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The Minigun is a 7.62 mm, multi-barrel machine gun with a high rate of fire (up to 6,000 rounds per minute), employing Gatling-style rotating barrels with an external power source. In popular culture, the term "minigun" has come to refer to any externally-powered Gatling gun of rifle caliber, though the term is sometimes used to refer to guns of similar rates of fire and configuration, regardless of power source and caliber. Specifically, minigun refers to a single weapon, originally produced by General Electric. The "mini" of the name is in comparison to designs that use a similar firing mechanism but larger shells, such as General Electric's earlier 20 mm M61 Vulcan. The basic weapon is a 6-barrel, air-cooled, and electrically driven machine gun. The electric drive rotates the weapon within its housing, with a rotating firing pin assembly and rotary chamber. The minigun's multibarrel design helps prevent overheating, but also serves other functions. Multiple barrels allow for a greater capacity for a high firing rate, since the serial process of firing/extraction/loading is taking place in all barrels simultaneously. Thus, as one barrel fires, two others are in different stages of shell extraction and another three are being loaded. The minigun is composed of multiple closed-bolt rifle barrels arranged in a circular housing. The barrels are rotated by an external power source: usually electric, pneumatic, or hydraulic. Other rotating-barrel cannons are powered by the gas pressure or recoil energy of fired cartridges. A gas-operated variant, designated the XM133, was also developed, but was not put into production. Various iterations of the minigun have also been used in a number of armament subsystems for helicopters, with most of these subsystems being created by the United States. The first systems utilized the weapon in a forward firing role, for a variety of helicopters, some of the most prominent examples being the M21 armament subsystem for the UH-1 Iroquois and the M27 for the OH-6 Cayuse. It also formed the primary turret mounted armament for a number of members of the AH-1 Cobra family. The weapon was also used as a pintle-mounted door gun on a wide variety of transport helicopters, a role it continues to serve in today. [READ THE REST OF THIS ARTICLE]



The North American Aviation P-51 Mustang was a long-range single-seat World War II fighter aircraft. Designed and built in just 117 days, the Mustang first flew in Royal Air Force (RAF) service as a fighter-bomber and reconnaissance aircraft before conversion to a bomber escort, employed in raids over Germany, helping ensure Allied air superiority from early 1944. The P-51 was in service with Allied air forces in Europe and also saw limited service against the Japanese in the Pacific War. The Mustang began the Korean War as the United Nations' main fighter, but was relegated to a ground attack role when superseded by jet fighters early in the conflict. Nevertheless, it remained in service with some air forces until the early 1980s. As well as being economical to produce, the Mustang was a fast, well-made, and highly durable aircraft. The definitive version, the P-51D, was powered by the Packard V-1650, a two-stage two-speed supercharged version of the legendary Rolls-Royce Merlin engine, and was armed with six .50 caliber (12.7 mm) M2 Browning machine guns. Chuck Yeager, flying a P-51D, was one of the first American pilots to shoot down a Me 262 when he surprised it during its landing approach. On 7 October 1944, Lt. Urban Drew of the 365th Fighter Group went him one better. During a fighter sweep, he surprised and shot down two Me 262s taking off. On the same day, Hubert Zemke, now flying Mustangs, shot down what he thought was a Bf 109, only to have his gun camera film reveal it to be an Me 262. After World War II and the Korean War, many Mustangs were converted for civilian use, especially air racing. The Mustang's reputation was such that, in the mid-1960s, Ford Motor Company's Designer John Najjar proposed the name for a new youth-oriented coupe automobile after the fighter. The most prominent firm to convert Mustangs to civilian use was Trans-Florida Aviation, later renamed Cavalier Aircraft Corporation, which produced the Cavalier Mustang. Modifications included a taller tailfin and wingtip tanks. A number of conversions included a Cavalier Mustang specialty: a "tight" second seat added in the space formerly occupied by the military radio and fuselage fuel tank. Ironically, in the late 1960s and early 1970s, when the United States Department of Defense wished to supply aircraft to South American countries and later Indonesia for close air support and counter insurgency, it turned to Cavalier to return some of their civilian conversions back to updated military specifications. The P-51 is perhaps the most sought-after of all warbirds on the civilian market; the average price usually exceeds $1 million, even for only partially restored aircraft. Some privately owned P-51s are still flying, often associated with organizations such as the Commemorative Air Force. [READ THE REST OF THIS ARTICLE]



A spitting cobra is one of several species of cobras that have the ability to eject venom from their fangs when defending themselves against predators. The sprayed venom is harmless to intact skin. However, it can cause permanent blindness if introduced to the eye and left untreated (causing chemosis and corneal swelling). Despite their name, these snakes do not actually spit their venom. The venom sprays out in distinctive geometric patterns, using muscular contractions upon the venom glands. These muscles squeeze the glands and force the venom out through forward facing holes at the tips of the fangs. The explanation that a large gust of air is expelled from the lung to propel the venom forward has been proven wrong. When cornered, some species can "spit" their venom a distance as great as two meters. While spitting is typically their primary form of defense, all spitting cobras are capable of delivering venom through a bite as well. Most species' venom exhibit significant hemotoxic effects, along with more typical neurotoxic effects of other cobra species. Some non-spitting cobras and vipers have been noted to spit occasionally. Certain, predominantly non-spitting, Asian cobras have the spitting tendency. The Rinkhals cobra (Hemachatus haemachatus) is another elapid species, which while not belonging to the Cobra genus Naja, is closely related, and is capable of spitting venom. It has been reported that several viper species (notably the Mangshan Pitviper) may "fling" or even spit venom forward in a spray when threatened. These sprays are often very consistent. [READ THE REST OF THIS ARTICLE]



The Mariana Trench is the deepest part of the world's oceans, and the lowest elevation of the surface of the Earth's crust. It is currently estimated to be up to 10,971 m (35,994 ft) deep. It is located in the western Pacific Ocean, to the east of the Mariana Islands. The trench is about 2,550 kilometres (1,580 mi) long but has a mean width of only 69 kilometres (43 mi). It reaches a maximum-known depth of about 10.91 kilometres (6.78 mi) at the Challenger Deep, a small slot-shaped valley in its floor, at its southern end, although some unrepeated measurements place the deepest portion at 11.03 kilometres (6.85 mi). If Mount Everest, the highest mountain on Earth at 8,848 metres (29,029 ft), was set in the deepest part of the Mariana Trench, there would be 2,076 metres (6,811 ft) of water left above it. The Mariana Trench is part of the Izu-Bonin-Mariana Arc geological boundary system that forms the boundary between two tectonic plates. In this system, the western edge of one plate, the Pacific Plate, is subducted beneath the smaller Mariana Plate that lies to the west. Because the Pacific plate is the largest of all the tectonic plates on Earth, crustal material at its western edge has had a long time since formation (up to 170 million years) to compact and become very dense; hence its great height-difference relative to the higher-riding Mariana Plate, at the point where the Pacific Plate crust is subducted. This deep area is the Mariana Trench proper. The movement of these plates is also responsible for the formation of the Mariana Islands. At the bottom of the trench, where the plates meet, the water column above exerts a pressure of 1,086 bars (15,750 psi), over one thousand times the standard atmospheric pressure at sea level. Because the Earth is not a perfect sphere, the trench is not the part of the seafloor closest to the center of the Earth parts of the Arctic Ocean seabed are at least 13,000 metres (43,000 ft) closer to the Earth's center than the Challenger Deep seafloor. [READ THE REST OF THIS ARTICLE]



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