Ship

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3

Cruisers

Modern cruisers measure from 162 to 243 m (533 to 796 ft) in length, travel about 30 knots, and have an average crew of 550. The mission of modern cruisers is to destroy enemy surface ships, submarines, aircraft, and missiles. They are equipped with 5-inch guns, Harpoon and Tomahawk guided missiles, antisubmarine warfare helicopters, and torpedoes. Many cruisers now have the Aegis surface-to-air missile system, a highly sophisticated and capable weapons system.

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Destroyers

The modern destroyer is a light, fast, ship that serves a great variety of functions because of its speed, armament, and maneuverability. It replaced the navy war sloop of the sailing era. Destroyers provide antiair, antisurface, and antisubmarine warfare capabilities. They carry 5-inch guns, a variety of antiship missiles, antisubmarine helicopters, and torpedoes. They range from 133 to 172 m (437 to 563 ft) in length, travel at speeds ranging from 30 to 33 knots, and have crews of about 400.

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Frigates

Like its sailing predecessor, the modern naval frigate serves as an ocean escort. It ranges from 126 to 136 m (414 to 445 ft) in length and cruises at below 30 knots. Modern frigates require crews of between 200 and 300 sailors. Most are lighter armed than destroyers, although some frigates carry missiles, antisubmarine rockets, and helicopters, torpedoes, or other weapon systems.

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Mine Craft

Mine craft include minesweepers and mine countermeasure ships. Minesweepers detect and clear, or sweep, explosive underwater mines so that ships can pass safely. They measure 57 m (188 ft) long and carry a crew of 45. Mine countermeasure ships detect and sweep underwater mines and serve as command and control facilities for mine countermeasure operations. Mine countermeasure ships measure 68 m (223 ft) in length and have a crew of 74.

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V

New Trends in Ship Design

Although the ship remains the most economical way to transport bulk cargoes over the world’s oceans, naval architects recognize that room for improvement remains. Most of today’s cargo vessels travel at a speed of about 20 to 23 knots, limited by their hull design. Naval architects are exploring the use of multiple hulls—instead of having one large hull, ships might have two or three hulls connected to each other. These designs are prominent in small- to medium-sized boats but have not been applied to bulk carriers. The catamaran (two hull) or trimaran (three hull) offers great stability with much less water resistance.

Concerns about applying such designs to bulk cargo carriers persist, however. Some question the potential strength of large, multiple-hulled ships in rough seas. Others argue that multiple-hulled cargo carriers would not have adequate carrying capacities to make them economical.

Naval architects are also exploring the use of narrower hulls in single-hulled cargo vessels. Military vessels throughout history have used slender hulls, which enable ships to travel faster because they experience less drag in the water. Many question the potential stability of the slender-hulled cargo ship, which will undoubtedly make transoceanic crossings with containers stacked high on its decks. Moreover, a narrow-hulled ship cannot carry as much cargo as a modern freighter of equivalent length.

The solution may lie in the semiplaning monohull. This hull design has a sharp V-shaped bow for cutting the waves and a wide, shallow rear with a slightly concave profile underwater. This design creates waves that help lift the vessel and reduce drag in the water. These hulls, similar to those used in many modern pleasure boats, would become more efficient as the ship goes faster.

New designs in ship propulsion will also increase the efficiency of ship transport. When compared to marine diesel engines of the same weight and volume, gas turbine engines produce far greater amounts of power without using more fuel. They also burn cleaner, emitting only 4 percent of the sulfur oxides and 5 percent of the nitrogen oxides emitted by diesels of the same power. Gas turbine engines currently power small passenger and car ferries, but they have been prohibitively expensive for use in bulk cargo transport.

In the future, water jet drive may replace the screw propeller. Both of these propulsion systems spin and push water to move the vessel. But while the screw propeller becomes less efficient at high speeds, the water jet drive gains efficiency as speed increases.

Such changes will undoubtedly make the ships of tomorrow faster and more efficient. Naval architects and engineers predict that a ship with a semiplaning monohull, gas turbine engine, and water jet drive will easily reach a speed of 45 knots. These and other innovative ship designs will cut the cargo crossing time between Europe and North America from 14 to 35 days to a week or less.

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