Basically, the San Antonio, which, at 25,000 tons, is larger than the Austin class ships it is intended to replace, carries 800 Marines and their vehicles, supplies and gear. Like other ships designed to deliver Marines to amphibious assaults, it is diesel powered.
They will have deck spots for operating and supporting up to 2 $100+ million MV-22 Osprey tilt-rotor aircraft, or 4 CH-46 Sea knights or comparable helicopters, or 6 AH-1 Super Cobra/ Viper attack helicopters, or 2 CH-53 Super Stallion heavy transport helicopters. Hangar space will accommodate only one V-22 Osprey tilt-rotor or CH-53 heavy-lift helicopter, or it could be used for up to 3 AH-1 attack helicopters, or 2 CH-46 or comparable-size helicopters, or any appropriate combination thereof.
These ships will also carry 2 LCAC hovercraft for ship-shore transport, plus 14 of the Marines' forthcoming Expeditionary Fighting Vehicles with swim-out capability up to 20 miles offshore.
It also has amenities like a 24 bed hospital, a water desalinization plant, and advanced sensor and communications gear, and better than average creature comforts, with an eye towards it serving as a flagship for a larger Marine force. It has only defensively oriented weapons: anti-aircraft missiles, a close in weapons system (largely designed for fending off small craft and cruise missiles) and .50 caliber machine guns (for small craft and individuals on docks). It is not equipped to actively fight submarines and warships, a task left to any Navy ships escorting it.
The only U.S. military combatant ships which are larger are aircraft carriers (i.e. supercarriers) which are about 97,000 tons, and amphibious assault ships (i.e. Harrier carriers), such as the Wasp and Tarawa class ships which are about 40,000 tons.
The San Antonio primarily replaces the Austin class of ships, although the Navy has pitched the San Antonio as also replacing a couple dozen other ships that have already been retired from service.
Navy sources note that the 9 scheduled ships of this class (reduced from 12) are slated to assume the functional duties of up to 41 previous ships. These include the USA's older LSD-36 USS Anchorage Class dock landing ships (all decommissioned as of 2004, LSD-36 and LSD-38 transferred to Taiwan) and its LPD-4 USS Austin Class ships (12 ships of class built and serving). The San Antonio Class ships may also replace two classes of ships currently mothballed and held in reserve status under the Amphibious Lift Enhancement Program (ALEP): the LST-1179 Newport Class tank landing ships, and LKA-113 Charleston Class amphibious cargo ships.
Like many defense projects, it was far over budget, was behind schedule, and was built in a manner characterized by "shoddy construction and basic workmanship problems." The San Antonio itself will end up costing $1.7 billion and was projected to cost a little under $1 billion. The next ship of its class, the New Orleans, will cost $1 billion, compared to a projected $0.76 billion. Stealth features are also not living up to promised standards.
The San Antonio does not represent any major conceptual shift from the prior regime, except perhaps, for replacing several smaller Marine transports with one larger one, intended to operate from over the horizon. The big open question is whether this still meets the needs of the Marines in this quantity, or whether bolder innovation was necessary.