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117-851: 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 (assisted by the Royal 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

234-407: A harbour ; or defensively, to create "safe" zones protecting friendly sea lanes, harbours, and naval assets. Mines allow the minelaying force commander to concentrate warships or defensive assets in mine-free areas giving the adversary three choices: undertake a resource-intensive and time-consuming minesweeping effort, accept the casualties of challenging the minefield, or use the unmined waters where

351-595: A blast upon tipping. Several mine-laying ships were destroyed when their cargo exploded. Beginning around the start of the 20th century, submarine mines played a major role in the defense of U.S. harbours against enemy attacks as part of the Endicott and Taft Programs . The mines employed were controlled mines, anchored to the bottoms of the harbours, and detonated under control from large mine casemates onshore. During World War I , mines were used extensively to defend coasts, coastal shipping, ports and naval bases around

468-484: A buoyancy chamber and 300 lb (140 kg) of TNT . Each mine was constructed of two steel hemispheres welded together. A Toxyl bursting charge was cast into the lower hemisphere. Toxyl was a mixture of 60% trinitro xylene (TNX) with 40% TNT used because the United States Army controlled United States TNT production and would not release sufficient quantities for the naval mine barrage. For transport,

585-419: A circuit with an insulated copper plate on the mine surface to actuate a detonating relay within the mine. The relay armature was initially set to complete the detonating circuit at 25 to 40 millivolts . The Bureau of Ordnance subsequently increased sensitivity to 10 to 25 millivolts, but this was later readjusted on the basis of field experience. Each mine had five separate spring-loaded safety switches in

702-552: A destroyer patrol to track down mines that had broken free of their moorings and gone adrift. Losses of civilian ships to North Sea mines continued; the origin of the mine in these cases was often difficult to determine. In 1919, twenty crewmen drowned when the Swedish steamship Hollander sank, minutes after striking a mine in October; and the steamer Kerwood struck a mine and sank on 1 December. Naval mine A naval mine

819-401: A harbour by hand. They can be inexpensive: some variants can cost as little as US $ 2,000, though more sophisticated mines can cost millions of dollars, be equipped with several kinds of sensors, and deliver a warhead by rocket or torpedo . Their flexibility and cost-effectiveness make mines attractive to the less powerful belligerent in asymmetric warfare . The cost of producing and laying

936-400: A major cause of premature detonations during a comparative field test minelaying excursion on 12 August. Subsequent investigations revealed copper sulfate deposits caused by antenna corrosion created a weak battery, increasing the probability of relay activation by shock wave accelerations when nearby mines detonated. Premature detonations dropped to four to six percent when sensitivity

1053-915: A mine is usually between 0.5% and 10% of the cost of removing it, and it can take up to 200 times as long to clear a minefield as to lay it. Parts of some World War II naval minefields still exist because they are too extensive and expensive to clear. Some 1940s-era mines may remain dangerous for many years. Mines have been employed as offensive or defensive weapons in rivers, lakes, estuaries, seas, and oceans, but they can also be used as tools of psychological warfare . Offensive mines are placed in enemy waters, outside harbours, and across important shipping routes to sink both merchant and military vessels. Defensive minefields safeguard key stretches of coast from enemy ships and submarines, forcing them into more easily defended areas, or keeping them away from sensitive ones. Shipowners are reluctant to send their ships through known minefields. Port authorities may attempt to clear

1170-524: A mined area, but those without effective minesweeping equipment may cease using the area. Transit of a mined area will be attempted only when strategic interests outweigh potential losses. The decision-makers' perception of the minefield is a critical factor. Minefields designed for psychological effect are usually placed on trade routes to stop ships from reaching an enemy nation. They are often spread thinly, to create an impression of minefields existing across large areas. A single mine inserted strategically on

1287-450: A point in the fluid is thought of as an infinitesimally small cube, then it follows from the principles of equilibrium that the pressure on every side of this unit of fluid must be equal. If this were not the case, the fluid would move in the direction of the resulting force. Thus, the pressure on a fluid at rest is isotropic ; i.e., it acts with equal magnitude in all directions. This characteristic allows fluids to transmit force through

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1404-442: 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. Hydrostatic It encompasses the study of the conditions under which fluids are at rest in stable equilibrium as opposed to fluid dynamics , the study of fluids in motion. Hydrostatics

1521-637: A safe distance. The submarine H. L. Hunley used one to sink USS  Housatonic on 17 February 1864. A Harvey torpedo was a type of floating mine towed alongside a ship and was briefly in service in the Royal Navy in the 1870s. Other "torpedoes" were attached to ships or propelled themselves. One such weapon called the Whitehead torpedo after its inventor, caused the word "torpedo" to apply to self-propelled underwater missiles as well as to static devices. These mobile devices were also known as "fish torpedoes". The American Civil War of 1861–1865 also saw

1638-577: A shipping route can stop maritime movements for days while the entire area is swept. A mine's capability to sink ships makes it a credible threat, but minefields work more on the mind than on ships. International law , specifically the Eighth Hague Convention of 1907 , requires nations to declare when they mine an area, to make it easier for civil shipping to avoid the mines. The warnings do not have to be specific; for example, during World War II, Britain declared simply that it had mined

1755-722: A sloop mined by the Peruvians. A similar fate occurred with the gunboat schooner Covadonga in front of the port of Chancay , on 13 September 1880, which having captured and checked a beautiful boat, it exploded when hoisting it on its side. During the Battle of Tamsui (1884), in the Keelung Campaign of the Sino-French War , Chinese forces in Taiwan under Liu Mingchuan took measures to reinforce Tamsui against

