iran tests 'world's fastest' sonar-evading torpedo, page-4

GZ,

To be totally honest "sonar evading technology" for a torpedo is quite simply useless. The majority of modern torpedoes are wire guided, meaning that they actually stay connected to the boat that fired them, receiving position and guidance information as it closes the target. Once the torpedo is within range (maybe 1-2km depending on how confident the attacker is with the exact position of the target) it goes active, using its own onboard active sonar to fine tune relative positions and then it closes in for the kill. The torpedo goes active, accelerates to about 60-80 knots (depending on type) and is at this stage, virtually impossible to avoid.

Passive sonar is unlikely to detect the sound of an approaching torpedo that is running in silent mode prior to going active, and submarines (despite what Greenpeace might think) do not go around the worlds ocean's pinging everything with active sonar. It kind of nullifies the boat's major stategic advantage - stealth!

This type of technology is used widely to maintain secrecy over the position of the boat that launched the torpedo. Often a torpedo will be sent 5 km away from the launch platform, then be guided in towards the target before going active. In this case, the target has absolutely no idea where the attacking boat is situated. The normal response to the loud ping of an incoming active torpedo, is to soil ones pants followed very quickly by firing a return torpedo down the bearing in which the attacking torpedo is approaching.

As you can see, building a torpedo to evade either active or passive sonar is pointless. It is the weapon platform that you want to be able to avoid any form of sonar detection and the US is decades ahead of anyone else in this technology.

Cheers

Badfish