U.S. and UK Navies to Begin Trident II D5 Submarine-Launched Missile Modernization in 2026.

The U.S. Navy and UK Royal Navy will launch the Trident II D5 Increment 8 modernization in October 2026, updating shipboard navigation systems across Ohio, Columbia, Vanguard, and Dreadnought submarines. The $3 billion effort, led by Lockheed Martin, aims to counter obsolescence and sustain the credibility of the allied sea-based deterrent through the 2080s.

The U.S. Navy and the UK Royal Navy will launch the Trident II D5 Increment 8 modernization in October 2026, a package focused on upgrading the shipboard navigation subsystem across Ohio and Columbia in the U.S. fleet and Vanguard and Dreadnought in the UK. The Navy plans to place the work with Lockheed Martin Rotary and Mission Systems, covering hardware and software design, testing, installation, repairs, spares, and fleet support to confront obsolescence while preserving accuracy and availability for continuous at-sea deterrent patrols.
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The Trident II D5 is a three-stage, solid-fuel SLBM carrying MIRVs with stellar-inertial guidance and a 12,000 km range, providing high-precision sea-based nuclear deterrence (Picture source: U.S. Navy).

Planning documents on the U.S. government’s contracting portal point to a performance window beginning October 1, 2026, with the requirement framed as product-based procurement augmented by targeted engineering services for the Strategic Weapon System shipboard navigation chain. This aligns with reports that Increment 8 will refresh navigation from sensor inputs through interfaces with fire control, ensuring fault-tolerant alignment on legacy hulls while fielding a common baseline for new construction boats.

The missile at the center of this effort remains the UGM-133A Trident II D5, a three-stage, solid-fueled, submarine-launched ballistic missile that entered service in 1990 and has undergone successive life extension campaigns to maintain reliability. Open-source technical data place the D5 at 13.42 meters in length with a 2.11-meter diameter and an approximate 59,090-kilogram launch weight. It carries up to 2,800 kilograms of payload with multiple independently targetable reentry vehicles and uses an inertial navigation system augmented by a stellar reference to guide the post-boost vehicle.

Increment 8 matters because navigation accuracy is the keystone of an SLBM fire control solution. The Trident II D5’s maximum range is estimated at roughly 12,000 kilometers, with a circular error probable near 90 meters, parameters that demand stable alignment through long patrols and rapid fine-tuning before launch. The Strategic Weapon System integrates launch, fire control, navigation, and support functions, so a navigation refresh touches every step from initialization to aim point generation. For operators, this promises tighter error budgets, improved resiliency to sensor drift, and more efficient maintenance through modularized navigation hardware that shortens yard periods without sacrificing accuracy.

The program enters this phase on the back of recent at-sea validation. In September 2025, an Ohio-class SSBN executed a test event off Florida to verify the performance of the latest D5 Life Extension configuration and to reaffirm system accuracy and reliability. Program officials have framed the life extension pathway as a methodical response to component obsolescence that sustains the weapon through the 2080s, a horizon that matches the service lives of Columbia and Dreadnought.

U.S.-UK cooperation on sea-based strategic systems is rooted in the Polaris Sales Agreement, signed in April 1963 and amended in 1982, which established a framework for the United States to supply submarine-launched ballistic missiles while the United Kingdom builds and operates its own boats and warheads. This bilateral accord has underpinned interoperability, common logistics, and synchronized modernization for decades. The arrangement yields a shared missile architecture and common navigation standards, reducing integration risk and cost while binding the two national deterrents to a single technical baseline.

Nearly 3 billion dollars from the U.S. Navy’s FY26 budget line is allocated to the Trident II life extension program, supplemented by roughly 400 million dollars from the One Big Beautiful Bill Act. The forthcoming Lockheed Martin effort is set to deliver a full stack of design, production, installation, and sustainment tasks against that funding, ensuring that the navigation refresh dovetails with fleet maintenance cycles and does not erode patrol availability. Earlier contracting actions and presolicitations already outline shipboard navigation support, incremental integration, and spares provisioning, indicating the industrial base is aligned for a smooth transition to the Increment 8 standard.

A more robust navigation backbone tightens aim point confidence from dispersed patrol boxes, preserves credible second-strike capability from undetected positions, and accelerates turnaround when boats cycle through upkeep. Commonality across Ohio and Vanguard to Columbia and Dreadnought simplifies training pipelines, reduces spares complexity, and enhances cyber and anti-interference posture in a threat environment shaped by peer adversaries investing heavily in counters to Western command, control, and precision guidance. Precision at launch remains the foundation of deterrent credibility, and Increment 8 is designed to keep that foundation intact as a new generation of SSBNs takes the watch.