1872-428: A small vertical pipe in the center of the cup that leads to the bottom. The height of this pipe is the same as the line carved into the interior of the cup. The cup may be filled to the line without any fluid passing into the pipe in the center of the cup. However, when the amount of fluid exceeds this fill line, fluid will overflow into the pipe in the center of the cup. Due to the drag that molecules exert on one another,

1989-407: A surfaced U-boat triggering a mine and a 33 per cent chance for a submerged U-boat. On the basis of the number of effective mines observed while sweeping the barrage, the actual odds were assessed at being closer to 20 per cent for a surfaced U-boat and 10 per cent for a submerged one. As the final mines were laid only a matter of days before the end of the war, it is impossible to assess the success of

2106-625: A time when the Chilean squadron was blockading the Peruvian ports, formed a brigade of torpedo boats under the command of the frigate captain Leopoldo Sánchez Calderón and the Peruvian engineer Manuel Cuadros , who perfected the naval torpedo or mine system to be electrically activated when the cargo weight was lifted. This is how, on 3 July 1880, in front of the port of Callao , the gunned transport Loa flies when capturing

2223-509: A variable number of ships to pass unharmed before detonating. This made them a great deal harder to sweep. Mining campaigns could have devastating consequences. The U.S. effort against Japan, for instance, closed major ports, such as Hiroshima , for days, and by the end of the Pacific War had cut the amount of freight passing through Kobe – Yokohama by 90%. When the war ended, more than 25,000 U.S.-laid mines were still in place, and

2340-432: Is a fundamental principle of fluid mechanics that states that any pressure applied to the surface of a fluid is transmitted uniformly throughout the fluid in all directions, in such a way that initial variations in pressure are not changed. Due to the fundamental nature of fluids, a fluid cannot remain at rest under the presence of a shear stress . However, fluids can exert pressure normal to any contacting surface. If

2457-445: Is a self-contained explosive device 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. Naval mines can be used offensively, to hamper enemy shipping movements or lock vessels into

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2574-487: Is a subcategory of fluid statics , which is the study of all fluids, both compressible or incompressible, at rest. Hydrostatics is fundamental to hydraulics , the engineering of equipment for storing, transporting and using fluids. It is also relevant to geophysics and astrophysics (for example, in understanding plate tectonics and the anomalies of the Earth's gravitational field ), to meteorology , to medicine (in

2691-1075: Is applied to the Navier–Stokes equations for viscous fluids or Euler equations (fluid dynamics) for ideal inviscid fluid, the gradient of pressure becomes a function of body forces only. The Navier-Stokes momentum equations are: ρ D u D t = − ∇ [ p − ζ ( ∇ ⋅ u ) ] + ∇ ⋅ { μ [ ∇ u + ( ∇ u ) T − 2 3 ( ∇ ⋅ u ) I ] } + ρ g . {\displaystyle \rho {\frac {\mathrm {D} \mathbf {u} }{\mathrm {D} t}}=-\nabla [p-\zeta (\nabla \cdot \mathbf {u} )]+\nabla \cdot \left\{\mu \left[\nabla \mathbf {u} +(\nabla \mathbf {u} )^{\mathrm {T} }-{\tfrac {2}{3}}(\nabla \cdot \mathbf {u} )\mathbf {I} \right]\right\}+\rho \mathbf {g} .} By setting

2808-418: Is conservative, so one can write the body force density as: ρ g = ∇ ( − ρ g z ) {\displaystyle \rho \mathbf {g} =\nabla (-\rho gz)} Then the body force density has a simple scalar potential: ϕ ( z ) = − ρ g z {\displaystyle \phi (z)=-\rho gz} And

2925-688: Is just one example of a ship that was struck by a magnetic mine during this time. On 21 November 1939, a mine broke her keel, which damaged her engine and boiler rooms, as well as injuring 46 men, one later died from his injuries. She was towed to Rosyth for repairs. Incidents like this resulted in many of the boats that sailed to Dunkirk being degaussed in a marathon four-day effort by degaussing stations. The Allies and Germany deployed acoustic mines in World War II, against which even wooden- hulled ships (in particular minesweepers ) remained vulnerable. Japan developed sonic generators to sweep these;

3042-417: Is known as the barometric formula , and may be derived from assuming the pressure is hydrostatic . If there are multiple types of molecules in the gas, the partial pressure of each type will be given by this equation. Under most conditions, the distribution of each species of gas is independent of the other species. Any body of arbitrary shape which is immersed, partly or fully, in a fluid will experience

3159-435: Is often called Stevin's law. One could arrive to the above formula also by considering the first particular case of the equation for a conservative body force field: in fact the body force field of uniform intensity and direction: ρ g ( x , y , z ) = − ρ g k → {\displaystyle \rho \mathbf {g} (x,y,z)=-\rho g{\vec {k}}}

3276-556: Is slightly north of Orkney, alignment of minefields within the central area A was skewed east-northeasterly from Orkney. Where possible, longitude was determined from a calibrated taut-wire anchored near a landmark and unreeled from a 140-mile (230 km) spool of piano wire aboard one of the cruisers acting as the minelaying formation guide. Latitude was checked from the elevation of the sun when atmospheric conditions permitted. The mine barrage required multiple missions, called "excursions", laying parallel rows of mines partway across

3393-416: Is the general form of Stevin's law: the pressure gradient equals the body force force density field. Let us now consider two particular cases of this law. In case of a conservative body force with scalar potential ϕ {\displaystyle \phi } : ρ g = − ∇ ϕ {\displaystyle \rho \mathbf {g} =-\nabla \phi }

3510-460: Is the practice of the removal of 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. There are also mines that release a homing torpedo rather than explode themselves. Mines can be laid in many ways: by purpose-built minelayers , refitted ships, submarines, or aircraft —and even by dropping them into

