Editing Torpedo (section)

==Guidance==
[[File: Sopwith Cuckoo.jpg|thumb|A torpedo dropped from a [[Sopwith Cuckoo]] during World War I]]
[[File:FiringGeometry.png|thumb|Illustration of General Torpedo Fire Control Problem]]

Torpedoes may be aimed at the target and fired unguided, similarly to a traditional [[artillery shell]], or they may be guided onto the target. They may be guided autonomously towards the target by some procedure, such as sound (homing), or by the operator, typically via commands sent over a signal-carrying cable ([[wire guidance]]).

===Unguided===
The Victorian-era [[Brennan torpedo]] could be steered onto its target by varying the relative speeds of its propulsion cables. However, the Brennan required a substantial infrastructure and was not suitable for shipboard use. Therefore, for the first part of its history, the torpedo was guided only in the sense that its course could be regulated to achieve an intended impact depth (because of the sine-wave running path of the Whitehead,<ref>Fitzsimons, Bernard, ed. "Bliss-Leavitt", in ''The Illustrated Encyclopedia of 20th Century Weapons and Warfare'' (London: Phoebus, 1978), Volume 4, p.386.</ref> this was a hit or miss proposition, even when everything worked correctly) and, through gyroscopes, a straight course. With such torpedoes the method of attack in [[Torpedo boats#Motor torpedo craft|small torpedo boats]], [[torpedo bomber]]s, and small submarines was to steer a predictable collision course abeam to the target and release the torpedo at the last minute, then veer away, all the time subject to defensive fire.

In larger ships and submarines, fire-control calculators gave a wider engagement envelope. Originally, plotting tables (in large ships), combined with specialized [[slide rule]]s (known in U.S. service as the "banjo" and "Is/Was"),<ref name=Beach55>{{cite book |first=Edward L. |last=Beach |title=Run Silent, Run Deep |url=https://books.google.com/books?id=v6D1DAAAQBAJ |orig-year=1955 |date=2016 |publisher=Naval Institute Press |isbn=978-1-68247-167-8}}</ref> reconciled the speed, distance, and course of a target with the firing ship's speed and course, together with the performance of its torpedoes, to provide a firing solution. By the Second World War, all sides had developed automatic electro-mechanical calculators, exemplified by the U.S. Navy's [[Torpedo Data Computer]].<ref>The British called theirs the "fruit machine".</ref> Submarine commanders were still expected to be able to calculate a firing solution by hand as a backup against mechanical failure, and because many submarines existed at the start of the war were not equipped with a TDC; most could keep the "picture" in their heads and do much of the calculations (simple trigonometry) mentally, from extensive training.<ref name=Beach55/>

Against high-value targets and multiple targets, submarines would launch a spread of torpedoes, to increase the probability of success. Similarly, squadrons of torpedo boats and torpedo bombers would attack together, creating a "fan" of torpedoes across the target's course. Faced with such an attack, the prudent thing for a target to do was to turn to parallel the course of the incoming torpedo and steam away from the torpedoes and the firer, allowing the relatively short-range torpedoes to use up their fuel. An alternative was to "comb the tracks", turning to parallel the incoming torpedo's course, but turning towards the torpedoes. The intention of such a tactic was still to minimize the size of the target offered to the torpedoes, but at the same time be able to aggressively engage the firer. This was the tactic advocated by critics of Jellicoe's actions at [[Battle of Jutland#Controversy|Jutland]], his caution at turning away from the torpedoes being seen as the reason the Germans escaped.

The use of multiple torpedoes to engage single targets depletes torpedo supplies and greatly reduces a submarine's [[combat endurance]].<ref>''The Attack Submarine'' suggests ''shorter'' patrols actually improve effectiveness.</ref> Endurance can be improved by ensuring that a target can be effectively engaged by a single torpedo, which gave rise to the guided torpedo.

===Pattern running===
[[File:Flachenabsuchender_Torpedo_type_I_-_running_pattern.svg|thumb|right|The functional concept of torpedoes running a ladder search pattern, launched by two submarines at a moving convoy.]]
During the Second World War, the Germans introduced programmable pattern-running torpedoes, which would run a predetermined pattern until they either ran out of fuel or hit something. These weapons would generally engage in a [[Water surface searches#Parallel track|ladder search pattern]], and were intended for engaging [[Convoy|convoys]] of vessels, commonly encountered in the Atlantic theater. The use of pattern-running torpedoes allowed a [[Wolfpack (naval tactic)|wolfpack]] of U-boats to lob large numbers of shots in the general area of a moving convoy, without concern that two different U-boats may be targeting the same vessel.

The earlier version of the weapon, FaT (''Flächenabsuchender'' - "planar seeker"), ran out after launch in a straight line, and then weaved backward and forwards parallel to that initial course, whilst the more advanced LuT (''Lageunabhängiger'' - "position-independent") could transit to a preprogrammed gyrocompass angle after reaching a set distance after launch, and then enter a more complex weaving pattern.<ref>{{cite web | title = U-boat Archive – Interrogation of U-Boat Survivors – Cumulative Edition | url =http://www.uboatarchive.net/KTB/KTBNotesArmamentCumulativeEdition.htm | access-date = 2017-04-13}}</ref>

Germany also used the Italian [[List of World War II torpedoes of Germany|LT 350 aerial torpedo]] for [[Anti-submarine warfare|ASW]]. The weapon lacked an acoustic seeker head, but it would be dropped in clusters over the approximate location of a lurking enemy submarine, and would thereafter engage in a chaotic movement pattern, in order to hit the target by random chance.

