US Navy to begin engine testing for future DDG(X) destroyer marking key step toward shipbuilding phase.

On July 8, 2025, Fairbanks Morse Defense (FMD) announced that it has been awarded a contract to deliver its FM 175D high-speed diesel generator engine for installation at the U.S. Navy’s land-based propulsion system test facility supporting the DDG(X) program. The award marks a key milestone in the development of the Navy’s next-generation guided-missile destroyer, designed to succeed the Ticonderoga-class cruisers and early Arleigh Burke-class destroyers.
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The DDG(X) program, designated PMS 460, was formally established in 2021 as part of the Navy’s Large Surface Combatant (LSC) initiative following the cancellation of the CG(X) program and the downsizing of the Zumwalt-class destroyers. (Picture source: US Navy)

The FM 175D will be integrated into the DDG(X) Integrated Power System (IPS) test site to support validation of energy production, fuel efficiency, and operational performance under simulated operational conditions. This effort is part of the Navy’s broader strategy to reduce design risk ahead of construction, with shipbuilding for the first DDG(X) hull currently planned to begin no earlier than 2032. Rear Admiral Bill Daly, Director of Surface Warfare, has described DDG(X) as a “clean-sheet imperative” in the Navy’s shipbuilding plan, requiring propulsion systems capable of supporting advanced combat technologies such as directed-energy weapons and hypersonic missiles, both of which demand unprecedented electrical output.

The FM 175D is among the most power-dense marine engines available in the U.S. market, designed to produce between 1,740 and 4,400 kilowatts of power depending on configuration. It features a 175 mm cylinder bore, a 215 mm piston stroke, and operates on a four-stroke cycle with a displacement of 5.17 liters per cylinder. The engine is available in 12, 16, or 20-cylinder arrangements and can function either as a mechanical propulsion system or a generator, delivering electrical output up to 3.8 megawatts. It operates at 1,800 to 2,000 RPM and supports a range of naval fuels including DMA, DMZ, F-75, and F-76. Designed to minimize life-cycle costs, the FM 175D integrates a high-efficiency turbocharger, a mounted control system, an advanced common-rail electronic fuel injection system, and four auxiliary power take-offs. The engine features extended service intervals and is intended for high availability under continuous naval operations. Physical dimensions and weights vary by configuration: for example, the 20V propulsion model measures approximately 3.94 meters in length and weighs 13.3 metric tons, while its generator equivalent extends to 6.5 meters and weighs 27 tons. The FM 175D was launched into the U.S. market in 2023 and is already deployed in military and commercial fleets globally, reinforcing its status as a proven, scalable, and fuel-efficient platform suitable for integration into next-generation surface combatants.

This engine will be installed at the Naval Surface Warfare Center in Philadelphia, where a full-scale land-based test site has been established to simulate DDG(X) propulsion operations. In 2023, the Navy announced plans to invest $122 million in developing this test infrastructure, which will support evaluation of the full IPS under ship-representative electrical loads. The test facility will be used to validate the ability of the FM 175D to generate consistent and reliable electrical power for the DDG(X)’s high-energy mission systems, propulsion drives, and shipboard operations. The testing will address load-following behavior, thermal efficiency, maintenance predictability, and generator performance under variable conditions. The Fiscal Year 2025 National Defense Authorization Act mandates that all key propulsion technologies for DDG(X) be tested in land-based environments, with a focus on engines capable of delivering at least 40 megawatts of reserve power. The IPS architecture, derived from the Zumwalt-class’s turbo-electric drive, will replace conventional mechanical transmission systems, using gas turbines and diesel engines to produce electric current that powers all ship systems. FMD’s FM 175D thus plays a pivotal role in de-risking IPS integration before installation on the first hull, ensuring compatibility and performance under conditions reflective of future destroyer operations.

