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US Navy TAGOS-25 Explorer-class ships: cost overruns delays and strategic importance in Anti-Submarine Warfare.


The report "Navy TAGOS-25 Ocean Surveillance Shipbuilding Program: Background and Issues for Congress", published on January 23, 2025, provides an in-depth analysis of the Navy's plan to procure seven TAGOS-25 class ships, recently renamed the Explorer class, while addressing critical issues such as cost overruns, schedule delays, and the strategic importance of countering submarine threats from adversaries like China and Russia.
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Artist rendering of the future TAGOS-25 Explorer-class Ocean Surveillance Ships. (Picture source: Austal USA)


The U.S. Navy’s TAGOS-25 class ocean surveillance ships, recently named the Explorer class, represent a modernization effort to enhance the Navy’s anti-submarine warfare (ASW) capabilities. Designed to replace the aging Victorious and Impeccable classes, these ships will serve as critical assets in the Navy’s Integrated Undersea Surveillance System (IUSS). However, the program faces challenges, including rising costs, procurement delays, and evolving operational requirements, prompting heightened scrutiny from Congress and defense stakeholders.

The TAGOS-25 class ships are designed to gather undersea acoustic data using the advanced Surveillance Towed-Array Sensor System (SURTASS). This data supports ASW missions by providing critical insights into submarine activities, particularly from near-peer adversaries such as China and Russia. The current TAGOS fleet comprises five vessels—four Victorious-class ships commissioned between 1991 and 1993, and one Impeccable-class ship commissioned in 2000. All are homeported in Yokohama, Japan, and feature the Small Waterplane Area Twin Hull (SWATH) design, which enhances stability in high seas, an essential attribute for extended surveillance operations.

The new TAGOS-25 class builds on this legacy, employing a larger and faster SWATH design to improve operational efficiency. Named the Explorer class in January 2025, the first two ships, Don Walsh and Victor Vescovo, honor pioneers in exploration, reflecting the Navy’s acknowledgment of the critical role these vessels will play in charting the future of undersea surveillance. The Navy plans to procure seven Explorer-class ships to replace the five aging vessels, but procurement schedules have been adjusted, with the second ship deferred from FY2025 to FY2026. The revised schedule anticipates the procurement of one ship annually from FY2026 to FY2029 under the Future Years Defense Plan (FYDP), with the final two ships planned beyond this timeline.

Cost escalation has become a major concern. The estimated cost of the first TAGOS-25 ship has risen to $789.6 million, marking an increase of nearly 82% over initial projections. Inflation, supply chain disruptions, and higher non-recurring engineering expenses are cited as contributing factors. Additionally, procurement costs for the sixth and seventh ships have been adjusted upward to reflect these trends, raising questions about whether similar adjustments will be necessary for earlier ships in the class. The first ship’s design and construction have also faced delays, with a reported one-year setback raising concerns about the program’s overall schedule.

The Navy awarded Austal USA a $113.9 million contract in May 2023 for the design of the TAGOS-25 class, with options for up to seven ships. If all options are exercised, the total contract value could reach $3.2 billion. In May 2024, Austal received a $516 million contract modification for long-lead materials and construction of the first ship, signaling progress but also highlighting the financial complexity of the program.

The decision to defer FY2025 funding for the TAGOS-25 program has drawn attention from Congress. Lawmakers have expressed concerns over the implications of this delay on fleet readiness, particularly as adversaries continue to modernize their submarine capabilities. The deferral aligns with broader budgetary adjustments but underscores the importance of maintaining momentum in delivering these critical assets.

Strategically, the TAGOS-25 program is essential to countering submarine threats from adversaries like China, which has made significant advancements in its nuclear-powered attack submarine fleet. The Explorer-class ships will provide enhanced surveillance capabilities, ensuring the Navy remains at the forefront of undersea warfare and maritime dominance.

While the program promises to strengthen the Navy’s ability to monitor global undersea activities, challenges such as cost growth, schedule delays, and shifting procurement timelines must be addressed to ensure its success.


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