3627-510: Is transmitted by fluids was formulated by the French mathematician and philosopher Blaise Pascal in 1647. The "fair cup" or Pythagorean cup , which dates from about the 6th century BC, is a hydraulic technology whose invention is credited to the Greek mathematician and geometer Pythagoras. It was used as a learning tool. The cup consists of a line carved into the interior of the cup, and

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3744-540: The Petropavlovsk struck them near Port Arthur , sending the holed vessel to the bottom and killing the fleet commander, Admiral Stepan Makarov , and most of his crew in the process. The toll inflicted by mines was not confined to the Russians, however. The Japanese Navy lost two battleships, four cruisers, two destroyers and a torpedo-boat to offensively laid mines during the war. Most famously, on 15 May 1904,

3861-651: The Grand Fleet —was skeptical about the value of the operation and did not feel it justified the large logistical and manufacturing commitment required. A minefield across the North Sea would require mining water 900 feet (270 m) deep, while no previous minefield had been established in waters more than 300 ft (91 m) deep. A minefield across the North Sea had been estimated to require 400,000 conventional anchored mines. An "antenna" mine developed in July 1917

3978-535: The Gulf of Finland during the Crimean War of 1853–1856. The mining of Vulcan led to the world's first minesweeping operation. During the next 72 hours, 33 mines were swept. The Jacobi mine was designed by German-born, Russian engineer Jacobi, in 1853. The mine was tied to the sea bottom by an anchor. A cable connected it to a galvanic cell which powered it from the shore, the power of its explosive charge

4095-596: The Korean War , mines laid by North Korean forces caused 70% of the casualties suffered by U.S. naval vessels and caused 4 sinkings. During the Iran–Iraq War from 1980 to 1988, the belligerents mined several areas of the Persian Gulf and nearby waters. On 24 July 1987, the supertanker SS Bridgeton was mined by Iran near Farsi Island. On 14 April 1988, USS  Samuel B. Roberts struck an Iranian mine in

4212-453: The absolute pressure compared to vacuum is where Δ z {\displaystyle \Delta z} is the total height of the liquid column above the test area to the surface, and p 0 is the atmospheric pressure , i.e., the pressure calculated from the remaining integral over the air column from the liquid surface to infinity. This can easily be visualized using a pressure prism . Hydrostatic pressure has been used in

4329-408: The flow velocity u = 0 {\displaystyle \mathbf {u} =\mathbf {0} } , they become simply: 0 = − ∇ p + ρ g {\displaystyle \mathbf {0} =-\nabla p+\rho \mathbf {g} } or: ∇ p = ρ g {\displaystyle \nabla p=\rho \mathbf {g} } This

4446-475: The 70,177 mines laid to form the North Sea mine barrage. The WWI Mine Memorial on Boston Common, Massachusetts, United States The mine barrage consisted of 18 rows of mines laid in an east–west direction. Ten rows of mines were laid at a depth of 80 ft (24 m) to be detonated by ships traveling on the surface. Submerged submarines were targeted by four rows of mines at 160 ft (49 m), and another four rows at 240 ft (73 m). Since Utsira

4563-460: The Admiralty. Most damaged ships were repaired, but SC-38 was declared a total loss. Three more men of the minesweeping force were killed in individual accidents involving sweeping gear before Strauss declared the barrage cleared on 30 September 1919. The minesweepers found only about 25 to 30 percent of the mines laid a year earlier; but it was assumed the others had either broken free, sunk to

4680-475: The British. In 1855, 301 more Jacobi mines were laid around Krostadt and Lisy Nos . British ships did not dare to approach them. In the 19th century, mines were called torpedoes , a name probably conferred by Robert Fulton after the torpedo fish , which gives powerful electric shocks . A spar torpedo was a mine attached to a long pole and detonated when the ship carrying it rammed another one and withdrew

4797-554: The English Channel, North Sea and French coast. Naval mines were first invented by Chinese innovators of Imperial China and were described in thorough detail by the early Ming dynasty artillery officer Jiao Yu , in his 14th-century military treatise known as the Huolongjing . Chinese records tell of naval explosives in the 16th century, used to fight against Japanese pirates ( wokou ). This kind of naval mine

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4914-701: The French; they planted nine torpedo mines in the river and blocked the entrance. During the Boxer Rebellion , Imperial Chinese forces deployed a command-detonated mine field at the mouth of the Hai River before the Dagu forts , to prevent the western Allied forces from sending ships to attack. The next major use of mines was during the Russo-Japanese War of 1904–1905. Two mines blew up when

5031-461: The Mk 6 mine hydrostatic safety devices would minimize the risks of this procedure, but sweeping gear losses increased after unreliability of these safety devices was recognized. Countermining sequences initiated by destruction of a swept mine causing detonation of an undetected mine closer to one of the minesweepers were another source of damage. Some of this countermining was attributed to acceleration of

5148-555: The Navy Franklin D. Roosevelt appealed directly to President Woodrow Wilson to overcome opposition to the project from Vice Admiral William Sims , who commanded all United States naval forces in Europe. The U.S. Navy tendered an order for the Mk 6 mines in October 1917 with 80,000,000  ft (15,000  mi ; 24,000  km ) of steel wire rope required to moor the mines to the seabed. Project spending of $ 40 million

5265-666: The Navy proved unable to sweep them all, limiting efforts to critical areas. After sweeping for almost a year, in May 1946, the Navy abandoned the effort with 13,000 mines still unswept. Over the next thirty years, more than 500 minesweepers (of a variety of types) were damaged or sunk clearing them. The U.S. began adding delay counters to their magnetic mines in June 1945. Since World War II , mines have damaged 14 United States Navy ships, whereas air and missile attacks have damaged four. During

