A nautical mile is a unit of measurement used in both air and marine navigation, for the definition of territorial waters. It was defined as one minute of a degree of latitude. Today it is defined as 1852 metres; the derived unit of speed is one nautical mile per hour. There is no single internationally agreed symbol. M is used as the abbreviation for the nautical mile by the International Hydrographic Organization and by the International Bureau of Weights and Measures. NM is used by the International Civil Aviation Organization. Nm is used by the U. S. National Oceanic and Atmospheric Administration. Nmi is used by the Institute of Electrical and Electronics Engineers and the United States Government Publishing Office. Nq is used by the French Navy in the ship's logs. While using M itself, the International Bureau of Weights and Measures recognises that NM, Nm and nmi are in use; the word mile is from the Latin word for a thousand paces: mille passus. Navigation at sea was done by eye until around 1500 when navigational instruments were developed and cartographers began using a coordinate system with parallels of latitude and meridians of longitude.
In 1617 the Dutch scientist Willebrord Snell assessed the circumference of the Earth at 24,630 Roman miles. Around that time British mathematician Edmund Gunter improved navigational tools including a new quadrant to determine latitude at sea, he reasoned that the lines of latitude could be used as the basis for a unit of measurement for distance and proposed the nautical mile as one minute or one-sixtieth of one degree of latitude. As one degree is 1/360 of a circle, one minute of arc is 1/21600 of a circle; these sexagesimal units originated in Babylonian astronomy. Gunter used Snell's circumference to define a nautical mile as 6,080 feet, the length of one minute of arc at 48 degrees latitude. Since the earth is not a perfect sphere but is an oblate spheroid with flattened poles, a minute of latitude is not constant, but about 1861 metres at the poles and 1843 metres at the Equator, with a mean value of 1852.3 metres. France and other countries measured the minute of arc at 45 degrees latitude, making the nautical mile 1852 metres.
The Admiralty measured mile, or British nautical mile, 6,080 feet, was derived from the Admiralty knot, 6,080 imperial feet per hour. The U. S. nautical mile was 6,080.20 feet, based in the Mendenhall Order foot of 1893. In 1929, the international nautical mile was defined by the First International Extraordinary Hydrographic Conference in Monaco as 1,852 metres; the United States did not adopt the international nautical mile until 1954. Britain adopted it in 1970, references to the obsolete unit are converted to 1853 metres; the metre was defined as 1⁄10000000 of the meridian arc from the North pole to the equator passing through Dunkirk. The Earth's circumference is therefore 40,000 km; the equatorial circumference is longer than the polar circumference – the measurement based on this (40,075.017 km × 1/60 × 1/360 = 1855.3 metres is known as the geographical mile. Conversion of units Orders of magnitude
A depth charge is an anti-submarine warfare weapon. It is intended to destroy a submarine by being dropped into the water nearby and detonating, subjecting the target to a powerful and destructive hydraulic shock. Most depth charges use high explosive charges and a fuze set to detonate the charge at a specific depth. Depth charges can be dropped by ships, patrol aircraft, helicopters. Depth charges were developed during World War I, were one of the first effective methods of attacking a submarine underwater, they were used in World War I and World War II. They remained part of the anti-submarine arsenals of many navies during the Cold War. Depth charges have now been replaced by anti-submarine homing torpedoes. A depth charge fitted with a nuclear warhead is known as a "nuclear depth bomb"; these were designed to be dropped from a patrol plane or deployed by an anti-submarine missile from a surface ship, or another submarine, located a safe distance away. All nuclear anti-submarine weapons were withdrawn from service by the United States, the United Kingdom, France and China in or around 1990.
They were replaced by conventional weapons whose accuracy and range had improved as ASW technology improved. The first attempt to fire charges against submerged targets was with aircraft bombs attached to lanyards which triggered them. A similar idea was a 16 lb guncotton charge in a lanyarded can. Two of these lashed together became known as the "depth charge Type A". Problems with the lanyards tangling and failing to function led to the development of a chemical pellet trigger as the "Type B"; these were effective at a distance of around 20 ft. A 1913 Royal Navy Torpedo School report described a device intended for countermining, a "dropping mine". At Admiral John Jellicoe's request, the standard Mark II mine was fitted with a hydrostatic pistol preset for 45 ft firing, to be launched from a stern platform. Weighing 1,150 lb, effective at 100 ft, the "cruiser mine" was a potential hazard to the dropping ship; the design work was carried out by Herbert Taylor at the RN Torpedo and Mine School, HMS Vernon.
