A True Siren of the Deep.

Navy submarines are at their most vulnerable when they must surface, where they are detectable by sonar, radar naked eye, Their next vulnerable state whilst underway is when they come up to a depth shallow enough to communicate - albeit for the shortest time possible, only to dive again to the safety of the deep. The reason submarines must come close to the surface to communicate involves the physics of underwater sonar transmissions, posing direct problems for communications between surface vessels and the boat itself. It is extremely difficult to send signals reliably underwater as the signals never travel the same way twice, with temperature, waves, salinity and other variables acting to weaken or distort the signal. A new technology from RRK combines the acoustic and electronics experience of ex-naval officer Robert Kerr to overcome these hindrances with the batwinged Deep Siren, described by Kerr as "an underwater loudspeaker inside a kite". Deep sea trials in November 1996 resulted in the Deep Siren transmitting successfully from 1000 metres minimum and 1700 metres maximum out to a range of 75 Nm. and in 2000 a successful demonstration of the equipment integrated with a low earth orbit satcom sonar buoy system saw (or heard) contact with the buoy at 30 Nm from depths between 600 and 3000 metres. The signals received were then uplinked via Leo satellite and decoded on the transmit vessel. The Deep Siren vessel is currently undergoing engineering improvements and the development of an expendable A-size sonar buoy transmitter model has been proposed. Further information may be collected at www.deepsiren.com.