5382-404: The North Sea between Norway and Orkney. Mine Squadron One made thirteen two-day minelaying excursions laying parallel rows of mines while steaming in columns 500 yards (460 m) apart, with the last ship in each column dropping mines at 100 yd (91 m) intervals. As a minelayer exhausted its supply of mines, another minelayer in that column would drop back to the last position to continue

5499-492: The North Sea, the British East Coast, Straits of Dover, and Heligoland Bight is estimated at 190,000 and the total number during the whole of WWI was 235,000 sea mines. Clearing the barrage after the war took 82 ships and five months, working around the clock. It was also during World War I, that the British hospital ship , HMHS  Britannic , became the largest vessel ever sunk by a naval mine . The Britannic

5616-710: 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 idea of a mine barrage across the North Sea was first proposed in the summer of 1916 by Admiral Reginald Bacon and was agreed at the Allied Naval Conference on 5 September 1917. The Royal Navy—and in particular Admiral Beatty as Commander in Chief of

5733-721: The Russian minelayer Amur planted a 50-mine minefield off Port Arthur and succeeded in sinking the Japanese battleships Hatsuse and Yashima . Following the end of the Russo-Japanese War, several nations attempted to have mines banned as weapons of war at the Hague Peace Conference (1907) . Many early mines were fragile and dangerous to handle, as they contained glass containers filled with nitroglycerin or mechanical devices that activated

5850-478: The Stevin equation becomes: ∇ p = − ∇ ϕ {\displaystyle \nabla p=-\nabla \phi } That can be integrated to give: Δ p = − Δ ϕ {\displaystyle \Delta p=-\Delta \phi } So in this case the pressure difference is the opposite of the difference of the scalar potential associated to

5967-467: The U.S. coast. Initially, contact mines (requiring a ship to physically strike a mine to detonate it) were employed, usually tethered at the end of a cable just below the surface of the water. Contact mines usually blew a hole in ships' hulls. By the beginning of World War II, most nations had developed mines that could be dropped from aircraft, some of which floated on the surface, making it possible to lay them in enemy harbours. The use of dredging and nets

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6084-411: The action of a net force in the opposite direction of the local pressure gradient. If this pressure gradient arises from gravity, the net force is in the vertical direction opposite that of the gravitational force. This vertical force is termed buoyancy or buoyant force and is equal in magnitude, but opposite in direction, to the weight of the displaced fluid. Mathematically, where ρ is the density of

6201-599: The antenna fuze relay armature or seawater leaking into damaged mines rather than sympathetic detonation of explosives. The minesweepers were sometimes able to continue sweeping, but the trawlers were less durable. Seven men drowned when the Richard Bulkeley was sunk by a mine detonation on 12 July. Strauss discontinued use of the trawlers for minesweeping, but retained six for transporting replacement sweeping gear to minesweepers when wires were destroyed by exploding mines. The remaining 13 trawlers were returned to

6318-478: The arteriolar end of the capillary. This pressure forces plasma and nutrients out of the capillaries and into surrounding tissues. Fluid and the cellular wastes in the tissues enter the capillaries at the venule end, where the hydrostatic pressure is less than the osmotic pressure in the vessel. Statistical mechanics shows that, for a pure ideal gas of constant temperature in a gravitational field, T , its pressure, p will vary with height, h , as where This

6435-1161: The body force. In the other particular case of a body force of constant direction along z: g = − g ( x , y , z ) k → {\displaystyle \mathbf {g} =-g(x,y,z){\vec {k}}} the generalised Stevin's law above becomes: ∂ p ∂ z = − ρ ( x , y , z ) g ( x , y , z ) {\displaystyle {\frac {\partial p}{\partial z}}=-\rho (x,y,z)g(x,y,z)} That can be integrated to give another (less-) generalised Stevin's law: p ( x , y , z ) − p 0 ( x , y ) = − ∫ 0 z ρ ( x , y , z ′ ) g ( x , y , z ′ ) d z ′ {\displaystyle p(x,y,z)-p_{0}(x,y)=-\int _{0}^{z}\rho (x,y,z')g(x,y,z')dz'} where: For water and other liquids, this integral can be simplified significantly for many practical applications, based on

6552-489: The bottom, or been destroyed by premature explosions. Strauss was recognized as a Knight Commander of St Michael and St George for his efforts; but doubts about effectiveness of the minesweeping effort persisted into the 21st century. As 1919 drew to a close, the onset of winter forced the suspension of sweeping for moored buoyant mines, but the Royal Navy resumed minesweeping operations the following spring, continuing to clear sunken mines from fishing grounds, and maintaining

6669-407: The builders of boats, cisterns , aqueducts and fountains . Archimedes is credited with the discovery of Archimedes' Principle , which relates the buoyancy force on an object that is submerged in a fluid to the weight of fluid displaced by the object. The Roman engineer Vitruvius warned readers about lead pipes bursting under hydrostatic pressure. The concept of pressure and the way it

6786-509: The central Persian Gulf shipping lane , wounding 10 sailors. In the summer of 1984, magnetic sea mines damaged at least 19 ships in the Red Sea . The U.S. concluded Libya was probably responsible for the minelaying. In response the U.S., Britain, France, and three other nations launched Operation Intense Look , a minesweeping operation in the Red Sea involving more than 46 ships. On

6903-684: The coasts of these countries. London P&I Club issued a warning to freight ships in the area, advising them to "maintain lookouts for mines and pay careful attention to local navigation warnings". Ukrainian forces have mined "from the Sea of Azov to the Black Sea which banks the critical city of Odesa." Naval mines may be classified into three major groups; contact, remote and influence 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

