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LPD-17 SAN ANTONIO Class Design
(formerly LX Class)

Amphibious transport docks, both the 15 LPDs in previous ship classes and the San Antonio class, have a well deck in the after part of the ship. The ship ballasts her stern to either completely flood the well deck for launching and recovering conventional landing craft or only partially for Expeditionary Fighting Vehicles. These egress or enter when the stern gate is opened. The ship then deballasts and operates with a dry well. The well deck is not flooded for LCAC, air cushion landing craft operations. Well deck operations may be conducted pierside, at anchor, or at sea while moving through the water.

The combat power of this ship is it's embarked Marines and their equipment. Defense against surface threats will be provided by two Mark 46 30mm gun systems. The ship also incorporates the latest quality of life standards for the embarked sailors and Marines, including sit-up berthing, a ship services mall, a fitness center and a learning resource center/electronic classroom with the flexibility to accommodate mixed gender sailors and Marines. Medical facilities include 124 beds and two operating rooms. They are the first USN ships designed from the outset to accommodate women crewmembers.

The LPD 17 has an LPD-4 class sized docking well to accommodate two LCAC air-cushion landing craft or four LCM(8) or nine LCM(6) or 20 LVT. There are two spots for helicopters of up to CH-53 size; three AH-1W or two CH-46 or one CH-53 or MV-22 Osprey are to be accommodated in the hangar. It is also able to support AV-8B+ Harrier aircraft and also AH-1W attack helicopters. Resembling a greatly enlarged LPD, it does not have a significantly greater payload. Sulzer-Westinghouse 12ZA40S (10,000 bhp each) diesels are employed in the propulsion plant, and the ships have seven 700 kW air-conditioning plants. The ships have bow bulb, twin rudders, and no side-thrusters.

Reduced operational costs and an improved capability to incorporate technological advances over its 40-year service life are also essential design objectives for LPD 17. In working to accomplish these objectives, the design team incorporated hundreds of suggestions and recommendations from more than 1,000 sailors and Marines in the "Design for Ownership" process to ensure that these ships will meet their needs throughout the first half of the 21st century.

The San Antonio class design integrates the latest in command, control, communications, computers, intelligence, surveillance and reconnaissance (C4ISR) capability. These capabilities are further enhanced by additional, dedicated intelligence, mission planning, and command and control spaces. The shipboard wide area network (SWAN) developed for LPD 17 is a fiber optic shipwide large area computer network. The SWAN supports everything from combat systems to ship systems to command and control nodes to an integrated training system. This network also provides e-mail and internet access capability.

Combat systems include the Advanced Combat Direction System (ACDS) Block I, USQ-119C(V)27 Joint Maritime Command Information System (JMCIS), KSQ-1 amphibious assault direction system, SPQ-12(V) radar display distribution system, KSQ-1 amphibious assault direction system, and Mk 1 Ship Self-Defense System (SSDS). In addition, all have the Cooperative Engagement Capability (CEC) system and will have Link 4A, 11, and 16 capability. Navigation suite to include WSN-5 inertial system, WRN-6(V)1 GPS receiver, WQN-1 channel-finder sonar, SSN-6 digital mapping system, UQN-4A echo-sounder, and WQN-2 doppler speed log.

The ship's automated combat system includes a highly capable sensor suite and weapons capability that provides for a robust self defense capability. The initial three units do not have the MK41 vertical SAM launch-cell group on the forecastle; space is reserved for the addition of further groups of Mk 41 cells forward. Two Mk 15 Mod. 12 Phalanx 20-mm CIWS were originally to have been installed and may still be on the initial units due to delays in the Sea Sparrow ESSM development program. LPD 22 is the first to have the Project Akcita air-defense sensor and weapon integration system, which will be backfitted in earlier units; a new D-band radar would replace the SPS-48E.

Ensuring that the ship maintains a robust self defense capability as threat systems evolve is key to survivability in the littoral environment where the ship will fight. In June 1996, the Navy received Milestone II approval for the baseline design of the LPD-17 ship class. The design included a self-defense suite consisting of a SPS-48E radar, a SPQ-9B radar, a SLQ-32(V2) electronic warfare system or its successor, a Ship Self Defense System MK-2, a Cooperative Engagement Capability node for sensor fusion, two Rolling Airframe Missile launchers, an Evolved Sea Sparrow Missile (ESSM) vertical launcher and associated target illuminators, and a decoy launcher. At that time, the Navy realized that the ESSM program schedule would not mesh with the production schedule of the first two ships in the class and decided to reserve space and weight in the ship design for the missile system and launcher. However, the Navy still planned to build the remaining 10 ships in the class with the ESSM and its launcher.