The first effective depth charge, the Type D, became available in January 1916. It was a barrel-like casing containing a high explosive. There were two sizes—Type D, with a 300 lb charge for fast ships, Type D* with a 120 lb charge for ships too slow to leave the danger area before the more powerful charge detonated. A hydrostatic pistol actuated by water pressure at a pre-selected depth detonated the charge. Initial depth settings were 40 or 80 ft; because production could not keep up with demand, anti-submarine vessels carried only two depth charges, to be released from a chute at the stern of the ship. The first success was the sinking of U-68 off Kerry, Ireland, on 22 March 1916, by the Q-ship Farnborough. Germany became aware of the depth charge following unsuccessful attacks on U-67 on 15 April 1916, U-69 on 20 April 1916; the only other submarines sunk by depth charge during 1916 were UC-19 and UB-29. Numbers of depth charges carried per ship increased to four in June 1917, to six in August, 30-50 by 1918.
The weight of charges and racks caused ship instability unless heavy guns and torpedo tubes were removed to compensate. Improved pistols allowed greater depth settings in 50-foot increments, from 50 to 200 ft. Slower ships could safely use the Type D at below 100 ft and at 10 kn or more, so the ineffective Type D* was withdrawn. Monthly use of depth charges increased from 100 to 300 per month during 1917 to an average of 1745 per month during the last six months of World War I; the Type D could be detonated as deep as 300 ft by that date. By the war's end, 74,441 depth charges had been issued by the RN, 16,451 fired, scoring 38 kills in all, aiding in 140 more; the United States requested full working drawings of the device in March 1917. Having received them, Commander Fullinwider of the U. S. Bureau of Naval Ordnance and U. S. Navy engineer Minkler made some modifications and patented it in the U. S, it has been argued. The Royal Navy Type D depth charge was designated the "Mark VII" in 1939. Initial sinking speed was 7 ft/s with a terminal velocity of 9.9 ft/s at a depth of 250 ft if rolled off the stern, or upon water contact from a depth charge thrower.
Cast iron weights of 150 lb were attached to the Mark VII at the end of 1940 to increase sinking velocity to 16.8 ft/s. New hydrostatic pistols increased the maximum detonation depth to 900 ft; the Mark VII's 290 lb amatol charge was estimated to be capable of splitting a 7⁄8 inch submarine pressure hull at a distance of 20 ft, forcing the submarine to surface at twice that. The change of explosive to Torpex at the end of 1942 was estimated to increase those distances to 26 and 52 ft; the British Mark X depth charge weighed 3,000 pounds and was launched from 21-inch torpedo tubes of older destroyers to achieve a sinking velocity of 21 ft/s. The launching ship needed to clear the area at 11 knots to avoid damage, the charge was used. Only 32 were fired, they were known to be troublesome; the teardrop-shaped United States Mark 9 depth charge entered service in the spring of 1943. The charge was 200 lb of Torpex with a sinking speed of 14.4 ft/s and depth settings of up to 600 ft. Versions increased depth to 1,000 ft and sinking
Swan Hunter known as Swan Hunter & Wigham Richardson, is a shipbuilding design and management company, based in Wallsend and Wear, England. At its apex, the company represented the combined forces of three powerful shipbuilding families: Swan and Wigham Richardson; the company was responsible for some of the greatest ships of the early 20th century, most famously RMS Mauretania which held the Blue Riband for the fastest crossing of the Atlantic, RMS Carpathia which rescued survivors from RMS Titanic. In 2006 Swan Hunter ceased vessel construction on Tyneside, but continues to provide design engineering services. Swan & Hunter was founded by George Burton Hunter, who formed a partnership with the widow of Charles Sheridan Swan under the name in 1880. In 1903, C. S. Swan & Hunter merged with Wigham Richardson to bid for the important contract to build RMS Mauretania on behalf of Cunard, their bid was successful, the new company, Swan Hunter and Wigham Richardson Ltd, went on to build what was to become, in its day, the most famous oceangoing liner in the world.
