Editing Steam turbine (section)

==Marine propulsion==
{{Redirect|Turbine Steam Ship||TS (disambiguation)}}
{{see also|Marine steam engine}}
[[File:Turbinia At Speed.jpg|thumb|''[[Turbinia]]'', 1894, the first steam turbine-powered ship]]
[[File:SS MAUI high and low pressure turbines 1917.png|thumb|High and low pressure turbines for {{SS|Maui|1916|6}}]]
[[File:Wirnik turbiny parowej ORP Wicher.jpg|thumb|Parsons turbine from the 1928 Polish destroyer {{ORP|Wicher|1928|2}}]]

In [[steamship]]s, advantages of steam turbines over reciprocating engines are smaller size, lower maintenance, lighter weight, and lower vibration. A steam turbine is efficient only when operating in the thousands of RPM, while the most effective propeller designs are for speeds less than 300 RPM; consequently, precise (thus expensive) reduction gears are usually required, although numerous early ships through [[World War I]], such as ''[[Turbinia]]'', had direct drive from the steam turbines to the propeller shafts. Another alternative is [[turbo-electric transmission]], in which an electrical generator run by the high-speed turbine is used to run one or more slow-speed electric motors connected to the propeller shafts; precision gear cutting may be a production bottleneck during wartime. Turbo-electric drive was most used in large US warships designed during World War I and in some fast liners, and was used in some troop transports and mass-production [[Buckley-class destroyer escort|destroyer escorts]] in [[World War II]].

The higher cost of turbines and the associated gears or generator/motor sets is offset by lower maintenance requirements and the smaller size of a turbine in comparison with a reciprocating engine of equal power, although the fuel costs are higher than those of a diesel engine because steam turbines have lower [[thermal efficiency]]. To reduce fuel costs the thermal efficiency of both types of engine have been improved over the years.

===Early development===
The development of steam turbine marine propulsion from 1894 to 1935 was dominated by the need to reconcile the high efficient speed of the turbine with the low efficient speed (less than 300 rpm) of the ship's propeller at an overall cost competitive with [[marine steam engine|reciprocating engines]]. In 1894, efficient reduction [[gear]]s were not available for the high powers required by ships, so [[direct drive]] was necessary. In ''Turbinia'', which has direct drive to each propeller shaft, the efficient speed of the turbine was reduced after initial trials by directing the steam flow through all three direct drive turbines (one on each shaft) in series, probably totaling around 200 turbine stages operating in series. Also, there were three propellers on each shaft for operation at high speeds.{{sfn|Parsons|1911|pp=26-31}} The high shaft speeds of the era are represented by one of the first US turbine-powered [[destroyer]]s, {{USS|Smith|DD-17|6}}, launched in 1909, which had direct drive turbines and whose three shafts turned at 724 rpm at {{convert|28.35| kn}}.{{sfn|Friedman|2004|p=23–24}}

The use of turbines in several casings exhausting steam to each other in series became standard in most subsequent marine propulsion applications, and is a form of [[#Types|cross-compounding]]. The first turbine was called the high pressure (HP) turbine, the last turbine was the low pressure (LP) turbine, and any turbine in between was an intermediate pressure (IP) turbine. A much later arrangement than ''Turbinia'' can be seen on {{RMS|Queen Mary}} in [[Long Beach, California]], launched in 1934, in which each shaft is powered by four turbines in series connected to the ends of the two input shafts of a single-reduction gearbox. They are the HP, 1st IP, 2nd IP, and LP turbines.

===Cruising machinery and gearing===
The quest for economy was even more important when cruising speeds were considered. Cruising speed is roughly 50% of a warship's maximum speed and 20-25% of its maximum power level. This would be a speed used on long voyages when fuel economy is desired. Although this brought the propeller speeds down to an efficient range, turbine efficiency was greatly reduced, and early turbine ships had poor cruising ranges. A solution that proved useful through most of the steam turbine propulsion era was the cruising turbine. This was an extra turbine to add even more stages, at first attached directly to one or more shafts, exhausting to a stage partway along the HP turbine, and not used at high speeds. As reduction gears became available around 1911, some ships, notably the [[battleship]] {{USS|Nevada|BB-36|6}}, had them on cruising turbines while retaining direct drive main turbines. Reduction gears allowed turbines to operate in their efficient range at a much higher speed than the shaft, but were expensive to manufacture.

