Modelling of Acoustic Signatures of New Modern Multitask Submarine Concept with Reinforced Plastic Parts

Since the late eighties the sonar performance model ALMOST for active and passive sonar has been under development at TNO. Modelling of active detection performance was first started for a point target, with a single Target Strength value dependent on parameters like aspect angle and frequency, based on measurements or other sources in literature. However by now there is a growing demand for more realistic Target Strength of ships and wakes with actual dimensions and characteristics. In the newly developed REATES module of ALMOST, any generic submarine can be modelled in
realistic dimensions using a pixel file of 3-D positions together with a number of additional parameters, describing the detailed structure and materials used. For modelling of the hull reflection, an acoustic time domain model has been developed and implemented, taking into account the submarine construction in a more detailed way. The method uses additional scattering pixels, describing thickness, multiple scattering and damping of the hull layer dependent on the material constants. Acoustic modelling results are presented for a new concept of a modern multi-purpose submarine, with a number of parts made from fibre reinforced plastic, improving buoyancy necessary for operational multi-purpose use. Results of measurements on actual submarines (not presented here) show encouraging validation results for the modelling. The Target Strength of the new concept submarine is evaluated using some actual active sonar pulse types, which is important for counter detection threat. The Target Strength results are compared with a modified full steel version, showing that the new concept helps to minimize the signature.