View source for Submarine

{{Short description|Watercraft capable of independent underwater operation}}
{{About|watercraft designed for submerged operation}}
{{pp-semi-indef}}
{{Infobox machine
| image             = US Navy 040730-N-1234E-002 PCU Virginia (SSN 774) returns to the General Dynamics Electric Boat shipyard.jpg
| caption           = US {{sclass|Virginia|submarine|1}} underway in [[Groton, Connecticut]], July&nbsp;2004
| classification    = [[Watercraft]]
| industry          = [[Arms industry|Arms]]
| application       = [[Underwater warfare]]
| inventor          = [[Cornelis Drebbel]]<ref>Fontenoy (2007), p. 1.</ref>
| invented          = {{start date and age|1620|df=y|p=y}}
}}
[[File:Submarine Vepr by Ilya Kurganov crop.jpg|thumb|upright=1.35|Russian [[Akula-class submarine|''Akula''-class submarine]] of the [[Northern Fleet]], in 2008]]
[[File:US Navy submarine types of 1940s and 1950s drawing 1967.png|thumb|upright=1.35|{{unbulleted list|World War II [[fleet submarine]] ([[Gato-class submarine|''Gato'']], [[Balao-class submarine|''Balao'']] or [[Tench-class submarine|''Tench'']] class), commissioned 1941–1945|The first [[nuclear-powered submarine]] {{USS|Nautilus|SSN-571}}, commissioned 1954|The first [[ballistic missile submarine]] {{USS|George Washington|SSBN-598}}, commissioned 1959}}]]

A '''submarine''' (or '''sub''') is a [[watercraft]] capable of independent operation underwater. (It differs from a [[submersible]], which has more limited underwater capability.)<ref>{{cite web | url=https://oceanexplorer.noaa.gov/edu/oceanage/04widder/transcript.html#:~:text=The%20difference%20between%20a%20submarine,launch%20it%20and%20recover%20it. | title=Marine Biologist and Bioluminescence Specialist Edith A. Widder: Video Transcript: Ocean Exploration Careers: NOAA Office of Ocean Exploration and Research }}</ref><!-- This is an important technical claim and must be supported by an appropriate reliable technical reference --> The term “submarine” is also sometimes used historically or informally to refer to [[remotely operated vehicle]]s and [[Autonomous underwater vehicle|robots]], or to medium-sized or smaller vessels (such as the [[midget submarine]] and the [[wet sub]]). Submarines are referred to as ''boats'' rather than ''ships'' regardless of their size.<ref name="cutler">{{cite magazine |last1=Cutler |first1=Thomas J. |title=Of Ships and Boats and ... |url=https://www.usni.org/magazines/naval-history-magazine/2017/october/bluejackets-manual-ships-and-boats-and |volume=31 |issue=5 |access-date=9 November 2022 |department=Bluejacket's Manual |magazine=[[Naval History (magazine)|Naval History]] |publisher=[[U.S. Naval Institute]] |date=1 October 2017 |language=en}}</ref>

Although experimental submarines had been built earlier, submarine design took off during the 19th century, and submarines were adopted by several navies. They were first used widely during [[World War I]] (1914–1918), and are now used in many [[navy|navies]], large and small. Their military uses include: attacking enemy surface [[ship]]s (merchant and military) or other submarines; [[aircraft carrier]] protection; [[Blockade runner|blockade running]]; [[Ballistic missile submarine|nuclear deterrence]]; stealth operations in denied areas when gathering intelligence and doing [[reconnaissance]]; denying or influencing enemy movements; conventional land attacks (for example, launching a [[cruise missile]]); and covert insertion of [[frogman|frogmen]] or [[special forces]]. Their civilian uses include: [[marine science]]; [[Marine salvage|salvage]]; exploration; and facility inspection and maintenance. Submarines can be modified for specialized functions such as search-and-rescue missions and [[undersea cable]] repair. They are also used in the tourism industry and in [[undersea archaeology]]. Modern deep-diving submarines derive from the [[bathyscaphe]], which evolved from the [[diving bell]].

Most large submarines consist of a cylindrical body with hemispherical (or conical) ends and a vertical structure, usually located amidships, which houses communications and sensing devices as well as [[periscope]]s. In modern submarines, this structure is called the "[[Sail (submarine)|sail]]" in American usage and "fin" in European usage. A feature of earlier designs was the "[[conning tower]]": a separate pressure hull above the main body of the [[boat]] that enabled the use of shorter periscopes. There is a propeller (or pump jet) at the rear, and various hydrodynamic control fins. Smaller, deep-diving, and specialty submarines may deviate significantly from this traditional design. Submarines dive and resurface by using [[diving plane]]s and by changing the amount of water and air in [[ballast tank]]s to affect their [[buoyancy]].

Submarines encompass a wide range of types and capabilities. They range from small, autonomous examples, such as one- or two-person subs that operate for a few hours, to vessels that can remain submerged for six months, such as the Russian {{sclass2|Typhoon|submarine|4}}, (the biggest submarines ever built). Submarines can work at depths that are greater than what is practicable (or even survivable) for human [[Underwater diving|divers]].<ref>{{cite web|title=Worlds Biggest Submarine|url=http://englishrussia.com/2009/04/14/worlds-biggest-submarine/ |last=Sherman|first=Chris |date=14 April 2009|website=English Russia |access-date=21 May 2013}}</ref>

==History==
{{Main|History of submarines}}

=== Etymology ===
The word ''submarine'' means 'underwater' or 'under-sea' (as in [[submarine canyon]], [[submarine pipeline]]) though as a noun it generally refers to a vessel that can travel underwater.<ref>[https://www.oed.com/view/Entry/192795?rskey=sQhrJW&result=1&isAdvanced=false#eid ''Submarine''] at [[OED]]; retrieved 4 September 2021</ref> The term is a contraction of ''submarine boat''.<ref>[https://www.oed.com/view/Entry/192795?redirectedFrom=submarine+boat#eid227775172 ''Submarine boat''] at [[OED]]; retrieved 4 September 2021</ref><ref>''The New Shorter Oxford English Dictionary'', Clarendon Press, Oxford, 1993, Vol. 2 N–Z</ref> and occurs as such in several languages, e.g. French ({{lang|fr|sous-marin}}), and Spanish ({{lang|es|submarino}}), although others retain the original term, such as Dutch ({{lang|nl|Onderzeeboot}}), German ({{lang|de|Unterseeboot}}), Swedish ({{lang|sv|Undervattensbåt}}), and Russian ({{lang|ru|подводная лодка}}: {{transliteration|ru|podvodnaya lodka}}), all of which mean 'submarine boat'. By [[naval tradition]], submarines are usually referred to as ''boats'' rather than as ''ships'', regardless of their size.<ref name="cutler"/> Although referred to informally as ''boats'',<ref>{{Cite book |url=https://books.google.com/books?id=Zo0LzmyjP-4C&q=boat |title=Blind Man's Bluff: The Untold Story Of American Submarine Espionage |last1=Sontag |first1=Sherry |last2=Drew |first2=Christopher |last3=Drew |first3=Annette Lawrence |date=19 October 1998 |publisher=PublicAffairs |isbn=9781891620089 |language=en}}</ref><ref>{{Cite book |url=https://books.google.com/books?id=qU4rAQAAQBAJ&q=boat |title=Stealth Boat: Fighting the Cold War in a Fast Attack Submarine |last=McHale |first=Gannon |date=15 September 2013 |publisher=Naval Institute Press |isbn=9781612513461 |language=en}}</ref> U.S. submarines employ the designation USS ([[United States Ship]]) at the beginning of their names, such as {{USS|Alabama|SSBN-731 |6}}. In the Royal Navy, the designation HMS can refer to "His Majesty's Ship" or "His Majesty's Submarine", though the latter is sometimes rendered "HMS/m"<ref>[https://acronyms.thefreedictionary.com/HMS%2FM ''HMS/m''] at acronyms.thefreedictionary; retrieved 4 September 2021</ref><ref group=Note>For example, see [https://www.iwm.org.uk/collections/item/object/205160540 HMS/m ''Tireless''], at [[Imperial War Museum|IWM]], [https://historicengland.org.uk/listing/the-list/list-entry/1000043 HMS/m ''A.1''] at [[Historic England]]</ref> and submarines are generally referred to as ''boats'' rather than ''ships''.<ref group="Note">The Submarine service page on the official website of the Royal Navy refers to "These powerful boats"[https://www.royalnavy.mod.uk/the-equipment/submarines], and in at a speech in Washington, Adm. Sir Philip Jones announced "that the name ''Dreadnought'' will return as lead boat and class name" for [[Dreadnought-class submarine|Britain's latest ballistic missile submarines]].[https://www.royalnavy.mod.uk/news-and-latest-activity/news/2016/october/22/161022-first-sea-lord-trafalgar-night-speech-in-washington]</ref>

===Early human-powered submersibles===
[[File:Van Drebbel.jpg|thumb|An early submersible craft, built by [[Cornelis Drebbel]], propelled by oars]]

====16th and 17th centuries====
According to a report in ''Opusculum [[Jean Taisnier|Taisnieri]]'' published in 1562:<ref>Joann Taisnier Hannon ([[Jean Taisnier]] (1508–1562)), ''Opusculum perpetua memoria dignissimum, de natura magnetis et eius effectibus'' [Most fitting work in perpetual remembrance, on the nature of the magnet and its effects] (Köln (Cologne, "Colonia"), (Germany): Johann Birckmann, 1562), pp. 43–45.  Available from: [https://bildsuche.digitale-sammlungen.de/index.html?c=viewer&bandnummer=bsb00022856&pimage=49&v=100&nav=&l=en Bavarian State Library] From p. 43: ''"Ne autem Lector nostra dicta videatur refutare, arbitratus ea, quae miracula putat, naturae limites excedere, unica demonstratione elucidabo, quomodo scilicet quis in fundum alicuius aquae aut fluvij, sicco corpore intrare possit, quod me vidisse in celebri Oppido & Regno Tolleti affirmavi, coram piae memoriae Carolo Quinto Imperatore, & infinitis aliis spectatoribus."'' (Nevertheless, reader, our statement is seen to refute something witnessed, which one considers a wonder, exceeding the limits of nature; I will elucidate a unique demonstration, namely, how one can penetrate to the bottom of any water or river while remaining dry, which, I assert, I saw in the celebrated city and kingdom of Toledo in the presence of Emperor Charles V of blessed memory and a multitude of other spectators.) From p. 44: ''"Nunc venio ad experientiam praedictam, Tolleti demonstratam a duobus Graecis, qui Cacabo magnae amplitudinis accepto, orificio inverso, funibus in aere pendente, tabem & asseres in medio concavi Cacabi affigunt, ... "'' (Now I come to the experiment mentioned above: in Toledo, it was shown by two Greeks, who, I understand, attached to a cauldron (''cacabus'') of great size — [which had its] opening inverted [and which was] held in the air by ropes — a beam and poles inside of the hollow cauldron ... [The beam and poles formed seats for the divers.]) The German Jesuit scientist [[Gaspar Schott]] (1608–1666) quoted Taisnier's account and mentioned that Taisnier had witnessed the demonstration in 1538.  Gaspar Schott, ''Technica Curiosa, sive Mirabilia Artis, Libris XII. ... '' [Curious works of skill, or marvelous works of craftsmanship, in 12 books ... ] (Nuremberg (Norimberga), (Germany): Johannes Andreas Endter & Wolfgang Endter, 1664), ''Liber VI: Mirabilium Mechanicorum'' (Book 6: Wonders of mechanics), [https://books.google.com/books?id=dhRTAAAAcAAJ&q=icon&pg=PA393 p. 393.] From p. 393: ''" ... quod nihilominus Anno 1538 in Hispaniae oppido Toleto &c. coram piae memoriae Carolo V. Imperatore, cum decem propemodum millibus hominum experientia vidi."'' ( ... that nevertheless I saw the experiment in the year 1538 in Spain in the city of Toledo, etc., in the presence of Emperor Charles V of blessed memory, with almost ten thousand people.)</ref>
{{blockquote|Two Greeks submerged and surfaced in the river [[Tagus]] near the City of [[Toledo, Spain|Toledo]] several times in the presence of [[Charles V, Holy Roman Emperor|The Holy Roman Emperor Charles V]], without getting wet and with the flame they carried in their hands still alight.<ref>{{cite web|url=http://hemeroteca.abc.es/nav/Navigate.exe/hemeroteca/madrid/abc/1980/03/07/089.html|title=Espańa, Precursora de la Navegación Submarina|archive-url=https://web.archive.org/web/20150721145006/http://hemeroteca.abc.es/nav/Navigate.exe/hemeroteca/madrid/abc/1980/03/07/089.html|archive-date=July 21, 2015|url-status=live|date=March 7, 1980|work=[[ABC (newspaper)|ABC]]}}</ref>}}

In 1578, the English mathematician [[William Bourne (mathematician)|William Bourne]] recorded in his book ''Inventions or Devises'' one of the first plans for an underwater navigation vehicle.<ref>Delgado (2011), p. 13.</ref> A few years later the Scottish mathematician and theologian [[John Napier]] wrote in his ''Secret Inventions'' (1596) that "These inventions besides devises of sayling under water with divers, other devises and strategems for harming of the enemyes by the Grace of God and worke of expert Craftsmen I hope to perform." It is unclear whether he carried out his idea.<ref name = Tiere/>

[[Jerónimo de Ayanz y Beaumont]] (1553–1613) created detailed designs for two types of air-renovated submersible vehicles. They were equipped with oars, autonomous floating snorkels worked by inner pumps, portholes and gloves used for the crew to manipulate underwater objects. Ayanaz planned to use them for warfare, using them to approach enemy ships undetected and set up timed gunpowder charges on their hulls.<ref>{{cite web|url=https://www.xataka.com/historia-tecnologica/jeronimo-ayanz-da-vinci-olvidado-que-diseno-submarino-sistemas-aire-acondicionado-espana-austrias|title=Jerónimo de Ayanz, el Da Vinci olvidado que diseñó un submarino y sistemas de aire acondicionado en la España de los Austrias|date=September 26, 2021|access-date=October 17, 2022|publisher=Xataka|language=Spanish}}</ref>

The first submersible of whose construction there exists reliable information was designed and built in 1620 by [[Cornelis Drebbel]], a Dutchman in the service of [[James VI and I|James I of England]]. It was propelled by means of oars.<ref name = Tiere>{{Citation|last=Tierie|first=Gerrit|title=Cornelis Drebbel (1572–1633)|type=Thesis|publisher=Rijksuniversiteit te Leiden|place=Amsterdam|pages=92|date=10 June 1932|language=en|url=http://www.drebbel.net/Tierie.pdf}}</ref>

====18th century====
By the mid-18th century, over a dozen patents for submarines/submersible boats had been granted in England. In 1747, Nathaniel Symons patented and built the first known working example of the use of a ballast tank for submersion. His design used leather bags that could fill with water to submerge the craft. A mechanism was used to twist the water out of the bags and cause the boat to resurface. In 1749, the [[Gentlemen's Magazine]] reported that a similar design had initially been proposed by [[Giovanni Borelli]] in 1680. Further design improvement stagnated for over a century, until application of new technologies for propulsion and stability.<ref name="vector">{{cite web|url=http://inventors.about.com/od/sstartinventions/a/Submarines.htm|archive-url=https://archive.today/20120709102159/http://inventors.about.com/od/sstartinventions/a/Submarines.htm|url-status=dead|archive-date=July 9, 2012|title=The Invention Of The Submarine|author=Mary Bellis|access-date=16 April 2014}}</ref>

The first military submersible was {{ship||Turtle|submersible|2}} (1775), a hand-powered acorn-shaped device designed by the American [[David Bushnell]] to accommodate a single person.<ref>{{cite web|title=The Submarine Turtle: Naval Documents of the Revolutionary War |url=http://www.history.navy.mil/library/online/sub_turtle.htm |archive-url=https://web.archive.org/web/20080917024301/http://www.history.navy.mil/library/online/sub_turtle.htm |url-status=dead |archive-date=17 September 2008 |publisher=Navy Department Library |access-date=21 May 2013 }}</ref> It was the first verified submarine capable of independent underwater operation and movement, and the first to use [[Propeller|screws]] for propulsion.<ref>[https://web.archive.org/web/20030415051537/http://web.mit.edu/invent/iow/bushnelld.html Inventor of the Week: Archive]. mit.edu</ref>

====19th century====
[[File:Fulton's submarine design.jpg|alt=Illustration by Robert Fulton showing a "plunging boat"|thumb|1806 illustration by Robert Fulton showing a "plunging boat"]]

In 1800, France built {{ship||Nautilus|1800 submarine|2}}, a human-powered submarine designed by American [[Robert Fulton]]. They gave up on the experiment in 1804, as did the British, when they reconsidered Fulton's submarine design.