In 1903 the Company took a controlling interest in the Wallsend Slipway & Engineering Company, an early licensed manufacturer of Parsons steam turbine engines, which enabled Mauretania to achieve her great speed. Mauretania was launched from Wallsend on 20 September 1906 by the Duchess of Roxburghe; the firm expanded in the early part of the twentieth century, acquiring the Glasgow-based Barclay Curle in 1912. In 1966 Swan Hunter & Wigham Richardson merged with Smiths Dock Company to form Associated Shipbuilders, which became Swan Hunter Group. Following the publication of the Geddes Report recommending rationalisation in British shipbuilding, the Company went on to acquire Clelands Shipbuilding Company and John Readhead & Sons in 1967. Meanwhile, Swan Hunter inherited both the Naval Yard at High Walker on the River Tyne of Vickers-Armstrongs and the Hebburn Yard of Hawthorn Leslie in 1968. In 1973 further expansion came with the purchase of Palmers Dock at Hebburn from Vickers-Armstrongs. In 1977, Swan Hunter Group was nationalised as part of British Shipbuilders.
The former flagship of the Royal Navy, HMS Ark Royal was built at Swan Hunter during this period, entering service in 1985. The Company was privatised again in 1987 but decided to close its Neptune Yard in 1988, it was forced to call in the receivers when the UK government awarded the contract for HMS Ocean to Kvaerner Govan in 1993. The receiver took steps to break up the business. However, the main shipyard in Wallsend was bought out from receivership by Jaap Kroese, a Dutch millionaire; the yard subsequently undertook several ad-hoc ship repair and conversion projects for private-sector customers. In 2000 Swan Hunter was awarded the contract to design and build two Landing Ship Dock ships for the Royal Fleet Auxiliary with two other ships being built by BAE Systems Naval Ships: the cost of the two Swan Hunter ships was to be £210 million including £62 million for lead yard services, with an inservice date of 2004. By July 2006, the costs had risen to £309 million and only one ship had been delivered.
As result of this, the second ship RFA Lyme Bay was transferred to BAE Systems Govan in Glasgow for completion. In 2001 Swan Hunter acquired Kværner's Port Clarence offshore yard at Teesside but in 2006 sold it to Wilton Engineering Group. In November 2006, after the failure to complete Lyme Bay within budget and resulting exclusion from future Royal Navy shipbuilding projects, Jaap Kroese announced that the business was finished and placed the Wallsend Yard's iconic cranes up for sale, he said that he was looking for a buyer for the land. During this time, Lyme Bay's earlier sister ship, Largs Bay, was noted as the last ship to be built and completed by Swan Hunter. In April 2007, Swan Hunter's cranes, along with its floating dock and other equipment, were sold to Bharati Shipyards, India's second-largest private-sector shipbuilder; the entire plant machinery and equipment from Swan Hunter was dismantled and transported to India over six months to be rebuilt at Bharati Shipyards. Swan's performed the conceptual design of Pioneering Spirit, provisionally named Pieter Schelte, the world's largest platform installation/decommissioning and pipelay vessel.
