Abstract:
Stealthiness of submarines makes them lethal weapon for any naval force, thus these can play decisive role in naval warfare. Perhaps, this is the reason why, nations are trying to increase the role of submarines in naval warfare by equipping their submarines with more lethal weapon systems and by using various stealthy materials on submarine hull. Conventional electric/diesel submarines survivability lays in stealthiness. For this, submarines rely on quiet operational manoeuvrability when enemy SONAR is in passive mode. On the other hand, if the enemy SONAR is in active mode these submarines rely on the anechoic tiles (fixed at the outer hull), to reduce the return echo. Most submarines have cylindrical shape thus, its body resonates upon incoming SONAR pings depending on the wavelength of the in coming frequency. In response to this resonance phenomenon, the return echo strength increases by +3dB to +30dB depending upon the size and shape of the submarine aspect, which is in contact with the in coming SONAR ping. One solution to this problem is to manoeuvre submarine in a manner so that the minimum area of submarine body remains in contact with the in coming SONAR ping. Second method is to put anechoic tiles on the submarine hull. Third, is in the design phase where careful attention to the shape and orientation of the external surfaces of a submarine can reduce echoes/scattering. These returned echoes with increased signal strength are termed as target strength (TS). In publications, generalized numerical values of the TS of underwater objects including submarines are given but these values are targeted for SONAR designers, to give them rough idea of TS. For the submarine crew, designers and maintainers, these values are practically measured. For instance, on weapon frequencies (>20 kHz) both casing and pressure hull are good reflectors and echoes can be expected from the external casing, pressure hull, fin, rudder, hydrophones, stabilizers and propeller. Unless, the actual TS is quantified, the submarine crew will never know which aspect of the submarine should they face towards the incoming weapon/torpedo, and submarine designer will never know what kind of anechoic tiles should they place on the hull. In addition to that, measurement of the TS will also empower the designer to modify its design in a way so as to achieve low TS. This paper will encompass the general criteria and methods of measuring TS at sea. Although, the main object for the paper is submarines but method discussed here can be equally applied for TS measurement of surface vessels, torpedoes, underwater mines and towed arrays. Additionally, the same setup can be utilized for beam pattern calculation of active/passive hydrophone arrays.
Page(s):
105-110
DOI:
DOI not available
Published:
Journal: Proceedings 5th International Bhurban Conference on Applied Sciences and Technology , Volume: 0, Issue: 0, Year: 2007