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Some aspects of submarine design. Part 2. Shape of a submarine 2026 (2006)

Authors: Joubert, P.N. 
Release Authority: Chief, Maritime Platforms Division 
Pages: 25 
References: 30 
Terms: Submarines 

Abstract
A shape for a next generation submarine has been drawn based on a survey of available knowledge. The reasons for each detailed portion of the shape are explained. The aim of the design is to produce a submarine with minimum practical resistance and with minimum water flow noise especially over the forward passive sonar while still carrying out all its normal functions. It is assumed the role of the submarine would be little different from the current vessel but may be powered differently and carry different equipment. The diameter of the hull has been increased while the length has been decreased compared to the present vessel. It is estimated the comparative resistance will be reduced by ten percent. The larger diameter will allow an extra deck over a portion of the length of the vessel giving greater flexibility to internal arrangements. All openings in the first five metres of the shape have been moved elsewhere including the torpedo tubes and interceptor array, to give the smoothest possible flow over the forward passive sensors. The nose shape is derived from a NACA forebody with a 14.2 percent thickness-length ratio and shows a favourable value of the minimum pressure over its length. The question of achieving natural laminar flow over this short length is discussed and found to be possible but is unproven.

Executive Summary
In about the year 2026, the present class of Australian submarines, the Collins class, will be approaching obsolescence. The machinery, the structure, communications, sensors, weaponry will need updating and replacing and the hull structure will have reached the end of its design life. This represents an opportunity to improve certain aspects of the design which is only possible with a new vessel. One of the most important aspects of submarine operation is to move as silently as possible and to be able to detect others with passive sonar. Consequently this exercise in developing the shape of a new design has three aims, 1) to move as silently as possible with the lowest practical resistance, thus giving a greater top speed and less fuel consumption at transit speeds, 2) to give the best possible flow over the forward passive sonar and 3) a more flexible interior volume with more deck space. All this should be possible without in any way compromising all the other functions and operations. A shape is shown with the best practical ratio of length-to-diameter which gives the minimum resistance. The diameter has been increased while the length has been decreased compared to Collins. The increase in diameter allows an extra deck over portion of the length of the vessel but should not increase the draft to a limit which would interfere with navigation in ports or when docking. It will add to the minimum depth for dived operations where a mission justifies risking the submarine. It will also add to the minimum operational depth of water which enables a submarine to duck under a ship. In order to maintain the same diving depth as Collins, the frames need to stronger. This should be accomplished by deeper webs. A mathematically derived nose shape has been drawn which maintains perfect symmetry over the first five meters from the nose. This shape should give the planned pressure distribution and properly constructed to the finest tolerances, will probably give laminar flow in this region...

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