In 1850, [[Wilhelm Bauer]]'s {{ship||Brandtaucher}} was built in Germany. It remains the oldest known surviving submarine in the world.<ref>{{cite book |last=Delgado |first=James P. |url=https://books.google.com/books?id=8ue6CwAAQBAJ&pg=PA224|title=Silent Killers: Submarines and Underwater Warfare|publisher=Bloomsbury Publishing|date=2011|page=224|isbn=9781849088602}}</ref>

In 1864, late in the [[American Civil War]], the [[Confederate navy]]'s {{ship||H. L. Hunley|submarine|2}} became the first military submarine to sink an enemy vessel, the Union [[sloop-of-war]] {{USS|Housatonic|1861|6}}, using a gun-powder-filled keg on a spar as a torpedo charge. The ''Hunley'' also sank. The explosion's shock waves may have killed its crew instantly, preventing them from pumping the bilge or propelling the submarine.<ref>{{Cite web |last=Lance |first=Rachel |author-link=Rachel Lance |title=The New Explosive Theory About What Doomed the Crew of the 'Hunley' |url=https://www.smithsonianmag.com/history/new-explosive-theory-what-doomed-crew-hunley-180974159/ |access-date=24 November 2020 |website=Smithsonian Magazine |language=en}}</ref>

In 1866, {{ship||Sub Marine Explorer}} was the first submarine to successfully dive, cruise underwater, and resurface under the crew's control. The design by German American [[Julius H. Kroehl]] (in German, ''Kröhl'') incorporated elements that are still used in modern submarines.<ref>{{cite journal|author=James P. Delgado|title=Archaeological Reconnaissance of the 1865 American-Built Sub Marine Explorer at Isla San Telmo, Archipielago de las Perlas, Panama|journal=International Journal of Nautical Archaeology Journal|volume=35|issue=2|pages=230–252|year=2006|doi=10.1111/j.1095-9270.2006.00100.x|bibcode=2006IJNAr..35..230D |s2cid=162403756|author-link=James P. Delgado|issn = 1057-2414}}</ref>

In 1866, {{ship||Flach|submarine|2}} was built at the Chilean government's request by [[Karl Flach]], a German engineer and immigrant. It was the fifth submarine built in the world<ref>{{cite news |title=Recovering Chile's 19th Century Shipwrecks in Valparaiso's Port |date=25 November 2006 |url=http://www.tcgnews.com/santiagotimes/index.php?nav=story&story_id=12293&topic_id=1 |work=The Santiago Times |access-date=17 April 2007 |url-status=dead |archive-url=https://web.archive.org/web/20080124142651/http://www.tcgnews.com/santiagotimes/index.php?nav=story&story_id=12293&topic_id=1 |archive-date=24 January 2008 }}</ref> and, along with a second submarine, was intended to defend the port of [[Valparaiso]] against attack by the [[Spanish Navy]] during the [[Chincha Islands War]].

===Mechanically powered submarines===
Submarines could not be put into widespread or routine service use by navies until suitable engines were developed. The era from 1863 to 1904 marked a pivotal time in submarine development, and several important technologies appeared. A number of nations built and used submarines. [[Diesel–electric transmission|Diesel electric]] propulsion became the dominant power system and equipment such as the periscope became standardized. Countries conducted many experiments on effective tactics and weapons for submarines, which led to their large impact in [[World War I]].

====1863–1904====
[[File:Plongeur.jpg|thumb|upright=1.3|left|The French submarine [[French submarine Plongeur|''Plongeur'']]]]

The first submarine not relying on human power for propulsion was the French {{ship|French submarine|Plongeur||2}} (''Diver''), launched in 1863, which used compressed air at {{cvt|180|psi|disp=flip|lk=on}}.{{citation needed|date=December 2022}} [[Narcis Monturiol i Estarriol|Narcís Monturiol]] designed the first [[air-independent power|air-independent]] and [[combustion]]-powered submarine, {{ship||Ictíneo II}}, which was launched in [[Barcelona]], Spain in 1864.

The submarine became feasible as potential weapon with the development of the [[Whitehead torpedo]], designed in 1866 by British engineer [[Robert Whitehead]], the first practical self-propelled or "locomotive" torpedo.<ref>{{cite web|title=Torpedo History: Whitehead Torpedo Mk1|url=http://www.history.navy.mil/museums/keyport/html/part2.htm|publisher=Naval History and Heritage Command|access-date=28 May 2013|archive-date=15 September 2014|archive-url=https://web.archive.org/web/20140915054904/http://www.history.navy.mil/museums/keyport/html/part2.htm|url-status=dead}}</ref> The [[spar torpedo]] that had been developed earlier by the Confederate States Navy was considered to be impracticable, as it was believed to have sunk both its intended target, and ''H. L. Hunley'', the submarine that deployed it.

The Irish inventor [[John Philip Holland]] built a model submarine in 1876 and in 1878 demonstrated the [[Holland I]] prototype. This was followed by a number of unsuccessful designs. In 1896, he designed the Holland Type VI submarine, which used internal combustion engine power on the surface and electric [[battery (electricity)|battery]] power underwater. Launched on 17 May 1897 at Navy Lt. [[Lewis Nixon (naval architect)|Lewis Nixon]]'s [[Crescent Shipyard]] in [[Elizabeth, New Jersey]], ''Holland VI'' was purchased by the [[United States Navy]] on 11 April 1900, becoming the Navy's first commissioned submarine, christened {{USS|Holland|SS-1|6}}.<ref>{{cite encyclopedia |url=http://www.britannica.com/eb/article-9040797/John-Philip-Holland |title=John Philip Holland |encyclopedia=Encyclopædia Britannica |access-date=1 April 2015}}</ref>

Discussions between the English clergyman and inventor [[George Garrett (inventor)|George Garrett]] and the Swedish industrialist [[Thorsten Nordenfelt]] led to the first practical steam-powered submarines, armed with torpedoes and ready for military use. The first was ''Nordenfelt I'', a 56-tonne, {{convert|19.5|m|ft|adj=on}} vessel similar to Garrett's ill-fated {{ship||Resurgam}} (1879), with a range of {{convert|240|km|nmi mi}}, armed with a single [[torpedo]], in 1885.

[[File:Peral1888.jpg|thumb|''[[Spanish submarine Peral|Peral]]'' at [[Cartagena, Spain|Cartagena]], 1888]]
A reliable means of propulsion for the submerged vessel was only made possible in the 1880s with the advent of the necessary electric battery technology. The first electrically powered boats were built by [[Isaac Peral y Caballero]] in Spain (who built {{ship|Spanish submarine|Peral||2}}), [[Henri Dupuy de Lôme|Dupuy de Lôme]] (who built {{ship|French submarine|Gymnote|Q1|2}}) and [[Gustave Zédé]] (who built [[French submarine Gustave Zédé (1893)|''Sirène'']]) in France, and James Franklin Waddington (who built ''Porpoise'') in England.<ref>{{cite book|url=https://books.google.com/books?id=ohYiAQAAIAAJ|title=The Garrett Enigma and the Early Submarine Pioneers|first=Paul |last=Bowers|year=1999|publisher=Airlife|page=167|isbn=978-1-84037-066-9}}</ref> Peral's design featured torpedoes and other systems that later became standard in submarines.<ref>{{Cite news|url=http://www.elmundo.es/elmundo/2013/08/14/ciencia/1376474198.html|title=Isaac Peral, el genio frustrado|last=Sanmateo|first=Javier|date=5 September 2013|work=El Mundo|access-date=12 December 2017|language=es}}</ref><ref>{{Cite book|title=Silent Killers: Submarines and Underwater Warfare|last1=Delgado|first1=James P.|last2=Cussler|first2=Clive|publisher=Bloomsbury Publishing|year=2011|isbn=978-1849088602|pages=89}}</ref>

[[File:USS Plunger - NH 85735 - cropped.jpg|thumb|{{USS|Plunger|SS-2|6}}, launched in 1902]]
[[File:Akula&Ryurik1913.jpg|thumb|{{ship|Russian submarine|Akula|1908|2}} (launched in 1907) was the first Russian submarine able to cruise long distances.]]
Commissioned in June 1900, the French steam and electric {{ship|French submarine|Narval|Q4|2}} employed the now typical double-hull design, with a pressure hull inside the outer shell. These 200-ton ships had a range of over {{cvt|100|mi|disp=flip}} underwater. The French submarine [[French submarine Aigrette|''Aigrette'']] in 1904 further improved the concept by using a diesel rather than a gasoline engine for surface power. Large numbers of these submarines were built, with seventy-six completed before 1914.

The Royal Navy commissioned five {{sclass2|Holland|submarine|2}}s from [[Vickers]], [[Barrow-in-Furness]], under licence from the [[Holland Torpedo Boat Company]] from 1901 to 1903. Construction of the boats took longer than anticipated, with the first only ready for a diving trial at sea on 6 April 1902. Although the design had been purchased entirely from the US company, the actual design used was an untested improvement to the original Holland design using a new {{convert|180|hp}} petrol engine.<ref>Galantin, Ignatius J., Admiral, USN (Ret.). Foreword to ''Submariner'' by Johnnie Coote, p. 1</ref>

These types of submarines were first used during the [[Russo-Japanese War]] of 1904–05. Due to the blockade at [[Port Arthur, China|Port Arthur]], the Russians sent their submarines to [[Vladivostok]], where by 1 January 1905 there were seven boats, enough to create the world's first "operational submarine fleet". The new submarine fleet began patrols on 14 February, usually lasting for about 24 hours each. The first confrontation with Japanese warships occurred on 29 April 1905 when the Russian submarine [[Som-class submarine|''Som'']] was fired upon by Japanese torpedo boats, but then withdrew.<ref>Olender p. 175</ref>

====World War I====
[[File:U9Submarine.jpg|thumb|left|The German submarine {{SMU|U-9}}, which sank three British [[cruiser]]s in [[Action of 22 September 1914|less than an hour in September 1914]]]]

Military submarines first made a significant impact in [[World War I]]. Forces such as the [[U-boat]]s of Germany saw action in the [[First Battle of the Atlantic]], and were responsible for sinking {{RMS|Lusitania}}, which was sunk as a result of [[unrestricted submarine warfare]] and is often cited among the reasons for the entry of the United States into the war.<ref>{{cite book|title=Germany and the Americas|author=Thomas Adam|page=1155}}</ref>

At the outbreak of the war, Germany had only twenty submarines available for combat, although these included vessels of the diesel-engined ''[[SM U-19 (Germany)|U-19]]'' class, which had a sufficient range of {{convert|5000|mi|km|sigfig=1}} and speed of {{convert|8|kn|km/h}} to allow them to operate effectively around the entire British coast.,<ref>Douglas Botting, pp. 18–19 "The U-Boats", {{ISBN|978-0-7054-0630-7}}</ref> By contrast, the Royal Navy had a total of 74 submarines, though of mixed effectiveness. In August 1914, a flotilla of ten U-boats sailed from their base in [[Heligoland]] to attack Royal Navy warships in the [[North Sea]] in the first submarine war patrol in history.<ref>Gibson and Prendergast, p. 2</ref>

The U-boats' ability to function as practical war machines relied on new tactics, their numbers, and submarine technologies such as combination diesel–electric power system developed in the preceding years. More submersibles than true submarines, U-boats operated primarily on the surface using regular engines, submerging occasionally to attack under battery power. They were roughly triangular in cross-section, with a distinct [[keel]] to control rolling while surfaced, and a distinct bow. During World War I more than 5,000 [[Allies of World War I|Allied]] ships were sunk by U-boats.<ref>Roger Chickering, Stig Förster, Bernd Greiner, German Historical Institute (Washington, D.C.) (2005). "''[https://books.google.com/books?id=evVPoSwqrG4C&pg=PA73 A world at total war: global conflict and the politics of destruction, 1937–1945]''". Cambridge University Press. {{ISBN|978-0-521-83432-2}}, p. 73</ref>

The British responded to the German developments in submarine technology with the creation of the [[British K-class submarine|K-class submarines]]. However, these submarines were notoriously dangerous to operate due to their various design flaws and poor maneuverability.<ref>{{cite web |title=1915-1926: K Class |url=http://rnsubs.co.uk/boats/subs/k-class.html |website=RN Subs |publisher=Barrow Submariners Association |access-date=24 February 2019}}</ref><ref>{{cite web |url=https://www.theguardian.com/commentisfree/2017/nov/04/k-class-submarines-disaster-navy-britain-hms-vigilant |title=From the K-class to the party boat, submarines have a history of disaster |newspaper=The Guardian |date=4 November 2017 |author=Ian Jack |access-date=13 January 2022}}</ref>

====World War II====
{{See also|List of submarines of World War II}}
[[File:I400 2.jpg|thumb|The [[Imperial Japanese Navy]]'s {{sclass|I-400|submarine|2}}, the largest submarine type of WWII]]
[[File:U-47.jpg|thumb|A model of [[Günther Prien]]'s {{GS|U-47|1938|2}}, German WWII [[Type VII submarine|Type VII]] diesel–electric hunter]]

During [[World War II]], Germany used submarines to devastating effect in the [[Battle of the Atlantic]], where it attempted to cut Britain's supply routes by sinking more [[merchant ship]]s than Britain could replace. These merchant ships were vital to supply Britain's population with food, industry with raw material, and armed forces with fuel and armaments. Although the U-boats had been updated in the interwar years, the major innovation was improved communications, encrypted using the [[Enigma machine|Enigma cipher machine]]. This allowed for mass-attack [[naval tactics]] (''Rudeltaktik'', commonly known as "[[Wolfpack (naval tactic)|wolfpack]]"), which ultimately ceased to be effective when [[Cryptanalysis of the Enigma|the U-boat's Enigma was cracked]]. By the end of the war, almost 3,000 [[Allies of World War II|Allied]] ships (175 warships, 2,825 merchantmen) had been sunk by U-boats.<ref>{{cite book|last=Crocker III|first=H. W.|title=Don't Tread on Me|publisher=Crown Forum|year=2006|location=New York|page=[https://archive.org/details/donttreadonme40000croc/page/310 310]|isbn=978-1-4000-5363-6|url=https://archive.org/details/donttreadonme40000croc/page/310}}</ref><!--not solely by torpedo, I wager...--> Although successful early in the war, Germany's U-boat fleet suffered heavy casualties, losing 793 U-boats and about 28,000 submariners out of 41,000, a casualty rate of about 70%.<ref>{{cite news |title=The Battle of the Atlantic: The U-boat peril |url=https://www.bbc.co.uk/history/worldwars/wwtwo/battle_atlantic_01.shtml |work=BBC |date=30 March 2011}}</ref>

The [[Imperial Japanese Navy]] operated the most varied fleet of submarines of any navy, including ''[[Kaiten]]'' crewed torpedoes, midget submarines ({{sclass2|Type A Ko-hyoteki|submarine|5}} and {{sclass|Kairyu|submarine|4}}es), medium-range submarines, purpose-built supply submarines and long-range [[fleet submarine]]s. They also had submarines with the highest submerged speeds during World War II ({{sclass|I-201|submarine|2}}s) and submarines that could carry multiple aircraft ({{sclass|I-400|submarine|2}}s). They were also equipped with one of the most advanced torpedoes of the conflict, the oxygen-propelled [[Type 95 torpedo|Type 95]]. Nevertheless, despite their technical prowess, Japan chose to use its submarines for fleet warfare, and consequently were relatively unsuccessful, as warships were fast, maneuverable and well-defended compared to merchant ships.

The submarine force was the most effective anti-ship weapon in the American arsenal. Submarines, though only about 2 percent of the U.S. Navy, destroyed over 30 percent of the Japanese Navy, including 8 aircraft carriers, 1 battleship and 11 cruisers. US submarines also destroyed over 60 percent of the Japanese merchant fleet, crippling Japan's ability to supply its military forces and industrial war effort. [[Allied submarines in the Pacific War]] destroyed more Japanese shipping<!--because "shipping" means "merchant", generally, & that's the important factor--> than all other weapons combined. This feat was considerably aided by the Imperial Japanese Navy's failure to provide adequate escort forces for the nation's merchant fleet.

