U.S. Navy completes first Los Angeles-class fast attack submarine refueling overhaul.

The U.S. Navy has completed a Service Life Extension Program refueling overhaul for USS Cheyenne (SSN 773) at Portsmouth Naval Shipyard, marking the first submarine to undergo an SLEP overhaul. The milestone extends Cheyenne’s service life beyond 44 years and highlights the Navy’s strategy to ease attack submarine shortages by sustaining existing platforms.

According to information published by the U.S. Department of War on December 23, 2025, the U.S. Navy has completed a major Service Life Extension Program refueling overhaul for USS Cheyenne (SSN 773), the last-built Los Angeles-class fast attack submarine and the first submarine to undergo an overhaul under the SLEP initiative. Conducted at Portsmouth Naval Shipyard in Kittery, Maine, the effort restores the submarine’s nuclear propulsion core, upgrades critical combat systems, and extends Cheyenne’s total service life to beyond 44 years, returning a key undersea asset to operational readiness amid growing fleet demand.
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The upgraded U.S. Navy Los Angeles-class fast attack submarine USS Cheyenne (SSN 773) departs Portsmouth Naval Shipyard for post-overhaul sea trials in December 2025. (Picture source: U.S. Department of War))

The Los Angeles-class, known in U.S. Navy nomenclature as the 688-class, comprises nuclear-powered fast attack submarines (SSNs) designed for high-speed, deep-ocean operations. First introduced in the 1970s, these boats were built to counter Soviet naval capabilities during the Cold War and remain among the fastest and most maneuverable submarines ever produced. With submerged speeds exceeding 30 knots and a dive depth estimated at more than 800 feet, these submarines are optimized for anti-submarine warfare (ASW), intelligence collection, strike missions using Tomahawk cruise missiles, and special operations delivery. Their compact reactor design and low acoustic signature make them highly survivable and lethal in contested environments.

Out of the original 62 Los Angeles-class submarines constructed between 1972 and 1996, approximately 28 remain in active service as of late 2025. While newer Virginia-class SSNs have begun replacing them, industrial capacity constraints and delays in Virginia-class production have created a readiness gap, especially as global operational demands rise in regions such as the South China Sea, North Atlantic, and Arctic. The decision to refuel and extend the life of select Los Angeles-class hulls, such as Cheyenne, represents a stopgap solution to sustain undersea dominance while new construction accelerates.

The Service Life Extension Program (SLEP) for Los Angeles-class submarines is a multi-phase engineering effort designed to restore nuclear propulsion capability, modernize electronic and sensor suites, and ensure structural integrity for continued deployment. The centerpiece of the program is the Engineered Refueling Overhaul (ERO), which involves replacing the nuclear reactor’s expended fuel with a new core - a highly complex and hazardous task conducted at only a few specialized naval shipyards. In addition to the refueling, SLEP includes hull preservation, propulsion plant modernization, sonar and combat system upgrades, and habitability improvements. For Cheyenne, this also meant integrating the latest AN/BQQ-10 sonar processing systems and AN/BYG-1 combat control suite, aligning her sensor and weapons capabilities with the most modern platforms in the fleet.

Unlike standard mid-life overhauls, which may only extend service by a few years, SLEP combined with refueling can yield an additional 10 to 15 years of high-tempo deployment. This approach is cost-effective when compared to new construction, with a typical Virginia-class SSN costing over $3.5 billion and taking seven years or more from contract award to fleet delivery. In contrast, SLEP allows the Navy to regain a fully mission-capable platform at a fraction of the cost and in half the time, assuming industrial throughput is maintained.

“The Cheyenne Project Team has essentially reset the technical playbook for how we sustain and extend our nuclear-powered attack submarines,” said Shipyard Commander Capt. Jesse Nice. “This overhaul wasn’t just about refueling - it was a comprehensive reset of propulsion, combat systems, and platform survivability. The result is a submarine ready to go to war today.”

With USS Cheyenne now back in the fleet, Navy planners are analyzing which additional hulls from the 688 Improved subclass - those built with quieter machinery and vertical launch systems (VLS) - can follow suit. The operational logic is clear: retain proven assets with recent combat upgrades while bridging to the Columbia-class SSBN and Block V Virginia-class programs.

According to internal Navy sources familiar with submarine availability rates, the service has already identified up to five additional Los Angeles-class boats as strong candidates for SLEP, contingent on budget approval in FY2026. The priorities include SSNs with strong maintenance histories and viable structural conditions. If authorized, this could restore several gigawatts of nuclear-powered combat power to the fleet by the early 2030s, precisely when U.S. undersea presence is most at risk of being outpaced by Chinese PLAN submarine growth.

The return of Cheyenne also highlights the Navy's growing focus on industrial reform. PNSY delivered the overhaul nearly two months ahead of its rebaselined schedule, a rare victory in a shipyard system that has faced persistent criticism over backlogs and workforce constraints. Commodore of Submarine Squadron TWO, Capt. Jason Deichler emphasized the operational urgency. “This is industrial velocity at work. The Cheyenne team answered the Secretary’s call, and we’re seeing the results in steel and capability back on the waterfront.”

As the U.S. Congress weighs the FY2026 defense appropriations and the submarine industrial base continues to absorb the dual pressure of Virginia-class and Columbia-class demands, the success of Cheyenne’s overhaul offers compelling proof of concept. For defense planners and fleet operators alike, SLEP is no longer theoretical - it’s afloat, mission-ready, and armed for the future.

Written by Alain Servaes – Chief Editor, Army Recognition Group
Alain Servaes is a former infantry non-commissioned officer and the founder of Army Recognition. With over 20 years in defense journalism, he provides expert analysis on military equipment, NATO operations, and the global defense industry.