Dynamics and Control of Electrodynamic Tether Systems

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Electrodynamic tethers (EDTs) are an innovative approach to generate propulsion for boost and deorbit maneuver and electricity onboard spacecraft without consuming propellant. Over the past five decades, 12 out of 26 orbital and suborbital tether missions flew with EDTs. However, the system is prone to the long-term instability caused by the time-varying excitation of Lorentz force. Thus, a thorough understanding of the long-term dynamic stability of an EDT system is essential for its useful application in space. In spite of great achievements in the EDT theory and electrodynamic tethered systems, a number of interesting challenges still exists in the fundamentals of coupled EDT dynamics and long-term dynamic stability. Therefore, the objectives of this discovery program are to systematically study the coupled electro-mechanical dynamics and optimal control of the long-term stability of EDT systems. In this new approach, we will formulate a multiphysics model of dynamics of a bare and flexible EDT coupled with electricity generation by orbit motion limited theory. Based on the new multiphysics model, the parameters of EDT systems will be optimized by applying multiobjective optimization procedure for (a) fastest time in boost or deorbit maneuver or (b) maximum energy generation for given payloads onboard spacecraft, while minimizing the EDT length and end masses. The long-term dynamic stability of an EDT system will be achieved by finding an optimal balance between a stable oscillation of a time-varying EDT system and given mission objectives using the nonlinear-programming optimization procedure and the robust finite receding horizon control theory. Finally, ground testing will be conducted to validate the dynamics and control strategy. The outcome of the proposed research program will be (i) a high-fidelity multiphysics EDT model essential for EDT systems, (ii) a robust optimal control algorithm, and (iii) training of 14 HQP in an interdisciplinary and collaborative environment. It will advance our knowledge in new propulsion or power generation for future space exploration and enhance the competitiveness of Canadian space industry.