During World War II, 314&nbsp;submarines served in the US Navy, of which nearly 260 were deployed to the Pacific.<ref name="O'Kane, p. 333">O'Kane, p. 333</ref> When the Japanese attacked Hawaii in December 1941, 111 boats were in commission; 203 submarines from the {{sclass|Gato|submarine|5}}, {{sclass|Balao|submarine|5}}, and {{sclass|Tench|submarine|4}}es were commissioned during the war. During the war, 52 US submarines were lost to all causes, with 48 directly due to hostilities.<ref>Blair, Clay, Jr. ''Silent Victory'', pp. 991–92. The others were lost to accidents or, in the case of {{USS|Seawolf|SS-197|2}}, [[friendly fire]].</ref> US submarines sank 1,560&nbsp;enemy vessels,<ref name="O'Kane, p. 333" /> a total tonnage of 5.3&nbsp;million tons (55% of the total sunk).<ref name="Blair, p. 878">Blair, p. 878</ref>

The [[Royal Navy Submarine Service]] was used primarily in the classic Axis [[blockade]]. Its major operating areas were around Norway, in the [[Mediterranean]] (against the Axis supply routes to North Africa), and in the Far East. In that war, British submarines sank 2 million tons of enemy shipping and 57 major warships, the latter including 35 submarines. Among these is the only documented instance of a submarine sinking another submarine while both were submerged. This occurred when {{HMS|Venturer|P68|6}} [[Action of 9 February 1945|engaged]] {{GS|U-864||2}}; the ''Venturer'' crew manually computed a successful firing solution against a three-dimensionally maneuvering target using techniques which became the basis of modern torpedo computer targeting systems. Seventy-four British submarines were lost,<ref>{{cite web |url=http://www.royalnavy.mod.uk/server/show/nav.2558 |title=Submarine History |publisher=The Royal Navy |access-date=18 April 2007 |url-status=dead |archive-url=https://web.archive.org/web/20070220150129/http://www.royalnavy.mod.uk/server/show/nav.2558 |archive-date=20 February 2007}}</ref> <!--something more than speculation on cause is wanted-->the majority, forty-two, in the Mediterranean.

====Cold-War military models====
[[File:HMAS Rankin at periscope depth.jpg|thumb|{{HMAS|Rankin|SSG 78|6}}, a {{sclass|Collins|submarine|2}} at periscope depth]]
[[File:USS Charlotte (SSN 766) steams in a close formation at RIMPAC 2014.jpg|thumb|upright|{{USS|Charlotte|SSN-766|6}}, a {{sclass|Los Angeles|submarine|2}} runs with submarines from partner nations during [[Exercise RIMPAC|RIMPAC]] 2014.]]

The first launch of a [[cruise missile]] ([[SSM-N-8 Regulus]]) from a submarine occurred in July 1953, from the deck of {{USS|Tunny|SSG-282|6}}, a World War II fleet boat modified to carry the missile with a [[nuclear weapon|nuclear warhead]]. ''Tunny'' and its sister boat, {{USS|Barbero|SSG-317|2}}, were the United States' first nuclear deterrent patrol submarines. In the 1950s, [[Nuclear marine propulsion|nuclear power]] partially replaced diesel–electric propulsion. Equipment was also developed to extract [[oxygen]] from sea water. These two innovations gave submarines the ability to remain submerged for weeks or months.<ref>{{cite web |url=https://ussnautilus.org/history-of-uss-nautilus/ |title=History of USS Nautilus (SSN 571)|publisher=[[Submarine Force Library and Museum|Submarine Force Museum]]|year=2006|access-date=16 January 2012}}</ref><ref>{{cite magazine|author=Tony Long|url=https://www.wired.com/science/discoveries/news/2007/05/dayintech_0510|title=10 May 1960: USS ''Triton'' Completes First Submerged Circumnavigation|magazine=Wired|date=10 May 2007|access-date=18 April 2010}}</ref> Most of the naval submarines built since that time in the US, the Soviet Union (now Russia), the UK, and France have been powered by a [[nuclear reactor]].

In 1959–1960, the first [[ballistic missile submarine]]s were put into service by both the United States ({{sclass|George Washington|submarine|4}}) and the Soviet Union ({{sclass2|Golf|submarine|4}}) as part of the [[Cold War]] [[nuclear deterrent]] strategy.

During the Cold War, the US and the Soviet Union maintained large submarine fleets that engaged in cat-and-mouse games. The Soviet Union lost at least four submarines during this period: {{ship|Soviet submarine|K-129|1960|2}} was lost in 1968 (a part of which the [[CIA]] retrieved from the ocean floor with the [[Howard Hughes]]-designed ship [[Hughes Glomar Explorer|''Glomar Explorer'']]), {{ship|Soviet submarine|K-8||2}} in 1970, {{ship|Soviet submarine|K-219||2}} in 1986, and {{ship|Soviet submarine|Komsomolets||2}} in 1989 (which held a depth record among military submarines—{{convert|1000|m|ft|abbr=on}}). Many other Soviet subs, such as {{ship|Soviet submarine|K-19||2}} (the first Soviet nuclear submarine, and the first Soviet sub to reach the North Pole) were badly damaged by fire or radiation leaks. The US lost two nuclear submarines during this time: {{USS|Thresher|SSN-593|6}} due to equipment failure during a test dive while at its operational limit, and {{USS|Scorpion|SSN-589|6}} due to unknown causes.

During the [[Indo-Pakistani War of 1971]], the [[Pakistan Navy]]'s {{ship|PNS|Hangor|S131|2}} sank the Indian frigate {{INS|Khukri|1958|6}}. This was the first sinking by a submarine since World War II.{{citation needed|date=December 2022}} During the same war, {{ship|PNS|Ghazi||2}}, a ''Tench''-class submarine on loan to Pakistan from the US, was sunk by the [[Indian Navy]]. It was the first submarine combat loss since World War II.<ref name="BR">{{cite web|url=http://www.bharat-rakshak.com/MONITOR/ISSUE4-2/harry.html |title=The Sinking of the Ghazi |work=Bharat Rakshak Monitor, 4(2) |access-date=20 October 2009 |url-status=dead |archive-url=https://web.archive.org/web/20111128104709/http://www.bharat-rakshak.com/MONITOR/ISSUE4-2/harry.html |archive-date=28 November 2011 }}</ref> In 1982 during the [[Falklands War]], the Argentine cruiser {{ship|ARA|General Belgrano||2}} was sunk by the British submarine {{HMS|Conqueror|S48|6}}, the first sinking by a nuclear-powered submarine in war.<ref>{{Cite book|title=Sink the Belgrano|last=Rossiter|first=Mike|publisher=Random House|year=2009|isbn=978-1-4070-3411-9|location=London|pages=305–18, 367–77|oclc=1004977305}}</ref> Some weeks later, on 16 June, during the [[1982 Lebanon War|Lebanon War]], an unnamed [[Gal-class submarine|Israeli submarine]] torpedoed and sank the Lebanese coaster ''Transit'',<ref name=":0">{{Cite web|last=|first=|date=|title=Stichting Maritiem Historische Data - Schip|url=https://www.marhisdata.nl/schip&id=2654|access-date=11 February 2021|website=www.marhisdata.nl|language=dutch}}</ref> which was carrying 56 Palestinian refugees to [[Cyprus]], in the belief that the vessel was evacuating anti-Israeli militias. The ship was hit by two torpedoes, managed to run aground but eventually sank. There were 25 dead, including her captain. The [[Israeli Navy]] disclosed the incident in November 2018.<ref>{{Cite web|last=|first=|date=22 November 2018|title=Israel admits it sank Lebanese refugee boat in 1982 war error, killing 25 — TV|url=https://www.timesofisrael.com/israel-admits-it-sank-lebanese-refugee-boat-in-1982-war-error-killing-25-tv/|access-date=11 February 2021|website=www.timesofisrael.com|language=en-US}}</ref><ref name=":0" />

==Usage==
{{split section|Military submarine|date=March 2024}}

===Military===
{{main|Submarine warfare|Attack submarine|Ballistic missile submarine|Cruise missile submarine|Nuclear submarine}}
[[File:German UC-1 class submarine.jpg|thumb|German [[German Type UC I submarine|''UC-1''-class]] World War I submarine. The wires running up from the bow to the conning tower are the [[jumping wire]]s]]
[[File:Allveelaev Lembit 2012.jpg|thumb|{{ship|EML|Lembit||6}} in the [[Estonian Maritime Museum]]. The ''Lembit'' is the only minelayer submarine of its series left in the world.<ref>{{cite news|title=World's oldest submerged submarine reaches land|author=Mattias, L.|url=http://ireport.cnn.com/docs/DOC-615075|work=CNN|date=30 May 2011|access-date=29 January 2013|archive-date=4 March 2016|archive-url=https://web.archive.org/web/20160304054336/http://ireport.cnn.com/docs/DOC-615075|url-status=dead}}</ref>]]

Before and during [[World War II]], the primary role of the submarine was anti-surface ship warfare. Submarines would attack either on the surface using deck guns, or submerged using [[torpedo]]es. They were particularly effective in sinking Allied transatlantic shipping in both World Wars, and in disrupting Japanese supply routes and naval operations in the Pacific in World War II.

[[Naval mine|Mine]]-laying submarines were developed in the early part of the 20th century. The facility was used in both World Wars. Submarines were also used for inserting and removing covert agents and military forces in [[special operations]], for intelligence gathering, and to rescue aircrew during air attacks on islands, where the airmen would be told of safe places to crash-land so the submarines could rescue them. Submarines could carry cargo through hostile waters or act as supply vessels for other submarines.

Submarines could usually locate and attack other submarines only on the surface, although {{HMS|Venturer|P68|6}} managed to sink {{GS|U-864||2}} with a four torpedo spread while both were submerged. The British developed a specialized anti-submarine submarine in WWI, the [[British R-class submarine|R class]]. After WWII, with the development of the homing torpedo, better [[sonar]] systems, and [[nuclear propulsion]], submarines also became able to hunt each other effectively.

The development of [[submarine-launched ballistic missile]] and submarine-launched [[cruise missile]]s gave submarines a substantial and long-ranged ability to attack both land and sea targets with a variety of weapons ranging from [[cluster bomb]]s to [[nuclear weapon]]s.

The primary defense of a submarine lies in its ability to remain concealed in the depths of the ocean. Early submarines could be detected by the sound they made. Water is an excellent conductor of sound (much better than air), and submarines can detect and track comparatively noisy surface ships from long distances. Modern submarines are built with an emphasis on [[Stealth technology|stealth]]. Advanced [[propeller]] designs, extensive sound-reducing insulation, and special machinery help a submarine remain as quiet as ambient ocean noise, making them difficult to detect. It takes specialized technology to find and attack modern submarines.

[[File:Trident II D5 launches from the USS Nebraska (SSBN 739), March 26, 2008.jpg|right|thumb|[[UGM-133 Trident II|Trident II D5]] is one of the most advanced [[submarine-launched ballistic missile]]s]]
[[Sonar#Active sonar|Active sonar]] uses the reflection of sound emitted from the search equipment to detect submarines. It has been used since WWII by surface ships, submarines and aircraft (via dropped buoys and helicopter "dipping" arrays), but it reveals the emitter's position, and is susceptible to counter-measures.

A concealed military submarine is a real threat, and because of its stealth, can force an enemy navy to waste resources searching large areas of ocean and protecting ships against attack. This advantage was vividly demonstrated in the 1982 [[Falklands War]] when the British [[nuclear-powered]] submarine {{HMS|Conqueror|S48|6}} sank the Argentine cruiser {{ship|ARA|General Belgrano||2}}. After the sinking the Argentine Navy recognized that they had no effective defense against submarine attack, and the Argentine surface fleet withdrew to port for the remainder of the war. An Argentine submarine remained at sea, however.<ref>{{cite book |last = Finlan |first = Alastair |title = The Royal Navy in the Falklands Conflict and the Gulf War: Culture and Strategy |publisher = Psychology Press |series = British Politics and Society |volume = 15 |date = 2004 |location = London |pages = 214 |url = https://books.google.com/books?id=TmP27lCid8AC&q=general+belgrano+naval+strategy&pg=PA84 |isbn = 978-0-7146-5479-9 }}</ref>

===Civilian===
Although the majority of the world's submarines are military, there are some civilian submarines, which are used for tourism, exploration, oil and gas platform inspections, and pipeline surveys. Some are also used in illegal activities.

The [[Submarine Voyage]] ride opened at [[Disneyland]] in 1959, but although it ran under water it was not a true submarine, as it ran on tracks and was open to the atmosphere.<ref name=perry>{{cite web|url=http://www.perry.com/disney/subs/subs.html|access-date=24 April 2010|title=Sail Away - The Last Voyages of the Disneyland Submarines}}</ref> The first tourist submarine was {{Ship||Auguste Piccard|PX-8|2}}, which went into service in 1964 at [[Expo64]].<ref>{{cite web|url=https://www.verkehrshaus.ch/en/members-donations/donations/mesoscaph|title=Mesoscaph "August Piccard"|work=Verkehrshaus der Schweiz|url-status=dead|archive-url=https://web.archive.org/web/20160307035900/https://www.verkehrshaus.ch/en/members-donations/donations/mesoscaph|archive-date=7 March 2016}}</ref> By 1997, there were 45 tourist submarines operating around the world.<ref>{{cite book|publisher=CABI|title=The Encyclopedia of Ecotourism|url=https://archive.org/details/encyclopediaecot00weav|url-access=limited|author=David Bruce Weaver|year=2001|page=[https://archive.org/details/encyclopediaecot00weav/page/n289 276]|isbn=978-0-85199-368-3}}</ref> Submarines with a [[Submarine depth ratings#Crush depth|crush depth]] in the range of {{convert|400|-|500|ft}} are operated in several areas worldwide, typically with bottom depths around {{convert|100|to|120|ft}}, with a carrying capacity of 50 to 100 passengers.

In a typical operation a surface vessel carries passengers to an offshore operating area and loads them into the submarine. The submarine then visits underwater points of interest such as natural or artificial reef structures. To surface safely without danger of collision the location of the submarine is marked with an air release and movement to the surface is coordinated by an observer in a support craft.

A recent development is the deployment of so-called [[narco-submarine]]s by South American drug smugglers to evade law enforcement detection.<ref>{{cite news|url=https://www.washingtonpost.com/wp-dyn/content/article/2009/06/05/AR2009060503718_3.html|newspaper=The Washington Post|first1=William|last1=Booth|first2=Juan|last2=Forero|title=Plying the Pacific, Subs Surface as Key Tool of Drug Cartels|date=6 June 2009}}</ref> Although they occasionally deploy [[narco-submarine#True submarines|true submarines]], most are self-propelled [[semi-submersible]]s, where a portion of the craft remains above water at all times. In September 2011, Colombian authorities seized a 16-meter-long submersible that could hold a crew of 5, costing about $2 million. The vessel belonged to [[FARC]] rebels and had the capacity to carry at least 7 tonnes of drugs.<ref>{{cite news|url=https://www.bbc.co.uk/news/world-latin-america-15051108|title=FARC's drug submarine seized in Colombia|date=5 September 2011|work=BBC News}}</ref>
{{Clear}}

<gallery mode="packed" heights="150" caption="Civilian submarines">
File:PX-8 Mésoscaphe - Swiss Submarine (15722856966).jpg|Model of the [[Auguste Piccard (PX-8)|Mésoscaphe ''Auguste Piccard'']]
File:AtlantisSubInterior3497.JPG|Interior of the tourist [[Atlantis submarine|submarine ''Atlantis'']] whilst submerged
File:AtlantisVIISubmarineClip3494.jpg|Tourist submarine ''Atlantis''
</gallery>

