Moon & Mars Orbiting Spinning Tether Transport - Tethers Unlimited

Tethers Unlimited, Inc.MMOSTT Final ReportC. Tether Facility ReboostA key factor in the economic competitiveness of a Tether Boost Facility will be the frequencywith which the facility can boost payloads. The throughput capacity of a tether facility will bedetermined largely by the time required to restore the facility’s orbit after each payload boostoperation. In this work we have investigated using electrodynamic tether propulsion to reboostthe orbit of the tether without requiring propellant consumption.As with the system design, the investigation of electrodynamic reboost has gone throughseveral iterations. In Appendix K, Tether Reboost Study, we present results of our initialanalytical and numerical investigations of the time required to reboost the orbit of the 5,000 kgpayload facility using electrodynamic tether propulsion. We used these results to guide thedesign of the tether facility described in the previous section. The results of the tether systemdesign were then fed back into the simulation effort. In the latter part of Appendix C, “Designand Simulation of a Tether Boost Facility for LEO⇒GTO Payload Transport” we present morerecent simulation results that use more advanced methods for optimizing the orbital reboost.These latest results indicate that a Tether Boost Facility sized for boosting 2,500 kg payloads toGTO once per month will require a solar power system of approximately 100 kW.Semimajor Axis (km)9550950094500 0.5 1 1.5 2 2.5 3Time (days)0.295Eccentricity0.290.285Thrust Efficiency (µN/W)0 0.5 1 1.5 2 2.5 3Time (days)60402000 0.5 1 1.5 2 2.5 3Time (days)Figure 7. Semimajor axis, eccentricity, and thrust efficiency during the first three days of the reboostoperation.12