Ship

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The Screw Propeller

A major development in ship propulsion was the screw propeller, fully submerged rotating blades that pushed the ship through the water. The screw propeller was first used in 1840 on the Archimedes, a river-going American steamer. British shipbuilder Brunel again pioneered ship design when he adopted the propulsion system of the Archimedes for his second ship, Great Britain, in 1853. At 98 m (322 ft), Great Britain was the largest steamship of its day, the first to be made of iron, and the first seagoing ship driven by a screw propeller. Great Britain’s propeller measured nearly 5 m (16 ft) in diameter and weighed more than 3 tons.

The earliest screw propellers used on ships had two long, narrow blades, resembling the propellers of early aircraft. Soon propellers with three, four, and even more blades were in use, and ships carried two, three, or more propellers. Multiple propellers increased speed and provided alternatives in the event that one propeller malfunctioned or was lost.

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Iron and Steel Hulls

Brunel combined elements from the Great Western and the Great Britain in his third and final ship, the Great Eastern, which launched in 1858. Iron-hulled and propelled by a combination of paddlewheels and screw propellers, Great Eastern dwarfed even the largest ships of the day. Before Great Eastern, the longest ship afloat measured 114 m (375 ft) and 3,300 tons. Great Eastern stretched 211 m (692 ft) in length and measured 19,000 tons. Despite its gargantuan proportions, the ship failed as a passenger liner. It went on to lay the first transatlantic electric telegraph cable.

Nonetheless, the Great Eastern proved a trendsetter. Following Brunel’s lead, most shipbuilders constructed ships from large iron plates riveted together. Iron ships had stiffer hulls, which helped to reduce vibration from the movement of the long propeller shaft. But iron presented a new set of challenges to builders. Iron was rigid, it fractured easily, and it rusted. Shipbuilders found an alternative in steel, a mixture of iron and other elements, which is stronger and easier to shape than iron. Steel’s exorbitant cost and relative scarcity made it an impractical choice until 1855, when English inventor Henry Bessemer improved the steel refining process. The Bessemer process made good quality steel available at a fraction of its earlier price. By the end of the 19th century, most of the great merchant and battleships featured steel hulls.

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Double- and Triple-Expansion Steam Engines

Steam engines also improved significantly. In early steam engines, steam from the boiler was directed to a cylinder, where it drove the movement of a single piston before it was expelled. These single-expansion engines wasted some of the steam’s energy. More efficient double-expansion engines used the steam expelled from one cylinder to power another cylinder. By 1873 even more efficient triple-expansion engines came into use.

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Steam Turbines

Further experimentation with steam engines led to the development of steam turbines, which used steam from the boilers to turn fan blades at high speed. This mechanical energy was harnessed to turn the propeller shaft. In 1897 British engineer and visionary Charles Parsons captured the attention of the British navy and royal family with his ship, Turbinia, the world’s first steam turbine-driven vessel. Parsons piloted Turbinia through a parade of British naval ships at an astounding 34.5 knots (63 km/h; 39 mph), shocking all in attendance. The Royal Navy’s fastest ships gave chase but could not catch up to the speeding Turbinia. Two years later Britain launched the first steam turbine-driven warship, HMS Viper, which made 36.5 knots.

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Diesel Engines

Despite its bulk, coal remained the fuel of choice until the beginning of the 20th century. In 1897, the same year that Parsons demonstrated the steam turbine before the British navy and royal family, German engineer Rudolf Christian Karl Diesel built an engine that ran on petroleum-based liquid fuel. Although early diesel engines could not match the speed of coal-fired steam engines, they were lighter and did not require boilers, water, and bulky coal to generate steam. Diesel engines could be operated by fewer crewmembers and did not require a team of firemen to shovel coal.

By the early 1900s diesel engines began to replace coal-fired engines. Diesel engines powered barges hauling crude oil up rivers from the Caspian Sea to northern Europe. The first sea-going vessel fitted with a diesel engine was Vulcanus, a small merchant vessel built for the Dutch East India Company in 1910. Despite their advantages over steam engines and turbines, diesel engines were slow to replace steam power in passenger liners, which highly valued speed.

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