The Convention on the International Regulations for Preventing Collisions at Sea (COLREGs) Rule 27(f) directs the light and shape requirements for vessels conducting mine clearance, but subsection (g) states, “Vessels of less than 12 meters in length . . . shall not be required to exhibit the lights and shapes prescribed in this Rule.” The littoral combat ship’s (LCS’s) mine countermeasure (MCM) unmanned surface vehicle (USV) measures just short of 12 meters, making it unnecessary for the Navy to meet the legal requirement for MCM lights and shapes. Meanwhile, its LCS mothership does not directly conduct MCM clearance and, therefore, is not obliged to display MCM shapes or lights (nor would they communicate anything useful, as motherships may not be within 1,000 meters of the threat).
This is a critical safety and communication gap. A broad category of legally compliant MCM operations involving multiple USVs less than 12 meters long over a wide area leaves mariners visually unaware of the MCM USVs’ restricted maneuvering status and surrounding danger.
Industry limited the MCM USV’s length partly to minimize additional requirements, which is sensible from a material and legal liability perspective. Current COLREG MCM lighting and shapes would require adding retractable yardarms to the MCM USV, imposing further reliability issues on an already complicated accordion mast limited by the overhead clearance of a deploying crane. Imposing Rule 27(f) on shorter vessels would make compact MCM USVs harder to build, reducing good options for mine clearance.
A Different Design Solution
Instead, for MCM USVs shorter than 12 meters, the U.S. Navy, NATO navies, and other allies and partner navies should establish a new light and shape that nearby mariners can clearly interpret. The light should be designed for simplicity and reliable deployment without the need for continual maintenance. For shapes, a black conical shape, apex downward, or over a ball would work well. Limited to two shapes in a single line, this shape would be easily stored and deployed from a simple mechanism on any USV mast or along a preexisting wire antenna. It would be easily associated with the potential dangers—an arrow pointing toward a mine-like shape below. Most important, this shape could not be confused for another configuration.
For lights, in lieu of the masthead lights prescribed in Rule 22, MCM USVs would show at the highest point, flashing “green over red” all-around lights. Green over red is an unused configuration that, in the absence of any other masthead lights, could not be confused for another. The flashing would provide additional differentiation and invite attention, much like the flashing lights on surfaced submarines and vessels conducting law enforcement or specialized safety operations. A mnemonic, “green over red, you could be dead,” also would be a helpful warning to mariners.
The shapes should apply to MCM USVs from 5 to 20 meters long, and the lights to all MCM USVs up to 20 meters long. Applying the rule to USVs up to 20 meters long would ease the design requirements for MCM USVs below the size that Rule 9(b) would consider large enough to be constrained by a channel. However, the rule would not apply to USVs less than five meters long because of a lack space for reliable remote-shape manipulation or a lighting mast. The goal of this new regime is to improve USV safety, not prevent production of smaller USV classes such as those used by the Marine Corps’ Littoral Explosive Ordnance Neutralization team.
The areas and types of MCM operations in which MCM USVs less than five meters long operate are limited and always close to a mothership or shore facility. For even greater simplicity, the U.S. Navy and other navies could change the rules for all MCM ships less than 50 meters (approximately 164 feet) long, manned or unmanned (there are very few manned MCM vessels less than 50 meters long, such as the Italian Navy’s Gaeta class). MCM USV maneuvers should not be unique—the rules make no special provision for unmanned vessels.
The COLREGs may be mariners’ commandments, but they are not set in stone. Rather than design all MCM USVs to comply with the rules, the Navy should adopt similarly effective rules that meet its needs and ensure the safety of mariners. The increase in unmanned surface MCM operations, with the accompanying challenges of compact USV design and reliability, invite updated rules with new shapes and lights that support good seamanship and help innocent mariners not get blown up.