A Comparative Mechanical Study of Net-, Tether-, and Robotic-Based Space Debris Capture Systems in Low Earth Orbit

The proliferation of space debris in Low Earth Orbit (LEO) has precipitated a critical inflection point in orbital sustainability, necessitating the transition from passive mitigation guidelines to active remediation strategies. While the astrodynamics of rendezvous and phasing are well-understood, the mechanical feasibility of physically capturing noncooperative, tumbling targets remains the primary engineering bottleneck preventing scalable Active Debris Removal (ADR). This paper presents an exhaustive comparative mechanical analysis of three predominant capture architectures: flexible netbased systems, tethered projectile (harpoon) systems, and rigid robotic grasping mechanisms. The study rigorously examines the dynamic interactions, structural loading requirements, and failure modes inherent to each architecture when interfacing with high-mass, high-inertia targets such as the European Space Agency’s Envisat satellite and the Soviet-era Zenit-2 rocket bodies. Analytical models utilizing discretized mass-spring-damper formulations for flexible tethers and nets, Johnson-Cook constitutive material models for high-strain-rate harpoon impacts, and Hertzian contact theories for robotic grasping are synthesized to evaluate performance boundaries. The analysis reveals that net-based systems offer superior compliance and reduced guidance precision requirements for tumbling targets but suffer from complex, stochastic deployment dynamics and potential entanglement uncertainties. Conversely, robotic manipulators provide deterministic control and rigid capture capability but demand high-bandwidth impedance control to manage contact instability and are severely limited by the target's tumbling rate due to actuator saturation limits. Tether-harpoon systems occupy a mechanical middle ground, offering rapid capture with high impulse transfer, yet introducing significant risks of structural fragmentation and recoil dynamics that threaten the chaser spacecraft. Through a systematic trade-off analysis focusing on structural complexity, deployment risk, and post-capture stabilization, this report concludes that no single mechanism is universally optimal; rather, the mechanical selection is strictly governed by the target’s angular momentum vector, structural integrity, and the acceptable risk profile of the mission. The results underscore that effective debris removal systems will ultimately depend on robust mechanical design capable of tolerating substantial dynamic uncertainties rather than conceptual novelty alone.