VESSEL REVIEW | Mariner & Ranger – US Navy launches new fleet of unmanned test vessels

The US Navy has begun operating two unmanned surface vehicles (USVs) as part of a US Department of Defense (DOD) project entailing the integration of autonomous navigation technology into existing seagoing vessels.

Sister vessels Mariner and Ranger were developed by a partnership formed by defence technology company Leidos and Franklin, Louisiana-based shipbuilder Gulf Craft. The 193- by 32-foot (59- by 10-metre) vessels are designated as medium unmanned surface vehicles (MUSVs), and each has a specific set of mechanical, engineering, and mission systems that will undergo testing as part of the DOD's Ghost Fleet Overlord program.

Both Mariner and Ranger utilise a design that was originally developed for fast crew transfer and supply duties in support of clients in the offshore oil and gas industry. Modifications on each boat include the addition of satellite communications, three radars of different bands, electro-optical and infrared sensors, and radios.

In the case of Mariner, an additional set of datalinks and systems will enable it to operate as a mothership for other unmanned vessels. This capability means the navy will reduce its dependence on traditionally crewed surface vessels such as destroyers for the mothership role, thus freeing up these more potent platforms for their core missions of anti-surface warfare and anti-air warfare. Mariner is also fitted with a lower-capability version of the Lockheed Martin Aegis combat system, enabling the vessel to also be employed for command and control functions.

The vessels still retain their cargo transport capability thanks to fore and aft decks that can carry two 20-foot and four 40-foot containers, though the containers will often house additional systems and sensors essential to the vessels' operations.

Power for each MUSV is provided by five 2,000hp (1,491kW) diesel engines connected to waterjets. Each diesel engine is fitted with three oil filters instead of one for redundancy purposes. The onboard systems draw electrical power from three generators.

The MUSVs are designed for unmanned operations, though the bridge control panel on each vessel also features an operator override function to enable an embarked small crew to assume control in an emergency.

Mariner and Ranger will undergo additional testing with the navy. The project team hopes to further modify the vessels to make them capable of being refuelled even with no crews on board. Sailings with this capability already incorporated are scheduled for 2023 at the earliest.

Parts of this article re-printed from Seapower, the official publication of the Navy League of the United States.