The DDG(X) program, designated PMS 460, emerged following the cancellation of the CG(X) cruiser program and the scaling down of Zumwalt-class destroyer procurement, which was reduced to three ships due to cost overruns and design complexity. In response, the Navy launched the Large Surface Combatant (LSC) initiative, which formally evolved into the DDG(X) program with the establishment of the PMS 460 office in 2021. The platform is intended to replace 22 Ticonderoga-class cruisers and 28 early Arleigh Burke destroyers as they reach the end of their service lives in the 2020s and early 2030s. Compared to the Flight III Arleigh Burke-class, which has reached its limits in terms of power, weight, and cooling capacity, the DDG(X) is designed to incorporate advanced weaponry, sensors, and modular systems that the existing hulls cannot support. The DDG(X) will provide greater range, improved endurance, and reduced fuel consumption, up to 25 percent lower than current destroyers, while increasing power generation by more than 75 megawatts. It will also introduce new hull forms, stealth features, and additional space for future upgrades, enabling the integration of systems not yet operational at the time of launch.

Throughout 2024 and 2025, several new renderings of the DDG(X) revealed evolving concepts. The most recent version, unveiled by the Program Executive Office (PEO) Ships during a ceremony for the outgoing DDG(X) program manager, omitted the traditional 5-inch Mk 45 Mod 4 naval gun from the bow, a fixture on current U.S. destroyers. The redesigned VLS array consists of four 8×2-cell Mk 41 blocks configured in a new layout, leaving space to accommodate larger-diameter missile cells such as the G-VLS under development by Lockheed Martin. Changes were also observed in the topside sensor configuration: two Mk 144 Guided Missile Launchers were repositioned, front-facing bridge windows were reduced or eliminated, and port/starboard AN/SLQ-32(V)7 arrays were removed or replaced with new modules. The revised exhaust system and new radome configurations suggest enhancements in both signature management and radar integration. These changes also reflect a broader shift toward reliance on active missile homing technologies, reducing the need for older fire-control illuminators such as the AN/SPG-62.

The DDG(X) is being designed with the explicit goal of enabling future upgrades without major structural modifications. Its open architecture will support evolving command, control, communication, computer, cyber, and intelligence (C5I) systems as well as enhanced electronic warfare capabilities. It will offer significantly more volume for vertical launch systems, payload bays, and directed-energy weapons. The Navy has confirmed the DDG(X) will be built with provisions for a Destroyer Payload Module (DPM), an additional mid-body hull section that can increase internal volume for new systems or armament. Its propulsion design is intended to support both current combat systems and emerging power-hungry technologies such as lasers in the 150–600 kilowatt range. The Flight III Arleigh Burke destroyers, including the USS Jack H. Lucas (DDG-125), already carry the AN/SPY-6(V)1 radar and Aegis Baseline 10, but the DDG(X) will scale those systems further with enhanced versions and integrated energy management. These upgrades position the class for eventual deployment of next-generation capabilities such as Intermediate-Range Conventional Prompt Strike (IRCPS) hypersonic missiles, currently being integrated into the Zumwalt-class.

The DDG(X) is projected to displace approximately 13,500 tons, nearly 40 percent more than the 9,700-ton Flight III Arleigh Burke-class, and will incorporate a modern Integrated Power System combining gas turbines and high-efficiency diesel engines like the FM 175D. Its baseline armament will include 96 Mk 41 VLS cells, with options to swap 32 of these for 12 larger launch cells for hypersonic missiles. The ship will likely be outfitted with two 21-cell RIM-116 Rolling Airframe Missile launchers, high-powered lasers, advanced radar arrays, and a full-length flight deck with hangar facilities for rotary-wing and unmanned aircraft. The hull will feature reduced infrared and acoustic signatures, improved underwater stealth, and enhanced survivability through distributed systems architecture and automated damage control. With electrical margins allowing for the integration of energy-intensive systems, the DDG(X) is expected to remain relevant through the 2060s, serving as the backbone of the Navy’s future surface combatant fleet and a primary enabler of distributed maritime operations in high-threat environments.