The U.S. Navy is preparing for final integration and sea trial tests for the amphibious assault ship America (LHA-6), the first in a series of planned next-generation “America-class” big-deck, hybrid-electric amphibs slated to enter the fleet in coming years, service officials said.
The USS America, the first of as many of 11 planned America-class amphibs, is now nearly 90-percent complete at a Huntington Ingalls Industries (HII) facility in Pascagoula, Miss., said Capt. Chris Mercer, Amphibious Warfare program manager.
Initial Operating Capability for the USS America is planned for September of 2016, once the ship finishes up its builder’s trails and acceptance trails, Mercer said.
“Eleven ships is our stated requirement for large-deck Amphibious Assault Ships. About every four or five years we are procuring a large-deck amphib. Eventually all of the America-class ships will replace all of the Wasp-class ships and all of the Tarawa-class ships,” Mercer explained.
The second America-class amphib, the USS Tripoli, is now also under construction at the same HII location in Mississippi.
Overall, the America-class amphibs are designed with a larger deck space, compared to prior Wasp-class ships; they are built to accommodate new and emerging Naval and Marine Corps air assets such as the MV-22 Osprey tilt-router helicopter, the Corps’ Vertical Take-off-and-Landing Harrier Jet as well as the Marine Corps’ short take off and landing variant of the F-35B Joint Strike Fighter aircraft, Mercer explained.
“The future USS America is all about aviation. Think about the power projection and sustained presence of joint or multi-national expeditionary warfare capability centered around ships loaded up with the capabilities that a JSF and MV-22 bring you,” Mercer said.
The amphibs will be the lead vessel in what the Navy calls Amphibious Ready Groups, groups of air, sea and ground assets designed for expeditionary warfare including an Amphibious Transport Dock and a Dock Landing Ship.
The Amphibious Ready Group is able to launch an air cushioned ship to shore transport vessel called the Landing Craft, Air Cushioned (LCAC). LCACs are engineered to transport cargo, personnel, weapons, equipment and even an M1 Abrams tank -- from over the horizon onto shore, Mercer explained.
Landing Craft Utility (LCU) vessels are also an integral part of an Amphibious Ready Group, Mercer said. In fact, the Navy is now working on an analysis of alternatives such that it can launch an acquisition program to acquire as many as 32 new LCUs.
The America and the Tripoli will also carry CH-53 Sea Stallion, MH-60 Sea Hawk and AH-1Z Super Cobra helicopters.
LHA 6 and LHA 7, both now under contract and under construction, are being built with what Mercer referred to as a Flight 0 configuration. They are designed as large-deck amphibs with no well-deck, yet engineered to transport a Marine Air Ground Task Force or a Marine Expeditionary Unit with supporting gear including ground and air assets -- such that they can project and sustain power as needed.
Following completion and delivery of the America and Tripoli, the next several America-class amphibs, however, will be built with what’s called a Flight 1 configuration with a new increment of capability that includes a well-deck.
LHA 8, 9 and 10 will be engineered with the re-introduction of a well-deck into a ship that is, by design, aviation centric, Mercer explained. Flight 1 America-class amphibs will also have a slightly smaller island so as to allow for more maintenance area for the large aircraft such as the MV-22 and JSF.
“Flight 1 ships will be the next-increment of capability. It is a balanced ship design where we have kept the aviation-support aspects of a large-deck. With Flight 1, we’ll be able to do maintenance without clobbering the flight line,” he said.
HYBRID-ELECTRIC PROPULSION
Unlike the largely steam-powered Wasp and Tawara-class Amphibious Assault Ships, the entire fleet of America-class Amphibs will be propelled by hybrid-electric drive technology, Mercer explained.
Hybrid-electric propulsion systems use a gas turbine engine as well as an electric motor and diesel generator. The electric motors can help propel the ship at speeds up to around 12 knots and the generator can help produce electricity for the ship. When it comes to traveling at speeds greater than 12 knots or so, the ship can then rely upon its gas-turbine engine.
At the same time, the generators can provide on-board power for many of the ships systems such as sensors, weapons and other electronics, Navy officials said.
“Future warships will have huge electrical demands, in addition to propulsion for things like radar, weapons and electronics,” said Ron Filadelfo, director, environment and energy research team, Center for Naval Analysis. “This is a big plus for the Navy because the system adds fuel efficiency at low speeds and does not detract anything at high speeds – so it seems to be a win-win.”
The hybrid-drive allows the ship to propel itself using either electric drives or a traditional gas turbine engine. Electric propulsion and turbine engine propulsion are both integrated through what’s called a main reduction gear (MRG), a portion of the ship’s propulsion system which helps convert energy into the revolutions needed for the propellers to move the ship through the water, according to Navy officials.
“This unique auxiliary propulsion system (APS) is designed with fuel efficiency in mind. The APS uses two induction-type auxiliary propulsion motors (APM) powered from the ship’s electrical grid instead of using main propulsion engines to power the ship’s shaft,” a Navy official said.
Instead of using its gas turbines which are less efficient at lower speeds, the ship will be able to use its APS for roughly 75 percent of the time the ship is underway, Mercer added.
“We’ve found the sweet spot in terms of something that is very affordable, regarding the 5,000-horsepower auxiliary propulsion motor that we integrate into our design. It is a good sweet spot, because for about 75-percent of the ship’s life it will be traveling under twelve knots. For that we can be utilizing the hybrid-electric drive,” Mercer said.
The Navy plans to continue studying and advancing hybrid-electric ship propulsion such that it can potentially be applied to other platforms and possibly evolve such that it can propel ships at even faster speeds, Mercer added.
“We’ve done studies and we will continue to do the studies to develop something that gives you a little more speed. We’re always studying ideas that give us even more energy efficiency,” he said.
“The semi-conductor industry is going to get better and better, so you are going to be able to deliver more power with a higher density.”
