Performance of an unmanned sailboat towing a sonar array system in various wind conditions

This paper proposes a novel unmanned sailboat towing a towed array sonar system (USTAS) and develops a framework for evaluating its speed performance in calm water under both steady and unsteady wind conditions. This study represents the first application of a previously developed lifting-body-theory-based unmanned sailboat dynamics model to USTAS, revealing its distinctive motion characteristics and underlying mechanisms. The core findings indicate that the large drag of the towed body shifts the system’s optimal propulsion mode from the lift-driven regime to the drag-driven regime, producing a heart-shaped speed polar whose maximum occurs in downwind conditions, which differs fundamentally from conventional sailboats. The results further show that unsteady winds can induce distinctive heading instability in the USTAS, while the towed system generally suppresses roll and affects pitch in a speed-dependent manner. These behaviours differ from those of conventional sailboats and provide theoretical guidance for navigation strategy development and system design for this novel ocean-observing platform.