The basic design of the lifting systems was completed by the end of 2008, detail design of the hulls by May 2010. In 2008 the company said. In 2016, Jaap Kroese died. At the time, the company had 40 contractors. In 2016, Swan Hunter was relaunched into the subsea industry by Gerard Kroese, the eldest son of former owner Jaap Kroese. Swan Hunter started to offer specialist equipment, engineering & project management services to the offshore renewables and subsea oil & gas energy markets. On 12 October 2016, the company announced the issue of a letter of intent for the design and build of a basket carousel loading tower; the company announced further equipment pool growth through a 15Te tensioner and 450Te reel drive system. Swan Hunter announced loading tower readiness on 5 May 2017 with completion of mobilisation onto EMAS Chiyoda Subsea's world-class multi-lay vessel'Lewek Constellation' shortly thereafter; the Company owned three main yards: The Neptune Yard at Walker-on-Tyne inherited from Wigham Richardson The Wallsend West Yard at Wallsend inherited from Charles Sheridan Swan The Naval Yard at High Wa
Horsepower is a unit of measurement of power, or the rate at which work is done. There are many different types of horsepower. Two common definitions being used today are the mechanical horsepower, about 745.7 watts, the metric horsepower, 735.5 watts. The term was adopted in the late 18th century by Scottish engineer James Watt to compare the output of steam engines with the power of draft horses, it was expanded to include the output power of other types of piston engines, as well as turbines, electric motors and other machinery. The definition of the unit varied among geographical regions. Most countries now use the SI unit watt for measurement of power. With the implementation of the EU Directive 80/181/EEC on January 1, 2010, the use of horsepower in the EU is permitted only as a supplementary unit; the development of the steam engine provided a reason to compare the output of horses with that of the engines that could replace them. In 1702, Thomas Savery wrote in The Miner's Friend: So that an engine which will raise as much water as two horses, working together at one time in such a work, can do, for which there must be kept ten or twelve horses for doing the same.
I say, such an engine may be made large enough to do the work required in employing eight, fifteen, or twenty horses to be maintained and kept for doing such a work… The idea was used by James Watt to help market his improved steam engine. He had agreed to take royalties of one third of the savings in coal from the older Newcomen steam engines; this royalty scheme did not work with customers who did not have existing steam engines but used horses instead. Watt determined; the wheel was 12 feet in radius. Watt judged. So: P = W t = F d t = 180 l b f × 2.4 × 2 π × 12 f t 1 m i n = 32, 572 f t ⋅ l b f m i n. Watt defined and calculated the horsepower as 32,572 ft⋅lbf/min, rounded to an 33,000 ft⋅lbf/min. Watt determined that a pony could lift an average 220 lbf 100 ft per minute over a four-hour working shift. Watt judged a horse was 50% more powerful than a pony and thus arrived at the 33,000 ft⋅lbf/min figure. Engineering in History recounts that John Smeaton estimated that a horse could produce 22,916 foot-pounds per minute.
John Desaguliers had suggested 44,000 foot-pounds per minute and Tredgold 27,500 foot-pounds per minute. "Watt found by experiment in 1782 that a'brewery horse' could produce 32,400 foot-pounds per minute." James Watt and Matthew Boulton standardized that figure at 33,000 foot-pounds per minute the next year. A common legend states that the unit was created when one of Watt's first customers, a brewer demanded an engine that would match a horse, chose the strongest horse he had and driving it to the limit. Watt, while aware of the trick, accepted the challenge and built a machine, even stronger than the figure achieved by the brewer, it was the output of that machine which became the horsepower. In 1993, R. D. Stevenson and R. J. Wassersug published correspondence in Nature summarizing measurements and calculations of peak and sustained work rates of a horse. Citing measurements made at the 1926 Iowa State Fair, they reported that the peak power over a few seconds has been measured to be as high as 14.9 hp and observed that for sustained activity, a work rate of about 1 hp per horse is consistent with agricultural advice from both the 19th and 20th centuries and consistent with a work rate of about 4 times the basal rate expended by other vertebrates for sustained activity.
When considering human-powered equipment, a healthy human can produce about 1.2 hp and sustain about 0.1 hp indefinitely. The Jamaican sprinter Usain Bolt produced a maximum of 3.5 hp 0.89 seconds into his 9.58 second 100-metre dash world record in 2009. When torque T is in pound-foot units, rotational speed is in rpm and power is required in horsepower: P / hp = T / × N / rpm 5252 The constant 5252 is the rounded value of /; when torque T is in inch pounds: P
Commerce raiding is a form of naval warfare used to destroy or disrupt logistics of the enemy on the open sea by attacking its merchant shipping, rather than engaging its combatants or enforcing a blockade against them. It is known, in French, as guerre de course and, in German, from the nations most committed to it as a strategy; the first sort of commerce raiding was for nations to commission privateers. Early instances of this type of warfare were by the English and Dutch against the Spanish treasure fleets of the 16th century, which resulted in financial gain for both captain and crew upon capture of enemy vessels. Privateers formed a large part of the total military force at sea during the 17th and 18th centuries. In the First Anglo-Dutch War, English privateers attacked the trade on which the United Provinces depended, capturing over 1,000 Dutch merchant ships. During the subsequent war with Spain and Flemish privateers in the service of the Spanish Crown, including the notorious Dunkirkers, captured 1,500 English merchant ships, helping to restore Dutch international trade.
