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Prairie-Masker
Prairie-Masker is a radiated noise reduction system fitted to some western warships, including the Oliver Hazard Perry-class frigate, ''Oliver Hazard Perry''-class frigates, ''Spruance-class destroyer, Spruance'' and ''Arleigh Burke-class destroyer, Arleigh Burke''-class destroyers, and the Ticonderoga-class cruiser, ''Ticonderoga''-class cruisers of the US Navy. The system was also installed during the 1960s on a limited number of post WWII Greater Underwater Propulsion Power Program, Guppy III modified, and later diesel submarines. The Masker and Prairie systems are designed to prevent the classification or identification of a warship's acoustic signature by another vessel, i.e. by a hostile submarine. Instead of hearing machinery, the ship sounds similar to rain on Sonar#Passive sonar, passive sonar. The Masker portion of the system is installed onto the hull of a vessel, usually near its machinery spaces. The Prairie portion of the system is designed to silence the vessel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prairie-Masker
Prairie-Masker is a radiated noise reduction system fitted to some western warships, including the Oliver Hazard Perry-class frigate, ''Oliver Hazard Perry''-class frigates, ''Spruance-class destroyer, Spruance'' and ''Arleigh Burke-class destroyer, Arleigh Burke''-class destroyers, and the Ticonderoga-class cruiser, ''Ticonderoga''-class cruisers of the US Navy. The system was also installed during the 1960s on a limited number of post WWII Greater Underwater Propulsion Power Program, Guppy III modified, and later diesel submarines. The Masker and Prairie systems are designed to prevent the classification or identification of a warship's acoustic signature by another vessel, i.e. by a hostile submarine. Instead of hearing machinery, the ship sounds similar to rain on Sonar#Passive sonar, passive sonar. The Masker portion of the system is installed onto the hull of a vessel, usually near its machinery spaces. The Prairie portion of the system is designed to silence the vessel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bubble Curtain
A bubble curtain is a system that produces bubbles in a deliberate arrangement in water. It is also called pneumatic barrier. The technique is based on bubbles of air (gas) being let out under the water surface, commonly on the bottom. When the bubbles rise they act as a barrier, a curtain, breaking the propagation of waves or the spreading of particles and other contaminants. Uses It can be used for the following purposes: * to reduce propagation of shock waves (e.g. acoustic waves from engines or pile driving, explosions etcetera), * to reduce liquid or debris floating on the surface from spreading * to prevent salt intrusion * to control the movements of fish * for decoration and airing in aquariums In June 2010, Okaloosa County, Florida used air bubble curtains to help protect their Destin Pass coastline from oil produced in the Gulf of Mexico by the Deepwater Horizon oil spill. They hoped to push oil up to the surface for booms and skimming boats to collect the oil. Bri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Submarine Snorkel
A submarine snorkel is a device which allows a submarine to operate submerged while still taking in air from above the surface. British Royal Navy personnel often refer to it as the snort. A concept devised by Dutch engineers, it was widely used on German U-boats during the last year of World War II and known to them as a ''Schnorchel''. History Until the advent of nuclear power, submarines were designed to operate on the surface most of the time and submerge only for evasion or for daylight attacks. Until the widespread use of radar after 1940, at night a submarine was safer on the surface than submerged, because sonar could detect boats underwater but was almost useless against a surface vessel. However, with continued radar improvement as the war progressed, submarines (notably, the German U-boats in the Battle of the Atlantic) were forced to spend more time underwater, running on electric motors that gave speeds of only a few knots and very limited range. An early submar ... [...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] |
Cavitation
Cavitation is a phenomenon in which the static pressure of a liquid reduces to below the liquid's vapour pressure, leading to the formation of small vapor-filled cavities in the liquid. When subjected to higher pressure, these cavities, called "bubbles" or "voids", collapse and can generate shock waves that may damage machinery. These shock waves are strong when they are very close to the imploded bubble, but rapidly weaken as they propagate away from the implosion. Cavitation is a significant cause of wear in some engineering contexts. Collapsing voids that implode near to a metal surface cause cyclic stress through repeated implosion. This results in surface fatigue of the metal causing a type of wear also called "cavitation". The most common examples of this kind of wear are to pump impellers, and bends where a sudden change in the direction of liquid occurs. Cavitation is usually divided into two classes of behavior: inertial (or transient) cavitation and non-inertial c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acoustic Impedance
