UACE2017 Proceedings: A Target Echo Strength Reduction Technique

• Session:
  Target Echo Strength-Measurements and Modelling
• Paper:
  A Target Echo Strength Reduction Technique
• Author(s):
  Tom Avsic
• Abstract:
  During the last decades, considerable effort was made to successfully minimize the radiated acoustic noise of submarines – especially of the diesel-electric types. Such ultra-quiet submarines are difficult to detect by passive sonars; therefore, new active sonar ASW techniques were developed which dramatically increased the acoustic detection ranges of the nowadays submarines. This technological development motivates the reduction of the target echo strength (TES) of a new concept study.\nThe motivation to reduce the TES is not only to achieve stealth for a submarine being searched by an ASW task group; it is also to enable a submarine to act within an ASW task group as a friendly submarine. However, any cooperative ASW scenario can simultaneously also become potentially dangerous situations if an opponent submarine uses the same configuration to its own (bi-static sonar) advantage.\nA basic analysis of sound propagation at several oceanographic locations was used to determine the vertical threat sector. The stealth technique known from previous efforts in radar cross-section reduction was adopted for underwater sound impinging onto a submarine hull. The exposed hull areas ware shaped accordingly to refract the impinging sound out of the vertical threat sector. The shaping concept requires that the outer hull form be sufficiently opaque, so as not to allow the objects behind it (with potentially high TES levels) to determine the total TES. Therefore, a transmission-loss coating is applied over the outer hull casing of the submarine. The required transmission-loss properties of the acoustic coating were attained through sound reflection; hence the coating is also sometimes referred to as a reflective coating.\nThe stealth-shape reflects the incoming sound in a sharp beam away from the vertical threat sector. To ensure that the shape is properly formed, a concept of acoustic eigenray interaction was derived to verify that sound propagating along one acoustic path is not reflected onto another acoustic path.\nAfter deriving the vertical threat sector from sound propagation-analysis and presenting the ray interaction concept, the results of a stealth-optimized shaped submarine will be compared to a classical shaped submarine with and without an acoustic coating. This will be demonstrated on the model submarine denoted as “BeTTSi”.
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Contact details

• Contact person:
  Mr Tom Avsic
• e-mail:
  
• Affiliation:
  thyssenkrupp Marine Systems GmbH
• Country:
  Germany