When the Nautilus Struggles During a Dive

Abstract

Submarines are potentially vulnerable to collisions with the supporting structures of offshore wind farms. In order to warn underwater vessels a RAVE project was set up to develop what is known as a sonar transponder. The key requirements were that the sonar transponder should not transmit constantly, but only react to the corresponding submarine requests. At the same time it must not injure porpoises or seals and the signals should still be able to be received up to a distance of two kilometres away even in poor sea conditions. After various preliminary investigations, model calculations and measuring campaigns the project came up with a prototype that, once mounted on the foundation, has to be able to transmit at a sound level of 200 decibels (dB) in order to meet the required specifications. This would exceed the damage limit for marine mammals (179 dB). This is why the transponder does not start transmitting at full power immediately, but initially with a soft start in order to scare off animals swimming in the vicinity.