7020-433: The context of blood pressure ), and many other fields. Hydrostatics offers physical explanations for many phenomena of everyday life, such as why atmospheric pressure changes with altitude , why wood and oil float on water, and why the surface of still water is always level according to the curvature of the earth . Some principles of hydrostatics have been known in an empirical and intuitive sense since antiquity, by

7137-413: The cup will be emptied. Heron's fountain is a device invented by Heron of Alexandria that consists of a jet of fluid being fed by a reservoir of fluid. The fountain is constructed in such a way that the height of the jet exceeds the height of the fluid in the reservoir, apparently in violation of principles of hydrostatic pressure. The device consisted of an opening and two containers arranged one above

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7254-647: The decade following 1868, Major Henry Larcom Abbot carried out a lengthy set of experiments to design and test moored mines that could be exploded on contact or be detonated at will as enemy shipping passed near them. This initial development of mines in the United States took place under the purview of the U.S. Army Corps of Engineers , which trained officers and men in their use at the Engineer School of Application at Willets Point, New York (later named Fort Totten ). In 1901 underwater minefields became

7371-431: The detonating circuit held open by salt pellets which took about 20 minutes to dissolve in sea water after the mine was dropped overboard from the minelayer. Battery life for the detonating circuit was estimated at greater than two years. The mine barrage was within a belt 230 mi (200 nmi; 370 km) long and 15 mi (13 nmi; 24 km) to 35 mi (30 nmi; 56 km) wide divided into area B off

7488-589: The disadvantage of "sweeping" only a small strip. A better solution was found in the "Double-L Sweep" using electrical cables dragged behind ships that passed large pulses of current through the seawater. This created a large magnetic field and swept the entire area between the two ships. The older methods continued to be used in smaller areas. The Suez Canal continued to be swept by aircraft, for instance. While these methods were useful for clearing mines from local ports, they were of little or no use for enemy-controlled areas. These were typically visited by warships, and

7605-651: The east coast of Orkney, area C near the Norwegian coast between Utsira and Bergen , and the longest central area A connecting the two coastal areas between 0° 50′ West and 3° 10′ East. The Royal Navy laid mines in areas B and C while the United States Navy mined area A. The Royal Navy left a 10 mi (8.7 nmi; 16 km) channel open for navigation adjacent to Orkney. Because of neutrality regulations no mines were laid within Norwegian territorial waters. The United States North Sea Mine Force

7722-531: The explosion. Ships that had successfully run the gantlet of the Atlantic crossing were sometimes destroyed entering freshly cleared British harbours. More shipping was being lost than could be replaced, and Churchill ordered the intact recovery of one of these new mines to be of the highest priority. The British experienced a stroke of luck in November 1939, when a German mine was dropped from an aircraft onto

7839-572: The failed "floating petard". Weapons of this type were apparently tried by the English at the Siege of La Rochelle in 1627. American David Bushnell developed the first American naval mine, for use against the British in the American War of Independence . It was a watertight keg filled with gunpowder that was floated toward the enemy, detonated by a sparking mechanism if it struck a ship. It

7956-999: The first routine sweep of the United States minesweepers on 29 April 1919. After the first sweep took two days to clear 221 mines, Strauss requested more ships in the hope of clearing the mine barrage that summer. Twenty Admiralty trawlers with American crews, 16 more Lapwing class minesweepers, and another repair ship Panther were assigned to his command. Panther was given responsibility for tending trawlers William Ashton , Thomas Blackhorne , Thomas Buckley , Richard Bulkeley , George Burton , Pat Caharty , William Caldwell , George Clarke , John Clay , George Cochrane , John Collins , William Darnold , Sam Duffy , John Dunkin , John Fitzgerald , John Graham , Thomas Graham , Thomas Henrix , William Johnson , Thomas Laundry , and submarine chasers SC-37 , 38 , 40 , 44 , 45 , 46 , 47 , 48 , 95 , 110 , 164 , 178 , 181 , 182 , 206 , 207 , 208 , 254 , 256 , 259 , 272 , 329 , 354 and 356 . Blackhawk provided tender services for

8073-507: The first to be so fitted were the carrier HMS  Ark Royal and the liners RMS  Queen Mary and RMS  Queen Elizabeth . It was a photo of one of these liners in New York harbour, showing the degaussing coil, which revealed to German Naval Intelligence the fact that the British were using degaussing methods to combat their magnetic mines. This was felt to be impractical for smaller warships and merchant vessels, mainly because

8190-547: The first trial sweep in December. Sweeping was accomplished by suspending a serrated wire between two ships on a parallel course. While held underwater by planing devices called "kites", the wire would foul the cables suspending the buoyant mines above their anchors. If the serrated wire parted the mine mooring cable, the mine would bob to the surface to be destroyed by gunfire. The smacks swept and destroyed six mines before winter weather halted further work at sea. The winter

8307-403: The fluid, g is the acceleration due to gravity, and V is the volume of fluid directly above the curved surface. In the case of a ship , for instance, its weight is balanced by pressure forces from the surrounding water, allowing it to float. If more cargo is loaded onto the ship, it would sink more into the water – displacing more water and thus receive a higher buoyant force to balance

8424-421: The following two assumptions. Since many liquids can be considered incompressible , a reasonable good estimation can be made from assuming a constant density throughout the liquid. The same assumption cannot be made within a gaseous environment. Also, since the height Δ z {\displaystyle \Delta z} of the fluid column between z and z 0 is often reasonably small compared to

