Moon & Mars Orbiting Spinning Tether Transport - Tethers Unlimited

IAF-00-S.6.04The LEO⇒GTO Tether Boost Facility will boostpayloads from low-LEO to geostationary transfer orbits(GTO). In sizing the facility design, we have sought tobalance two somewhat competing drivers: first, thedesire to be able to have a fully-operational, revenuegeneratingtether boost facility that can be deployed in asingle launch on a rocket expected to be available in the2010 timeframe, and second, the desire for the tetherfacility to be capable of gaining as large as possible amarket share of the projected GEO traffic. Recent projectionsof GEO traffic, shown in Figure 11, indicatethat the general trend for GEO payloads is to becomemore and more massive. Over the timeframe coveredby the projections, payloads in the range of 4-6 metrictons are expected to account for roughly 80% of thecommercial market. Consequently, it would be highlydesirable to design the Tether Boost Facility to handlepayloads on the order of 5,000 kg. On the other hand,a tether facility designed to toss payloads to GTO mustmass roughly 9 times the mass of the payloads it canhandle (due primarily to tether sizing, orbital mechanics,and conservation-of-momentum considerations). Ifthe tether facility is to provide an operational capability2520151050Projected GEO Traffic2000 2002 2004 2006 2008 2010 2012 2014COMSTAC Projections, May 1999YearFigure 11. GEO traffic projections for 2000-20015.Below 2,000 kg2,000 - 4,000 kg4,000 - 5,500 kg> 5,500 kgExtended Forecastafter one launch, the tether facility must fit within thepayload capacity of an available launch vehicle. In the2010 timeframe, the largest payload-to-LEO anticipatedis that of the Delta-IV-Heavy rocket, which will be ableto place 20,500 kg into LEO.Consequently, we have chosen to follow a modulardevelopment approach in which the initial Tether BoostFigure 10. The LEO⇒GTO Tether Boost Facility7