It could fire torpedoes, lay mines and land covert groups on an enemy coast. The submarine with its torpedoes proved a very potent weapon during the two world wars in the first half of the 20th Century in spite of its limited range of military missions. Nowadays hulls are often made from glass reinforced plastics and much of the equipment is specially made from materials with low magnetic properties, see also chapter 9, section 9.3.4. Because mine countermeasure vessels themselves are a target for the mines they are trying to destroy, the ship signatures must be extremely low and the hulls very robust. The charge is usually laid by a remotely operated underwater vehicle. They can then be destroyed by placing a small charge alongside the mine to trigger it. They need to be hunted, detection being usually by a high-resolution sonar. Since sweeping mines depends upon either cutting their securing wires or setting them off by simulated signatures, to which they will react, the latest mines are virtually unsweepable. All these features make them difficult to render harmless. They may only react after a selected number of ships have passed nearby, or only at selected times. They may then explode under the target or release a homing weapon. Modern mines can lie on the bottom and only become active when they sense a target with quite specific signature characteristics. Mine countermeasure ships may be either sweepers or hunters of mines, or combine the two functions in one hull. 2.5.7.1 Frigates and destroyersįigure 2.18. The range of sensors provided must match the requirements of the weapons fitted. Then there will be long and medium range missile systems on the cruisers and destroyers, decoy systems to seduce the incoming weapon and, finally, a close-in weapon system. If a carrier is present its aircraft will provide a long range surveillance and attack capability. The task force will exercise defence in depth – a layered defence. Thus a frigate will often act as an escort and must be sufficiently fast and manoeuvrable to hold and change station as the group changes course. This will be reflected in their attributes. It will be realized that various ship types usually operate as a group or task force. It is not possible to describe all these types but the following notes will provide a flavour of what is involved in warship design. Warships are categorized by their function, for instance the:
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