The Navy’s New Ships

Stephen J. Mraz
Staff Editor

If U.S. military planners are correct, much of the naval action in the future will take place close to shore, the littoral zones, in places like the Persian Gulf and along the coast of the Mediterranean Sea. The days of blue-water air and sea battles against another superpower, like the Soviet Union, are probably long gone. So the Navy is redesigning its fleet and preparing to launch a pair of new combat vessels; the Littoral Combat Ship (LCS), and DDG-1000, the next generation destroyer.

LCS
The first LCS, the USS Freedom, was christened and launched two years ago at in Mainette, Wis., and delivered to the Navy last year by its prime contractor Lockheed Martin Corp. Besides being built for speed and agility, it will make the most of shared data networks and advanced communications. Its modular design will let Navy commanders load their choice of hardware packages, depending on the ship’s upcoming mission. Currently, plans call for three mission packages: antisubmarine, mine warfare, and surface combat. Each will consist of specialized crewmen, hardware, deployable sensors, and manned and unmanned planes and boats.

The ship measures 377 ft stem to stern, with a beam of 57 ft, and displaces 3,089 tons, but it can operate in waters as shallow as 13 ft. Its steel monohull is semiplaning, meaning it rides partially atop the waves at a top speed in excess of 40 knots rather than plowing through them.

Two Rolls-Royce MT30 36MW gas turbines and two Fairbanks Morse Colt-Pielstick diesel engines power four large Rolls-Royce Kamewa waterjets. Two of the jets are for steering and reversing, and the other two are forward motion. There are no propellers.

The waterjets let the Freedom turn 360° in less than eight ship lengths (about 3,000 ft) at sprint speed, and can accelerate it from 0 to 40 knots in less than 2 min. Waterjets also eliminate problems such as vibration, noise, and cavitation which can alert faraway enemy subs to the ship’s presence. The LCS will carry enough fuel to travel 3,500 miles.

The ship’s flight deck is 50% larger and its hangar twice as large as those on standard surface ships, a hint it will be relying a lot on helicopters and other VTOL aircraft. The hangar is sized to hold two SH-60 Seahawk helicopters or one Seahawk and three drones.

The LCS also has at least two points from which to launch, service, and recover small manned and unmanned boats. Stern doors on the rear of the hull let the ship deal with hard-bottomed boats as well as high-speed craft used by special forces, even while the LCS is underway. On the starboard (or right) side of the ship, a second waterline-level door with a roll-on/roll-off ramp accommodates smaller boats, as well as at-sea refueling and replenishment of the LCS. A single overhead crane can extend overboard near both the stern and side doors to lift any craft the LCS can carry. There’s also a crane in the mission bay for changing out mission-specific hardware and taking on supplies.

For weapons, a modular weapons zone on the front deck can carry a 57-mm gun turret or missile launcher. A rolling airframe missile launcher mounts above the hangar for short-range defense against airborne threats. (The rolling airframe missile got its name due to the fact that in flight, it rolls to maintain stability.) The ship also has .50-caliber gun mounts topside.

The core crew of the Freedom with be 40 officers and sailors, but a mission-specific crew and aviation detachment will bring the total to about 75.

The Navy plans to have 30 to 60 LCSs, with the Freedom homeported in San Diego.

DDG-1000
The Navy’s next destroyer will be the DDG-1000 (previously the DD(X) and DD 21), and has been named the USS Zumwalt for Admiral Elmo Zumwalt Jr, onetime Chief of Naval Operations. The Navy had hoped to build more than 30 of these ships, a number they later cut to 24, then 7, due to predicted cost overruns on still experimental weapons and technologies. And even now, Congress has only approved funding for two, so it is still unknown whether the DDG-1000 will be the first in a class of many ships or lead to a lower-cost destroyer in the future.

The current version of the DDG-1000, which is being built by Northrop Grumman in Passacaglia, Miss., will be 600-ft long, have a beam of 80 ft, a navigational draft of 28 ft, and displace 14,500 tons.The crew will consist of 142, and that includes an aviation detachment.

