Magnetic pistol is the term for the device on a torpedo or naval mine that detects its target by its magnetic field, and triggers the fuse for detonation. A device to detonate a torpedo or mine on contact with a ship or submarine is known as a contact pistol.
A magnetic pistol on a mine will allow the mine to detonate in proximity to a target, rather than actual contact, allowing the mine to cover a larger effective area.
A magnetic pistol on a torpedo allows the torpedo to detonate underneath the ship, instead of upon impact with the side of the ship. As an explosion underneath a ship is contained between water and the ship, far more damage will result to the ship. The explosion will lift the ship out of the water and may break the keel of the ship, splitting it in two. Any hole created by the explosion will be on the bottom, causing more flooding.
A contact pistol on a torpedo will require the torpedo to strike the side of the ship. Any hole created by the explosion will be closer towards the waterline, reducing flooding. The explosion will also dissipate into the air, reducing the damage. If the torpedo is fired too deep, the torpedo will not hit the ship. If the ship has a round or sloping bottom, the torpedo may glance off the bottom and not detonate.
In World War I, German U-boats were using magnetic pistols by 1917, but it would not be until 1918 that Britain would find examples of these while salvaging U-boat SM UB-110. They proved problematic, often firing prematurely. [1]
During World War II, magnetic pistols often exploded prematurely or not at all. The reason was that magnetic lines are more horizontal close to the equator than towards the poles. For example, the US Mark 6 magnetic pistol was designed and tested only once at 41° latitude (60° geomagnetic latitude) at Narragansett Bay, but was primarily used in equatorial latitudes. [2] At the equator, the signal strength to the Mark 6 magnetic pistol was only about half that of where the Mark 6 was tested. Moreover, relative velocity (i.e. when a torpedo is fired from behind or in front of a ship) would additionally change the abruptness of the magnetic signal, resulting in the magnetic pistol being triggered prematurely or not at all.
Eventually, the US Mark 6 magnetic pistol was replaced by contact pistols (which, in the cases of the US Mark 14 submarine torpedo and Mark 15 ship torpedo, proved to be unreliable as well).
Some ships carry degaussing equipment to reduce the signal detected by a magnetic pistol.
During World War II, Japan employed a mechanical remote detonator in order to replicate the functionality of magnetic proximity fuzes used by torpedoes of other navies, such as Germany and the United States. Using a mechanical device circumvented the problems inherent with magnetometric influence sensing. This device, called the Type 1 Detonator T-Device (一式起爆装置T装置, Isshiki Kibaku Sōchi T-Sōchi), featured a tethered underwater kite (凧) which deployed from the head of the torpedo after launch, unreeling the tether under gradual tension. The device resembled a small winged torpedo. The kite would physically collide with the hull of a target surface vessel, whereupon it would sever the tether. A retraction mechanism in the torpedo would sense the sudden slack in the tether, detonating the torpedo warhead, which would by that point be positioned below the target vessel's keel. [3]
A naval mine is a self-contained explosive weapon placed in water to damage or destroy surface ships or submarines. Similar to anti-personnel and other land mines, and unlike purpose launched naval depth charges, they are deposited and left to wait until, depending on their fuzing, they are triggered by the approach of or contact with any vessel.
A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, such a device was called an automotive, automobile, locomotive, or fish torpedo; colloquially a fish. The term torpedo originally applied to a variety of devices, most of which would today be called mines. From about 1900, torpedo has been used strictly to designate a self-propelled underwater explosive device.
U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. The term is an anglicized version of the German word U-Boot, a shortening of Unterseeboot, though the German term refers to any submarine. Austro-Hungarian Navy submarines were also known as U-boats.
A depth charge is an anti-submarine warfare (ASW) weapon designed to destroy submarines by detonating in the water near the target and subjecting it to a destructive hydraulic shock. Most depth charges use high explosives with a fuze set to detonate the charge, typically at a specific depth from the surface. Depth charges can be dropped by ships, patrol aircraft and helicopters.
The Hedgehog was a forward-throwing anti-submarine weapon that was used primarily during the Second World War. The device, which was developed by the Royal Navy, fired up to 24 spigot mortars ahead of a ship when attacking a U-boat. It was deployed on convoy escort warships such as destroyers and corvettes to supplement the depth charges.
An anti-submarine weapon (ASW) is any one of a number of devices that are intended to act against a submarine and its crew, to destroy (sink) the vessel or reduce its capability as a weapon of war. In its simplest sense, an anti-submarine weapon is usually a projectile, missile or bomb that is optimized to destroy submarines.
Minesweeping is the practice of removing explosive naval mines, usually by a specially designed ship called a minesweeper using various measures to either capture or detonate the mines, but sometimes also with an aircraft made for that purpose. Minesweeping has been practiced since the advent of naval mining in 1855 during the Crimean War. The first minesweepers date to that war and consisted of British rowboats trailing grapnels to snag the mines.