===Polar operations===
[[File:USS Annapolis ICEX.jpg|thumb|US Navy attack submarine {{USS|Annapolis|SSN-760|6}} rests in the Arctic Ocean after surfacing through one metre of ice during Ice Exercise 2009 on 21 March 2009.]]
* 1903 – [[Simon Lake]] submarine ''Protector'' surfaced through ice off [[Newport, Rhode Island]].<ref name="proceedings">McLaren, Alfred S., CAPT USN "Under the Ice in Submarines" ''United States Naval Institute Proceedings'' July 1981, pp. 105–9</ref>
* 1930 – {{USS|O-12|SS-73|6}} operated under ice near [[Spitsbergen]].<ref name="proceedings"/>
* 1937 – Soviet submarine ''Krasnogvardeyets'' operated under ice in the [[Denmark Strait]].<ref name="proceedings"/>
* 1941–45 – German U-boats operated under ice from the [[Barents Sea]] to the [[Laptev Sea]].<ref name="proceedings"/>
* 1946 – {{USS|Atule|SS-403|6}} used upward-beamed fathometer in [[Operation Nanook (1946)|Operation Nanook]] in the [[Davis Strait]].<ref name="proceedings"/>
* 1946–47 – {{USS|Sennet|SS-408|6}} used under-ice [[sonar]] in [[Operation High Jump]] in the Antarctic.<ref name="proceedings"/>
* 1947 – {{USS|Boarfish|SS-327|6}} used upward-beamed echo sounder under pack ice in the [[Chukchi Sea]].<ref name="proceedings"/>
* 1948 – {{USS|Carp|SS-338|6}} developed techniques for making vertical ascents and descents through [[polynya]]s in the Chukchi Sea.<ref name="proceedings"/>
* 1952 – {{USS|Redfish|SS-395|6}} used an expanded upward-beamed sounder array in the [[Beaufort Sea]].<ref name="proceedings"/>
* 1957 – {{USS|Nautilus|SSN-571|6}} reached 87 degrees north near Spitsbergen.<ref name="proceedings"/>
* 3 August 1958 – ''Nautilus'' used an [[inertial navigation system]] to reach the North Pole.<ref name="proceedings"/>
* 17 March 1959 – {{USS|Skate|SSN-578|6}} surfaced through the ice at the north pole.<ref name="proceedings"/>
* 1960 – {{USS|Sargo|SSN-583|6}} transited {{convert|900|mi}} under ice over the shallow ({{convert|125|to|180|ft|disp=or}} deep) Bering-Chukchi shelf.<ref name="proceedings"/>
* 1960 – {{USS|Seadragon|SSN-584|6}} transited the [[Northwest Passage]] under ice.<ref name="proceedings"/>
* 1962 – Soviet {{sclass2|November|submarine|2}} {{ship|Soviet submarine|K-3 Leninsky Komsomol||2}} reached the north pole.<ref name="proceedings"/>
* 1970 – {{USS|Queenfish|SSN-651|6}} carried out an extensive undersea mapping survey of the Siberian continental shelf.<ref>{{cite news|author=William J. Broad|title=Queenfish: A Cold War Tale|url=https://www.nytimes.com/2008/03/18/science/18arctic.html?_r=1|newspaper=New York Times|date=18 March 2008|access-date=17 February 2010}}</ref>
* 1971 – {{HMS|Dreadnought|S101|6}} reached the North Pole.<ref name="proceedings"/>
* {{USS|Gurnard|SSN-662|6}} conducted three Polar Exercises: 1976 (with US actor [[Charlton Heston]] aboard); 1984 joint operations with {{USS|Pintado|SSN-672|6}}; and 1990 joint exercises with {{USS|Seahorse|SSN-669|6}}.<ref>{{cite web| url = http://websitesbycook.com/gurnard/| title = History of the USS ''Gurnard'' and Polar Operations}}</ref>
* 6 May 1986 – {{USS|Ray|SSN-653|6}}, {{USS|Archerfish|SSN-678|6}} and {{USS|Hawkbill|SSN-666|6}} meet and surface together at the [[Geographic North Pole]]. First three-submarine surfacing at the Pole.<ref>{{cite web|url=http://www.navsource.org/archives/08/08666.htm |title=NavSource Online: Submarine Photo Archive |publisher=navsource.org |date=14 November 2016 |access-date=3 March 2017}}</ref>
* 19 May 1987 – {{HMS|Superb|S109|6}} joined {{USS|Billfish|SSN-676|6}} and {{USS|Sea Devil|SSN-664|6}} at the North Pole.<ref>{{cite web|url=http://www.britainsnavy.co.uk/Ships/HMS%20Superb/HMS%20Superb%20(1976)%20SSN%209.htm |title=HMS Superb (1976) (9th) |publisher=britainsnavy.co.uk |date=12 January 2013 |access-date=4 March 2017}}</ref>
* March 2007 – {{USS|Alexandria|SSN-757|6}} participated in the Joint US Navy/[[Royal Navy]] Ice Exercise 2007 (ICEX-2007) in the Arctic Ocean with the {{sclass|Trafalgar|submarine|2}} {{HMS|Tireless|S88|6}}.<ref>{{cite news|title=Submarine Force Participates in Ice Exercise 2007|url=http://infoweb.newsbank.com/resources/doc/nb/news/1180850B346D95C8?p=WORLDNEWS|access-date=1 February 2017|publisher=Government Press Releases (USA)|date=20 March 2007}}</ref>
* March 2009 – {{USS|Annapolis|SSN-760|6}} took part in [[Ice Exercise 2009]] to test submarine operability and war-fighting capability in Arctic conditions.<ref>{{cite web |url=http://www.navy.mil/submit/display.asp?story_id=43706 |title=CNO Attends ICEX 2009 |publisher=navy.mil |date=24 March 2009 |access-date=3 March 2017 |archive-date=3 March 2017 |archive-url=https://web.archive.org/web/20170303124736/http://www.navy.mil/submit/display.asp?story_id=43706 |url-status=dead }}</ref>

==Technology==
{{See also|Timeline of underwater technology}}

===Buoyancy and trim===
[[File:Submarine control surfaces2.svg|thumb|upright=2.0|An illustration showing submarine control surfaces and trim tanks]]
[[File:USS Seawolf (SSN 21) Control Room HighRes.jpg|thumb|{{USS|Seawolf|SSN-21}} Ship Control Panel, with yokes for control surfaces (planes and rudder), and Ballast Control Panel (background), to control the water in tanks and ship's trim]]

All surface ships, as well as surfaced submarines, are in a positively [[buoyancy|buoyant]] condition, weighing less than the volume of water they would displace if fully submerged. To submerge hydrostatically, a ship must have negative buoyancy, either by increasing its own weight or decreasing its displacement of water. To control their displacement and weight, submarines have [[ballast tank]]s, which can hold varying amounts of water and air.<ref name="Navpers 16166" >{{cite web |url=https://maritime.org/doc/fleetsub/trim/index.htm |title=The Fleet Type Submarine Online: Submarine Trim and Drain Systems. Navpers 16166|website=maritime.org |access-date=1 January 2022 |via=San Francisco Maritime National Park Association }}</ref>

For general submersion or surfacing, submarines use the main ballast tanks (MBTs), which are ambient pressure tanks, filled with water to submerge or with air to surface. While submerged, MBTs generally remain flooded, which simplifies their design,<ref name="Navpers 16166" /> and on many submarines, these tanks are a section of the space between the light hull and the pressure hull. For more precise control of depth, submarines use smaller depth control tanks (DCTs)—also called hard tanks (due to their ability to withstand higher pressure) or trim tanks. These are [[variable buoyancy pressure vessel]]s, a type of buoyancy control device. The amount of water in depth control tanks can be adjusted to hydrostatically change depth or to maintain a constant depth as outside conditions (mainly water density) change.<ref name="Navpers 16166" /> Depth control tanks may be located either near the submarine's [[center of gravity]], to minimise the effect on trim, or separated along the length of the hull so they can also be used to adjust static trim by transfer of water between them.

When submerged, the water pressure on a submarine's hull can reach {{convert|4|MPa|psi|abbr=on|lk=on}} for steel submarines and up to {{convert|10|MPa|psi|abbr=on}} for [[titanium]] submarines like {{ship|Soviet submarine|K-278 Komsomolets||2}}, while interior pressure remains relatively unchanged. This difference results in hull compression, which decreases displacement. Water density also marginally increases with depth, as the [[salinity]] and pressure are higher.<ref name=nave>{{cite web|title=Bulk Elastic Properties|author=Nave, R.|work=HyperPhysics|publisher=[[Georgia State University]]|url=http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html|access-date=26 October 2007}}</ref> This change in density incompletely compensates for hull compression, so buoyancy decreases as depth increases. A submerged submarine is in an unstable equilibrium, having a tendency to either sink or float to the surface. Keeping a constant depth requires continual operation of either the depth control tanks or control surfaces.<ref name="Physics Of Liquids & Gases">{{cite web|url=http://www.vectorsite.net/tpecp_08.html|title=Physics Of Liquids & Gases|access-date=7 October 2006|work=Elementary Classical Physics}}</ref><ref>{{cite book|author=Richard O'Kane|title=Wahoo|url=https://archive.org/details/wahoopatrolsofam00okan|url-access=registration|publisher=Presidio Press|year=1987|page=[https://archive.org/details/wahoopatrolsofam00okan/page/12 12]|isbn=9780891413011}}</ref>

Submarines in a neutral buoyancy condition are not intrinsically trim-stable. To maintain desired longitudinal trim, submarines use forward and aft trim tanks. Pumps move water between the tanks, changing weight distribution and pitching the sub up or down. A similar system may be used to maintain transverse trim.<ref name="Navpers 16166" />

===Control surfaces===
[[File:Kiosk Casabianca.jpg|thumb|[[Sail (submarine)|Sail]] of the French nuclear submarine {{ship|French submarine|Casabianca|S603|2}}; note the diving planes, [[camouflage]]d masts, periscope, electronic warfare masts, hatch, and [[wikt:deadlight|deadlight]].]]

The hydrostatic effect of variable ballast tanks is not the only way to control the submarine underwater. Hydrodynamic maneuvering is done by several control surfaces, collectively known as [[diving plane]]s or hydroplanes, which can be moved to create hydrodynamic forces when a submarine moves longitudinally at sufficient speed. In the classic cruciform stern configuration, the horizontal stern planes serve the same purpose as the trim tanks, controlling the trim. Most submarines additionally have forward horizontal planes, normally placed on the bow until the 1960s but often on the sail on later designs, where they are closer to the center of gravity and can control depth with less effect on the trim.<ref>{{cite book|title=Concepts In Submarine Design|author1=Roy Burcher |author2=Louis Rydill |publisher=Cambridge University Press|year=1995|page=170}}</ref>

[[File:sor.jpeg|thumb|upright|left|Rear view of a model of Swedish submarine [[HSwMS Sjöormen (Sor)|HMS ''Sjöormen'']], the first production submarine to feature an x-stern]]
An obvious way to configure the control surfaces at the stern of a submarine is to use vertical planes to control yaw and horizontal planes to control pitch, which gives them the shape of a cross when seen from astern of the vessel. In this configuration, which long remained the dominant one, the horizontal planes are used to control the trim and depth and the vertical planes to control sideways maneuvers, like the rudder of a surface ship.

Alternatively, the rear control surfaces can be combined into what has become known as an X-stern or an X-form rudder.<ref>{{cite web |url= https://www.twz.com/sea/chinas-latest-submarine-features-x-shaped-stern |title= China's Latest Submarine Features X-Shaped Stern |author= Thomas Newdick |date=29 July 2024|website= The War Zone |publisher= |language= }}</ref> Although less intuitive, such a configuration has turned out to have several advantages over the traditional cruciform arrangement. First, it improves maneuverability, horizontally as well as vertically.{{clarify|how does it improve maneuverability?|date=January 2022}} Second, the control surfaces are less likely to get damaged when landing on, or departing from, the seabed as well as when mooring and unmooring alongside. Finally, it is safer in that one of the two diagonal lines can counteract the other with respect to vertical as well as horizontal motion if one of them accidentally gets stuck.<ref>{{cite journal |last1=Wang|first1=Wenjin|display-authors=etal|date=2020|title=A Fault-tolerant Steering Prototype for X-rudder Underwater Vehicles|journal=Sensors |volume=20|issue=7|page=1816|doi=10.3390/s20071816|pmid=32218145|pmc=7180876|bibcode=2020Senso..20.1816W|doi-access=free}}</ref>{{clarify|how the counteraction works|date=January 2022}}

[[File:USS Albacore (2018) 13.jpg|thumb|right|[[USS Albacore (AGSS-569)|USS ''Albacore'']], the first submarine to use an x-rudder in practice, now on display in [[Portsmouth, New Hampshire]]]]
The x-stern was first tried in practice in the early 1960s on the [[USS Albacore (AGSS-569)|USS ''Albacore'']], an experimental submarine of the US Navy. While the arrangement was found to be advantageous, it was nevertheless not used on US production submarines that followed due to the fact that it requires the use of a computer to manipulate the control surfaces to the desired effect.<ref>{{cite news |url=http://news.usni.org/news-analysis/news/ohio-class-replacement-details |title=Ohio-class Replacement Details|work=US Naval Institute|date=1 November 2012|access-date=26 May 2020}}</ref> Instead, the first to use an x-stern in standard operations was the Swedish Navy with its [[Sjöormen-class submarine|''Sjöormen'' class]], the lead submarine of which was launched in 1967, before the ''Albacore'' had even finished her test runs.<ref>{{cite book|last=Granholm|first=Fredrik|title=Från Hajen till Södermanland: Svenska ubåtar under 100 år|publisher=Marinlitteraturföreningen|year=2003|page=56|isbn=9185944-40-8}}</ref> Since it turned out to work very well in practice, all subsequent classes of Swedish submarines ([[Näcken-class submarine|''Näcken'']], [[Västergötland-class submarine|''Västergötland'']], [[Gotland-class submarine|''Gotland'']], and [[Blekinge-class submarine|''Blekinge'']] class) have or will come with an x-rudder.

[[File:HMS Neptun (Nep) MM10732.jpg|thumb|right|The x-rudder of [[HSwMS Neptun (Nep)|HMS ''Neptun'']], a [[Näcken-class submarine|''Näcken''-class]] submarine in service with the Swedish Navy 1980–1998, now on display at [[Marinmuseum]] in [[Karlskrona]]]]

The [[Saab Kockums|Kockums shipyard]] responsible for the design of the x-stern on Swedish submarines eventually exported it to Australia with the [[Collins-class submarine|''Collins'' class]] as well as to Japan with the [[Sōryū-class submarine|''Sōryū'' class]]. With the introduction of the [[Type 212 submarine|type 212]], the German and Italian Navies came to feature it as well. The US Navy with its [[Columbia-class submarine|''Columbia'' class]], the British Navy with its [[Dreadnought-class submarine|''Dreadnought'' class]], and the French Navy with its [[Barracuda-class submarine (France)|''Barracuda'' class]] are all about to join the x-stern family. Hence, as judged by the situation in the early 2020s, the x-stern is about to become the dominant technology.

When a submarine performs an emergency surfacing, all depth and trim control methods are used simultaneously,{{citation needed|date=January 2022}} together with propelling the boat upwards. Such surfacing is very quick, so the vessel may even partially jump out of the water, potentially damaging submarine systems.{{clarify|how systems would be damaged, and which systems are vulnerable|date=January 2022}}

===Hull===
{{main|Submarine hull}}

====Overview====
[[File:USS Greeneville (SSN 772) - dry dock Pearl Harbor (1).jpg|thumb|The [[US Navy]] {{sclass|Los Angeles|submarine|0}} {{USS|Greeneville|SSN-772|6}} in dry dock, showing cigar-shaped hull]]

Modern submarines are cigar-shaped. This design, also used in very early submarines, is sometimes called a "[[teardrop hull]]". It reduces hydrodynamic [[drag (physics)|drag]] when the sub is submerged, but decreases the sea-keeping capabilities and increases drag while surfaced. Since the limitations of the propulsion systems of early submarines forced them to operate surfaced most of the time, their hull designs were a compromise. Because of the slow submerged speeds of those subs, usually, well below 10&nbsp;[[knot (unit)|kt]] (18&nbsp;km/h), the increased drag for underwater travel was acceptable. Late in World War II, when technology allowed faster and longer submerged operation and increased aircraft surveillance forced submarines to stay submerged, hull designs became teardrop shaped again to reduce drag and noise. {{USS|Albacore|AGSS-569}} was a unique research submarine that pioneered the American version of the teardrop hull form (sometimes referred to as an "Albacore hull") of modern submarines. On modern military submarines the outer hull is covered with a layer of sound-absorbing rubber, or [[anechoic tile|anechoic plating]], to reduce detection.

The occupied pressure hulls of deep-diving submarines such as {{ship|DSV|Alvin}} are spherical instead of cylindrical. This allows a more even distribution of stress and efficient use of materials to withstand external pressure as it gives the most internal volume for structural weight and is the most efficient shape to avoid buckling instability in compression. A frame is usually affixed to the outside of the pressure hull, providing attachment for ballast and trim systems, scientific instrumentation, battery packs, [[syntactic foam|syntactic flotation foam]], and lighting.

A raised tower on top of a standard submarine accommodates the [[periscope]] and electronics masts, which can include radio, [[radar]], [[electronic warfare]], and other systems. It might also include a snorkel mast. In many early classes of submarines (see history), the control room, or "conn", was located inside this tower, which was known as the "[[conning tower]]". Since then, the conn has been located within the hull of the submarine, and the tower is now called the [[Sail (submarine)|"sail" or "fin"]]. The conn is distinct from the "bridge", a small open platform in the top of the sail, used for observation during surface operation.

"Bathtubs" are related to conning towers but are used on smaller submarines. The bathtub is a metal cylinder surrounding the hatch that prevents waves from breaking directly into the cabin. It is needed because surfaced submarines have limited [[freeboard (nautical)|freeboard]], that is, they lie low in the water. Bathtubs help prevent swamping the vessel.