A somewhat similar concept for a chaotic underwater pattern search was experimented with by Japan during the Second World War with their [[Japanese 45 cm torpedo#Bomb-Torpedoes|Kūrai No.6 and No.7]] circling ASW bomb-torpedoes. These weapons did not possess homing capabilities, nor a propulsion system; the design resembled a [[Dart_(missile)|dart]], and would glide at high speed when launched. The functional concept envisioned multiple such weapons launched directly by an aircraft at a surfaced submarine, or at the approximate location of a submerged one. After splashdown, the weapons would move in a spiral pattern as they sank, their forward movement being enacted by the Earth's gravity.

Acoustic homing torpedoes usually possess the capability to engage in simple search patterns at the launching entity's discretion; the most common of these are the snake (weave left and right while moving forward, to achieve a wider forward-facing detection cone) and the circle (continuously travel in a circle, for omnidirectional detection around the epicenter of the circle) search patterns. A good example of a weapon possessing both of these search patterns is the [[Mark 46 torpedo|Mark 46]] lightweight torpedo, used in large numbers worldwide.

===Radio and wire guidance===
{{See also|Command guidance}}
Though Luppis' original design had been rope-guided, and numerous early examples of torpedoes possessed [[Manual command to line of sight|MCLOS]] wire guidance and radio guidance, wire-guided torpedoes did not become common until the 1960s.

[[File:PSM V56 D0325 Launching of patrick torpedo from the ways.png|thumb|A Patrick wire-guided torpedo in launch configuration, circa 1899.]]

[[File:PSM V56 D0325 Patrick torpedo moving at 23 knots per hour.png|thumb|A Patrick wire-guided torpedo moving at 23 knots. The flags were used for line-of-sight control.]]

One of the earliest examples of an electrical wire-guided torpedo was the Lay torpedo, designed by [[John Louis Lay]] between 1867 and 1872.<ref>{{cite web|last = Rigby|first = Rebecca|title = The Lay Torpedoes|url = https://www.torp.esrc.unimelb.edu.au/biogs/E000124b.htm|website = 19th Century Torpedoes, An Annotated Bibliography|access-date = 8 May 2025}}</ref> It would eventually be developed into the Patrick torpedo circa 1899, which was capable of speeds up to {{cvt|23|kn|kph}}.<ref>{{cite web|last = Rigby|first = Rebecca|title = The Patrick Torpedo|url = https://www.torp.esrc.unimelb.edu.au/biogs/E000113b.htm|website = 19th Century Torpedoes, An Annotated Bibliography|access-date = 8 May 2025}}</ref>

The [[Brennan torpedo]] of 1877 was a wire-guided weapon which had an all-mechanical control scheme, and also utilized the control wires as a source of propulsive energy. By selectively putting more or less tension on the control wires as they were payed out, the weapon could be steered left and right. Line-of-sight control was accomplished by observing a tracking mast which projected above the water from the weapon's body.<ref>{{cite web|last = Rigby|first = Rebecca|title = The Brennan Torpedo|url = https://www.torp.esrc.unimelb.edu.au/biogs/E000123b.htm|website = 19th Century Torpedoes, An Annotated Bibliography|access-date = 8 May 2025}}</ref>

One of the most sophisticated early examples of a radio-controlled torpedo was the Sims-Edison torpedo (circa 1890), later known as the Sims-Shoemaker torpedo (after 1902). The weapon carried a {{cvt|500|lb|kg}} [[Gelignite|nitrogelatin]] warhead and was capable of a speed of {{cvt|20|kn|kph}}.<ref>{{cite web|author = Scientific American|title = The Sims-Edison Electric Torpedo - The Torpedo at Full Speed - Sectional View of the Torpedo|url = https://web.archive.org/web/20130527115531/http://www.scientificamericanpast.com/Scientific%20American%201890%20to%201899/1/lg/sci7261890.htm|website = scientificamericanpast.com|date = 26 July 1890|access-date = 8 May 2025}}</ref><ref>{{cite web|last = Rigby|first = Rebecca|title = The Sims-Edison Torpedo|url = https://www.torp.esrc.unimelb.edu.au/biogs/E000115b.htm|website = 19th Century Torpedoes, An Annotated Bibliography|access-date = 8 May 2025}}</ref> Control signals utilized code sequences transmitted via radio, in a manner similar to a [[Teleprinter|teletype]]; aside from steering, the weapon could also be remotely armed and detonated, sped up or slowed down, and halted entirely at the operator's discretion. The weapon was effectively impossible to hijack even if an identical command console were possessed by the adversary, and the brevity of command signals would have also enormously complicated radio signal detection and jamming.<ref>{{cite book|first = H. R.|last = Everett|title = Unmanned Systems of World Wars I and II|publisher = [[Massachusetts Institute of Technology]]|date = 2015|isbn = 978-0-262-02922-3|pages=205-211}}</ref>

[[File:330-ps-9119 15540094799 o.jpg|thumb|Artist's impression of a USN Mark 39 wire-guided torpedo approaching a hostile submarine.]]

