Editing Submarine (section)

===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.<ref>{{cite magazine |last=van de Put |first=F.A. |date=September 1986 |title=2. "X" – Roeren.|url=https://www.klaarvooronderwater.nl/kvo/Kvo-016.pdf|magazine=Klaar Voor Onderwater|location=Den Helder|publisher=Onderzeedienst Reünistenvereniging|issue=16|language=Dutch|pages=3–6}}</ref>{{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}}