====Single and double hulls====
[[File:U995 2004 1.jpg|thumb|{{GS|U-995||2}}, Type VIIC/41 U-boat of World War II, showing the ship-like lines of the outer hull for surface travel, blended into the cylindrical pressure hull structure.]]

Modern submarines and submersibles usually have, as did the earliest models, a single hull. Large submarines generally have an additional hull or hull sections outside. This external hull, which actually forms the shape of submarine, is called the outer hull (''[[Casing (submarine)|casing]]'' in the Royal Navy) or [[light hull]], as it does not have to withstand a pressure difference. Inside the outer hull there is a strong hull, or [[pressure hull]], which withstands sea pressure and has normal atmospheric pressure inside.

As early as World War I, it was realized that the optimal shape for withstanding pressure conflicted with the optimal shape for seakeeping and minimal drag at the surface, and construction difficulties further complicated the problem. This was solved either by a compromise shape, or by using two layered hulls: the internal strength hull for withstanding pressure, and an external fairing for hydrodynamic shape. Until the end of World War II, most submarines had an additional partial casing on the top, bow and stern, built of thinner metal, which was flooded when submerged. Germany went further with the [[Type XXI]], a general predecessor of modern submarines, in which the pressure hull was fully enclosed inside the light hull, but optimized for submerged navigation, unlike earlier designs that were optimized for surface operation.

[[File:SRH025-p40.jpg|thumb|left|[[Type XXI]] U-boat, late World War II, with pressure hull almost fully enclosed inside the light hull]]
After World War II, approaches split. The Soviet Union changed its designs, basing them on German developments. All post-World War II heavy Soviet and Russian submarines are built with a [[double hull]] structure. American and most other Western submarines switched to a primarily single-hull approach. They still have light hull sections in the bow and stern, which house main ballast tanks and provide a hydrodynamically optimized shape, but the main cylindrical hull section has only a single plating layer. Double hulls are being considered for future submarines in the United States to improve payload capacity, stealth and range.<ref>[http://www.nationaldefensemagazine.org/issues/2000/May/Virginia-Class.htm]. National Defense magazine. {{webarchive|url=https://web.archive.org/web/20080405194626/http://www.nationaldefensemagazine.org/issues/2000/May/Virginia-Class.htm|date=5 April 2008}}</ref>

====Pressure hull====
[[File:Bathyscaphe Trieste.jpg|thumb|In 1960, [[Jacques Piccard]] and [[Don Walsh]] were the first people to explore the [[Challenger Deep|deepest part]] of the world's [[ocean]], and the deepest location on the surface of the Earth's crust, in the {{ship|Bathyscaphe|Trieste}} designed by [[Auguste Piccard]].]]
{{See also|Pressure hull}}

The pressure hull is generally constructed of thick high-strength steel with a complex structure and high strength reserve, and is separated by watertight [[bulkhead (partition)|bulkheads]] into several [[Compartmentalization (fire protection)|compartments]]. There are also examples of more than two hulls in a submarine, like the {{sclass2|Typhoon|submarine|4}}, which has two main pressure hulls and three smaller ones for control room, torpedoes and steering gear, with the missile launch system between the main hulls, all surrounded and supported by the outer light hydrodynamic hull. When submerged the pressure hull provides most of the buoyancy for the whole vessel.

The [[Submarine depth ratings|dive depth]] cannot be increased easily. Simply making the hull thicker increases the structural weight and requires reduction of onboard equipment weight, and increasing the diameter requires a proportional increase in thickness for the same material and architecture, ultimately resulting in a pressure hull that does not have sufficient buoyancy to support its own weight, as in a [[bathyscaphe]]. This is acceptable for civilian research submersibles, but not military submarines, which need to carry a large equipment, crew, and weapons load to fulfill their function. Construction materials with greater [[specific strength]] and [[specific modulus]] are needed.

WWI submarines had hulls of [[carbon steel]], with a {{convert|100|m|ft|adj=on}} maximum depth. During WWII, high-strength [[alloy]]ed steel was introduced, allowing {{convert|200|m|ft|adj=on}} depths. High-strength alloy steel remains the primary material for submarines today, with {{convert|250|-|400|m|ft|adj=on}} depths, which cannot be exceeded on a military submarine without design compromises. To exceed that limit, a few submarines were built with [[titanium]] hulls. Titanium alloys can be stronger than steel, lighter, and most importantly, have higher immersed [[specific strength]] and [[specific modulus]]. Titanium is also not [[ferromagnetism|ferromagnetic]], important for stealth. Titanium submarines were built by the Soviet Union, which developed specialized high-strength alloys. It has produced several types of titanium submarines. Titanium alloys allow a major increase in depth, but other systems must be redesigned to cope, so test depth was limited to {{convert|1000|m|ft}} for the {{ship|Soviet submarine|K-278 Komsomolets}}, the deepest-diving combat submarine. An {{sclass2|Alfa|submarine|2}} may have successfully operated at {{convert|1300|m|ft}},<ref>{{cite web|url=https://fas.org/man/dod-101/sys/ship/deep.htm|title=Federation of American Scientists|publisher=Fas.org|access-date=18 April 2010}}</ref> though continuous operation at such depths would produce excessive stress on many submarine systems. Titanium does not flex as readily as steel, and may become brittle after many dive cycles. Despite its benefits, the high cost of titanium construction led to the abandonment of titanium submarine construction as the Cold War ended. Deep-diving civilian submarines have used thick [[Poly(methyl methacrylate)|acrylic]] pressure hulls. Although the specific strength and specific modulus of acrylic are not very high, the density is only 1.18g/cm<sup>3</sup>, so it is only very slightly denser than water, and the buoyancy penalty of increased thickness is correspondingly low.

The deepest [[deep-submergence vehicle]] (DSV) to date is [[Bathyscaphe Trieste|''Trieste'']]. On 5 October 1959, ''Trieste'' departed San Diego for [[Guam]] aboard the freighter ''Santa Maria'' to participate in ''[[Project Nekton]]'', a series of very deep dives in the [[Mariana Trench]]. On 23 January 1960, ''Trieste'' reached the ocean floor in the Challenger Deep (the deepest southern part of the Mariana Trench), carrying [[Jacques Piccard]] (son of Auguste) and Lieutenant [[Don Walsh]], USN.<ref>{{cite web|url=http://www.history.navy.mil/danfs/t8/trieste.htm |title=Trieste |publisher=History.navy.mil |access-date=18 April 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100317120249/http://www.history.navy.mil/danfs/t8/trieste.htm |archive-date=17 March 2010 }}</ref> This was the first time a vessel, crewed or uncrewed, had reached the deepest point in the Earth's oceans. The onboard systems indicated a depth of {{convert|11521|m|ft|0}}, although this was later revised to {{convert|10916|m|ft|0}} and more accurate measurements made in 1995 have found the Challenger Deep slightly shallower, at {{convert|10911|m|ft|0}}.

Building a pressure hull is difficult, as it must withstand pressures at its required diving depth. When the hull is perfectly round in cross-section, the pressure is evenly distributed, and causes only hull compression. If the shape is not perfect, the hull deflects more in some places and [[buckling]] instability is the usual [[failure mode]]. Inevitable minor deviations are resisted by stiffener rings, but even a one-inch (25&nbsp;mm) deviation from roundness results in over 30 percent decrease of maximal hydrostatic load and consequently dive depth.<ref>{{cite web|url=http://www.usna.edu/naoe/courses/en200/ch10.pdf|title=US Naval Academy}}</ref> The hull must therefore be constructed with high precision. All hull parts must be welded without defects, and all joints are checked multiple times with different methods, contributing to the high cost of modern submarines. (For example, each {{sclass|Virginia|submarine|0}} attack submarine costs US$2.6 [[1000000000 (number)|billion]], over US$200,000 per [[long ton|ton]] of displacement.)

===Propulsion===<!-- "diesel–electric transmission" has a see also linking here -->
{{Further|Marine propulsion|Air-independent propulsion|Nuclear marine propulsion|Nuclear submarine}}
[[File:HMCS Windsor SSK 877.jpg|thumb|{{HMCS|Windsor|SSK 877|6}}, a [[Royal Canadian Navy]] {{sclass|Victoria|submarine|0}} diesel–electric hunter-killer submarine]]

The first submarines were propelled by humans. The first mechanically driven submarine was the 1863 French {{ship|French submarine|Plongeur||2}}, which used compressed air for propulsion. Anaerobic propulsion was first employed by the Spanish ''[[Ictineo II]]'' in 1864, which used a solution of [[zinc]], [[manganese dioxide]], and [[potassium chlorate]] to generate sufficient heat to power a steam engine, while also providing [[oxygen]] for the crew. A similar system was not employed again until 1940 when the German Navy tested a [[hydrogen peroxide]]-based system, the [[Hellmuth Walter|Walter]] [[turbine]], on the experimental [[V-80 submarine]] and later on the naval {{GS|U-791||2}} and [[German Type XVII submarine|type XVII]] submarines;<ref>{{cite web|url=http://www.sharkhunters.com/typeadditional.htm|title=Details on German U-Boat Types|access-date=21 September 2008|work=Sharkhunters International|archive-date=24 February 2010|archive-url=https://web.archive.org/web/20100224042841/http://www.sharkhunters.com/typeadditional.htm|url-status=dead}}</ref> the system was further developed for the British {{sclass|Explorer|submarine|0}}, completed in 1958.<ref>{{cite book |author1=Miller, David |author2=Jordan, John |title=Modern Submarine Warfare |location=London |publisher=Salamander Books |year=1987 |isbn=0-86101-317-4 |page =63 }}</ref>

Until the advent of [[nuclear marine propulsion]], most 20th-century submarines used [[electric motor]]s and batteries for running underwater and [[internal combustion engine|combustion engines]] on the surface, and for battery recharging. Early submarines used [[gasoline]] (petrol) engines but this quickly gave way to [[kerosene]] (paraffin) and then [[Diesel fuel|diesel]] engines because of reduced flammability and, with diesel, improved fuel-efficiency and thus also greater range. A combination of diesel and electric propulsion became the norm.

Initially, the combustion engine and the electric motor were in most cases connected to the same shaft so that both could directly drive the propeller. The combustion engine was placed at the front end of the stern section with the electric motor behind it followed by the propeller shaft. The engine was connected to the motor by a clutch and the motor in turn connected to the propeller shaft by another clutch.

With only the rear clutch engaged, the electric motor could drive the propeller, as required for fully submerged operation. With both clutches engaged, the combustion engine could drive the propeller, as was possible when operating on the surface or, at a later stage, when snorkeling. The electric motor would in this case serve as a generator to charge the batteries or, if no charging was needed, be allowed to rotate freely. With only the front clutch engaged, the combustion engine could drive the electric motor as a generator for charging the batteries without simultaneously forcing the propeller to move.

The motor could have multiple armatures on the shaft, which could be electrically coupled in series for slow speed and in parallel for high speed (these connections were called "group down" and "group up", respectively).

====Diesel–electric transmission<span class="anchor" id="Diesel-electric transmission"></span>====
[[File:Submarine recharging (JMSDF).jpg|thumb|Recharging battery ([[Japan Maritime Self-Defense Force|JMSDF]])]]
{{Further|Diesel–electric powertrain}}

While most early submarines used a direct mechanical connection between the combustion engine and the propeller, an alternative solution was considered as well as implemented at a very early stage.<ref>{{cite book|last=Granholm|first=Fredrik|title=Från Hajen till Södermanland: Svenska ubåtar under 100 år|publisher=Marinlitteraturföreningen|year=2003|pages=12–13|isbn=9185944-40-8}}</ref> That solution consists in first converting the work of the combustion engine into electric energy via a dedicated generator. This energy is then used to drive the propeller via the electric motor and, to the extent required, for charging the batteries. In this configuration, the electric motor is thus responsible for driving the propeller at all times, regardless of whether air is available so that the combustion engine can also be used or not.

Among the pioneers of this alternative solution was the very first submarine of the [[Swedish Navy]], {{ill|HSwMS Hajen (1904)|sv|HMS Hajen (1904)|lt=HSwMS ''Hajen''}} (later renamed ''Ub no 1''), launched in 1904. While its design was generally inspired by the first submarine commissioned by the US Navy, [[USS Holland (SS-1)|USS ''Holland'']], it deviated from the latter in at least three significant ways: by adding a periscope, by replacing the gasoline engine by a semidiesel engine (a [[hot-bulb engine]] primarily meant to be fueled by kerosene, later replaced by a true diesel engine) and by severing the mechanical link between the combustion engine and the propeller by instead letting the former drive a dedicated generator.<ref>{{cite book|last=Granholm|first=Fredrik|title=Från Hajen till Södermanland: Svenska ubåtar under 100 år|publisher=Marinlitteraturföreningen|year=2003|pages=12–15|isbn=9185944-40-8}}</ref> By so doing, it took three significant steps toward what was eventually to become the dominant technology for conventional (i.e., non-nuclear) submarines.

[[File:Submarine Hajen 1.jpg|thumb|One of the first submarines with diesel–electric transmission, HMS ''Hajen'', on display outside [[Marinmuseum]] in [[Karlskrona]]]]
In the following years, the Swedish Navy added another seven submarines in three different classes ({{ill|2nd-class submarine|sv|2:a klass ubåt|lt=''2nd'' class}}, {{ill|Laxen-class submarine|sv|Laxen-klass|lt=''Laxen'' class}}, and {{ill|Braxen-class submarine|sv|Braxen-klass|lt=''Braxen'' class}}) using the same propulsion technology but fitted with true diesel engines rather than semidiesels from the outset.<ref>{{cite book|last=Granholm|first=Fredrik|title=Från Hajen till Södermanland: Svenska ubåtar under 100 år|publisher=Marinlitteraturföreningen|year=2003|pages=18–19, 24–25|isbn=9185944-40-8}}</ref> Since by that time, the technology was usually based on the diesel engine rather than some other type of combustion engine, it eventually came to be known as [[diesel–electric transmission]].

Like many other early submarines, those initially designed in Sweden were quite small (less than 200 tonnes) and thus confined to littoral operation. When the Swedish Navy wanted to add larger vessels, capable of operating further from the shore, their designs were purchased from companies abroad that already had the required experience: first Italian ([[Fiat S.p.A.|Fiat]]-[[Cesare Laurenti (engineer)|Laurenti]]) and later German ([[AG Weser|A.G. Weser]] and [[NV Ingenieurskantoor voor Scheepsbouw|IvS]]).<ref>{{cite book|last=Granholm|first=Fredrik|title=Från Hajen till Södermanland: Svenska ubåtar under 100 år|publisher=Marinlitteraturföreningen|year=2003|pages=16–17, 20–21, 26–29, 34–35, 82|isbn=9185944-40-8}}</ref> As a side-effect, the diesel–electric transmission was temporarily abandoned.

