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Expeditionary Sea Base (ESB)

Last updated: 21 Jan 2021


The Expeditionary Sea Base (ESB) ship class is a highly flexible platform used across various military operations. ESB ships are mobile sea-based assets and are a part of the critical access infrastructure that supports the deployment of forces, equipment, supplies, and warfighting capability. 

The ships were initially called the Mobile Landing Platform (MLP) and the MLP Afloat Forward Staging Base (AFSB), respectively. In September 2015, the Secretary of the Navy re-designated these hulls to conform to traditional three-letter ship designations. The design of these ships is based on the Alaska-class crude oil carrier built by General Dynamics National Steel and Shipbuilding Company (NASSCO). Leveraging commercial designs ensures design stability and lowers development costs.

The USS Lewis B. Puller (ESB 3), USS Hershel “Woody” Williams (ESB 4), USS Miguel Keith (ESB 5), and follow-on ships John L. Canley (ESB 6), Robert E. Simanek (ESB 7), and Hector A. Cafferata Jr. (ESB 8) support a variety of maritime based missions, including Special Operations Forces (SOF) and Airborne Mine Counter Measures (AMCM). ESBs have a four-spot flight deck, mission deck, and hangar, designed around four core capabilities: aviation facilities, berthing, equipment staging support, and command and control assets.

In August 2017, upon arrival in the U.S. 5th Fleet Area of Responsibility, ESB 3 was re-designated from USNS and commissioned as a USS. As a commissioned Navy ship, USS Lewis B. Puller (ESB 3) is commanded by a Navy O-6 with a permanently embarked military crew. In September 2019, the Secretary of the Navy approved the change in ship classification for all ESBs from auxiliary (USNS) ships to warships (USS). This re-designation allows combatant commanders greater operational flexibility in employing the ship.



The Navy awarded NASSCO a fixed-price incentive fee type contract for the Detail Design and Construction (DD&C) of T-ESD 1 and T-ESD 2 in May 2011. A DD&C was awarded to NASSCO for T-ESD 3 in February 2012. After receiving JROC approval, the ship configuration was subsequently changed to ESB 3 during construction via an engineering change proposal in March 2014. A DD&C contract for ESB 4 was awarded in December 2014, and the DD&C for ESB 5 was awarded in December 2016. In August 2019, NASSCO was awarded a DD&C contract for ESB 6 and 7. The DD&C for ESB 8 was awarded in August 2022. 

Fleet deliveries include T-ESD 1, T-ESD 2, ESB 3, ESB 4, ESB 5, and ESB 6. ESB 7 is under construction. ESB 8, the last ship in this class, started construction in August 2023 and will deliver in 2026.

General Characteristics, Expeditionary Sea Base (ESB)
Builder: NASSCO
Propulsion: Commercial Diesel Electric Propulsion
Length: 239.3 Meters (785 feet)
Beam: 50 Meters (164 feet)
Displacement: 90,000 tons (fully loaded)
Draft: 10.5 Meters (fully loaded); 12 Meters (load line)
Speed: 15 knots
Range: 9,500 nautical miles
Crew: 44 Military Sealift Command personnel
Military Crew: 101 military (Accommodations for 250)
USS Lewis B. Puller (ESB 3), Norfolk, Virginia
USS Hershel 'Woody' Williams (ESB 4), Souda Bay, Greece
USS Miguel Keith (ESB 5), San Diego, California
John L. Canley (ESB 6) - Delivered March 2023; Homeport TBD
Robert E. Simanek (ESB 7), Under Construction
Hector A. Cafferata Jr. (ESB 8), Under Construction


Point of Contact
Naval Sea Systems Command
Office of Corporate Communication (SEA 00D)

Washington, D.C. 20376

(202) 781-4123


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