Optimal Thruster Layout Design and Closed-Loop 6DOF Evaluation for Small Satellites

A systematic approach for the design and evaluation of thruster layouts allowing six-degrees-of-freedom (6-DOF) control of small cube satellites for rendezvous and proximity operations is introduced. Initiating from a symmetric 24-thruster layout, all feasible configurations are enumerated and assessed using a controllability analysis and a nonnegative least squares formulation to ensure full controllability under unidirectional thrust constraints. Among feasible configurations, candidate optimal layouts are identified by minimizing the cumulative thrust needed to generate unit force-torque commands. To connect configuration-level design with mission-level performance and evaluate the correlation between them, selected configurations are integrated into a model predictive control framework and evaluated in closed-loop simulations of rendezvous proximity operation maneuvers. The relative dynamic model uses the Tschauner–Hempel model with quaternion-based rotational kinematics. Fault tolerance performance is also analyzed through structured single-, dual-, and triple-thruster failure scenarios. Results show that although seven thrusters are sufficient for full 6DOF controllability, configurations with twelve thrusters provide a favorable balance between control authority, efficiency, and robustness. Moreover, a strong correlation between offline configuration metrics and online control performance is observed, providing a foundation for the practical deployment of the proposed methodology in autonomous small-satellite missions.