During the First World War, the U.S. Navy evaluated a radio controlled torpedo launched from a surface ship, called the Hammond torpedo.<ref>{{cite news| url=https://www.nytimes.com/1916/08/29/archives/to-test-hammond-torpedo-general-wood-named-as-head-of-board-to-pass.html | work=The New York Times | title=TO TEST HAMMOND TORPEDO; General Wood Named as Head of Board to Pass Judgment on Invention | date=29 August 1916}}</ref> A later version tested in the 1930s was claimed to have an effective range of {{convert|6|mi}}.<ref>{{cite magazine |url=https://books.google.com/books?id=p-IDAAAAMBAJ&pg=PA262 |title=Torpedo Controlled By Radio After Striking Water|magazine=Popular Mechanics |date=February 1930 |publisher=Hearst Magazines}}</ref>

The first major example of a wire-guided torpedo which was used against live targets in warfare was the German [[List of World War II torpedoes of Germany|G7ef ''"Spinne"'']], introduced in 1944, which was a [[G7e torpedo|G7e]] variant equipped with an electronic guidance wire, controlled by means of [[Beam riding|acoustic beam riding]] by the launching entity. Originally intended for use by land emplacements for strait defense, later examples were deployed by submarines.

Another example of a guided torpedo during the Second World War was the [[Helmover torpedo]], which was a colossal aerial torpedo with an overall mass of {{cvt|11500|lbs|kg}}, carrying a warhead filled with {{cvt|2204|lb|kg}} of [[RDX]] explosive. The Helmover torpedo possessed a vertical mast which projected above the water and shone infrared lights towards the guiding aircraft to indicate its location and orientation, in a manner similar to a [[Precision approach path indicator|PAPI array]]. Guidance signals to the torpedo were transmitted via radio.

The first truly modern electronically wire-guided torpedo was the [[USN]] [[Mark 39 torpedo|Mark 39]], introduced in 1946. It possessed three-dimensional acoustic homing and used a control wire for mid-course guidance. In 1956, the Mark 39 would be superseded by the [[Mark 37 torpedo|Mark 37]], which served as a mainstay [[Anti-submarine warfare|ASW]] weapon during the 1960s.

Another advancement in the field of teleoperated torpedoes was the [[Royal Navy]] [[British 21-inch torpedo#Mark 23 Grog|Mark 23 Grog]], first available in 1959, an ASW weapon which established a direct audio signal link between the hydrophones of the weapon's seeker head and the command console onboard the launching submarine. A human operator would directly listen to the sounds heard by the torpedo, allowing for sophisticated discrimination of acoustic decoys and target recognition.

Modern torpedoes use an [[Umbilical cable|umbilical wire]], which nowadays allows the computer processing power of the submarine or ship to be used. Torpedoes such as the USN [[Mark 48 torpedo|Mark 48]] can operate in a variety of modes, increasing tactical flexibility.

===Homing===
{{Main|Acoustic torpedo|Wake homing}}
Homing "[[fire and forget]]" torpedoes can use passive or active guidance or a combination of both. Passive [[acoustic torpedo]]es home in on emissions from a target. Active acoustic torpedoes home in on the reflection of a signal, or "ping", from the torpedo or its parent vehicle; this has the disadvantage of giving away the presence of the torpedo. In semi-active mode, a torpedo can be fired to the last known position or calculated position of a target, which is then acoustically illuminated ("pinged") once the torpedo is within attack range.

Later in the Second World War, torpedoes were given acoustic (homing) [[guidance system]]s, with the American [[Mark 24 mine]] and [[Mark 27 torpedo]] and the German [[G7es torpedo]]. Pattern-following and [[wake homing|wake-homing]] torpedoes were also developed. Acoustic homing formed the basis for torpedo guidance after the Second World War.

The homing systems for torpedoes are generally acoustic, though there have been other target sensor types used. A ship's [[acoustic signature]] is not the only emission a torpedo can home in on; to engage U.S. [[supercarrier]]s, the [[Soviet Union]] developed the [[53-65 torpedo|53–65]] [[Wake (physics)|wake]]-homing torpedo. As standard acoustic lures cannot distract a wake-homing torpedo, the US Navy has installed the Surface Ship Torpedo Defense on aircraft carriers that use a Countermeasure Anti-Torpedo to home in on and destroy the attacking torpedo.<ref>{{cite news |url=http://nationalinterest.org/blog/the-buzz/the-us-navys-master-plan-save-aircraft-carriers-lethal-17870 |title=The US Navy's Master Plan to Save Aircraft Carriers from Lethal Torpedo Attacks |last1=Osborn |first1=Kris |date=28 September 2016 |website=nationalinterest.org |publisher=The National Interest |access-date=13 October 2016}}</ref>