Cruising turbines competed at first with reciprocating engines for fuel economy. An example of the retention of reciprocating engines on fast ships was the famous {{RMS|Olympic}} of 1911, which along with her sisters {{RMS|Titanic}} and {{ship|HMHS|Britannic}} had triple-expansion engines on the two outboard shafts, both exhausting to an LP turbine on the center shaft. After adopting turbines with the {{sclass|Delaware|battleship|1}}s launched in 1909, the [[United States Navy]] reverted to reciprocating machinery on the {{sclass|New York|battleship|1}}s of 1912, then went back to turbines on ''Nevada'' in 1914. The lingering fondness for reciprocating machinery was because the US Navy had no plans for capital ships exceeding {{convert|21|kn}} until after World War I, so top speed was less important than economical cruising. The United States had acquired the [[Philippines]] and [[Hawaii]] as territories in 1898, and lacked the British [[Royal Navy]]'s worldwide network of [[coaling station]]s. Thus, the US Navy in 1900–1940 had the greatest need of any nation for fuel economy, especially as the prospect of war with [[Japan]] arose following World War I. This need was compounded by the US not launching any cruisers 1908–1920, so destroyers were required to perform long-range missions usually assigned to cruisers. So, various cruising solutions were fitted on US destroyers launched 1908–1916. These included small reciprocating engines and geared or ungeared cruising turbines on one or two shafts. However, once fully geared turbines proved economical in initial cost and fuel they were rapidly adopted, with cruising turbines also included on most ships. Beginning in 1915 all new Royal Navy destroyers had fully geared turbines, and the United States followed in 1917.

In the [[Royal Navy]], speed was a priority until the [[Battle of Jutland]] in mid-1916 showed that in the [[battlecruiser]]s too much armour had been sacrificed in its pursuit. The British used exclusively turbine-powered warships from 1906. Because they recognized that a long cruising range would be desirable given their worldwide empire, some warships, notably the {{sclass|Queen Elizabeth|battleship|1}}s, were fitted with cruising turbines from 1912 onwards following earlier experimental installations.

In the US Navy, the {{sclass|Mahan|destroyer|1}}s, launched 1935–36, introduced double-reduction gearing. This further increased the turbine speed above the shaft speed, allowing smaller turbines than single-reduction gearing. Steam pressures and temperatures were also increasing progressively, from {{convert|300| psi|abbr=on}}/{{convert|425| F }} [saturated steam] on the World War I-era {{sclass|Wickes|destroyer|4}} to {{convert|615| psi|abbr=on}}/{{convert|850| F }} [superheated steam] on some World War II {{sclass|Fletcher|destroyer|1}}s and later ships.<ref>{{cite web|url=http://destroyerhistory.org/goldplater/1500ton|title=1,500-ton destroyers in World War II|website=destroyerhistory.org|url-status=live|archive-url=https://web.archive.org/web/20131105215828/http://destroyerhistory.org/goldplater/1500ton/|archive-date=5 November 2013}}</ref>{{sfn|Friedman|2004|p=472}} A standard configuration emerged of an axial-flow high-pressure turbine (sometimes with a cruising turbine attached) and a double-axial-flow low-pressure turbine connected to a double-reduction gearbox. This arrangement continued throughout the steam era in the US Navy and was also used in some Royal Navy designs.{{sfn|Bowie|2010}}<ref>{{cite web |url=http://www.leander-project.homecall.co.uk/turbines.html |title=Steam Turbines |website=www.leander-project.homecall.co.uk |url-status=live |archive-url=https://web.archive.org/web/20131122092049/http://www.leander-project.homecall.co.uk/turbines.html |archive-date=22 November 2013}}</ref> Machinery of this configuration can be seen on many preserved World War II-era warships in several countries.<ref>{{cite web |url= http://www.hnsa.org/index.htm |title=Historic Naval Ships Association |url-status=dead |archive-url= https://web.archive.org/web/20130622175037/http://hnsa.org/index.htm |archive-date=22 June 2013}}</ref>

When US Navy warship construction resumed in the early 1950s, most surface combatants and aircraft carriers used {{convert|1200| psi|abbr=on}}/{{convert|950| F }} steam.{{sfn|Friedman|2004|p=477}} This continued until the end of the US Navy steam-powered warship era with the {{sclass|Knox|frigate}}s of the early 1970s. Amphibious and auxiliary ships continued to use {{convert|600| psi|abbr=on}} steam post-World War II, with {{USS|Iwo Jima|LHD-7|6}}, launched in 2001, possibly the last non-nuclear steam-powered ship built for the US Navy.

===Turbo-electric drive===
[[File:50letPob pole.JPG|thumb|{{ship|NS|50 Let Pobedy}}, a nuclear icebreaker with nuclear-turbo-electric propulsion]]

[[Turbo-electric transmission|Turbo-electric drive]] was introduced on the battleship {{USS|New Mexico|BB-40|6}}, launched in 1917. Over the next eight years the US Navy launched five additional turbo-electric-powered battleships and two aircraft carriers (initially ordered as {{sclass|Lexington|battlecruiser|1}}s). Ten more turbo-electric capital ships were planned, but cancelled due to the limits imposed by the [[Washington Naval Treaty]].

Although ''New Mexico'' was refitted with geared turbines in a 1931–1933 refit, the remaining turbo-electric ships retained the system throughout their careers. This system used two large steam turbine generators to drive an electric motor on each of four shafts. The system was less costly initially than reduction gears and made the ships more maneuverable in port, with the shafts able to reverse rapidly and deliver more reverse power than with most geared systems.

