Propulsion

Dreadnoughts were propelled by two to four screw propellers.[73] Dreadnought herself, and all British dreadnoughts, had screw shafts driven by steam turbines. However, the first generation of dreadnoughts built in other nations used the slower triple-expansion steam engine which had been standard in pre-dreadnoughts.[74]

Turbines offered more power than reciprocating engines for the same volume of machinery.[75][76] This, along with a guarantee on the new machinery from the inventor, Charles Parsons, persuaded the Royal Navy to use turbines in Dreadnought.[76] It is often said that turbines had the additional benefits of being cleaner and more reliable than reciprocating engines.[77] However, by 1905, new designs of reciprocating engine were available which were cleaner and more reliable than previous models.[75]

Turbines were not without disadvantages. At cruising speeds much slower than maximum speed, turbines were markedly less fuel-efficient than reciprocating engines. This was particularly important for navies which required a long range at cruising speeds—and hence for the U.S. Navy, which was planning in the event of war to cruise across the Pacific and engage the Japanese in the Philippines.[78]

The US Navy experimented with turbine engines from 1908 in the North Dakota, but was not fully committed to turbines until the Pennsylvania class in 1916. In the preceding Nevada class one ship, the Oklahoma, received reciprocating engines, while the Nevada received geared turbines. The two New York class ships of 1914 both received reciprocating engines, but all four ships of the Florida (1911) and Wyoming (1912) classes received turbines.

The disadvantages of the turbine were eventually overcome. The solution which eventually was generally adopted was the geared turbine, where gearing reduced the rotation rate of the propellers and hence increased efficiency. However, this solution required technical precision in the gears and hence was difficult to implement.[79]

One alternative was the turbo-electric drive where the steam turbine generated electrical power which then drove the propellers. This was particularly favored by the U.S. Navy, which used it for all dreadnoughts from late 1915–1922. The advantages of this method were its low cost, the opportunity for very close underwater compartmentalization, and good astern performance. The disadvantages were that machinery was heavy and vulnerable to battle damage, particularly the effects of flooding on the electrics.[A 7]

Turbines were never replaced in battleship design. Diesel engines were eventually considered by a number of powers, as they offered very good endurance and an engineering space taking up less of the length of the ship. However, they were also heavier, took up a greater vertical space, offered less power, and were considered unreliable.[80]