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Submarines. A submarine is a specialized watercraft that can operate underwater. Military submarines, first widely used in World War I, are used by all major navies today, especially the American and Russian navies. Civilian submarines and submersibles are used for marine and freshwater science and for work at depths too great for human divers. Nuclear powered submarines and other large submarines are classed as ships, but are customarily referred to by their crews as "boats". The term U-Boat is sometimes used for German submarines in English. This comes from the German word for submarine, 'U-Boot', itself an abbreviation for Unterseeboot ('undersea boat'). Submarines encompass one of the largest ranges in capabilities of any vessel. They range from small two-man vessels that can examine the sea floor for a few hours to the Russian Typhoon class, which can remain submerged for half a year and carry enough nuclear missiles to destroy hundreds of cities. There are also specialized submarines such as rescue submarines (like the DSRV or Priz) and tiny one-person human powered subs intended for competitions between universities. An older device for use in underwater exploration, salvage, construction and rescue is the diving bell. The word submarine was originally an adjective meaning "under the sea". Some firms who make diving gear but not parts for submarines, called their work "submarine engineering". "Submarine" as a noun meaning a submersible craft originated as short for "submarine boat" and older books such as Twenty Thousand Leagues Under the Sea always use this term. Civilian submarines and submersible. Civilian submarines are usually much smaller than military submarines. Tourist submarines work mainly in tropical resort areas or other areas with clear water and good visibility. By 1996 there were over fifty private submarines operating around the world, serving approximately two million passengers a year. Most of them carried between twenty-five and fifty passengers at a time and sometimes made ten or more dives per day. In design, these submarines borrow mainly from research subs, having large portholes for passengers' viewing and often placing significant mechanical systems outside the hull to conserve interior space. Nonetheless, even aboard tourist submarines the seating can be rather cramped. They are mainly battery-powered and very slow. As of January 2005, the largest tourist submarine in use was the Atlantis XIV based out of Waikiki beach. The largest Atlantis-class submarine of its fleet, launched in 1994, can carry 64 passengers and 3 crew (two guides and a pilot) to 150 feet (50 m) deep (this depth is set by the state) off the shores of the island of O'ahu in Hawai'i. There, tourists can view a great number of ocean specimens living around artificial reefs built by the Hawaiian university out of old ships, constructions of metal flotsam, and even a sunken plane, all designed to replace the reefs damaged or destroyed by human habitation of the island. In common usage, "submarine" means a ship that operates above and below the surface, untethered. Underwater vessels with limited mobility, intended to remain in one place during most of their use, such as those used for rescue, research or salvage purposes are usually called "submersibles". Submersibles are typically transported to their area of operation by surface ships or large submarines and have a very short range. Many submersibles operate on a "tether" or "umbilical", remaining connected to a tender (a submarine, surface vessel or platform). Bathyspheres are submersibles that lack self-propulsion and used for very deep diving. A predecessor of the bathysphere, the diving bell, consisted of a chamber with an open bottom, lowered into the water. Bathyscaphes are self-propelled deep-diving submersibles reliant on a mother ship on the surface. A fairly recent development, very small, unmanned submersibles called "marine remotely operated vehicles" (MROVs) are widely used today to work in water too deep or too dangerous for divers. For example, remotely operated vehicles (ROVs) repair offshore petroleum platforms and attach cables to sunken ships to hoist them. A thick cable providing power and communications tethers these remotely operated vehicles to a control center on a ship. Operators on the ship see video images sent back from the robot and may control its propellers and manipulator arm. The wreck of the Titanic was explored by such a vehicle, as well as by a manned vessel. Military submarines There are more military submarines in operation than civilian ones. Submarines are useful militarily because they are difficult to locate and, when deep below the surface, difficult to destroy. A great deal of attention in the design of a submarine is devoted to making its travel through the water as silent as possible in order to prevent its detection (sound travels underwater much more easily than light does, meaning that a submarine's sound is the distinctive feature most likely to allow its detection). If a submarine remains undetected, it is able to strike at close range.
PADI 5 Star National Geographic Instructor Development Center. 198/12 Rat-U-Thit Road, Patong, Phuket, Thailand. Phone: (+66) 076292052 Fax: (+66) 076293034
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