The design of small diameter neutrally buoyant electrooptic tether cables for maximum power transfer

Underwater vehicles that are tethered by an electrooptic cable normally have adequate endurance, ample power, and an abundance of bandwidth available for bi-directional communication and data transfer. The security of a hard link also facilitates the deployment, recovery, and tracking, and may in some cases aid in the maneuvering of the vehicle. Despite these advantages, a tethered system´s performance is often negatively impacted by the in-water weight of the cable and its associated drag. Tightly coupled to these problems is the ever present danger of fouling the tether on fixed or floating objects in the ocean. The disadvantages of cable drag and weight may be minimized by keeping the cable diameter and its associated in-water weight as small as possible. Careful design of the cable and of the power transfer and power distribution systems is required to achieve this goal. As the cable diameter is reduced, the power required to achieve system performance objectives is reduced. This benefit permits weight and space reductions in the vehicle and the tether management and surface power transfer systems. The paper develops a systematic method of exploring tradeoffs in cable diameter and weight within vehicle load regulation and power transfer constraints. It is shown that through careful consideration and design, the major drawbacks of a tethered system may be minimized without negatively impacting the overall robustness of the system