increase thepayload capacity of the Tether Boost Facility and enablefrequent round-trip travel to the surface of theMoon 1,2 and to Mars. 3In this paper we discuss an architectureand incremental development plan for anEarth-Moon-Mars Tether Transportation System.BackgroundMomentum-Exchange TethersIn a momentum-exchange tether system, a long, thin,high-strength cable is deployed in orbit and set intorotation around a massive central body. If the tetherfacility is placed in an elliptical orbit and its rotation istimed so that the tether will be oriented vertically below the central body and swinging backwards when thefacility reaches perigee, then a grapple assembly locatedat the tether tip can rendezvous with and acquire a payFigure 1. Momentum Exchange Tether catching and tossing payload.Copyright©2000 by Tethers Unlimited, Inc. Published by theAmerican Institute of Aeronautics and Astronautics with permission1