Bogachan Ondes, University of Florida; Norman Fitz-Coy, University of Florida
https://doi.org/10.64861/OHDQ4459
Keywords: Multiagent, Guidance, Navigation, Control, Optimization, ADR, Tether, Tracking
Abstract:
The proliferation of orbital debris poses an escalating threat to operational spacecraft and the long-term sustainability of the space environment. With tens of thousands of tracked objects larger than 10 cm and far more untracked fragments, the risk of collisional cascading (Kessler syndrome) motivates proactive mitigation strategies, including Active Debris Removal (ADR). However, most capture approaches reported in the ADR literature exhibit performance and safety limitations when applied to noncooperative, tumbling targets with uncertain inertial properties. A central challenge is that solid–solid contact in space is inherently unforgiving: successful capture often requires near-simultaneous satisfaction of relative position, relative attitude, and relative angular-rate alignment at the moment of contact. Even modest errors in pose estimation or timing can convert a planned “gentle” contact into a high-energy interaction because there is no atmospheric damping, very limited passive energy dissipation, and constrained ability to accommodate unexpected target motion. As a result, contact impulses can be large relative to the structural margins of appendages and interfaces, and they can excite coupled translational–rotational dynamics that quickly degrade controllability. In practice, this means that capture systems relying on precise contact placement must operate with tight navigation tolerances, careful approach geometry, and robust handling of target inertia uncertainty—requirements that become increasingly difficult as tumbling rates increase or as the target’s geometry becomes irregular.
Robotic manipulator capture—successful for cooperative spacecraft—illustrates this precision burden. It demands accurate pose estimation and tight trajectory/attitude synchronization to bring an end-effector to a specific grasp fixture (or a small subset of acceptable contact regions) while matching the target’s local surface velocity. As target rotation rates increase, the manipulator must track a rapidly changing pose in real time; failure to match target motion can drive actuator saturation, induce large impulsive contact loads, and amplify rebound or “push-off” events that compromise mission safety. Harpoon systems enable standoff engagement but concentrate loads and may penetrate or fracture target structures, potentially generating secondary debris; they also remain sensitive to pointing, impact angle, and local structural uncertainty at the strike location. Net-based capture provides large-area interception, but it complicates post-capture stabilization: the net–target system inherits the target’s angular momentum and can exhibit coupled, difficult-to-damp dynamics during detumble and towing. Moreover, deployment uncertainty can lead to interaction with sensitive appendages (e.g., solar arrays and antennas) and hazard zones (e.g., residual propellant tanks), while entanglement can create unpredictable load paths and limit controllability. Collectively, these contact-based methods impose stringent requirements on synchronization, contact placement, and deployment timing that degrade mission robustness for tumbling, noncooperative targets—particularly when the target’s inertial properties and structural state are poorly known. These constraints motivate capture architectures that relax contact-precision demands, expand the set of acceptable interaction geometries, and accommodate rotation through distributed, compliant interaction rather than relying on a single precisely timed, precisely located rigid contact event.
This work presents a dual agent tethered spacecraft architecture for noncooperative debris capture, in which two coordinated agents maneuver the endpoints of a flexible tether to encircle a tumbling target using distributed, compliant contact. The tethered capture medium reduces sensitivity to contact-point placement by (i) spreading interaction forces through elastic deformation and damping and (ii) providing geometric tolerance through its extended length and controllable endpoint kinematics, enabling reduced relative contact velocity during engagement. A multi-phase guidance and control framework is developed, consisting of tangential approach, coordinated spiral descent with independent radius tracking, and wrap execution via leader–follower angular-rate scheduling. Smooth phase transitions are achieved through velocity-based gain blending to maintain positive tether tension. The tether is modeled as a discretized mass–spring–damper chain with torsional stiffness under Hill–Clohessy–Wiltshire relative dynamics. Numerical simulations demonstrate successful 360° wrapping with tension continuity across phase boundaries, establishing a foundation for elastic-media capture of tumbling orbital debris.
Date of Conference: September 15-18, 2026
Track: Space Debris