Acoustic impedance and specific acoustic impedance are measures of the opposition that a system presents to the acoustic flow resulting from an acoustic pressure applied to the system. The SI unit of acoustic impedance is the pascal-second per cubic metre (), or in the MKS system the rayl per square metre (), while that of specific acoustic impedance is the pascal-second per metre (), or in the MKS system the rayl. There is a close analogy with electrical impedance, which measures the opposition that a system presents to the electric current resulting from a voltage applied to the system. Mathematical definitions Acoustic impedance For a linear time-invariant system, the relationship between the acoustic pressure applied to the system and the resulting acoustic volume flow rate through a surface perpendicular to the direction of that pressure at its point of application is given by: : p(t) = * Qt), or equivalently by : Q(t) = * pt), where * ''p'' is the acoustic pressure; * ... [...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] |
Explosive Forming
Explosive forming is a metalworking technique in which an explosive charge is used instead of a punch or press. It can be used on materials for which a press setup would be prohibitively large or require an unreasonably high pressure, and is generally much cheaper than building a large enough and sufficiently high-pressure press; on the other hand, it is unavoidably an individual job production process, producing one product at a time and with a long setup time. There are various approaches; one is to place metal plate over a die, with the intervening space evacuated by a vacuum pump, place the whole assembly underwater, and detonate a charge at an appropriate distance from the plate. For complicated shapes, a segmented die can be used to produce in a single operation a shape that would require many manufacturing steps, or to be manufactured in parts and welded together with an accompanying loss of strength at the welds. There is often some degree of work hardening from the explos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Defense Research Committee
The National Defense Research Committee (NDRC) was an organization created "to coordinate, supervise, and conduct scientific research on the problems underlying the development, production, and use of mechanisms and devices of warfare" in the United States from June 27, 1940, until June 28, 1941. Most of its work was done with the strictest secrecy, and it began research of what would become some of the most important technology during World War II, including radar and the atomic bomb. It was superseded by the Office of Scientific Research and Development in 1941, and reduced to merely an advisory organization until it was eventually terminated during 1947. Organization The NDRC was created by an order of President Franklin Delano Roosevelt on June 27, 1940. It was part of the Council of National Defense, which had been created during 1916 to coordinate industry and resources for national security purposes. Vannevar Bush, the director of the Carnegie Institution, had pressed for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oliver Hazard Perry-class Frigate
The ''Oliver Hazard Perry'' class is a class of guided-missile frigates named after U.S. Commodore Oliver Hazard Perry, the hero of the naval Battle of Lake Erie. Also known as the ''Perry'' or FFG-7 (commonly "fig seven") class, the warships were designed in the United States in the mid-1970s as general-purpose escort vessels inexpensive enough to be bought in large numbers to replace World War II-era destroyers and complement 1960s-era s. pp.42 In Admiral Elmo Zumwalt's "high low fleet plan", the FFG-7s were the low-capability ships, with the s serving as the high-capability ships. Intended to protect amphibious landing forces, supply and replenishment groups, and merchant convoys from aircraft and submarines. They were also later part of battleship-centered surface action groups and aircraft carrier battle groups/strike groups. 55 ships were built in the United States: 51 for the United States Navy and four for the Royal Australian Navy (RAN). Eight were built in Taiwan, six i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antisubmarine Warfare
Anti-submarine warfare (ASW, or in older form A/S) 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. Successful ASW operations typically involved a combination of sensor and weapon technologies, along with effective deployment strategies and sufficiently trained personnel. Typically, sophisticated sonar equipment is used for first detecting, then classifying, locating, and tracking a target submarine. Sensors are therefore a key element of ASW. Common weapons for attacking submarines include torpedoes and naval mines, which can both be launched from an array of air, surface, and underwater platforms. ASW capabilities are often considered of significant strategic importance, particularly following provocative instances of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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