|
Hedgehog (weapon)
The Hedgehog (also known as an ''Anti-Submarine Projector'') 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. As the mortar projectiles employed contact fuzes rather than time or barometric (depth) fuzes, detonation occurred directly against a hard surface such as the hull of a submarine making it more deadly than depth charges, which relied on damage caused by hydrostatic shockwaves. During WWII out of 5,174 British depth charge attacks there were 85.5 kills, a ratio of 60.5 to 1. In comparison, the Hedgehog made 268 attacks for 47 kills, a ratio of 5.7 to 1. Development The "Hedgehog", so named because the empty rows of its launcher spigots resembled the spines on the back of a hedgehog, was a repla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Royal Navy
The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against France. The modern Royal Navy traces its origins to the early 16th century; the oldest of the UK's armed services, it is consequently known as the Senior Service. From the middle decades of the 17th century, and through the 18th century, the Royal Navy vied with the Dutch Navy and later with the French Navy for maritime supremacy. From the mid 18th century, it was the world's most powerful navy until the Second World War. The Royal Navy played a key part in establishing and defending the British Empire, and four Imperial fortress colonies and a string of imperial bases and coaling stations secured the Royal Navy's ability to assert naval superiority globally. Owing to this historical prominence, it is common, even among non-Britons, to ref ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hedgehog
A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are seventeen species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introduction. There are no hedgehogs native to Australia and no living species native to the Americas. However, the extinct genus ''Amphechinus'' was once present in North America. Hedgehogs share distant ancestry with shrews (family Soricidae), with gymnures possibly being the intermediate link, and they have changed little over the last fifteen million years. Like many of the first mammals, they have adapted to a nocturnal way of life. Their spiny protection resembles that of porcupines, which are rodents, and echidnas, a type of monotreme. Etymology The name ''hedgehog'' came into use around the year 1450, derived from the Middle English ''heyghoge'', from ''heyg'', ''hegge'' ("hedge"), because it frequents hedgerows, and ''hoge'', ''hogge'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speed Of Sound
The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. At , the speed of sound in air is about , or one kilometre in or one mile in . It depends strongly on temperature as well as the medium through which a sound wave is propagating. At , the speed of sound in air is about . The speed of sound in an ideal gas depends only on its temperature and composition. The speed has a weak dependence on frequency and pressure in ordinary air, deviating slightly from ideal behavior. In colloquial speech, ''speed of sound'' refers to the speed of sound waves in air. However, the speed of sound varies from substance to substance: typically, sound travels most slowly in gases, faster in liquids, and fastest in solids. For example, while sound travels at in air, it travels at in water (almost 4.3 times as fast) and at in iron (almost 15 times as fast). In an exceptionally stiff material such as diamond, sound travels a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ASDIC
Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances (ranging), communicate with or detect objects on or under the surface of the water, such as other vessels. "Sonar" can refer to one of two types of technology: ''passive'' sonar means listening for the sound made by vessels; ''active'' sonar means emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar. Sonar may also be used for robot navigation, and SODAR (an upward-looking in-air sonar) is used for atmospheric investigations. The term ''sonar'' is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extrem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ellipse
In mathematics, an ellipse is a plane curve surrounding two focus (geometry), focal points, such that for all points on the curve, the sum of the two distances to the focal points is a constant. It generalizes a circle, which is the special type of ellipse in which the two focal points are the same. The elongation of an ellipse is measured by its eccentricity (mathematics), eccentricity e, a number ranging from e = 0 (the Limiting case (mathematics), limiting case of a circle) to e = 1 (the limiting case of infinite elongation, no longer an ellipse but a parabola). An ellipse has a simple algebraic solution for its area, but only approximations for its perimeter (also known as circumference), for which integration is required to obtain an exact solution. Analytic geometry, Analytically, the equation of a standard ellipse centered at the origin with width 2a and height 2b is: : \frac+\frac = 1 . Assuming a \ge b, the foci are (\pm c, 0) for c = \sqrt. The standard parametric e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circle
A circle is a shape consisting of all points in a plane that are at a given distance from a given point, the centre. Equivalently, it is the curve traced out by a point that moves in a plane so that its distance from a given point is constant. The distance between any point of the circle and the centre is called the radius. Usually, the radius is required to be a positive number. A circle with r=0 (a single point) is a degenerate case. This article is about circles in Euclidean geometry, and, in particular, the Euclidean plane, except where otherwise noted. Specifically, a circle is a simple closed curve that divides the plane into two regions: an interior and an exterior. In everyday use, the term "circle" may be used interchangeably to refer to either the boundary of the figure, or to the whole figure including its interior; in strict technical usage, the circle is only the boundary and the whole figure is called a '' disc''. A circle may also be defined as a special ki ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Millis Jefferis
