Unmanned systems at sea offer advantages and face challenges that are often different from those associated with airborne and ground-based systems. For example, in a patrol mission that calls for long endurance at low speed, the size of a manned ship is largely driven by the need to provide tolerable accommodation and stability for the crew—a limit that does not apply to an unmanned surface vessel (USV).
On the other hand, manned craft have long range and payload because of their size, and nobody is interested in a USV weighing several hundred tons. That means that USVs either need a mothership (launch and recovery techniques are still in the works) or may be confined to coastal roles. Also, sensor and communications line-of-sight distances are subject to the unbreakable laws of mast height and horizon distances.
Consequently, fielding USVs and autonomous underwater vehicles (AUVs) may be more a question of matching basic technology to the concept of operations (conops), while applying new technology selectively.
A major French effort, to be unveiled at the Euronaval show in Paris later this month, pulls together USV and AUV technology to create a unique minehunting system including three world-first technologies. The Espadon (Swordfish) project, launched by the DGA French procurement agency in July 2009, is being run by a team comprising naval systems group DCNS, robotics company ECA and Thales.
The centerpiece of Espadon is a 17-meter (58-ft.)-long, 25-ton, boxy-looking catamaran USV named Sterenn Du (“black star” in Breton). Because current French legislation forbids surface vessels from navigating without human beings aboard, Sterenn Du has a small pilot’s cabin, set to one side much like an aircraft carrier’s island. But the Sterenn Du can also be teleoperated or be completely autonomous.
Sterenn Du’s role is to deploy AUVs. It would be brought close to the mission zone by a dedicated mothership of 2,500—3,000 tons, which would remain a safe distance from the minefield. Aboard the Sterenn Du are three AUVs developed by ECA, which constitute its actual mine-hunting and destroying tools.