Moon & Mars Orbiting Spinning Tether Transport - Tethers Unlimited

Tethers Unlimited, Inc.Appendix R: MERITT Architectureorbit counts as well and the longer unbalanced grapple arm of the lightweight tether lets it grab a payload from ahigher energy tether orbit.SUMMARY OF MULTIPLE MERITT ANALYSESWe carried out analyses of a number of MERITT missions using a wide range of assumptions for the tether tip speedand whether or not aerobraking was used. The trip times for the various scenarios are shown in Table 1. As can beseen from Table 1, the system has significant growth potential. If more massive tethers are used, or strongermaterials become available, the tether tip speeds can be increased, cutting the transit time even further. The transittimes in Table 1 give the number of days from payload pickup at one planet until payload reentry at the other planet,and include tether "hang time" and coast of the payload between the patch points and the planets. Faster transittimes can be made with higher energy initial orbits for the payload and the tether. With a 2.5 km/s tip speed on thePlanetWhip tethers and using aerobraking at Mars the Earth orbit-Mars orbit transit time can be made about 94 days.TABLE 3. MERITT Interplanetary Transfer Times.Tether Tip Speed System to Payload Transfer Direction Tether-to-Tether Aeroslowing(km/s) Mass Ratio From -> To (days) (days)2.0 15x Earth -> Mars 155 116Mars -> Earth 155 1372.5 30x Earth -> Mars 133 94Mars -> Earth 142 126CONCLUSIONSWe have shown that two rapidly spinning tether systems in highly elliptical orbits about Earth and Mars, can becombined into a tether transport architecture that provides rapid interplanetary transport from a suborbital trajectoryabove the Earth's atmosphere to a suborbital trajectory above the Martian atmosphere and back again.ACKNOWLEDGMENTSThis research has been supported in part by the NASA Institute for Advanced Concepts, Dr. Robert A. Cassanova,Director; and in part by the Tethers Unlimited, Inc. IR&D program.REFERENCESCosmo, M.L, and E.C. Lorenzini, E.C., Tethers In Space Handbook - Third Edition, prepared for NASA/MSFC by SmithsonianAstrophysical Observatory, Cambridge, MA, 1997.Forward, Robert L. "Tether Transport from LEO to the Lunar Surface," Paper AIAA-91-2322, 27th AIAA/SAE/ASME/ASEEJoint Propulsion Conference, Sacramento, CA, 1991.Hoyt, Robert P., "LEO-Lunar Tether Transport System," Paper AIAA-97-2794, 33rd AIAA/SAE/ASME/ASEE Joint PropulsionConference, Seattle, WA, 1997.Forward, Robert L., and Nordley, Gerald D., "Mars-Earth Rapid Interplanetary Tether Transport (MERITT) System: I. InitialFeasibility Analysis," Paper AIAA-99-2151, 35th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, LosAngeles, CA, 1999.R-7