Guidance strategies for controlled Earth reentry of small spacecraft in low Earth orbit

A small spacecraft equipped with a hybrid thruster system providing 100 N-class thrust and a small reentry capsule with a capability of aeroassist maneuver, can deorbit from low Earth orbit, enter a reentry trajectory into Earth atmosphere, and descend toward the target landing point. During the deorbit maneuver, an attitude control system stabilizes the thrust direction, while spin-stabilization method is achieved using cold-gas thrusters. Numerical studies confirm the feasibility of deorbit control, regardless of uncertainties, such as the position of the center of gravity of the spacecraft and the tilt angle of the thrust vector. After a deorbit maneuver, an aeroassist maneuver in the atmosphere can guide a small reentry capsule to a target ground point. In this study, the performance of a real-time predictor-corrector guidance method is improved, a strategy that exhibits high potential as a non-scheduling guidance method in terms of the control accuracy to the target point and the maximum aerodynamic load using a lift-and-drag estimator and terminal bank angle guidance. The resulting algorithm, a robust aeroassist method, outperforms conventional aeroassist maneuvers, even with variations in aerodynamic characteristics due to capsule recession and an offset in the center of gravity of the capsule. The proposed autonomous guidance technique integrates the deorbit and aeroassist maneuver strategies for controlled Earth reentry of small spacecraft with immense potential for application in astronautics. • Autonomous guidance techniques for controlled Earth reentry of small spacecraft are developed. • A small spacecraft is equipped with a 100 N-class propulsion system and a reentry capsule. • Small spacecraft can deorbit from low Earth orbit, enter Earth's atmosphere, and descend to the target landing point. • Spin control performance for attitude stabilization during hybrid thruster firing is evaluated. • The proposed aeroassist maneuver demonstrates high robustness against flight uncertainties.