The ship is designed for surface and antiaircraft combat, and to provide naval gunfire support for land-based missions. The ship is stealthier than previous warships, as its illustrations suggest. Lockheed says the ship should have one-fiftieth the radar cross section of the DDG-51 Arleigh Burke Class destroyers. There are no rotating radars, the superstructure is faceted with flat, slanted sides made of composite materials and there is little clutter on the decks. The ship is also low to the water, thanks to its tumblehome hull design. (A tumblehome hull is widest at the waterline and narrows as it goes up. Most ships have a flared hull in which the widest part is the top deck) The DDG’s hull also has a pronounced wave-piercing bow. The exaggerated front is supposed to let it pass through waves rather than ride over them. This, in turn, should make the ship more stable. But some naval architects believe the tumblehome design is unstable and that when hit by waves from behind, the ship could pitch down, not have the energy to right itself, and roll over. The Navy, however, has tested the tumblehome hull and is proceeding with it.

For firepower, the destroyer was first slated for a pair of vertical gun, ones in which the barrel is fixed (and pointing more or less straight up) and the munitions are more like missiles with some having propulsion as well as guidance. Development for the vertical gun’s “shells” was behind schedule and costs were way over budget. So the Navy scaled back to the Advanced Gun System (AGS). It’s a 6.1-in. gun with a water-cooled barrel that can fire up to 12 rounds/min from an automated magazine holding 600 rounds. Some of those rounds, such as the Long Range Attack Projectile (LRAP) developed by Lockheed Martin and Science Applications International Corp., can hit targets up to 100 miles away. AGS can also fire several rounds timed for simultaneous impact on the same target up to 75 miles. It does this by changing trajectories for each shot.

It is said that the DDG-1000’s two AGS have the same firepower as an entire battalion of 155-mm howitzers, which is made up of 18 guns. The battalion also requires 58 cargo trucks, 42 utility trucks, 28 cargo trailers, two tow trucks, five water trailers, two ambulances, and 640 personnel. Critics, however, contend the new destroyer can’t deliver that much firepower for long. Each gun’s magazine will have a limited number of long-range munitions (over 75 miles). But even if all munitions are long range, 600 rounds doesn’t last long at 12 rounds/min.

A pair of 40-mm guns firing up to 200 rounds/min will defend against close-in attacks by ships, aircraft, and missiles.

The ship will also carry 80 missiles in 20 Peripheral Vertical Launch Systems (PVLS) lining the outer edge of the forward top deck. This prevents loss of the entire store of missiles, and most likely the entire ship, if there was only a single missile magazine and it was hit. The PVLSs, if hit, are designed to explode outward, away from the ship. The ships will be able to carry Sea Sparrow missiles for close in defense against airborne threats, SM-2 anti-aircraft missiles for planes in the 40 to 90 mile range, antisub missiles, and Tomahawk cruise missiles.

For propulsion and power, the ship boasts two Rolls-Royce MareinTrent- 30 gas turbines and two emergency diesel generators, with each pair capable of generating 78 MW of electricity. That’s said to be 10 times more than current destroyers, and they will feed an integrated power system (IPS), a first for naval ships. The IPS can power the propulsion system, which are all electric, as well as the rest of the ship.

Initially, the ship’s generators were to power permanent-magnet motors (PMM). Northrop even built the world’s largest PMM to test the idea. But finally the PMM was dropped because it just wasn’t ready for real-world operations. Instead, heavier, larger induction motors will be used. Still, the drives will remain all-electric, with no driveshafts or reduction gears.

The DDG-1000 could also be the starting point for the Navy’s next cruiser, currently designated the CG(X). It will have the same hull as the DDG-1000, but carry more missiles and AGS. Currently, the Navy wants about 19 new cruisers to replace its Ticonderoga class Aegis cruisers.