TAGOS-25 class will be part of the tactical auxiliary general ocean surveillance (TAGOS) ships fleet operated by the Military Sealift Command (MSC) of the US Navy.
The vessels will contribute to the navy’s anti-submarine warfare (ASW) operations to ensure enhanced security for the fleets in the Atlantic and Pacific regions.
The TAGOS-25 programme is potentially a response to the submarine modernisation efforts being made by countries such as China and Russia.
The first TAGOS-25 class ship is expected to be delivered in 2025. The remaining ships are planned to be procured between 2025 and 2028 at the rate of one ship a year. The TAGOS-25 class ships will have an expected service life of 30 years.
TAGOS-25 programme background
The US Navy posted the request for proposals (RFP) for the detailed design and construction contract for the TAGOS-25 ocean surveillance shipbuilding programme, previously referred to as TAGOS(X), in November 2021 and amended it in December 2021.
The US Navy awarded a $113.9m contract to shipbuilding company Austal USA for the detailed design of the TAGOS-25 class lead ship in May 2023. The detailed design is expected to be completed by November 2024. The procurement cost of the lead ship in the class is estimated to be $789.6m.
The contract includes options for detailed design and construction of up to seven TAGOS-25 class ships, bringing the cumulative value of the contract to approximately $3.2bn. The detailed design work will extend until June 2034, if the options are exercised.
The project is expected to support the US Navy in replacing its five old in-service TAGOS ships with seven larger and faster TAGOS-25 class ships. The vessels planned to be retired include four Victorious (TAGOS-19) class ships (TAGOS 19 through 22) that entered service between 1991 and 1993 and one Impeccable (TAGOS-23) class ship, which entered service in 2000.
TAGOS-25 class ocean surveillance ships design and details
TAGOS-25 class ships will be 356ft (110m) long and feature a steel small waterplane area twin hull (SWATH) design. The upper section of the ship is supported by two struts that reach down to a set of submerged hulls resembling those of a submarine. The struts feature a slender profile where they meet the waterline, resulting in a minimal waterplane area.
The ships will have an 8,500t displacement and accommodation for 68 personnel. They will support the navy’s Integrated Undersea Surveillance System (IUSS) for collecting underwater acoustical data, using Surveillance Towed-Array Sensor System (SURTASS) equipment. The high stability of the SWATH design in adverse weather conditions is useful for SURTASS operations.
The other associated electronic equipment on the ships will help in processing and transmitting the data to shore stations through satellite, for evaluation. The ship will be able to sail at a maximum speed of 20 knots.
SURTASS system details
SURTASS is a low-frequency, passive and active, acoustic surveillance system, which is installed on TAGOS ships as a component of the IUSS.
The IUSS consists of stationary, movable, and deployable acoustic arrays that offer crucial tactical information to ASW units. It serves as the primary means for detecting both nuclear and diesel-powered submarines.
The SURTASS capability enables the timely dissemination of surveillance data to ASW commanders. The system ensures real-time reporting of crucial surveillance information.
Austal USA has collaborated with L3Harris Technologies (L3Harris), Noise Control Engineering (NCE), TAI Engineering and Thoma-Sea Marine Constructors (Thoma-Sea) to deliver the TAGOS-25 programme.
L3Harris is an aerospace and defence company based in the US while NCE is an acoustical engineering consultant based in Australia. TAI Engineering is an engineering company and Thoma-Sea is a marine vessel repair and construction company, both of which are based in the US.
The ships will be built at Austal’s new state-of-the-art steel shipbuilding facility in Mobile, Alabama, US.