However, diesel–electric transmission was immediately reintroduced when Sweden began designing its own submarines again in the mid-1930s. From that point onwards, it has been consistently used for all new classes of Swedish submarines, albeit supplemented by [[Air-independent propulsion|air-independent propulsion (AIP)]] as provided by [[Stirling engine]]s beginning with [[HSwMS Näcken (Näk)|HMS ''Näcken'']] in 1988.<ref>{{cite book|last=Granholm|first=Fredrik|title=Från Hajen till Södermanland: Svenska ubåtar under 100 år|publisher=Marinlitteraturföreningen|year=2003|pages=40–43, 48–49, 52–61, 64–67, 70–71|isbn=9185944-40-8}}</ref>

[[File:Hajen & Neptun Marinmuseum Karlskrona 002.jpg|thumb|Two widely different generations of Swedish submarines but both with diesel–electric transmission: {{ill|HSwMS Hajen (1904)|sv|HMS Hajen (1904)|lt=HSwMS ''Hajen''}}, in service 1905–1922, and [[HSwMS Neptun (Nep)|HMS ''Neptun'']], in service 1980–1998]]
Another early adopter of diesel–electric transmission was the [[United States Navy|US Navy]], whose Bureau of Engineering proposed its use in 1928. It was subsequently tried in the [[United States S-class submarine|S-class submarines]] {{USS|S-3|SS-107|2}}, {{USS|S-6|SS-111|2}}, and {{USS|S-7|SS-112|2}} before being put into production with the [[United States Porpoise-class submarine|''Porpoise'' class]] of the 1930s. From that point onwards, it continued to be used on most US conventional submarines.<ref name="Book1">{{cite book|last=Friedman|first=Norman|title=U.S. submarines through 1945: an illustrated design history|publisher=Naval Institute Press|year=1995|pages=259–260|isbn=978-1-55750-263-6}}</ref>

Apart from the British [[British U-class submarine|U-class]] and some submarines of the Imperial Japanese Navy that used separate diesel generators for low speed running, few navies other than those of Sweden and the US made much use of diesel–electric transmission before 1945.<ref name="Book1" /> After World War II, by contrast, it gradually became the dominant mode of propulsion for conventional submarines. However, its adoption was not always swift. Notably, the Soviet Navy did not introduce diesel–electric transmission on its conventional submarines until 1980 with its [[Kilo-class submarine|''Paltus'' class]].<ref>{{cite web|url=http://www.deepstorm.ru/DeepStorm.files/45-92/dts/877/list.htm|title=Проект "Пaлтyc" (NATO-"Kilo")|last=Никoлaeв|first=A.C.|website=Энциклопедия отeчествeннoгo подводнoгo флотa|access-date=2 June 2020}}</ref>

If diesel–electric transmission had only brought advantages and no disadvantages in comparison with a system that mechanically connects the diesel engine to the propeller, it would undoubtedly have become dominant much earlier. The disadvantages include the following:<ref name="electrotechnical-officer.com">{{cite web|url=https://electrotechnical-officer.com/what-is-motivations-for-ship–electric-propulsion/|title=What is motivations for ship electric propulsion|website=Electro-technical officer|access-date=2 June 2020}}{{Dead link|date=February 2022 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name="diesel eletric drives guideline">{{cite web|url=https://marine.mandieselturbo.com/docs/librariesprovider6/marine-broschures/diesel–electric-drives-guideline.pdf|title=Diesel–electric Propulsion Plants: A brief guideline how to engineer a diesel–electric propulsion system|website=MAN Energy Solutions|pages=3–4|access-date=2 June 2020}}{{Dead link|date=February 2022 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
* It entails a loss of fuel-efficiency as well as power by converting the output of the diesel engine into electricity. While both generators and electric motors are known to be very efficient, their efficiency nevertheless falls short of 100 percent.
* It requires an additional component in the form of a dedicated generator. Since the electric motor is always used to drive the propeller it can no longer step in to take on generator service as well.
* It does not allow the diesel engine and the electrical motor to join forces by simultaneously driving the propeller mechanically for maximum speed when the submarine is surfaced or snorkeling. This may, however, be of little practical importance inasmuch as the option it prevents is one that would leave the submarine at a risk of having to dive with its batteries at least partly depleted.

The reason why diesel–electric transmission has become the dominant alternative in spite of these disadvantages is of course that it also comes with many advantages and that, on balance, these have eventually been found to be more important. The advantages include the following:<ref name="electrotechnical-officer.com"/><ref name="diesel eletric drives guideline" />
* It reduces external noise by severing the direct and rigid mechanical link between the relatively noisy diesel engine(s) on the one hand and the propeller shaft(s) and hull on the other. With [[Stealth ship|stealth]] being of paramount importance to submarines, this is a very significant advantage.
* It increases the [[Crash dive|readiness to dive]], which is of course of vital importance for a submarine. The only thing required from a propulsion point of view is to shut down the diesel(s).
* It makes the speed of the diesel engine(s) temporarily independent of the speed of the submarine. This in turn often makes it possible to run the diesel(s) at close to optimal speed from a fuel-efficiency as well as durability point of view. It also makes it possible to reduce the time spent surfaced or snorkeling by running the diesel(s) at maximum speed without affecting the speed of the submarine itself.
* It eliminates the clutches otherwise required to connect the diesel engine, the electric motor, and the propeller shaft. This in turn saves space, increases reliability and reduces maintenance costs.
* It increases flexibility with regard to how the driveline components are configured, positioned, and maintained. For example, the diesel no longer has to be aligned with the electric motor and propeller shaft, two diesels can be used to power a single propeller (or vice versa), and one diesel can be turned off for maintenance as long as a second is available to provide the required amount of electricity.
* It facilitates the integration of additional primary sources of energy, beside the diesel engine(s), such as various kinds of [[Air-independent propulsion|air-independent power (AIP)]] systems. With one or more electric motors always driving the propeller(s), such systems can easily be introduced as yet another source of electric energy in addition to the diesel engine(s) and the batteries.

====Snorkel====
{{Main|Submarine snorkel}}
[[File:Submarine snorkel, 1942, the first used by the Swedish Navy, used on Neptun and later Nacken - Marinmuseum, Karlskrona, Sweden - DSC08950.JPG|thumb|right|Head of the snorkel mast from German [[type XXI submarine]] [[German submarine U-3503|''U-3503'']], scuttled outside [[Gothenburg]] on 8 May 1945 but raised by the Swedish Navy and carefully studied for the purpose of improving future Swedish submarine designs]]

During World War II the Germans experimented with the idea of the ''schnorchel'' (snorkel) from captured Dutch submarines but did not see the need for them until rather late in the war. The ''schnorchel'' is a retractable pipe that supplies air to the diesel engines while submerged at [[periscope depth]], allowing the boat to cruise and recharge its batteries while maintaining a degree of stealth.

Especially as first implemented however, it turned out to be far from a perfect solution. There were problems with the device's valve sticking shut or closing as it dunked in rough weather. Since the system used the entire pressure hull as a buffer, the diesels would instantaneously suck huge volumes of air from the boat's compartments, and the crew often suffered painful ear injuries. Speed was limited to {{convert|8|kn|km/h}}, lest the device snap from stress. The ''schnorchel'' also created noise that made the boat easier to detect with sonar, yet more difficult for the on-board sonar to detect signals from other vessels. Finally, allied radar eventually became sufficiently advanced that the ''schnorchel'' mast could be detected beyond visual range.<ref>{{cite book |last=Ireland |first=Bernard |title=Battle of the Atlantic |publisher=Pen & Sword Books |year=2003 |location=Barnsley, UK |page=187 |isbn=978-1-84415-001-4}}</ref>

While the snorkel renders a submarine far less detectable, it is thus not perfect. In clear weather, diesel exhausts can be seen on the surface to a distance of about three miles,<ref>{{cite book|last1=Schull|first1=Joseph|title=The Far Distant Ships|date=1961|publisher=Queen's Printer, Canada|location=Ottawa|pages=259}}</ref> while "periscope feather" (the wave created by the snorkel or periscope moving through the water) is visible from far off in calm sea conditions. Modern radar is also capable of detecting a snorkel in calm sea conditions.<ref>{{cite book|last1=Lamb|first1=James B.|title=On the triangle run|date=1987|publisher=Totem Books|location=Toronto|isbn=978-0-00-217909-6|pages=[https://archive.org/details/ontrianglerun0000lamb/page/25 25, 26]|url=https://archive.org/details/ontrianglerun0000lamb/page/25}}</ref>

[[File:U-3008 Turm.jpg|thumb|right|[[German submarine U-3008|USS ''U-3008'']] (former German submarine ''U-3008'') with her snorkel masts raised at Portsmouth Naval Shipyard, Kittery, Maine]]
The problem of the diesels causing a vacuum in the submarine when the head valve is submerged still exists in later model diesel submarines but is mitigated by high-vacuum cut-off sensors that shut down the engines when the vacuum in the ship reaches a pre-set point. Modern snorkel induction masts have a fail-safe design using [[compressed air]], controlled by a simple electrical circuit, to hold the "head valve" open against the pull of a powerful spring. Seawater washing over the mast shorts out exposed electrodes on top, breaking the control, and shutting the "head valve" while it is submerged. US submarines did not adopt the use of snorkels until after WWII.<ref>{{Cite book|url=https://books.google.com/books?id=GLy8quRc-YYC&q=submarine+snorkel&pg=PA86|title=The Submarine|last=Navy|first=United States|date=September 2008|publisher=United States Printing Office|isbn=978-1-935327-44-8|language=en}}</ref>

====Air-independent propulsion====
{{main|Air-independent propulsion}}
[[File:2004-Bremerhaven U-Boot-Museum-Sicherlich retouched.jpg|thumb|[[German Type XXI submarine]]]]
[[File:SS X-1 Midget Submarine.jpg|thumb|American X-1 Midget Submarine]]

During World War II, [[German Type XXI submarine]]s (also known as "''Elektroboote''") were the first submarines designed to operate submerged for extended periods. Initially they were to carry hydrogen peroxide for long-term, fast air-independent propulsion, but were ultimately built with very large batteries instead. At the end of the War, the [[United Kingdom|British]] and Soviets experimented with hydrogen peroxide/kerosene (paraffin) engines that could run surfaced and submerged. The results were not encouraging. Though the Soviet Union deployed a class of submarines with this engine type (codenamed {{sclass2|Quebec|submarine|5}} by NATO), they were considered unsuccessful.

The United States also used hydrogen peroxide in an experimental [[midget submarine]], [[USS X-1|X-1]]. It was originally powered by a hydrogen peroxide/diesel engine and battery system until an explosion of her hydrogen peroxide supply on 20 May 1957. X-1 was later converted to use diesel–electric drive.<ref>{{cite web|title=SS X-1 |url=http://www.hnsa.org/ships/x1.htm |publisher=Historic Naval Ships Association |access-date=24 February 2014 |url-status=dead |archive-url=https://web.archive.org/web/20130818031654/http://www.hnsa.org/ships/x1.htm |archive-date=18 August 2013 }}</ref>

Today several navies use air-independent propulsion. Notably [[Sweden]] uses [[Stirling engine|Stirling technology]] on the {{sclass|Gotland|submarine|0}} and {{sclass|Södermanland|submarine|2}}s. The Stirling engine is heated by burning diesel fuel with [[liquid oxygen]] from [[cryogenic]] tanks. A newer development in air-independent propulsion is [[hydrogen]] [[fuel cell]]s, first used on the [[Germany|German]] [[Type 212 submarine]], with nine 34&nbsp;kW or two 120&nbsp;kW cells. Fuel cells are also used in the new [[Spanish Navy|Spanish]] {{sclass2|S-80|submarine|2}}s although with the fuel stored as ethanol and then converted into hydrogen before use.<ref>{{cite news|publisher=Defense Industry Daily|title=S-80: A Sub, for Spain, to Sail Out on the Main|date=15 December 2008|url=http://www.defenseindustrydaily.com/s80-a-sub-for-spain-to-sail-out-on-the-main-02517/|url-access=registration}}</ref>

One new technology that is being introduced starting with the Japanese Navy's eleventh [[Sōryū-class submarine|''Sōryū''-class submarine]] (JS ''Ōryū'') is a more modern battery, the [[lithium-ion battery]]. These batteries have about double the electric storage of traditional batteries, and by changing out the lead-acid batteries in their normal storage areas plus filling up the large hull space normally devoted to [[Air-independent propulsion|AIP]] engine and fuel tanks with many tons of lithium-ion batteries, modern submarines can actually return to a "pure" diesel–electric configuration yet have the added underwater range and power normally associated with AIP equipped submarines.{{citation needed|date=October 2018}}

====Nuclear power====
{{main|Nuclear submarine|Nuclear marine propulsion}}
[[File:Battery well of USS Nautilus.jpg|thumb|Battery well containing 126 cells on {{USS|Nautilus|SSN-571|6}}, the first nuclear-powered submarine]]

Steam power was resurrected in the 1950s with a nuclear-powered steam turbine driving a generator. By eliminating the need for atmospheric oxygen, the time that a submarine could remain submerged was limited only by its food stores, as breathing air was recycled and fresh water [[Distillation|distilled]] from seawater. More importantly, a nuclear submarine has unlimited range at top speed. This allows it to travel from its operating base to the combat zone in a much shorter time and makes it a far more difficult target for most anti-submarine weapons. Nuclear-powered submarines have a relatively small battery and diesel engine/generator powerplant for emergency use if the reactors must be shut down.

Nuclear power is now used in all large submarines, but due to the high cost and large size of nuclear reactors, smaller submarines still use diesel–electric propulsion. The ratio of larger to smaller submarines depends on strategic needs. The US Navy, [[French Navy]], and the British [[Royal Navy]] operate only [[nuclear submarine]]s,<ref name="Submarine Warfare">{{cite web|url=http://www.odu.edu/ao/hrnrotc/students/ns_courses/101odu/sumbmarine%20presentation%202005.ppt|archive-url=https://web.archive.org/web/20060908003323/http://www.odu.edu/ao/hrnrotc/students/ns_courses/101odu/sumbmarine%20presentation%202005.ppt|url-status=dead|archive-date=8 September 2006|title=Submarine Warfare|access-date=7 October 2006}}</ref><ref>{{cite web|url=http://www.nti.org/db/submarines/france/index.html|title=France Current Capabilities|publisher=Nti.org|access-date=18 April 2010}}</ref> which is explained by the need for distant operations. Other major operators rely on a mix of nuclear submarines for strategic purposes and diesel–electric submarines for defense. Most fleets have no nuclear submarines, due to the limited availability of nuclear power and submarine technology.

Diesel–electric submarines have a stealth advantage over their nuclear counterparts. Nuclear submarines generate noise from coolant pumps and turbo-machinery needed to operate the reactor, even at low power levels.<ref>{{cite book|last=Thompson|first=Roger|title=Lessons Not Learned|publisher=US Naval Institute Press|year=2007|isbn=978-1-59114-865-4|page=34}}</ref><ref>{{Cite book|last=Lee|first=T. W.|url=https://books.google.com/books?id=-nrZqzQs3jMC&q=Ohio+class+submarine+noise&pg=PA343|title=Military Technologies of the World [2 volumes]|date=30 December 2008|publisher=ABC-CLIO|isbn=978-0-275-99536-2|pages=344|language=en}}</ref> Some nuclear submarines such as the American {{sclass|Ohio|submarine|4}} can operate with their reactor coolant pumps secured, making them quieter than electric subs.{{Citation needed|date=April 2020}} A conventional submarine operating on batteries is almost completely silent, the only noise coming from the shaft bearings, propeller, and flow noise around the hull, all of which stops when the sub hovers in mid-water to listen, leaving only the noise from crew activity. Commercial submarines usually rely only on batteries, since they operate in conjunction with a mother ship.

Several [[nuclear and radiation accidents by death toll|serious nuclear and radiation accidents]] have involved nuclear submarine mishaps.<ref name=johnston2007/><ref name=timenuke/> The {{ship|Soviet submarine|K-19}} reactor accident in 1961 resulted in 8 deaths and more than 30 other people were over-exposed to radiation.<ref name=rad>[http://www.iaea.org/Publications/Magazines/Bulletin/Bull413/article1.pdf Strengthening the Safety of Radiation Sources] {{webarchive|url=https://web.archive.org/web/20090326181428/http://www.iaea.org/Publications/Magazines/Bulletin/Bull413/article1.pdf |date=26 March 2009 }} p. 14</ref> The {{ship|Soviet submarine|K-27}} reactor accident in 1968 resulted in 9 fatalities and 83 other injuries.<ref name=johnston2007>{{cite web|url=http://www.johnstonsarchive.net/nuclear/radevents/radevents1.html|title=Deadliest radiation accidents and other events causing radiation casualties|author=Johnston, Robert|date=23 September 2007|publisher=Database of Radiological Incidents and Related Events}}</ref> The {{ship|Soviet submarine|K-431}} accident in 1985 resulted in 10 fatalities and 49 other radiation injuries.<ref name=timenuke>{{cite news|url=http://www.time.com/time/photogallery/0,29307,1887705,00.html|archive-url=https://web.archive.org/web/20090328130544/http://www.time.com/time/photogallery/0,29307,1887705,00.html|url-status=dead|archive-date=28 March 2009|title=The Worst Nuclear Disasters|work=[[Time (magazine)|Time]]|access-date=1 April 2015|date=25 March 2009}}</ref>

====Alternative====
Oil-fired steam turbines powered the British [[British K-class submarine|K-class submarines]], built during [[World War I]] and later, to give them the surface speed to keep up with the battle fleet. The K-class subs were not very successful, however.

Toward the end of the 20th century, some submarines—such as the British ''Vanguard'' class—began to be fitted with [[pump-jet]] propulsors instead of propellers. Though these are heavier, more expensive, and less efficient than a propeller, they are significantly quieter, providing an important tactical advantage.