Some ocean liners were also built with turbo-electric drive, as were some troop transports and mass-production [[Buckley-class destroyer escort|destroyer escorts]] in [[World War II]]. However, when the US designed the "treaty cruisers", beginning with {{USS|Pensacola|CA-24|6}} launched in 1927, geared turbines were used to conserve weight, and remained in use for all fast steam-powered ships thereafter.

===Current usage===
Since the 1980s, steam turbines have been replaced by [[gas turbine]]s on fast ships and by [[diesel engine]]s on other ships; exceptions are [[nuclear marine propulsion|nuclear-powered ships and submarines]] and [[LNG carrier]]s.<ref>{{cite web |url=http://www.ship-technology.com/news/newsmitsubishi-heavy-starts-construction-of-first-sayaendo-series-lng-carrier/ |title=Mitsubishi Heavy starts construction of first Sayaendo series LNG carrier |date=December 2012 |url-status=live |archive-url=https://web.archive.org/web/20140807050807/http://www.ship-technology.com/news/newsmitsubishi-heavy-starts-construction-of-first-sayaendo-series-lng-carrier |archive-date=7 August 2014}}</ref> Some [[auxiliary ship]]s continue to use steam propulsion.

In the U.S. Navy, the conventionally powered steam turbine is still in use on all but one of the [[Wasp-class amphibious assault ship|Wasp-class]] amphibious assault ships. The [[Royal Navy]] decommissioned its last conventional steam-powered surface warship class, the {{sclass|Fearless|landing platform dock}}, in 2002, with the [[Italian Navy]] following in 2006 by decommissioning its last conventional steam-powered surface warships, the {{sclass|Audace|destroyer}}s. In 2013, the [[French Navy]] ended its steam era with the decommissioning of its last {{sclass|Tourville|frigate}}. Amongst the other [[blue-water navies]], the Russian Navy currently operates steam-powered {{sclass|Kuznetsov|aircraft carrier}}s and {{sclass|Sovremenny|destroyer}}s. The [[Indian Navy]] currently operates INS ''Vikramaditya'', a modified {{sclass|Kiev|aircraft carrier}}; it also operates three {{sclass|Brahmaputra|frigate}}s commissioned in the early 2000s. The Chinese Navy currently operates steam-powered {{sclass|Kuznetsov|aircraft carrier}}s, {{sclass|Sovremenny|destroyer}}s along with {{sclass|Luda|destroyer}}s and the lone [[Type 051B destroyer]]. Most other naval forces have either retired or re-engined their steam-powered warships. As of 2020, the [[Mexican Navy]] operates four steam-powered former U.S. {{sclass|Knox|frigate}}s. The [[Egyptian Navy]] and the [[Republic of China Navy]] respectively operate two and six former U.S. {{sclass|Knox|frigate}}s. The [[Ecuadorian Navy]] currently operates two steam-powered {{sclass|Condell|frigate}}s (modified {{sclass|Leander|frigate}}s).

Today, propulsion steam turbine cycle efficiencies have yet to break 50%, yet diesel engines routinely exceed 50%, especially in marine applications.{{sfn|Deckers|2003|p=14–15}}{{sfn|Leyzerovich|2002}}<ref name="TakaishiEtAl2008">{{Cite web|url=https://www.mhi.co.jp/technology/review/pdf/e451/e451021.pdf|title=Approach to High Efficiency Diesel and Gas Engines|last1=Takaishi|first1=Tatsuo|last2=Numata|first2=Akira|date=March 2008|work=Technical Review|publisher=Mitsubishi Heavy Industries|access-date=6 May 2019|last3=Nakano|first3=Ryouji|last4=Sakaguchi|first4=Katsuhiko|volume=45|issue=1}}</ref> Diesel power plants also have lower operating costs since fewer operators are required. Thus, conventional steam power is used in very few new ships. An exception is [[LNG carrier]]s which often find it more economical to use [[LNG carrier#Reliquefaction and boil-off|boil-off gas]] with a steam turbine than to re-liquify it.

[[Nuclear marine propulsion|Nuclear-powered ships and submarines]] use a nuclear reactor to create steam for turbines. Currently, the main propulsion steam turbines for [[United States Navy]] nuclear-powered [[Nimitz-class aircraft carrier|Nimitz]] and [[Gerald R. Ford-class aircraft carrier|Ford]] class [[Aircraft carrier|aircraft carriers]] are manufactured by [[Curtiss-Wright]], while the steam turbines for [[Virginia-class submarine|Virginia]] and [[Columbia-class submarine|Columbia]] class [[Submarines in the United States Navy|submarines]] are manufactured by [[Northrop Grumman]].  

Nuclear power is often chosen where diesel power would be impractical (as in [[submarine]] applications) or the logistics of refuelling pose significant problems (for example, [[icebreaker]]s). It has been estimated that the reactor fuel for the [[Royal Navy]]'s {{sclass|Vanguard|submarine|1}}s is sufficient to last 40 circumnavigations of the globe – potentially sufficient for the vessel's entire service life. Nuclear propulsion has only been applied to a very few [[Nuclear marine propulsion#Civilian nuclear ships|commercial vessels]] due to the expense of maintenance and the regulatory controls required on nuclear systems and fuel cycles.