A spar torpedo is a weapon consisting of a bomb placed at the end of a long pole, or spar, and attached to a boat. The weapon is used by running the end of the spar into the enemy ship. Spar torpedoes were often equipped with a barbed spear at the end, so it would stick to wooden hulls. A fuse could then be used to detonate it.
The G7e torpedo was the standard electric torpedo used by the German Kriegsmarine submarines in World War II. It came in 20 different versions, with the initial model G7e(TII) in service at the outbreak of the war. Due to several problems, leading to the German "Torpedokrise" which lasted until the end of 1941, the improved G7e(TIII) took over as the standard electric torpedo used by German U-boats for the rest of the war. G7e torpedoes measured 533.4 mm (21.00 in) in diameter and about 7.2 m (24 ft) in length. Depending on the type, the warhead contained a main charge of 250–280 kg (550–620 lb) of Schießwolle 36, a mixture of dipicrylamine and TNT. All were powered by 60–72 kW (80–100 hp) electric motors and lead-acid batteries which required onboard maintenance to maintain their functionality.
A limpet mine is a type of naval mine attached to a target by magnets. It is so named because of its superficial similarity to the shape of the limpet, a type of sea snail that clings tightly to rocks or other hard surfaces.
Anti-submarine warfare is a branch of underwater warfare that uses surface warships, aircraft, submarines, or other platforms, to find, track, and deter, damage, or destroy enemy submarines. Such operations are typically carried out to protect friendly shipping and coastal facilities from submarine attacks and to overcome blockades.
The North Sea Mine Barrage, also known as the Northern Barrage, was a large minefield laid easterly from the Orkney Islands to Norway by the United States Navy during World War I. The objective was to inhibit the movement of U-boats from bases in Germany to the Atlantic shipping lanes bringing supplies to the British Isles. Rear Admiral Lewis Clinton-Baker, commanding the Royal Navy minelaying force at the time, described the barrage as the "biggest mine planting stunt in the world's history." Larger fields with greater numbers of mines were laid during World War II.
The Mark 14 torpedo was the United States Navy's standard submarine-launched anti-ship torpedo of World War II. This weapon was plagued with many problems which crippled its performance early in the war. It was supplemented by the Mark 18 electric torpedo in the last two years of the war. From December 1941 to November 1943 the Mark 14 and the destroyer-launched Mark 15 torpedo had numerous technical problems that took almost two years to fix. After the fixes, the Mark 14 played a major role in the devastating blow U.S. Navy submarines dealt to the Japanese naval and merchant marine forces during the Pacific War.
Geophysical MASINT is a branch of Measurement and Signature Intelligence (MASINT) that involves phenomena transmitted through the earth and manmade structures including emitted or reflected sounds, pressure waves, vibrations, and magnetic field or ionosphere disturbances.
The paravane is a towed winged (hydrofoiled) underwater object—a water kite. Paravanes have been used in sport or commercial fishing, marine exploration and industry, sports and military applications. The wings of paravanes are sometimes in a fixed position, else positioned remotely or by actions of a human pilot. Pioneer parafoil developer Domina Jalbert considered water kites hardly different from air kites. However, paravanes generally orient themselves in respect to the water surface. They may have sensors that record or transmit data or are used entirely for generating a holding force like a sea anchor does. While a sea-anchor allows a vessel to drift more slowly downwind, the paravane travels sideways at several times the downwind speed. Paravanes are, like air kites, often symmetrical in one axis and travel in two directions, the change being effected by gybing, shunting, or flipping over.
In military munitions, a fuze is the part of the device that initiates its function. In some applications, such as torpedoes, a fuze may be identified by function as the exploder. The relative complexity of even the earliest fuze designs can be seen in cutaway diagrams.
A magnetic proximity fuse was patented by P.J. Eliomarkakis, although similar devices had been in service for nearly a decade. It is a type of proximity fuze that initiates a detonator in a piece of ordnance such as a land mine, naval mine, depth charge, or shell when the fuse's magnetic equilibrium is upset by a magnetic object such as a tank or a submarine.
Operationsbefehl Hartmut was the code word to begin German submarine operations during Operation Weserübung - Nazi Germany's invasion of Denmark and Norway. Occasionally these operations are termed Operation Hartmut. The orders involved submarine screening actions for the German invasion fleet and reconnaissance - particularly off Narvik and Trondheim. The orders also resulted in a number of attacks on Allied forces - particularly in or near the fjords of the Norwegian coast.
The modern era of defending American harbors with controlled mines or submarine mines began in the post-Civil War period, and was a major part of US harbor defenses from circa 1900 to 1947.
The Mark 6 exploder was a United States Navy torpedo exploder developed in the 1920s. It was the standard exploder of the Navy's Mark 14 torpedo and Mark 15 torpedo.