Editing Naval mine (section)

=== Contact mines ===
The earliest mines were usually of this type. They are still used today, as they are extremely low cost compared to any other anti-ship weapon and are effective, both as a psychological weapon and as a method to sink enemy ships. Contact mines need to be touched by the target before they detonate, limiting the damage to the direct effects of the explosion and usually affecting only the vessel that triggers them.

Early mines had mechanical mechanisms to detonate them, but these were superseded in the 1870s by the "Hertz horn" (or "chemical horn"), which was found to work reliably even after the mine had been in the sea for several years. The mine's upper half is studded with hollow lead protuberances, each containing a glass vial filled with [[sulfuric acid]]. When a ship's hull crushes the metal horn, it cracks the vial inside it, allowing the acid to run down a tube and into a [[lead–acid battery]] which until then contained no acid electrolyte. This energizes the battery, which detonates the explosive.<ref name="hartshorn.us">{{cite web |url=http://www.hartshorn.us/Navy/navy-mines-01.htm |title=Moored-contact |first=Derick S. |last=Hartshorn |publisher=Mineman Memories |date=2010-04-17 |access-date=2011-12-31 |archive-date=12 July 2012 |archive-url=https://web.archive.org/web/20120712040904/http://www.hartshorn.us/Navy/navy-mines-01.htm |url-status=dead }}</ref>

Earlier forms of the detonator employed a vial of sulfuric acid surrounded by a mixture of [[potassium perchlorate]] and sugar. When the vial was crushed, the acid ignited the perchlorate-sugar mix, and the resulting flame ignited the gunpowder charge.<ref>{{cite book |title=The Russian Rockefellers: the Saga of the Nobel Family and the Russian Oil Industry |last=Tolf |first=Robert W. |year=1982 |publisher=Hoover Institution Press |isbn=978-0-8179-6581-5 |page=[https://archive.org/details/russianrockefell00robe/page/18 18] |url-access=registration |url=https://archive.org/details/russianrockefell00robe/page/18 }}</ref>

During the initial period of World War I, the Royal Navy used contact mines in the English Channel and later in large areas of the North Sea to hinder patrols by German submarines. Later, the American antenna mine was widely used because submarines could be at any depth from the surface to the seabed. This type of mine had a copper wire attached to a buoy that floated above the explosive charge which was weighted to the seabed with a steel cable. If a submarine's steel hull touched the copper wire, the slight voltage change caused by contact between two dissimilar metals was amplified{{clarify|reason=amplified by what?|date=December 2015}} and detonated the explosives.<ref name="hartshorn.us"/>

==== Limpet mines ====
{{Main|Limpet mine}}
Limpet mines are a special form of contact mine that are manually attached to the target by magnets and remain in place. They are named because of the similarity to the [[limpet]], a [[mollusk]].

==== Moored contact mines ====
[[File:Mine (AWM 304925).jpg|thumb|A German contact mine [[Axis naval activity in Australian waters|laid in Australian waters]] during World War II]]

Generally, this type of mine is set to float just below the surface of the water or as deep as five meters. A steel cable connecting the mine to an anchor on the seabed prevents it from drifting away. The explosive and detonating mechanism is contained in a buoyant metal or plastic shell. The depth below the surface at which the mine floats can be set so that only deep draft vessels such as aircraft carriers, battleships or large cargo ships are at risk, saving the mine from being used on a less valuable target. In [[littoral]] waters it is important to ensure that the mine does not become visible when the sea level falls at low tide, so the cable length is adjusted to take account of tides. During WWII there were mines that could be moored in {{cvt|300|m|ft|adj=on}}-deep water.

Floating mines typically have a mass of around {{cvt|200|kg|lb}}, including {{cvt|80|kg|lb}} of explosives e.g. [[Trinitrotoluene|TNT]], [[Minol (explosive)|minol]] or [[amatol]].<ref>{{Cite web|url=http://victoriancollections.net.au/items/4f72bb6697f83e03086060cb|title=World War 2 Era Contact Sea Mine - Victorian Collections|website=victoriancollections.net.au|access-date=2019-10-26|archive-date=15 November 2023|archive-url=https://web.archive.org/web/20231115004947/https://victoriancollections.net.au/items/4f72bb6697f83e03086060cb|url-status=live}}</ref>

===== Moored contact mines with plummet =====
[[File:Legen_einer_Ankertaumine.svg|thumb|Sequence of laying a moored contact mine with a plummet]]
A special form of moored contact mines are those equipped with a plummet. When the mine is launched (1), the mine with the anchor floats first and the lead plummet sinks from it (2). In doing so, the plummet unwinds a wire, the deep line, which is used to set the depth of the mine below the water surface before it is launched (3). When the deep line has been unwound to a set length, the anchor is flooded and the mine is released from the anchor (4). The anchor begins to sink and the mooring cable unwinds until the plummet reaches the sea floor (5). Triggered by the decreasing tension on the deep line, the mooring cable is clamped. The anchor continues sinking down to the bottom of the sea, pulling the mine below the water surface to a depth equal to the length of the deep line (6). Thus, even without knowing the exact seafloor depth, an exact depth of the mine below the water surface can be set, limited only by the maximum length of the mooring cable.

==== Drifting contact mines ====
Drifting mines were occasionally used during World War I and World War II. However, they were more feared than effective. Sometimes floating mines break from their moorings and become drifting mines; modern mines are designed to deactivate in this event. After several years at sea, the deactivation mechanism might not function as intended and the mines may remain live. [[John Jellicoe, 1st Earl Jellicoe|Admiral Jellicoe]]'s British fleet did not pursue and destroy the outnumbered German High Seas Fleet when it turned away at the [[Battle of Jutland]] because he thought they were leading him into a trap: he believed it possible that the Germans were either leaving floating mines in their wake, or were drawing him towards submarines, although neither of these was the case.

After World War I the drifting contact mine was banned, but was occasionally used during World War II. The drifting mines were much harder to remove than tethered mines after the war, and they caused about the same damage to both sides.<ref>{{cite web|url=https://www.strausscenter.org/hormuz/mines.html|title=Mines – Hormuz|access-date=26 October 2015|archive-date=30 July 2019|archive-url=https://web.archive.org/web/20190730230012/https://www.strausscenter.org/hormuz/mines.html|url-status=dead}}</ref>

Churchill promoted "[[Operation Royal Marine]]" in 1940 and again in 1944 where floating mines were put into the [[Rhine]] in France to float down the river, becoming active after a time calculated to be long enough to reach German territory.