The Navajo-class is a new series of towing, salvage and rescue ships (T-ATS) being constructed for the US Navy. The new T-ATS ships will provide ocean-going tug, salvage and rescue capabilities to support US Navy fleet operations.
The vessels will replace the existing Powhatan-class T-ATF fleet ocean tugs and Safeguard-class T-ARS rescue and salvage ships in service with the US Military Sealift Command. The T-ATF 166 Powhatan-class and T-ARS 50 Safeguard-class ships are nearing the end of their anticipated service life.
The keel for the lead ship of the class, T-ATS 6, was laid in October 2019. Designated T-ATS 7, the second ship was laid in February 2020. The first five ships in the class are called Navajo, Cherokee Nation, Saginaw Ojibwe Anishinabek, Lenni Lenape and Muscogee Creek Nation.
The Navajo-class will be deployed to support a range of missions such as towing, rescue, salvage, humanitarian assistance, oil spill response and wide-area search and surveillance operations using unmanned underwater vehicles (UUV) and unmanned aerial vehicles (UAV).
Navajo-class T-ATS orders and deliveries
Gulf Island Shipyards received a contract to design and build up to eight towing, salvage and rescue vessels for the US Navy in March 2018.
The US Navy exercised its option for the construction of the fourth and fifth vessels through a modification contract in March 2020. The first three ships are scheduled for delivery in 2021, with the next two ships planned for 2022. After this, one ship a year will be delivered until 2025.
In April 2021, Gulf Island sold its long-term vessel construction contracts, including the T-ATS contract, along with the assets of its shipyard division to Bollinger Shipyards in a deal worth $28.6m.
T-ATS design and features
T-ATS is a multi-mission common hull platform with a length of 263ft (80m), beam of 59ft (17.98m) and draft of 17.7ft (5.39m). It has a displacement of 5,110t and load carrying capacity of 1,796t. The winning design of Gulf Island was based on the Wartsila VS 4612 anchor handling tug supply (AHTS) vessel.
The hull form of the T-ATS has a bulbous bow that will enable improved seakeeping capabilities and enhanced fuel efficiency.
The US Navy programme calls for a ship that can accommodate 65 persons, including 23 crew and 42 non-crew members.
The T-ATS steel-hulled ships are designed to provide 6,000ft² of deck space to accommodate stand-alone or interchangeable systems. The bridge of the T-ATS will offer a 360° view. The open deck area on the ship is designed to accommodate future mission systems. The ship will offer a bollard pull of 176 short tonnes for above-threshold towing and de-beaching force.
The T-ATS platform can support the integration of modular payloads with hotel services and relevant interfaces to allow future rapid capabilities.
Its design allows the embarkation of any type of containerised, stand-alone systems, ranging from cyber and electronic warfare (EW) to decoy and surveillance packages.
Equipped with the Wartsila – DP2 dynamic positioning system, the ships can also be used in submarine rescue operations.
Further requirements of the US Navy include a traction winch for towing, mission equipment stowage and off-ship firefighting.
Propulsion and performance of Navajo-class ships
The propulsion system includes a diesel-mechanical propulsion plant with shaft generators. The ship has an installed power of 9,408kW with two 900kW bow thrusters and one 900kW stern thruster.
The new Navajo-class ships can achieve a speed of 15.1k and have a maximum range of 8,170nm (15,130km) while cruising at a speed of 10k.
Singapore-based maritime cargo and load handling company MacGregor was awarded a contract to supply deck handling systems for the T-ATS class vessels in July 2020. The company previously received an order for three shipsets for the Navajo-class T-ATS ships.
The contractual scope includes deck machinery, shark jaws, towing and traction winch, towing pins or pop-up pins, offshore crane, stern roller and other accessories.
American shipbuilder Austal USA was awarded a contract worth $3.6m for the functional design of the Navajo-class T-ATS ships in May 2021. The company is required to define detailed requirements to build, test and deliver T-ATS ships that will meet the ship specifications outlined by the US Government.