KITTERY, Maine – After years of meticulous work at Portsmouth Naval Shipyard, the nuclear-powered attack submarine USS Cheyenne (SSN 773) returned to sea in December 2025, completing a landmark refueling and overhaul that extends its service life well into the 2040s. The completion of the overhaul, and the submarine’s subsequent departure for sea trials, marks a significant milestone for both the Navy and the shipyard, demonstrating a renewed focus on maintaining a robust undersea fleet.
The Cheyenne, the final submarine of the Los Angeles class, underwent an Engineered Refueling Overhaul (ERO) at the shipyard, a complex process involving the removal of its spent nuclear fuel and the installation of a new core. This overhaul, coupled with extensive repairs and modernization efforts, is projected to add at least a decade, and potentially up to 15 years, to the submarine’s operational lifespan, pushing its total service beyond 44 years. The work was completed roughly two months ahead of a revised schedule, according to Navy statements.
The decision to extend the life of the Cheyenne and other Los Angeles-class submarines comes as the Navy faces increasing demands for undersea capabilities in key strategic regions, including the South China Sea, the North Atlantic, and the Arctic. While newer Virginia-class submarines are being built, production capacity and scheduling delays have created a gap between retiring older vessels and the delivery of their replacements. Maintaining and upgrading existing Los Angeles-class submarines provides a cost-effective way to bridge this gap.
The Service Life Extension Program (SLEP) applied to the Cheyenne is not simply a patch job, but a comprehensive modernization effort. Beyond refueling, the overhaul included upgrades to the submarine’s combat systems, sonar, and hull. Specifically, the Cheyenne received the AN/BQQ-10 sonar processing system and the AN/BYG-1 combat control system, bringing its capabilities in line with those of newer attack submarines. These upgrades enhance the submarine’s ability to track targets, launch Tomahawk cruise missiles, and conduct intelligence gathering operations.
The cost of a SLEP overhaul is significantly less than the $3.5 billion-plus price tag of a new Virginia-class submarine, and can be completed in roughly half the time. This cost-benefit ratio is particularly appealing to Navy planners facing budgetary constraints and a rising submarine threat from the People’s Liberation Army Navy of China.
Portsmouth Naval Shipyard’s successful completion of the Cheyenne overhaul is as well being touted as a demonstration of improved efficiency and industrial reform within the Navy’s shipbuilding infrastructure. The shipyard has been working to address past issues of delays and maintenance backlogs, and the early delivery of the Cheyenne is seen as a positive sign. Faster turnaround times at public shipyards directly translate to more submarines available for deployment.
Following the success with the Cheyenne, Navy officials are evaluating other “688 Improved” Los Angeles-class submarines as candidates for similar SLEP overhauls. These later models, equipped with quieter machinery and vertical launch systems, are considered particularly valuable assets to retain in service. Internal assessments suggest as many as five additional submarines could be viable candidates, pending funding decisions in the 2026 defense budget.
Los Angeles-class submarines are designed for a wide range of missions, including tracking enemy submarines and surface ships, launching cruise missiles against land targets, conducting intelligence gathering, and deploying special operations forces. The Cheyenne’s upgraded systems and extended service life will allow it to continue performing these critical roles for years to come. Its low acoustic signature and compact reactor design contribute to its stealth and effectiveness in contested environments.
The Navy has not yet announced the Cheyenne’s next deployment or operational schedule. The submarine is currently undergoing post-overhaul sea trials to verify the effectiveness of the upgrades and ensure it is fully mission-ready.