8541-477: The force were several fireships , carrying 40 barrels of gunpowder and rigged to explode by a clockwork mechanism. In 1812, Russian engineer Pavel Shilling exploded an underwater mine using an electrical circuit . In 1842 Samuel Colt used an electric detonator to destroy a moving vessel to demonstrate an underwater mine of his own design to the United States Navy and President John Tyler . However, opposition from former president John Quincy Adams , scuttled

8658-543: The fuze of the naval mine. Although this is the rotating steel wheel's first use in naval mines, Jiao Yu described their use for land mines in the 14th century. The first plan for a sea mine in the West was by Ralph Rabbards, who presented his design to Queen Elizabeth I of England in 1574. The Dutch inventor Cornelius Drebbel was employed in the Office of Ordnance by King Charles I of England to make weapons, including

8775-439: The fuzes were conventional horns in the buoyant upper hemisphere of the mine. Each horn contained a glass ampoule of electrolyte which would connect an open circuit if an ampoule was broken by bending the soft metal horn. The novel fifth fuze was a copper wire antenna with a float to extend it above the mine. A ship's steel hull touching the copper antenna would form a battery , and seawater acted as an electrolyte completing

8892-475: The gear was not ready by war's end. The primary method Japan used was small air-delivered bombs. This was profligate and ineffectual; used against acoustic mines at Penang , 200 bombs were needed to detonate just 13 mines. The Germans developed a pressure-activated mine and planned to deploy it as well, but they saved it for later use when it became clear the British had defeated the magnetic system. The U.S. also deployed these, adding "counters" which would allow

9009-748: The globe. The Germans laid mines in shipping lanes to sink merchant and naval vessels serving Britain. The Allies targeted the German U-boats in the Strait of Dover and the Hebrides. In an attempt to seal up the northern exits of the North Sea, the Allies developed the North Sea Mine Barrage . During a period of five months from June 1918, almost 70,000 mines were laid spanning the North Sea's northern exits. The total number of mines laid in

9126-463: The greatest concentration of enemy firepower will be encountered. Although international law requires signatory nations to declare mined areas, precise locations remain secret, and non-complying parties might not disclose minelaying. While mines threaten only those who choose to traverse waters that may be mined, the possibility of activating a mine is a powerful disincentive to shipping. In the absence of effective measures to limit each mine's lifespan,

9243-566: The hazard to shipping can remain long after the war in which the mines were laid is over. Unless detonated by a parallel time fuze at the end of their useful life, naval mines need to be found and dismantled after the end of hostilities; an often prolonged, costly, and hazardous task. Modern mines containing high explosives detonated by complex electronic fuze mechanisms are much more effective than early gunpowder mines requiring physical ignition. Mines may be placed by aircraft, ships, submarines, or individual swimmers and boatmen. Minesweeping

9360-504: The insistence of Admiral Fyodor Litke . The Nobel mines were bought from Swedish industrialist Immanuel Nobel who had entered into collusion with the Russian head of navy Alexander Sergeyevich Menshikov . Despite their high cost (100 Russian rubles ) the Nobel mines proved to be faulty, exploding while being laid, failing to explode or detaching from their wires, and drifting uncontrollably, at least 70 of them were subsequently disarmed by

9477-465: The larger ships operating as six divisions. Common difficulties with the sweeping procedure involved mine cables becoming entangled in the kites attached to the sweeping wires. Sweeping gear was often lost if the mine detonated and cut the sweeping cables. Approximately one-third of the ships were damaged by exploding mines. Two men were killed in separate incidents while attempting to haul mines aboard to clear fouled sweeping kites. It had been assumed

9594-413: The length of pipes or tubes; i.e., a force applied to a fluid in a pipe is transmitted, via the fluid, to the other end of the pipe. This principle was first formulated, in a slightly extended form, by Blaise Pascal, and is now called Pascal's law . In a fluid at rest, all frictional and inertial stresses vanish and the state of stress of the system is called hydrostatic . When this condition of V = 0

9711-404: The majority of the fleet then underwent a massive degaussing process, where their hulls had a slight "south" bias induced into them which offset the concentration-effect almost to zero. Initially, major warships and large troopships had a copper degaussing coil fitted around the perimeter of the hull, energized by the ship's electrical system whenever in suspected magnetic-mined waters. Some of

9828-458: The mine and rushed it to the labs at HMS Vernon, where scientists discovered that the mine had a magnetic arming mechanism. A large ferrous object passing through the Earth's magnetic field will concentrate the field through it, due to its magnetic permeability; the mine's detector was designed to trigger as a ship passed over when the Earth's magnetic field was concentrated in the ship and away from

9945-489: The mine mooring cable attachment points to buffer wave loading during storms. Premature detonations increased to 14 percent for the fourth minelaying excursion because some mines had been assembled with the more sensitive antenna fuze relay settings made by the Bureau of Ordnance. The fifth minelaying excursion was halted when 19 percent of the mines detonated prematurely. San Francisco identified relay armature sensitivity as

10062-440: The mine rested atop a box-shaped steel anchor approximately 30 inches (76 cm) square. The anchor box had wheels allowing the mine assembly to be moved along a system of rails aboard the minelayer. The mine was connected to its 800-pound (360 kg) anchor box by a wire rope mooring cable stored on a reel. The depth of the mine below the water surface was controlled by allowing the steel mooring cable to unwind from its reel as

10179-417: The mine was dropped from the minelayer until a sensor suspended beneath the anchor reached the bottom. The sensor locked the cable reel so the falling anchor would pull the buoyant mine below the surface; and the float extended the antenna above the mine. Each mine had two hydrostatic safety features intended to render the mine safe if it detached from its mooring cable and floated to the surface. The first

