VESSEL REVIEW | AFDM 15 – US Navy acquires medium floating dry dock for surface ship maintenance

Austal USA has completed outfitting of AFDM 15, the first auxiliary floating drydock Medium (AFDM) to be built for the US Navy in more than 40 years, following the dock's launch into the Mobile River in Alabama on July 28, 2026.

The non-self-propelled dock is intended to give the navy a repair facility that can be positioned close to the fleet rather than tied to a home shipyard.

"From the US Navy's perspective, the core requirement and brief was straightforward: we needed a deployable asset capable of lifting ships completely out of the water to conduct essential maintenance and repairs anywhere in the world," a US Navy spokesperson told Baird Maritime.

AFDM 15 is a Rennie-type floating drydock. Its multiple sectional pontoons and uninterrupted wing walls provide the stability and displacement needed for the dock to submerge and then use buoyancy to raise vessels clear of the water. It measures 694 feet (212 metres) in length and 157 feet (47.9 metres) across the pontoons, has a design-rated lift capacity of 18,000 tons and offers 90,800 square feet (8,440 square metres) of clear working deck. Austal reported the dock itself at approximately 12,000 tons.

The spokesperson said the dock is, "designed to be highly mobile and capable of lifting a wide variety of navy vessels — from littoral combat ships (LCS) to cruisers and destroyers — completely out of the water for emergency repairs and regular maintenance."

Austal also identified dock landing ships of the Whidbey Island-class and Harpers Ferry-class as vessels that the AFDM can accommodate.

"AFDMs are typically deployed to forward-operating bases and major naval hubs to serve as mobile repair facilities," the spokesperson said.

In routine operation the dock ballasts down so that a damaged or maintenance-due warship can enter, then de-ballasts to lift the ship clear of the water. This gives engineers and shipbuilders dry access to the hull, propulsion systems and underwater appendages for repair, cleaning and painting.

Able to provide maintenance support even in low-threat environments

The navy describes the role as forward-deployed, depot-level maintenance. According to the spokesperson, placing floating docks in strategic locations removes the need for damaged or heavily fouled warships to transit thousands of miles back to the continental United States for drydocking, thereby increasing fleet readiness, operational availability and surge capacity in contested or remote theatres.

The dock is capable of operating in benign threat environments and can be relocated to address the fleet's maintenance needs in the future.

The dock has no traditional propulsion system and must be towed to its designated operating area by fleet ocean tugs such as the T-ATS class or by commercial heavy-lift tugs, the spokesperson said.

Automated systems ensuring more precise operations

The spokesperson said the dock's electronics fit centres on ballast control consoles, precision water level monitoring, stress and deflection monitoring systems, and localised command and control to ensure ships are lifted safely and level.

"Modern AFDMs integrate highly automated ballasting systems that can make micro-adjustments in real-time," the spokesperson told Baird Maritime. "This is particularly important for safely cradling vessels with complex or unconventional hull forms, such as the aluminium trimaran hulls of the Independence-variant LCS."

Deck equipment comprises high-capacity ballast pumps, heavy-duty travelling cranes running along the wing walls, capstans, and heavy mooring winches used to position ships over the keel blocks, along with extensive staging and scaffolding systems.

The original contract scope also included a vehicle bridge.

The spokesperson said the new AFDM includes several design features meant to enhance its own maintainability and operability. Austal said those features reflect knowledge gained through its ownership, operation and maintenance of a comparable drydock at its Mobile ship repair facility.

The dock also carries extensive hotel service connections.

"Because a warship must shut down its own engines and generators while high-and-dry, the drydock is equipped to provide the docked vessel with shore power, potable water, fire main pressure, and compressed air, acting as a fully self-sustaining base for the crew while repairs are underway," the spokesperson said.

Slated for US West Coast operation

Heger Dry Dock worked with Austal on the design of the AFDM. Austal received the detail design and construction contract in June 2022, with an initial firm-fixed-price award of US$128 million, and began construction in June 2023 on its steel assembly line. An US$11.6 million modification in December 2023 covered changes to the emergency diesel generator design and installation of an EPA Tier IV solution.

The dock was assembled at Alabama Shipyard, then Berard Transportation used self-propelled modular transporters to move it onto Dry Dock Alabama. After the transfer, Dry Dock Alabama was lowered in stages, with watertight integrity checks conducted between stages; AFDM 15 then floated free.

Austal said it is the largest vessel it has launched in its 26-year history. Before delivery, Austal still expects to install the crane, light off the generator, and conduct builder's and acceptance trials. Delivery is expected in the first quarter of 2027.

Heger Dry Dock President Premal Shah said in 2023 that the AFDM was intended for the naval base in San Diego.