Moon & Mars Orbiting Spinning Tether Transport - Tethers Unlimited

Tethers Unlimited, Inc.Appendixm M: TetherSim TETHER TRANSPORT SYSTEM DYNAMICS VERIFICATION THROUGH SIMULATIONRobert P. HoytTethers Unlimited, Inc.AbstractIn order to validate the orbital mechanics and tether dynamics of various tether transportsystem architectures, we have developed a numerical simulation of the system that includesmodels for the full 3D orbital mechanics in the Earth-Moon system, tether dynamics, tetherelectrodynamics, and other relevant physics. Using this code, we have designed and simulatedscenarios for transferring payloads from LEO to GEO, from LEO to the lunar surface, and fromsuborbital trajectories into Earth orbit.IntroductionThe operation of the tether facilities utilized in the tether transport systems such as the CislunarTether Transport System and the Mars-Earth Rapid Interplanetary Tether Transport (MERITT) systeminvolve many different interrelated phenomena, including orbital dynamics, tether librations andoscillations, interactions with the ionospheric plasma, day/night variations of the ionosphericdensity, solar and ohmic heating of the tether, magnetic vector variations around an orbit, and thebehavior of electron emission devices. In order to enable accurate analyses of the performance andbehavior of the this and other tether system, we have developed a numerical simulation ofelectrodynamic tethers called “TetherSim” that includes models for all of the aforementionedphysical phenomena. The TetherSim code is implemented in C++, and runs on BSD Unix and MacOSplatforms.The simulation is capable of simultaneously simulating multiple tethers of different types,satellites, payloads, and other vehicles. In the following sections we summarize the physics modelsused in the TetherSim program.Figure 1. Screen captures of the TetherSim program simulating orbital reboosting of a 25 kmHEFT Tether Facility (left) and simulating rendezvous between a 600 km long orbiting tether anda hypersonic airplane (right).Tether DynamicsTetherSim can utilize two different algorithms for propagating the dynamics of the tether, one aRunge-Kutta-based explicit algorithm, the other an implicit finite-element based algorithm. In bothM-1