10296-502: The mine. The mine detected this loss of the magnetic field which caused it to detonate. The mechanism had an adjustable sensitivity, calibrated in milligauss . From this data, known methods were used to clear these mines. Early methods included the use of large electromagnets dragged behind ships or below low-flying aircraft (a number of older bombers like the Vickers Wellington were used for this). Both of these methods had

10413-417: The minelaying sequence. The minelayers were preceded by Royal Navy destroyers sweeping for enemy mines and submarines. A covering force of battleships with Royal Navy cruiser squadrons maneuvered nearby to defend the minelaying formation, but no German surface warships attempted engagement. Buoys were dropped temporarily marking the end point of a mining excursion to avoid leaving an unmined gap when

10530-440: The mines and some Admiralty personnel assumed the field might be responsible for five more U-boats which disappeared without explanation. United States participation in the minesweeping effort was overseen by Rear Admiral Strauss aboard the repair ship Black Hawk , from which he had commanded the minelaying operation. Tugs Patapsco and Patuxent towed Admiralty wooden sailing smacks Red Rose and Red Fern out to conduct

10647-482: The mines; and mine spacing was increased from 250 ft (76 m) on the first minelaying excursion to 300 ft (91 m) on subsequent excursions to minimize leakage caused by detonation of nearby mines. About one percent of the mines deployed during the first excursion broke free of their mooring cables and washed ashore in Norway within a month. Mines used for the last eleven excursions had springs installed at

10764-496: The mudflats off Shoeburyness during low tide. Additionally, the land belonged to the army and a base with men and workshops was at hand. Experts were dispatched from HMS  Vernon to investigate the mine. The Royal Navy knew that mines could use magnetic sensors, Britain having developed magnetic mines in World War I, so everyone removed all metal, including their buttons, and made tools of non-magnetic brass . They disarmed

10881-441: The next excursion started. These buoys were subject to potential movement by storms or enemy action. Three to five percent of the new mines dropped into the North Sea detonated as soon as the salt pellets dissolved; and hydrophones detected premature detonations continuing for a week after minelaying. These premature detonations were initially attributed to activation of the horn fuze detonation circuits by seawater leaking into

10998-736: The orders of the Reagan administration , the CIA mined Nicaragua 's Sandino port in 1984 in support of the Contras . A Soviet tanker was among the ships damaged by these mines. In 1986, in the case of Nicaragua v. United States , the International Court of Justice ruled that this mining was a violation of international law. During the Gulf War , Iraqi naval mines severely damaged USS  Princeton and USS  Tripoli . When

11115-403: The other. The intermediate pot, which was sealed, was filled with fluid, and several cannula (a small tube for transferring fluid between vessels) connecting the various vessels. Trapped air inside the vessels induces a jet of water out of a nozzle, emptying all water from the intermediate reservoir. Pascal made contributions to developments in both hydrostatics and hydrodynamics. Pascal's Law

11232-600: The plan. Some contend the minefield was a major cause of the declining morale of the Imperial German Navy through the final months of the war, while others suggest Germany easily swept safe channels through the large, unguarded minefield. The official statistics on lost German submarines compiled on 1 March 1919 credited the North Sea mine barrage with the certain destruction of four U-boats, presumed destruction of two more and possible destruction of another two. Eight more boats were known to have been damaged by

11349-422: The preservation of foods in a process called pascalization . In medicine, hydrostatic pressure in blood vessels is the pressure of the blood against the wall. It is the opposing force to oncotic pressure . In capillaries, hydrostatic pressure (also known as capillary blood pressure) is higher than the opposing “colloid osmotic pressure” in blood—a “constant” pressure primarily produced by circulating albumin—at

11466-455: The pressure difference follows another time the Stevin's law: Δ p = − Δ ϕ = ρ g Δ z {\displaystyle \Delta p=-\Delta \phi =\rho g\Delta z} The reference point should lie at or below the surface of the liquid. Otherwise, one has to split the integral into two (or more) terms with the constant ρ liquid and ρ ( z ′) above . For example,

11583-693: The project as "not fair and honest warfare". In 1854, during the unsuccessful attempt of the Anglo-French (101 warships) fleet to seize the Kronstadt fortress, British steamships HMS  Merlin (9 June 1855, the first successful mining in Western history), HMS  Vulture and HMS Firefly suffered damage due to the underwater explosions of Russian naval mines. Russian naval specialists set more than 1,500 naval mines, or infernal machines , designed by Moritz von Jacobi and by Immanuel Nobel , in

11700-422: The radius of the Earth, one can neglect the variation of g . Under these circumstances, one can transport out of the integral the density and the gravity acceleration and the law is simplified into the formula where Δ z {\displaystyle \Delta z} is the height z − z 0 of the liquid column between the test volume and the zero reference point of the pressure. This formula

11817-910: The responsibility of the US Army's Artillery Corps, and in 1907 this was a founding responsibility of the United States Army Coast Artillery Corps . The Imperial Russian Navy , a pioneer in mine warfare, successfully deployed mines against the Ottoman Navy during both the Crimean War and the Russo-Turkish War (1877-1878) . During the War of the Pacific (1879-1883), the Peruvian Navy , at

11934-440: The ships lacked the generating capacity to energise such a coil. It was found that "wiping" a current-carrying cable up and down a ship's hull temporarily canceled the ships' magnetic signature sufficiently to nullify the threat. This started in late 1939, and by 1940 merchant vessels and the smaller British warships were largely immune for a few months at a time until they once again built up a field. The cruiser HMS  Belfast