Major-General Sir Millis Rowland Jefferis KBE MC (9 January 1899 – 5 September 1963) was a British military officer who founded a special unit of the British Ministry of Supply which developed unusual weapons during the Second World War. Early career Born at Merstham, Surrey on 9 January 1899, Jefferis was educated at Tonbridge School and Royal Military Academy, Woolwich. From Woolwich he was commissioned into the Royal Engineers on 6 June 1918, during the final months of World War I, and after passing through the School of Military Engineering at Chatham, he was posted to the First Field Squadron RE in the British Army of the Rhine (BAOR).''Sir Millis Jefferis New Weapons of War (Obituary)''. ''The Times'', 7 September 1963 p10 column E. In 1920 he went to India and served with the Queen's Own Madras Sappers and Miners in the Third Field Troop at Sialkot. In 1922 he went into the Works Services in India as garrison engineer at Kohat and then at Khaisora which is today i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MIR(c)
Ministry of Defence 1 (MD1), also known as "Churchill's Toyshop", was a British weapon research and development organisation of the Second World War. Its two key figures were Major Millis Jefferis and Stuart Macrae, former editor of ''Armchair Science'' magazine. History MD1 began in "Military Intelligence Research" (MIR). MIR was a department of the War Office set up in 1939 under Lt-Col Joe Holland RE. Holland was the General Staff Officer Grade 1 (GSO1) and brought in Jefferis, also a Royal Engineers sapper and explosives expert, with experience in India, as GSO2 to head MIR(c) a division of MIR that was to develop weapons for irregular warfare. Needing special magnets, Jefferis brought in Macrae initially as an outside contractor but later to be brought into uniform and serve as his deputy. Between them they produced the limpet mine, a timed explosive that could be stuck to the underside of a ship. started in a room at the War Office, Macrae initially secured offices and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PIAT
The Projector, Infantry, Anti Tank (PIAT) Mk I was a British man-portable anti-tank weapon developed during the Second World War. The PIAT was designed in 1942 in response to the British Army's need for a more effective infantry anti-tank weapon and entered service in 1943. The PIAT was based on the spigot mortar system, and projected (launched) a 2.5 pound (1.1 kg) shaped charge bomb using a cartridge in the tail of the projectile. It possessed an effective range of approximately in a direct fire anti-tank role, and in an indirect fire role. The PIAT had several advantages over other infantry anti-tank weapons of the period: it had greatly increased penetration power over the previous anti-tank rifles, it had no back-blast which might reveal the position of the user or accidentally injure friendly soldiers around the user, and it was simple in construction. However, the device also had some disadvantages: powerful recoil, a difficulty in cocking the weapon, and early prob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blacker Bombard
The Blacker Bombard, also known as the 29-mm Spigot Mortar, was an infantry anti-tank weapon devised by Lieutenant-Colonel Stewart Blacker in the early years of the Second World War. Intended as a means to equip Home Guard units with an anti-tank weapon in case of German invasion, at a time of grave shortage of weapons, it was accepted only after the intervention of Churchill. Although there were doubts about the effectiveness of the Bombard, many were issued. Few, if any, saw combat. Development With the end of the Battle of France and the evacuation of the British Expeditionary Force from the port of Dunkirk between 26 May and 4 June 1940, a German invasion of Great Britain seemed likely. However, the British Army was not well-equipped to defend the country in such an event; in the weeks after the Dunkirk evacuation it could field only twenty-seven divisions.Lampe, p. 3 (The German Army had more than 100 divisions at that time.) The Army was particularly short of anti-tank g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infantry
Infantry is a military specialization which engages in ground combat on foot. Infantry generally consists of light infantry, mountain infantry, motorized infantry & mechanized infantry, airborne infantry, air assault infantry, and marine infantry. Although disused in modern times, heavy infantry also commonly made up the bulk of many historic armies. Infantry, cavalry, and artillery have traditionally made up the core of the combat arms professions of various armies, with the infantry almost always comprising the largest portion of these forces. Etymology and terminology In English, use of the term ''infantry'' began about the 1570s, describing soldiers who march and fight on foot. The word derives from Middle French ''infanterie'', from older Italian (also Spanish) ''infanteria'' (foot soldiers too inexperienced for cavalry), from Latin '' īnfāns'' (without speech, newborn, foolish), from which English also gets '' infant''. The individual-soldier term ''infantry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Royal Artillery
The Royal Regiment of Artillery, commonly referred to as the Royal Artillery (RA) and colloquially known as "The Gunners", is one of two regiments that make up the artillery arm of the British Army. The Royal Regiment of Artillery comprises thirteen Regular Army regiments, the King's Troop Royal Horse Artillery and five Army Reserve regiments. History Formation to 1799 Artillery was used by the English army as early as the Battle of Crécy in 1346, while Henry VIII established it as a semi-permanent function in the 16th century. Until the early 18th century, the majority of British regiments were raised for specific campaigns and disbanded on completion. An exception were gunners based at the Tower of London, Portsmouth and other forts around Britain, who were controlled by the Ordnance Office and stored and maintained equipment and provided personnel for field artillery 'traynes' that were organised as needed. These personnel, responsible in peacetime for maintaining the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
_-_filtered.jpg "Click for more on -> Speed Of Sound")