During internal deliberations on the Navy's fiscal year 1999 budget, the Navy decided to remove projected funding for the ESSM and its launcher from the LPD-17 budget in order to fund the cruiser conversion program and other shipbuilding and conversion efforts. However, the Navy directed Avondale Industries to reserve space and weight for the ESSM in the design of all 12 LPD-17 class ships.

In 1998, various congressional committees directed the Navy to prepare an analysis of alternatives to the LPD-17 baseline design, including an evaluation of the AN/SPY-1 radar and its associated Aegis combat system, multifunction radar, and the ESSM. The March 1999 results of the Navy analysis confirmed that the baseline design without the ESSM could meet the near- and mid-term threat at the least cost. As a result of this assessment, the Navy did not plan to equip the LPD-17 class ships with the ESSM. However, if the threat materializes as currently predicted, the Navy could later add improved variants of the ESSM and the Rolling Airframe Missile as weapon modifications on these ships. These improved variants are yet to be developed. In addition, if the threat warranted, the Navy could also back-fit multifunction and volume search radar on the LPD-17, when they become available.

The SPS-73 system is a commercial surface search radar that replaced the SPS-67 and SPS-64 radars. More reliable than the other two radars, the SPS-73 consolidates training requirements, reduces maintenance, and possesses lower acquisition costs. The net result is a better radar that will save as much as $30 million dollars over the lifetime of the 12-ship LPD 17 class.

The hull is designed to reduce cost of fabrication and shaped to reduce radar cross-section. LPD 20 and later were initially intended to have additional reduced radar cross-section features, which were brought forward to be incorporated from the outset. LPD 17's design optimizes radar cross section signature by streamlining topside design and incorporating reduced radar cross section signature technologies including a boat valley instead of boat deck, removable coverings over the rescue boat and fueling at sea stations, and accommodation ladders that fold into the ship's hull. The advanced enclosed mast/sensors, which enclose the ship's radars and communications antennas, characterizes the ship's distinctive profile.

The Advanced Enclosed Mast/Sensor (AEM/S) System was selected for installation on SAN ANTONIO-class amphibious transport dock ships. The LPD-17 AEM/S System is an octagonal, detachable structure that enables affordable modular upgrade of future combat sensors and Command, Control, Communications, Computer, and Intelligence (C4I) systems. The Office of Naval Research and the LPD-17 program office undertook a risk mitigation effort to leverage the Navy's investment in the AEM/S System ATD. The LPD-17 transition built on and extend the technology developed by the demonstration, significantly reducing cost and risk. Construction started on the Advanced Enclosed Mast/Sensors (AEM/S) in mid-2002.

The AEM/S System mast [a 93-foot-high hexagonal structure 35 feet in diameter] is constructed of a multi-layer, frequency-selective composite material designed to allow passage of own-ship sensor frequencies with very low loss while reflecting other frequencies. The mast's shape is designed to provide a smooth silhouette to reduce radar cross section. Signature and electro-magnetic design requirements are based on criteria associated with sensor and antenna performance, electro-magnetic interference, lighting protection electromagnetic shielding, and electrical bonding and grounding.

The AEM/S System mast is an enclosed structure that protects radars and communication antennas from weather exposure and provides access for repairs, thus greatly reducing maintenance costs and risk of failure. The top half is divided into two radome-like compartments; the upper compartment houses the Mk 23 Target Acquisition System (TAS) antenna and the lower encloses the AN/SPS-40 air search antenna. Structural design requirements for strength and stiffness meet Fleet requirements for vibration, shock, and fatigue.

Participating in the development, design, and construction of the AEM/S System were representatives of the Office of Naval Research, Naval Sea Systems Command, Naval Research Laboratory, Carderock and Dahlgren Divisions of the Naval Surface Warfare Center, Naval Command and Control and Ocean Surveillance Center, and Norfolk Naval Shipyard. Industry participants were Ingalls Shipbuilding, Seemann Composites, Mission Research Corporation, Material Sciences Corporation, Ohio State University, and Analysis & Technology.

LPDs' boat and cargo crane are a "reduced radar cross section signature" hydraulic crane. The 22,000 lb. rated, 65 ft. knuckleboom crane will be able to move Rigid Hull Inflatable Boats from the boat valley to the waterline, recover the boats, or load cargo pierside or at sea. The newly designed crane utilizes a positive control "Derrick Head" capturing device that affords safe boat operations through Sea State 3 conditions (3-4 feet seas).

The LPD 17 class will have minimal and manageable environmental impact. The pollution mitigation devices installed in the LPD 17 class are state-of-the-art for warships and meet the requirements of regulatory agencies and present day law. The design has space and weight margins in place to accommodate back fit of future environmentally required systems. The ship has an oil pollution control system capable of processing bilge water to meet current Federal requirements with the capability of returning water for further processing if output requirements are exceeded, and its air conditioning, refrigeration, and fire suppression systems are free of chlorofluorocarbons - a Navy first.



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