12051-468: The successful use of mines. The first ship sunk by a mine, USS  Cairo , foundered in 1862 in the Yazoo River . Rear Admiral David Farragut 's famous/apocryphal command during the Battle of Mobile Bay in 1864, " Damn the torpedoes, full speed ahead! " refers to a minefield laid at Mobile , Alabama. After 1865 the United States adopted the mine as its primary weapon for coastal defense . In

12168-560: The war concluded, eight countries conducted clearance operations. Houthi forces in the Yemeni Civil War have made frequent use of naval mines, laying over 150 in the Red Sea throughout the conflict. In the first month of the 2022 Russian invasion of Ukraine , Ukraine accused Russia of deliberately employing drifting mines in the Black Sea area. Around the same time, Turkish and Romanian military diving teams were involved in defusing operations, when stray mines were spotted near

12285-704: Was the sister ship of the RMS Titanic , and the RMS ; Olympic . During World War II , the U-boat fleet, which dominated much of the battle of the Atlantic, was small at the beginning of the war and much of the early action by German forces involved mining convoy routes and ports around Britain. German submarines also operated in the Mediterranean Sea , in the Caribbean Sea , and along

12402-423: Was adjusted to 30 to 45 millivolts for mines deployed by the last five minelaying excursions. Supply problems and technical difficulties caused some delays. More minelaying excursions to complete the barrage were cancelled when the approaching end of hostilities was recognized after the thirteenth minelaying excursion on 26 October 1918. The design of the minefield meant there was a theoretical 66 per cent chance of

12519-461: Was an open switch in the detonation circuit closed by hydrostatic pressure. The second was a spring pushing the detonator away from the explosive charge into the buoyancy chamber unless compressed by hydrostatic pressure. The mines were intended to be safe at depths less than 25 ft (7.6 m). The mines contained a dry cell battery each with an electrical detonating circuit which could be initiated by any one of five parallel fuzes . Four of

12636-535: Was commanded by Rear Admiral Joseph Strauss aboard the Atlantic Fleet Mine Force flagship USS  Black Hawk . Strauss was an ordnance specialist and had been chief of the Bureau of Ordnance from 1913 to 1916. Mine Squadron One, under the command of Captain Reginald R. Belknap , assembled at Inverness, Scotland in June 1918. Over the following five months, these ships planted 56,571 of

12753-402: Was effective against this type of mine, but this consumed valuable time and resources and required harbours to be closed. Later, some ships survived mine blasts, limping into port with buckled plates and broken backs. This appeared to be due to a new type of mine, detecting ships by their proximity to the mine (an influence mine) and detonating at a distance, causing damage with the shock wave of

12870-507: Was effective at the assumed maximum submarine depth of 200 ft (61 m), and 100,000 of these new Mk 6 mines would be adequate to form the North Sea mine barrage. The United States was altogether more enthusiastic about the operation, as the loss of trans-Atlantic shipping was a major domestic concern and this plan allowed the United States to play an active part in tackling this, while playing to their industrial strength and with minimal risk of American casualties. Assistant Secretary of

12987-722: Was equal to 14 kg (31 lb) of black powder . In the summer of 1853, the production of the mine was approved by the Committee for Mines of the Ministry of War of the Russian Empire . In 1854, 60 Jacobi mines were laid in the vicinity of the Forts Pavel and Alexander ( Kronstadt ), to deter the British Baltic Fleet from attacking them. It gradually phased out its direct competitor the Nobel mine on

13104-459: Was further disguised by wearing dark clothes and a black cap. His task was to approach the French ship, hook the torpedo to the anchor cable and, having activated the device by removing a pin, remove the paddles and escape before the torpedo detonated. Also to be deployed were large numbers of casks filled with gunpowder, ballast and combustible balls. They would float in on the tide and on washing up against an enemy's hull, explode. Also included in

13221-472: Was loaded in a wooden box, sealed with putty . General Qi Jiguang made several timed, drifting explosives, to harass Japanese pirate ships. The Tiangong Kaiwu ( The Exploitation of the Works of Nature ) treatise, written by Song Yingxing in 1637, describes naval mines with a ripcord pulled by hidden ambushers located on the nearby shore who rotated a steel wheel flint mechanism to produce sparks and ignite

13338-512: Was shared among 140 manufacturing contractors and over 400 sub-contractors. All mine components other than wire rope, explosives , and detonating circuitry were manufactured by Detroit automobile firms. Eight civilian steamships were converted to minelayers; and another 24 mine-carrying freighters, sailing at a rate of two or three per week, were required to transport manufactured mine components to assembly depots in Scotland. The objective

13455-471: Was spent testing an electrical protective device to reduce the risk of sweeping the antenna mines with steel-hulled ships. Patapsco and Patuxent tested the protective device by sweeping 39 mines in March. Royal Navy minesweeping efforts involved 421 vessels manned by 600 officers and 15,000 men from 1 April to 30 November 1919. Twelve Lapwing class minesweepers and 18 submarine chasers were available for

13572-625: Was to prevent U-boats from operating in the North Atlantic and preying on trans-Atlantic shipping. A similar barrage had already been placed across the English Channel , which had resulted in U-boats diverting north around Scotland. The North Sea Mine Barrage was intended to close this alternative route, and it also made it hard for the U-boats to get supplies. The Mk 6 mine was a 34-inch-diameter (86 cm) steel sphere containing

13689-469: Was used on the Delaware River as a drift mine, destroying a small boat near its intended target, a British warship. The 1804 Raid on Boulogne made extensive use of explosive devices designed by inventor Robert Fulton . The 'torpedo-catamaran' was a coffer-like device balanced on two wooden floats and steered by a man with a paddle. Weighted with lead so as to ride low in the water, the operator

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