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A. Medina Vega
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Guidance System Design for Collision Avoidance in Satellite Constellations
An Application of Low-Thrust Nonlinear Model Predictive Orbit Control
Low-thrust collision avoidance is becoming a routine operational necessity for satellite constellations. Existing guidance methods treat avoidance and orbital recovery as separate, open-loop problems, and restore the nominal orbit rather than the satellite's assigned slot. This study develops a two-phase, receding-horizon Nonlinear Model Predictive Control (NMPC) framework that unifies the avoidance manoeuvre and the return-to-slot in a single closed-loop trajectory optimisation scheme. Each guidance update is solved online using sequential quadratic programming with acados, an embedded optimal-control software package, and propagated by the TU Delft Astrodynamics Toolbox (Tudat), which in this case serves as the high-fidelity plant. The results show that the receding-horizon system compensates for both the prediction model errors and the environmental uncertainties. Across the sampled uncertainties, every trial kept the spacecraft outside the keep-out zone and returned it to its assigned orbital slot within a tolerance of 400~m. The different conjunctions analysed show that propellant demand falls as warning time increases, returning to the nominal orbit is cheaper than re-acquiring the slot, and along-track actuation is sufficient and the most propellant-optimal across different encounter geometries. The main limitation of the NMPC guidance system is that it requires the mission timeline to be fixed before the manoeuvre, so it does not trade recovery time with propellant usage.
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Low-thrust collision avoidance is becoming a routine operational necessity for satellite constellations. Existing guidance methods treat avoidance and orbital recovery as separate, open-loop problems, and restore the nominal orbit rather than the satellite's assigned slot. This study develops a two-phase, receding-horizon Nonlinear Model Predictive Control (NMPC) framework that unifies the avoidance manoeuvre and the return-to-slot in a single closed-loop trajectory optimisation scheme. Each guidance update is solved online using sequential quadratic programming with acados, an embedded optimal-control software package, and propagated by the TU Delft Astrodynamics Toolbox (Tudat), which in this case serves as the high-fidelity plant. The results show that the receding-horizon system compensates for both the prediction model errors and the environmental uncertainties. Across the sampled uncertainties, every trial kept the spacecraft outside the keep-out zone and returned it to its assigned orbital slot within a tolerance of 400~m. The different conjunctions analysed show that propellant demand falls as warning time increases, returning to the nominal orbit is cheaper than re-acquiring the slot, and along-track actuation is sufficient and the most propellant-optimal across different encounter geometries. The main limitation of the NMPC guidance system is that it requires the mission timeline to be fixed before the manoeuvre, so it does not trade recovery time with propellant usage.
ARCH-E Design Report
Autonomous Reconfigurable Crew/Cargo Hauler for Exploration
Bachelor thesis
(2024)
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O.D. FitzGerald, D. Ispas, S.S. Swain, A. Medina Vega, N.R.E. Portheine, N. Steenhuis, A. Van den Heede, J.Y. Hu, J.P. Joos, B. Menekse, J.N.V. Smith, A. Cervone, D. Atmaca, H.F. Maathuis
In the renewed race for the Moon, there will be a high demand for transportation services to and from the lunar surface. The next generation of landers needs to have many capabilities, such as supporting longer exploration and global access, sustainability and versatility. ARCH-E, developed together with Airbus Defence and Space UK, fills this need as a reusable, crew/cargo-capable lander architecture. The lander's requirements and market are analysed, mission trajectory and landing are designed, followed by detailed subsystem design. The operations, risks, costs and sustainability considerations are assessed and highlighted. Finally, the design overview of a feasible lunar landing system is presented. Further design activities are recommended and a project timeline is laid out.
...
In the renewed race for the Moon, there will be a high demand for transportation services to and from the lunar surface. The next generation of landers needs to have many capabilities, such as supporting longer exploration and global access, sustainability and versatility. ARCH-E, developed together with Airbus Defence and Space UK, fills this need as a reusable, crew/cargo-capable lander architecture. The lander's requirements and market are analysed, mission trajectory and landing are designed, followed by detailed subsystem design. The operations, risks, costs and sustainability considerations are assessed and highlighted. Finally, the design overview of a feasible lunar landing system is presented. Further design activities are recommended and a project timeline is laid out.