Moon & Mars Orbiting Spinning Tether Transport - Tethers Unlimited

Commercial Tether Transport AIAA 2000-3842upon the launch service chosen and other business factors,current costs for this launch will be approximately$90M. If, however, a Tether Boost Facility is availablethat is capable of boosting the 5 metric ton payloadfrom a LEO holding orbit to GTO, the customer coulduse a smaller launch vehicle, such as a Delta-II 7920,with an estimated launch cost of $45M, or a vehiclecomparable to the Dnepr 1 (RS-20), with an estimatedsticker price of $13M. While exact comparisons at thislevel are difficult due to differing payload capacities ofeach vehicle and the dependence of launch pricing uponother business factors, these estimates indicate that areusable Tether Boost Facility could enable commercialand governmental customers to reduce their launchcosts by 50% to 85%. Thus there is a significant opportunityfor tether transportation systems to offer largecost savings in the LEO⇒GTO market. The key to thecommercial viability of the tether facility, then, will bein designing the system architecture so that the operatingcosts and the cost of amortizing the investment indevelopment and deployment are low enough that theLEO⇒GTO boost service can be offered at a price thatwill capture a large share of the market while sustainingthe business.The design of this LEO⇒GTO Tether Boost Facilityis discussed in more detail in an accompanying paper. 12The facility is designed to boost one 2,500 kg payloadto GTO once every month. Although the facility designis optimized for boosting 2,500 kg payloads to GTO, itcan also boost different-sized payloads to different orbits;the payload capacity depends upon the total ÆVto be given to the payload.As a result, in addition to boosting payloads to GTOand LTO, this Tether Boost Facility could also serve asa component of a transportation architecture for deliveringpayloads to other orbits and other destinations. Forexample, the initial (2,500 kg to GTO) Facility couldboost 5,000 kg payloads to the 20,335 km altitudeused by the GPS system. As a component in thetransportation system for Mars-bound payloads, thefacility could be used to inject a 5,000 kg spacecraftinto a highly elliptical equatorial orbit. At the apogeeof this holding orbit, the payload could then perform asmall ÆV maneuver to torque its orbit to the properinclination for a Mars trajectory, then perform its Trans-Mars-Injection burn at perigee. The tether facility thuscould reduce the ÆV requirements for a Mars missionby over 2 km/s.Lunar/Mars Boost FacilityBy adding more modular components to theLEO⇒GTO boost facility, we can build up its capacityto create a heavy-lift facility designed to boost 20-25metric ton payloads to Lunar Transfer Orbits and toMars transfer trajectories. This facility would provide alow-cost capability for transporting large quantities ofcargo such as food, fuel, and construction supplies toFigure 8. LEO⇒ Lunar/Mars Tether Boost Facilityfacilitate the deployment of manned lunar and marsbases.Cislunar Tether Transport SystemThis heavy-lift Boost Facility could then be used todeploy a second tether facility in polar lunar orbit.This facility, called a ÒLunavator ª Ó would be capable ofcatching payloads sent from Earth on minimum-energytransfer trajectories and delivering them to the surface ofthe Earth. The Lunavator facility could also be builtincrementally. The first system would be sized to catchpayloads from minimum-energy lunar transfers anddrop them into low lunar orbit (LLO) or suborbitalFigure 9. Lunavator ª orbit before and after catchinga payload sent from Earth.Figure 10. The Cislunar Tether Transport System.7