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All or nothing is a method of armoring battleships, which involves heavily armoring the areas most important to a ship while the rest of the ship receives significantly less armor. The "all or nothing" concept avoided light or moderate thicknesses of armor: armor was used in the greatest practicable thickness or not at all, thereby providing "either total or negligible protection".〔Friedman, Norman. ''Battleship Design and Development 1905-1945''. Conway Maritime Press 1978; ISBN 0-85177-135-1, page65〕 Compared to previous armoring systems, "all or nothing" ships had thicker armor covering a smaller proportion of the hull. The ironclad battleship launched in 1876 had featured a heavily armored central citadel, with relatively unarmored ends; however, by the era of , battleships were armored over the length of the ship with varying zones of heavy, moderate or light armor. The U.S. Navy adopted what was formally called "all or nothing" armor in the Standard-type battleships, starting with the laid down in 1912.〔Robert Gardiner (Ed.). ''Conway’s All the World’s Fighting Ships, 1906-1921''. Conway Maritime Press, 1985. ISBN 0-85177-245-5, 1906-1921, page 115〕 "All or nothing" armor was later adopted by other navies after the First World War, beginning with the Royal Navy in its . ==Rationale== Traditionally, a warship's armor system was designed both separate from, and after, the design layout. The design and location of various component subsystems (propulsion, steering, fuel storage & management, communications, range-finding, etc.) were laid out and designed in a manner that presented the most efficient and economical utilization of the hull’s displacement. Then armorers would attempt to design the application of barriers and deflectors which would protect vital areas of the hull, the superstructure, and its interior compartments from enemy shellfire, underwater mines, and torpedo attacks. There would also be attention paid to the limiting of sympathetic damage to hull compartments and spaces, caused as a consequence of primary damage to those hull compartments that directly received shellfire or underwater explosions. The result of this approach was that armorers were “decorating” a warship’s hull, interior compartments, and spaces with armor, not according to any overall scheme or protective design. And taken collectively, the total weight of armor yielded by this absence of an overall plan for protection was in total, far greater than a realistic hull displacement could float. Consequently, naval architects of the hull and its propulsion system would demand a reduction in the weight of armor applied; until the hull displacement and deadweight of hull returned the ship’s hull form to the range, speed, and stability of the original design performance as specified. However, the continuing advances of larger caliber guns, greater muzzle velocities, more accurate fire at longer ranges, and more energetic explosive fills of the shells fired demanded drastic improvements in armor protection. Some means had to be found to integrate armor protection into the total design of the warship (at its inception), and to rationally apply armor protection, to achieve the most efficient use of the hull’s displacement to provide buoyancy to the deadweight of the ship’s armor. “All or Nothing” was the design solution. The "all-or-nothing" philosophy of armor design required the complete rethinking of battleship design, armor systems, and the integration of the ship’s design architecture with the armor protection system. With this rethinking of design, naval architects had to examine every system and function of a warship, and determine which functions and systems were critical (and in what priority); how they were related to each other, and where they should, or must, be located within the hull and superstructure, to ensure the survival and mission accomplishment of the warship. The all or nothing system was intended to ensure that battleships could survive against the heaviest armor-piercing shells in use in the early part of the 20th century, while at the same time being able to carry a powerful armament and retain useful speed and endurance. This was made possible by dispensing with the large areas of relatively light armor which had been used in previous battleship designs; the weight saved was used to strengthen the armor protecting the vital areas of the ship; and to design a more compact interior space, where more; and, more vital systems would be located. The logic of the design was simple: If the ship was hit in vital areas (the ammunition and propellant magazines; the propulsion plant; the fire-control, command and communications sections), her survival was in jeopardy. On the other hand, if the ship was hit in non-vital areas (non-explosive stores, crew berthing and rest areas, offices and administrative areas), it would most likely not result in the ship's destruction. In the ideal form of the system, all of a battleship's armor was concentrated to form an armored "citadel" around the ship's magazine spaces: an armored box of uniform thickness designed to defend against the largest enemy guns. When battle stations were called, the whole crew retreated into this area behind armored bulkheads and armored watertight doors, which were sealed so that each compartment within, and the armored citadel as a whole, were virtually immune to enemy action other than concentrated and direct attack. Save for the turrets, the ammunition hoists, the conning tower and part of the steering gear, nothing in the way of armor protected the remainder of the ship. By stripping away the armor from all other parts of the ship, the armor of the citadel could be made thicker. The propulsion plant, communications systems, weapons, ammunition stores, and command & control of the ship were located in a single area within and beneath the armored citadel. Everything else resided outside this structure. The armored citadel can be visualized as an open-bottomed (closed top) rectangular armored raft with sloped sides sitting within the hull of the ship. From this box, shafts known as barbettes would lead upwards to the ship's main gun turrets and conning tower. Although it was desirable for the citadel to be as small as possible the space enclosed was an important source of reserve buoyancy, and helped prevent the ship from foundering when other compartments had flooded. Through compartmentalization and the redundancy of key systems, any damage done to the ship outside this armored box would likely be survivable, and as long as those systems within the box remained intact, the ship could continue to fight. In effect, the scheme accepted vulnerability to medium-caliber and high-explosive shells striking the unarmored sections of the hull, in order to improve resistance against large-caliber armor-piercing shells without increasing the overall weight of armor. The unarmored parts of the ship would not offer enough resistance to armor-piercing shells to trigger their firing mechanisms (designed to explode after penetrating armor) so the shells would pass through without exploding, while the vital parts could have armor thick enough to resist the heaviest shells. To maximize the thickness of armor available for a given weight it was desirable that the citadel be as small as possible. This was achieved by concentrating the ship's main battery in three turrets of triple or even two turrets of quadruple (quad) gun mountings, as opposed to World War I battleships which typically had four twin turrets for their large caliber guns (with ''HMS'' Agincourt having seven twin turrets). In some cases the turrets had an all-forward layout, such as the Royal Navy's and the French navy's . 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「All or nothing (armor)」の詳細全文を読む スポンサード リンク
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