===Armament===
[[File:Ocelot-TorpedoTubes.JPG|thumb|The forward torpedo tubes in HMS ''Ocelot'']]
[[File:Sukellusveneestä.jpg|thumb|The torpedo room of ''[[Finnish submarine Vesikko|Vesikko]]'']]
The success of the submarine is inextricably linked to the development of the [[torpedo]], invented by [[Robert Whitehead]] in 1866. His invention (essentially the same now as it was 140 years ago), allowed the submarine make the leap from novelty to a weapon of war. Prior to the development and miniaturization of sonar sensitive enough to track a submerged submarine, attacks were exclusively restricted to ships and submarines operating near or at the surface. Targeting of unguided torpedoes was initially done by eye, but by World War II [[Torpedo Data Computer|analog targeting computers]] began to proliferate, being able to calculate basic firing solutions. Nonetheless, multiple "straight-running" torpedoes could be required to ensure a target was hit. With at most 20 to 25 torpedoes stored on board, the number of attacks a submarine could make was limited. To increase [[combat endurance]] starting in World War I submarines also functioned as submersible gunboats, using their [[deck gun]]s against unarmed targets, and diving to escape and engage enemy warships. The initial importance of these deck guns encouraged the development of the unsuccessful [[cruiser submarine|Submarine Cruiser]] such as the French {{ship|French submarine|Surcouf||2}} and the [[Royal Navy]]'s {{HMS|X1||2}} and [[British M-class submarine|M-class]] submarines. With the arrival of [[anti-submarine warfare]] (ASW) aircraft, guns became more for defense than attack. A more practical method of increasing combat endurance was the external torpedo tube, loaded only in port.

The ability of submarines to approach enemy harbours covertly led to their use as [[minelayer]]s. Minelaying submarines of World War I and World War II were specially built for that purpose. Modern submarine-laid [[Naval mine|mines]], such as the British Mark 5 [[Stonefish (mine)|Stonefish]] and Mark 6 Sea Urchin, can be deployed from a submarine's torpedo tubes.

After World War II, both the US and the USSR experimented with submarine-launched [[cruise missile]]s such as the [[SSM-N-8 Regulus]] and [[P-5 Pyatyorka]]. Such missiles required the submarine to surface to fire its missiles. They were the forerunners of modern submarine-launched cruise missiles, which can be fired from the torpedo tubes of submerged submarines, for example, the US [[Tomahawk (missile family)|BGM-109 Tomahawk]] and Russian [[RPK-2 Viyuga]] and versions of surface-to-surface [[anti-ship missile]]s such as the [[Exocet]] and [[Boeing Harpoon|Harpoon]], encapsulated for submarine launch. Ballistic missiles can also be fired from a submarine's torpedo tubes, for example, missiles such as the anti-submarine [[SUBROC]]. With internal volume as limited as ever and the desire to carry heavier warloads, the idea of the external launch tube was revived, usually for encapsulated missiles, with such tubes being placed between the internal pressure and outer streamlined hulls. Guided torpedoes also proliferated extensively during and after World War II, even further increasing the combat endurance and lethality of submarines and allowing them to engage other submarines at depth (with the latter now being one of the primary missions of the modern [[attack submarine]]).

The strategic mission of the SSM-N-8 and the P-5 was taken up by [[submarine-launched ballistic missile]] beginning with the US Navy's [[UGM-27 Polaris|Polaris]] missile, and subsequently the [[UGM-73 Poseidon|Poseidon]] and [[Trident (missile)|Trident]] missiles.

Germany is working on the torpedo tube-launched short-range [[IDAS (missile)|IDAS missile]], which can be used against ASW helicopters, as well as surface ships and coastal targets.

===Sensors===
{{main|Sonar}}

A submarine can have a variety of sensors, depending on its missions. Modern military submarines rely almost entirely on a suite of passive and active [[sonar]]s to locate targets. Active sonar relies on an audible "ping" to generate echoes to reveal objects around the submarine. Active systems are rarely used, as doing so reveals the sub's presence. Passive sonar is a set of sensitive hydrophones set into the hull or trailed in a towed array, normally trailing several hundred feet behind the sub. The towed array is the mainstay of NATO submarine detection systems, as it reduces the flow noise heard by operators. Hull mounted sonar is employed in addition to the towed array, as the towed array can not work in shallow depth and during maneuvering. In addition, sonar has a blind spot "through" the submarine, so a system on both the front and back works to eliminate that problem. As the towed array trails behind and below the submarine, it also allows the submarine to have a system both above and below the [[thermocline]] at the proper depth; sound passing through the thermocline is distorted resulting in a lower detection range.

Submarines also carry radar equipment to detect surface ships and aircraft. Submarine captains are more likely to use radar detection gear than active radar to detect targets, as radar can be detected far beyond its own return range, revealing the submarine. Periscopes are rarely used, except for position fixes and to verify a contact's identity.

Civilian submarines, such as the {{ship|DSV|Alvin}} or the [[MIR (submersible)|Russian ''Mir'' submersibles]], rely on small active sonar sets and viewing ports to navigate. The human eye cannot detect sunlight below about {{convert|300|ft|m}} underwater, so high intensity lights are used to illuminate the viewing area.

===Navigation===
{{main|Submarine navigation}}
[[File:Ocelot-Periscopes.JPG|thumb|The larger search [[periscope]], and the smaller, less detectable attack periscope on HMS ''Ocelot'']]

Early submarines had few navigation aids, but modern subs have a variety of navigation systems. Modern military submarines use an [[inertial guidance system]] for navigation while submerged, but drift error unavoidably builds over time. To counter this, the crew occasionally uses the [[Global Positioning System]] to obtain an accurate position. The [[periscope]]—a retractable tube with a [[prism (optics)|prism]] system that provides a view of the surface—is only used occasionally in modern submarines, since the visibility range is short. The {{sclass|Virginia|submarine|0}} and {{sclass|Astute|submarine|2}}s use [[photonics mast]]s rather than hull-penetrating optical periscopes. These masts must still be deployed above the surface, and use electronic sensors for visible light, infrared, laser range-finding, and electromagnetic surveillance. One benefit to hoisting the mast above the surface is that while the mast is above the water the entire sub is still below the water and is much harder to detect visually or by radar.

===Communication===
{{main|Communication with submarines}}

Military submarines use several systems to communicate with distant command centers or other ships. One is [[VLF]] (very low frequency) radio, which can reach a submarine either on the surface or submerged to a fairly shallow depth, usually less than {{convert|250|ft|m}}. [[Extremely low frequency|ELF]] (extremely low frequency) can reach a submarine at greater depths, but has a very low bandwidth and is generally used to call a submerged sub to a shallower depth where VLF signals can reach. A submarine also has the option of floating a long, buoyant wire antenna to a shallower depth, allowing VLF transmissions by a deeply submerged boat.

By extending a radio mast, a submarine can also use a "[[burst transmission]]" technique. A burst transmission takes only a fraction of a second, minimizing a submarine's risk of detection.

To communicate with other submarines, a system known as Gertrude is used. Gertrude is basically a [[underwater telephone|sonar telephone]]. Voice communication from one submarine is transmitted by low power speakers into the water, where it is detected by passive sonars on the receiving submarine. The range of this system is probably very short, and using it radiates sound into the water, which can be heard by the enemy.

Civilian submarines can use similar, albeit less powerful systems to communicate with support ships or other submersibles in the area.

===Life support systems===
With [[nuclear reactor|nuclear power]] or [[air-independent propulsion]], submarines can remain submerged for months at a time. Conventional diesel submarines must periodically resurface or run on [[Submarine snorkel|snorkel]] to recharge their batteries. Most modern military submarines generate breathing [[oxygen]] by [[electrolysis]] of fresh water (using a device called an "[[Elektron (ISS)#Elektron|Electrolytic Oxygen Generator]]"). Emergency oxygen can be produced by burning [[sodium chlorate]] candles.<ref name="Smarter every day 251" >{{cite AV media|url=https://www.youtube.com/watch?v=g3Ud6mHdhlQ |title=How Do Nuclear Submarines Make Oxygen? |publisher= Smarter Every Day 251 |first= |last= |type=video |website=www.youtube.com |date=21 February 2021 |access-date=26 January 2022}}</ref> Atmosphere control equipment includes a [[Carbon dioxide scrubber]], which uses a spray of [[Amine gas treating|monoethanolamine]] (MEA) absorbent to remove the gas from the air, after which the MEA is heated in a boiler to release the CO<sub>2</sub> which is then pumped overboard. Emergency scrubbing can also be done with lithium hydroxide, which is consumable.<ref name="Smarter every day 251" /> A machine that uses a [[catalyst]] to convert [[carbon monoxide]] into carbon dioxide (removed by the {{CO2}} scrubber) and bonds [[hydrogen]] produced from the ship's storage battery with oxygen in the atmosphere to produce water, is also used.{{citation needed|date=January 2022}} An atmosphere monitoring system samples the air from different areas of the ship for [[nitrogen]], oxygen, hydrogen, [[Dichlorodifluoromethane|R-12]] and [[1,2-Dichlorotetrafluoroethane|R-114]] refrigerants, carbon dioxide, [[carbon monoxide]], and other gases.<ref name="Smarter every day 251" /> Poisonous gases are removed, and oxygen is replenished by use of an oxygen bank located in a main ballast tank.{{citation needed|date=January 2022}}{{clarify|Is storage of oxugen banks in main ballast tanks a common arrangement, or a special case?|date=January 2022}} Some heavier submarines have two oxygen bleed stations (forward and aft). The oxygen in the air is sometimes kept a few percent less than atmospheric concentration to reduce fire risk.

Fresh water is produced by either an evaporator or a [[reverse osmosis]] unit. The primary use for fresh water is to provide feedwater for the reactor and steam propulsion plants. It is also available for showers, sinks, cooking and cleaning once propulsion plant needs have been met. Seawater is used to flush toilets, and the resulting [[Blackwater (waste)|"blackwater"]] is stored in a sanitary tank until it is blown overboard using pressurized air or pumped overboard by using a special sanitary pump. The blackwater-discharge system requires skill to operate, and isolation valves must be closed before discharge.<ref name="Smarter every day 256" >{{cite AV media |url=https://www.youtube.com/watch?v=SYFuA3xnkUE |title=How to Poop on a Nuclear Submarine (256)|publisher=Smarter Every Day |type=video |website=www.youtube.com |date=9 May 2021 |access-date=27 January 2022 }}</ref> The German [[Type VII submarine|Type VIIC]] boat {{GS|U-1206||2}} was lost with casualties because of [[human error]] while using this system.<ref>{{cite web|url=http://www.uboat.net/boats/u1206.htm|title=U-1206|publisher=Uboat.net|access-date=18 April 2010}}</ref> Water from showers and sinks is stored separately in "[[greywater|grey water]]" tanks and discharged overboard using drain pumps.

Trash on modern large submarines is usually disposed of using a tube called a Trash Disposal Unit (TDU), where it is compacted into a galvanized steel can. At the bottom of the TDU is a large ball valve. An ice plug is set on top of the ball valve to protect it, the cans atop the ice plug. The top breech door is shut, and the TDU is flooded and equalized with sea pressure, the ball valve is opened and the cans fall out assisted by scrap iron weights in the cans. The TDU is also flushed with seawater to ensure it is completely empty and the ball valve is clear before closing the valve.{{citation needed|reason=Totally plausible, but a reference would be nice|date=January 2022}}

==Crew==
[[File:E class submarine interior IWM Q 18650.jpg|thumb|The interior of a [[British E-class submarine]]. An officer supervises submerging operations, c. 1914–1918.]]

A typical nuclear submarine has a crew of over 80; conventional boats typically have fewer than 40. The conditions on a submarine can be difficult because crew members must work in isolation for long periods of time, without family contact, and in cramped conditions.<ref>{{cite web | url=https://www.businessinsider.com/step-inside-nuclear-submarine-2016-7 | title=Cramped and heavily armed — see what life is like aboard a nuclear submarine with these photos | website=[[Business Insider]] }}</ref> Submarines normally maintain [[radio silence]] to avoid detection. Operating a submarine is dangerous, even in peacetime, and many submarines have been lost in accidents.<ref>{{cite web |last1=Bateman |first1=Sam |title=CO07012 {{!}} Perils of the Deep: The Dangers of Submarine Operations in Asia |url=https://www.rsis.edu.sg/rsis-publication/idss/895-perils-of-the-deep-the-danger/ |website=[[S. Rajaratnam School of International Studies]] |publisher=[[Nanyang Technological University, Singapore]] |access-date=24 April 2021}}</ref>

===Women===
[[File:US Navy 100603-N-0000X-053 Midshipmen learn to pilot the submarine by training in the duties of the helm and planesman while underway aboard the Ohio-class ballistic-missile submarine USS West Virginia (SSBN 736).jpg|thumb|[[Midshipman|Midshipmen]] learn to pilot {{USS|West Virginia|SSBN-736|6}}.]]

Most navies prohibited women from serving on submarines, even after they had been permitted to serve on surface warships. The [[Royal Norwegian Navy]] became the first navy to allow women on its submarine crews in 1985. The [[Royal Danish Navy]] allowed female submariners in 1988.<ref name="fesub">{{cite web|url=http://www.nato.int/docu/review/2001/0102-09.htm|title=NATO Review – Vol.49 – No 2 – Summer 2001: Women in uniform|publisher=Nato.int|date=31 August 2001|access-date=18 April 2010|archive-date=8 February 2016|archive-url=https://web.archive.org/web/20160208185604/http://www.nato.int/docu/review/2001/0102-09.htm|url-status=dead}}</ref> Others followed suit including the [[Swedish Navy]] (1989),<ref name="swedfem">{{cite web|url=http://www.rekryc.mil.se/article.php?id=11756|title=Historik|archive-url=https://web.archive.org/web/20070927045646/http://www.rekryc.mil.se/article.php?id=11756 |archive-date=27 September 2007 |language=sv }}</ref><!-- might be earlier, but not before Norway; this figure is for the armed forces as a whole --> the [[Royal Australian Navy]] (1998), the [[Spanish Navy]] (1999),<ref>{{cite journal |last1=Virseda |first1=María del Carmen |title=La Mujer En Las Fuerzas Armadas |journal=Temas Profesionales |date=2014 |url=http://www.armada.mde.es/archivo/rgm/2014/11/cap06.pdf}}</ref><ref>{{Cite web|url=https://www.boe.es/eli/es/l/1999/05/18/17|title=BOE-A-1999-11194 Ley 17/1999, de 18 de mayo, de Régimen del Personal de las Fuerzas Armadas.|pages=18751–18797}}</ref> the [[German Navy]] (2001) and the [[Royal Canadian Navy|Canadian Navy]] (2002). In 1995, [[Solveig Krey]] of the Royal Norwegian Navy became the first female officer to assume command on a military submarine, [[Kobben-class submarine|HNoMS ''Kobben'']].<ref>{{cite web|url=http://www.mil.no/felles/fms/utdanning/start/jenter/historikk/|title=Forsvarsnett: Historikk|archive-url=https://web.archive.org/web/20060209224033/http://www.mil.no/felles/fms/utdanning/start/jenter/historikk/ |archive-date=9 February 2006 |language=no}}</ref>

On 8 December 2011, British [[Secretary of State for Defence|Defence Secretary]] [[Philip Hammond]] announced that the [[United Kingdom|UK]]'s ban on women in submarines was to be lifted from 2013.<ref name="Guardian women">{{cite news|first=Nick|last=Hopkins|title=Royal Navy will allow women to serve on submarines|url=https://www.theguardian.com/uk/2011/dec/08/royal-navy-women-submarines|newspaper=The Guardian|date=8 December 2011|access-date=1 April 2012|location=London}}</ref> Previously there were fears that women were more at risk from a build-up of carbon dioxide in the submarine. But a study showed no medical reason to exclude women, though pregnant women would still be excluded.<ref name="Guardian women"/> Similar dangers to the pregnant woman and her fetus barred women from submarine service in Sweden in 1983, when all other positions were made available for them in the Swedish Navy. Today, pregnant women are still not allowed to serve on submarines in Sweden. However, the policymakers thought that it was discriminatory with a general ban and demanded that women should be tried on their individual merits and have their suitability evaluated and compared to other candidates. Further, they noted that a woman complying with such high demands is unlikely to become pregnant.<ref name="swedfem"/> In May 2014, three women became the RN's first female submariners.<ref>{{cite news|title=Royal Navy gets first female submariners|url=https://www.bbc.co.uk/news/uk-27278588|access-date=5 May 2014|newspaper=BBC|date=5 May 2014}}</ref>

