In late 2016 the U.S. Navy received the USNS Lewis B. Puller, which is the first of two T-ESB ships. The “ESB” part of a recent trend and stands for Expeditionary Mobile Base. This design was previously known as MLP (Mobile Landing Platform) or AFSB (Afloat Forward Staging Base). T-ESB is a 78,000 ton ship that is basically a modified oil tanker. The flight deck can handle the heavy (33 ton) CH-53 transport helicopters as well as the MV-22 tilt rotor aircraft. A structure on the hanger deck mine-clearing gear used by the helicopters (like four mine clearing sleds towed by the helicopters). The hanger deck carries boats and unmanned surface and underwater vehicles weighing up to 11 tons (the max that the cranes can handle.) There are accommodations for an additional 298 personnel (commandos, marines, specialists of any sort). There are plans to add a gym and other facilities for troops. The flight deck can also operate many types of UAVs. There is a lot of cargo space for supplies and fuel. The ship is highly automated and only needs a crew of 34.
In early 2013 the U.S. Navy received the first (USNS Montford Point) of three T-ESD (Expeditionary Transfer Dock, formerly T-MLP) ships. Montford Point successfully completed its sea trials and entered service in early 2014. The navy completed another T-ESD in 2013. Instead of building more of this design the navy switched to different (but similar) design; T-ESB. Originally the navy sought to use the T-ESD design as floating bases to support commando type operations ashore. The T-ESDs are 34,500 ton vessels that, in effect, serve as seagoing piers for situations where there is no friendly port handy. Each is 239 meters (785 feet) long and has up to 2,322 square meters (25,000 square feet) of space for storage of vehicles and aircraft. The second two T-ESD was to be equipped as an AFSB (Afloat Forward Staging Base) with command and control equipment (electronics and communications gear) added as well as distinct flight deck area.
The T-ESD looks like a container ship with the main deck lowered to approximately the height of a dock. On the side of the T-ESD are mooring fenders (so cargo ships can, literally, tie up like at a dock). The T-ESD also has ramps for getting cargo from ships or a dock. Cargo would be transferred to landing craft or LCAC (air-cushion high speed landing craft which can carry 60 tons of cargo). The T-ESD can also partially submerge itself so that its deck is underwater. Landing craft can then move over the deck and the T-ESD can bring its deck back out of the water so the landing craft can be loaded. T-ESDs are to each carry three LCACs. The AFSB variants can also carry helicopters and MV-22 tilt rotor aircraft. The navy plans to increase the fire resistance of part of the deck so that the AFSBs can also handle vertical takeoff version of the F-35.
The T-ESD and T-ESB are built to commercial (not military) ship standards and use civilian crews (as is the case with all USNS ships). They can be equipped with defensive (anti-missile) systems.
Work on these concepts began earlier. In 2012 an American LPD (amphibious ship with a dock in the rear for small boats) USS Ponce, an Austin class amphibious ship, was rapidly (five months) modified to be a support ship (for mine clearing mainly, but also disaster relief or supporting commando operations). Normally these LPDs carry a reinforced battalion of marines, plus six CH-46 helicopters and 39 landing craft (24 of them AAV infantry fighting vehicles). The Ponce is a 17,000 ton ship with a crew of 420, plus space for 900 marines and vehicles or cargo. The shipyard conversion saw a lot of berthing spaces for the marines converted to work areas (for headquarters or training). Since the converted ship gets by with half as many crew, the crew quarters are remodeled to make them roomier and more comfortable. The modified Ponce was equipped to support smaller mine clearing ships and helicopters as well as serving as a floating base for MH-53 mine clearing helicopters. There is also more communications gear and special equipment, like UAVs and UUVs (unmanned submarines the size of torpedoes used for finding mines). Its designation was changed from LPD-15 to AFSB-15.
This was not a new concept as in 2006 Austin class amphibious ship was sent to the Indian Ocean without the normal complement of marines. That ship was instead used as a floating base for UAVs and SOF (special operations forces). A similar task was assigned a navy carrier in 2002, to support SOF operations in Afghanistan. In 2006, it was believed that the amphibious ship was also supporting SOF operations ashore in Somalia or Iran. The Austins are normally armed with two 25mm autocannon, two 20mm Phalanx for anti-missile work, and eight 12.7mm machine-guns.