Dutch privateers and others attacked British trade, whether coastal, Atlantic, or Mediterranean, in the Second and Third Anglo-Dutch wars. During the Nine Years War, French policy encouraged privateers, including the famous Jean Bart, to attack English and Dutch shipping. England lost 4,000 merchant ships during the war. In the following War of Spanish Succession, privateer attacks continued, Britain losing 3,250 merchant ships. Parliament passed an updated Cruisers and Convoys Act in 1708, allocating regular warships to the defence of trade. In the War of Austrian Succession, the Royal Navy was able to concentrate more on defending British ships. Britain lost 3,238 merchantmen, a smaller fraction of her merchant marine than the enemy losses of 3,434. While French losses were proportionally severe, the smaller but better-protected Spanish trade suffered the least, Spanish privateers enjoyed much of the best allied plunder of British trade in the West Indies. During Britain's wars against revolutionary and Napoleonic France, the Royal Navy dominated the seas.
France adopted a guerre de course strategy by licensing civilian privateers to seize British shipping. British East Indiamen of the time were therefore armed to protect themselves against such raids, at the cost of considerable speed and maneuverability; some East Indiamen, such as the Arniston, were able to fend off these attacks in other parts of the world. U. S. and British privateers actively raided each other's shipping during the War of 1812. During the American Civil War, the Confederate Navy operated a fleet of commissioned Confederate States Navy commerce raiders; these differed from privateers as they were state-owned ships with orders to destroy enemy commerce rather than owned ships with letters of marque. These included Sumter, Florida and Shenandoah. Most of the ships used in this period were built in Britain. By the 1880s, the navies of Europe began to deploy warships made of steel; the natural evolution that followed was the installation of more powerful guns to penetrate the new steel warships.
No longer would navies fight for "prizes", in which capture of the enemy warship meant financial gain for captain and crew as well as government when the prize and her cargo were auctioned. The advent of steel armor and high explosive and armor-piercing shells meant the destruction and sinking of enemy "men o' war" was the priority. First seen at the Sinope in 1853, the change was little appreciated until 1905, when at Tsushima seven pre-dreadnoughts were sent to the bottom, the only prizes were those that had voluntarily surrendered. World War I saw Germany conducting a commerce war against Britain and her allies, principally with U-boats, but with merchant raiders and light cruisers, occasionally with naval airships. During World War II, the Battle of the Atlantic saw Nazi Germany conducting guerre de course against Britain and its allies, again using U-boats, auxiliary cruisers, small groups of cruisers and battleships. Limitations set by the Treaty of Versailles meant Germany could not build a large battle fleet as she had in the time leading up to the World War I, chose to covertly develop her submarines instead.
U-boats were cheaper and quicker to build than capital ships, Germany built up a submarine force rather than a surface fleet. This meant Germany was not able to fight a war of "guerre d'escadre", therefore pursued guerre de course. In addition, a number of commercial vessels were converted the most famous being Atlantis. During World War II, elements of the United States Navy based in Brazil conducted operations in the Atlantic against German commerce raiders and blockade runners. In the Pacific, the U. S. Navy operated against Japanese merchant shipping, as well as engaging in offensive operations against ships of the Japanese Imperial Navy; the bulk of the Japanese merchant marine was sunk by American submarines. By the end of the war, only 12% of Japan's pre-war merchant tonnage was still afloat; the Indian Ocean raid was a naval sortie by the Carrier Striking Task Force of the Japanese Navy from 31 March to 10 April 1942 against Allied shipping and bases in the Indian Ocean. It was an early engagement of the Pacific campaign of World War II.
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