Women have served on US Navy surface ships since 1993, and {{as of|lc=y|2011|alt=as of 2011–2012}}, began serving on submarines for the first time. Until presently, the Navy allowed only three exceptions to women being on board military submarines: female civilian technicians for a few days at most, women [[midshipman|midshipmen]] on an overnight during summer training for Navy [[ROTC]] and [[United States Naval Academy|Naval Academy]], and family members for one-day dependent cruises.<ref>[http://www.chinfo.navy.mil/navpalib/ships/submarines/centennial/faqs.html question #10] {{webarchive |url=https://web.archive.org/web/20060927230332/http://www.chinfo.navy.mil/navpalib/ships/submarines/centennial/faqs.html |date=27 September 2006 }}</ref> In 2009, senior officials, including then-Secretary of the Navy [[Ray Mabus]], Joint Chief of Staff Admiral [[Michael Mullen]], and Chief of Naval Operations Admiral [[Gary Roughead]], began the process of finding a way to implement women on submarines.<ref name="Women should serve">{{cite news|newspaper=Navy Times|title=SecNav, CNO: Women should serve on subs|author1=William H. McMichael |author2=Andrew Scutro |name-list-style=amp |date=27 September 2009|url=http://www.navytimes.com/news/2009/09/navy_roughead_subs_092409w/}}</ref> The US Navy rescinded its "no women on subs" policy in 2010.<ref name="women-on-virginia"/>

Both the US and British navies operate nuclear-powered submarines that deploy for periods of six months or longer. Other navies that permit women to serve on submarines operate conventionally powered submarines, which deploy for much shorter periods—usually only for a few months.<ref>{{Cite web|url=https://www.csp.navy.mil/|title=Commander, Submarine Force, U.S. Pacific Fleet|website=www.csp.navy.mil}}</ref> Prior to the change by the US, no nation using nuclear submarines permitted women to serve on board.<ref>{{cite news|url=https://www.washingtonpost.com/wp-dyn/content/article/2009/09/25/AR2009092503385.html?hpid=moreheadlines|title=Navy Seeks to Allow Women to Serve on Submarines|newspaper=The Washington Post|first=Ann|last=Scott Tyson|date=26 September 2009|access-date=18 April 2010}}</ref>

In 2011, the first class of female submarine officers graduated from Naval Submarine School's Submarine Officer Basic Course (SOBC) at the [[Naval Submarine Base New London]].<ref>{{cite web|author=Enter your Company or Top-Level Office|url=http://www.ct.gov/oma/cwp/view.asp?a=3422&q=483312|title=OMA: Female Sub School Grads Say They Fit Right In|publisher=Ct.gov|date=19 July 2011|access-date=27 December 2011}}</ref> Additionally, more senior ranking and experienced female supply officers from the surface warfare specialty attended SOBC as well, proceeding to fleet Ballistic Missile (SSBN) and Guided Missile (SSGN) submarines along with the new female submarine line officers beginning in late 2011.<ref>{{cite web|author=Commander, Submarine Group 10 Public Affairs|url=http://www.navy.mil/search/display.asp?story_id=52990|title=Navy Welcomes Women To Serve In Submarines|publisher=Navy.mil|access-date=27 December 2011|archive-date=6 May 2012|archive-url=https://web.archive.org/web/20120506230557/http://www.navy.mil/search/display.asp?story_id=52990|url-status=dead}}</ref> By late 2011, several women were assigned to the ''Ohio''-class ballistic missile submarine {{USS|Wyoming|SSBN-742|6}}.<ref>{{cite web|url=http://www.military.com/daily-news/2014/12/12/report-12-sailors-implicated-in-submarine-shower-scandal.html?comp=7000023435630&rank=4|title=Report: 12 Sailors Implicated in Submarine Shower Scandal|work=Military.com|access-date=1 April 2015}}</ref> On 15 October 2013, the US Navy announced that two of the smaller ''Virginia''-class attack submarines, {{USS|Virginia|SSN-774|6}} and {{USS|Minnesota|SSN-783|6}}, would have female crew-members by January 2015.<ref name="women-on-virginia">{{cite news|url=http://news.usni.org/2013/10/15/navy-names-first-two-attack-boats-female-crew|title=Navy Names First Two Attack Boats to Have Female Crew|publisher=USNI News|date=15 October 2013|access-date=9 January 2014}}</ref>

In 2020, Japan's national naval submarine academy accepted its first female candidate.<ref>{{Cite web|last=Staff|date=22 January 2020|title=First woman enters Japan's submarine academy after end of restrictions|url=https://www.japantimes.co.jp/news/2020/01/22/national/first-woman-enters-japans-submarine-academy/|access-date=16 July 2020|website=The Japan Times|language=en-US|archive-date=16 July 2020|archive-url=https://web.archive.org/web/20200716172443/https://www.japantimes.co.jp/news/2020/01/22/national/first-woman-enters-japans-submarine-academy/|url-status=dead}}</ref>

===Abandoning the vessel===
[[File:Submarine Escape Immersion Equipment suit.gif|thumb|Submarine Escape Immersion Equipment suit Mk 10]]
[[File:Submarine Escape Suit (at Visakha Museum).jpg|thumb|upright=0.8|A submarine escape suit with rebreather]]

In an emergency, submarines can contact other ships to assist in rescue, and pick up the crew when they abandon ship. The crew can use [[escape set]]s such as the [[Submarine Escape Immersion Equipment]] to abandon the submarine via an [[escape trunk]], which is a small [[airlock]] compartment that provides a route for crew to escape from a downed submarine at ambient pressure in small groups, while minimising the amount of water admitted to the submarine.<ref name=NSMRL1205>{{cite journal|author1=Frank, SJ |author2=Curley, MD |author3=Ryder, SJ |title=A Biomedical Review Of The US Navy Submarine Escape System: 1996|journal=Naval Submarine Medical Research Laboratory Technical Report|volume=NSMRL-1205|year=1997|url=http://archive.rubicon-foundation.org/8530|archive-url=https://archive.today/20130415180707/http://archive.rubicon-foundation.org/8530|url-status=usurped|archive-date=April 15, 2013|access-date=15 March 2013}}</ref> The crew can avoid lung injury from over-expansion of air in the lungs due to the pressure change known as [[Barotrauma#Pulmonary barotrauma|pulmonary barotrauma]] by maintaining an open airway and exhaling during the ascent.<ref name="pmid10642066">{{cite journal|vauthors=Benton PJ, Francis TJ, Pethybridge RJ|title=Spirometric indices and the risk of pulmonary barotrauma in submarine escape training|journal=Undersea and Hyperbaric Medicine Journal|volume=26|issue=4|pages=213–7|year=1999|pmid=10642066|url=http://archive.rubicon-foundation.org/2309|access-date=15 March 2013|archive-date=25 May 2013|archive-url=https://web.archive.org/web/20130525124304/http://archive.rubicon-foundation.org/xmlui/handle/123456789/2309|url-status=usurped}}</ref> Following escape from a pressurized submarine, in which the air pressure is higher than atmospheric due to water ingress or other reasons, the crew is at risk of developing [[decompression sickness]] on return to surface pressure.<ref name=Weathersby1999>{{cite journal|author1=Weathersby, PK|author2=Survanshi, SS|author3=Parker, EC|author4=Temple, DJ|author5=Toner, CB|title=Estimated DCS Risks in Pressurized Submarine Rescue.|journal=US Naval Medical Research Center Technical Report|volume=NMRC 1999-04|year=1999|url=http://archive.rubicon-foundation.org/7553|access-date=15 March 2013|archive-date=25 May 2013|archive-url=https://web.archive.org/web/20130525130725/http://archive.rubicon-foundation.org/xmlui/handle/123456789/7553|url-status=usurped}}</ref>

An alternative escape means is via a [[deep-submergence rescue vehicle]] that can dock onto the disabled submarine, establish a seal around the escape hatch, and transfer personnel at the same pressure as the interior of the submarine. If the submarine has been pressurised the survivors can lock into a [[decompression chamber]] on the [[submarine rescue ship]] and [[transfer under pressure]] for safe [[surface decompression]].<ref name=NSMRL1021>{{cite journal|author=Eckenhoff, RG|title=Pressurized Submarine Rescue|journal=Naval Submarine Medical Research Laboratory Technical Report|volume=NSMRL-1021|year=1984|url=http://archive.rubicon-foundation.org/8416|access-date=15 March 2013|archive-date=25 May 2013|archive-url=https://web.archive.org/web/20130525120435/http://archive.rubicon-foundation.org/xmlui/handle/123456789/8416|url-status=usurped}}</ref>

==See also==
{{div col|colwidth=30em}}
* [[Autonomous underwater vehicle]]
* [[Coastal submarine]]
* [[Columbia-class submarine]]
* [[Depth charge]]
* [[:Category:Fictional submarines|Fictional submarines]]
* [[Flying submarine]]
* [[List of ships sunk by submarines by death toll]]
* [[List of submarine actions]]
* [[List of submarine classes]]
* [[List of submarine incidents since 2000]]
* [[List of submarine museums]]
* [[List of submarines of World War II]]
* [[List of specifications of submarines of World War II]]
* [[List of sunken nuclear submarines]]
* [[Merchant submarine]]
* [[Nuclear navy]]
* [[Semi-submersible naval vessel]]
* [[Submarine films]]
* [[Submarine power cable]]
* [[Submarine simulator]], a computer game genre
* [[Supercavitation]]
* [[Unmanned underwater vehicle]]
{{div col end}}

===By country===
* [[List of submarine operators]]
* Australia – [[Collins-class submarine]]
* Bangladesh- [[List of active ships of the Bangladesh Navy|Submarines of the Bangladesh Navy]]
* Britain – [[List of submarines of the Royal Navy]], [[List of submarine classes of the Royal Navy]]
* China – [[Submarines of the People's Liberation Army Navy]]
* France – [[Submarine forces (France)|Submarines in the French Navy]], [[List of submarines of France|List of submarines of the French Navy]], [[List of submarines of France|List of French submarine classes and types]]
* Germany – [[List of U-boats of Germany]]
* India – [[Submarines of the Indian Navy]]
* Israel – [[Dolphin-class submarine]]
* Japan – [[Imperial Japanese Navy submarines]], {{section link|List of combatant ship classes of the Japan Maritime Self-Defense Force#SS : Submarine}}
* The Netherlands – [[List of submarines of the Netherlands]]
* Pakistan – {{section link|List of active Pakistan Navy ships#Submarines}}
* Romania – [[Romanian submarines of World War II]]
* Russia – [[List of Soviet and Russian submarine classes]], [[Future of the Russian Navy#Submarines|Future Russian submarines]]
* Soviet Union – {{section link|List of ships of the Soviet Navy#Submarines}}
* Spain – [[List of submarines of the Spanish Navy]]
* Singapore – {{section link|Republic of Singapore Navy#Submarines}}
* Turkey – [[List of submarines of the Turkish Navy]]
* United States – [[Submarines in the United States Navy|Submarines in the US Navy]], [[List of submarines of the United States Navy|List of submarines of the US Navy]], [[List of United States submarine classes|List of US submarine classes]], [[Naval Submarine Medical Research Laboratory]]

==Notes==
{{Reflist|group=Note}}

==References==
{{Reflist}}

==Bibliography==
{{Refbegin|30em}}
'''General history'''
* ''Histoire des sous-marins: des origines à nos jours'' by [[Jean-Marie Mathey]] and Alexandre Sheldon-Duplaix. (Boulogne-Billancourt: ETAI, 2002).
* {{cite book|first1=Michael|last1=DiMercurio|first2=Michael|last2=Benson|title=The complete idiot's guide to submarines|publisher=Alpha|year=2003|isbn=978-0-02-864471-4|oclc=51747264}}
* {{cite book |last=Delgado |first=James P. |date=2011 |title=Silent Killers: Submarines and Underwater Warfare |location=Oxford |publisher=Osprey Publishing |isbn=978-1-84908-860-2}}
* {{cite book |last=Fontenoy |first=Paul E. |date=2007 |title=Submarines: An Illustrated History of Their Impact |series=Weapons and Warfare |location=Santa Barbara |publisher=ABC-CLIO |isbn=978-1-85109-563-6}}
'''Culture'''
* Redford, Duncan. ''The Submarine: A Cultural History From the Great War to Nuclear Combat'' (I.B. Tauris, 2010) 322 pages; focus on British naval and civilian understandings of submarine warfare, including novels and film.
'''Submarines before 1914'''
* {{cite book|last=Gardiner|first=Robert|title=Steam, Steel and Shellfire, The steam warship 1815–1905|year=1992|location=Annapolis, Maryland|publisher=Naval Institute Press|isbn=978-1-55750-774-7|oclc=30038068}}
'''1900/Russo-Japanese War 1904–1905'''
* {{cite book|last=Jentschura|first=Hansgeorg|author2=Dieter Jung|author3=Peter Mickel|title=Warships of the Imperial Japanese Navy 1869–1945|year=1977|publisher=United States Naval Institute|location=Annapolis, Maryland|isbn=978-0-87021-893-4}}
* {{cite book|last=Olender|first=Piotr|title= Russo-Japanese Naval War 1904–1905 Vol. 2 Battle of Tsushima|year=2010|publisher=Stratus s.c.|location=Sandomierz, Poland|isbn=978-83-61421-02-3}}
* {{cite book|last=Showell|first=Jak|title=The U-Boat Century:German Submarine Warfare 1906–2006|year=2006|location=Great Britain|publisher=Chatham Publishing|isbn=978-1-86176-241-2}}
* {{cite book|last=Simmons|first=Jacques|title=A Grosset All-Color Guide WARSHIPS|year=1971|location=USA|publisher=Grosset & Dunlap, Inc.|isbn=978-0-448-04165-0}}
* {{cite book|last=Watts|first=Anthony J.|title=The Imperial Russian Navy|year=1990|location=London|publisher=Arms and Armour Press|isbn=978-0-85368-912-6}}
'''World War II'''
* {{cite book|last=Blair|first=Clay|author-link=Clay Blair|title=Silent Victory: The U.S. Submarine War Against Japan|year=1975|location=Philadelphia|publisher=Lippincott|isbn=978-0-397-00753-0|oclc=821363|url=https://archive.org/details/silentvictoryus00blai}}
* {{cite book|last=Lockwood|first=Charles A.|author-link=Charles A. Lockwood|title=Sink 'Em All: Submarine Warfare in the Pacific|year=1951|location=New York|publisher=Dutton|oclc=1371626|url=http://catalog.hathitrust.org/Record/000493723}}
* {{cite book|last=O'Kane|first=Richard H.|author-link=Richard O'Kane|title=Clear the Bridge!: The War Patrols of the USS Tang|year=1977|location=Chicago|publisher=Rand McNally|isbn=978-0-528-81058-9|oclc=2965421|url=https://archive.org/details/clearbridgewarpa0000okan}}
* {{cite book|last=O'Kane|first=Richard H.|author-link=Richard O'Kane|title=Wahoo: The Patrols of America's Most Famous World War II Submarine|year=1987|location=Novato, California|publisher=Presidio Press|isbn=978-0-89141-301-1|oclc=15366413|url=https://archive.org/details/wahoopatrolsofam00okan}}
* {{cite book|last=Werner|first=Herbert A.|author-link=Herbert Werner|title=Iron coffins: a personal account of the German U-Boat battles of World War II|year=1999|location=London|publisher=Cassell Military|isbn=978-0-304-35330-9|oclc=41466905|title-link=Herbert Werner}}
* {{cite book |last= Beach |first= Edward L. |title= Submarine! |publisher=H. Holt|year=1952|oclc=396382}}

'''Cold War'''
* ''Hide and seek: the untold story of [[Cold War]] espionage at sea'', by [[Peter Huchthausen]] and [[Alexandre Sheldon-Duplaix]]. (Hoboken, NJ: J. Wiley & Sons, 2008, {{ISBN|978-0-471-78530-9}})
* {{cite book|last=McHale|first=Gannon|title=Stealth boat: fighting the Cold War in a fast attack submarine|publisher=Naval Institute Press|year=2008|isbn=978-1-59114-502-8|oclc=216938657}}
{{Refend}}

==External links==
{{Commons category|Submarines}}
{{Spoken Wikipedia|En-Submarine-article.ogg|date=11 January 2006}}
* {{US patent|708553}} – ''Submarine boat''
* {{Internet Archive film |gov.dod.dimoc.20558 |The Submarine: Part II: Construction (1955)}}
* [https://web.archive.org/web/20071013034107/http://maritime.org/fleetsub/index.htm ''The Fleet Type Submarine Online''] US Navy submarine training manuals, 1944–1946
* American Society of Safety Engineers. Journal of Professional Safety. ''Submarine Accidents: A 60-Year Statistical Assessment''. C. Tingle. September 2009. pp.&nbsp;31–39. [https://www.asse.org/professionalsafety/indexes/2009.php Ordering full article] {{Webarchive|url=https://web.archive.org/web/20140704212300/http://www.asse.org/professionalsafety/indexes/2009.php |date=2014-07-04 }}; or [http://www.allbusiness.com/government/government-bodies-offices-government/12939133-1.html Reproduction without graphics/tables]

{{Submarines}}
{{Ship types}}
{{Warship types of the 19th & 20th centuries}}
{{Technology topics}}
{{Authority control}}

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