Увидеть полфотона от чёрной дыры
Попавсь!
A hunter that any north Atlantic operator quickly learns to respect. Hated having to keep track of them.
I was wondering this yesterday. what are you listening for if the kilo is at a dead stop? is it even detectable by passive sonar then?
Практические соображения
You have 1 way, and that's transients. Someone closes a door too hard. A noisy pump comes on. Someone drops something.
Outside of that, they are effectively invisible to sonar when submerged at a stop.
И теоретические
The assumption that a Kilo, or any high-end diesel submarine is “silent” on the battery or when dead in the water is false. A challenge yes, but not silent. All submarines, including submerged diesels, have continuously and intermittently operated machinery sources that are still detectable on the battery. Modern diesel submarines, even when submerged on the battery, are not “undetectable”; there are still sources of noise besides those from main propulsion that are detectable. The only exception to this is if a diesel submarine was bottomed with everything shut off, which is difficult and impractical to do.
И то, и другое
A diesel boat at dead stop is basically silent. They sound like a "hole in the water", an area of the sea where there's little to no ambient noise because the submarine's hull is blocking it from reaching your hydrophones. The only (or easiest) way to detect them is by taking the area where the ambient noise in the water is quietest as an estimate, and best-guessing its' location from there.
If your sonar is sensitive enough, you can hear them anyway - somebody aboard dropping a utensil, or stubbing their toe on a hatch coaming, or jumping off a ladder, or some piece of auxiliary machinery starting up, or whatever - it all makes some degree of noise and modern sonar equipment is pretty damn sensitive.
So, in short, you can still detect them, but it's very difficult, and needs incredibly sensitive sonar that can distinguish quiet ambient noise from no noise at all - which most modern sonars can do. They Kilos are still very quiet, just nowhere near as quiet as they were in the 1980s.
Критика инженерной фантастики Клэнси
I must admit, I am a little tired of hearing this "black hole" claim. Perhaps if you have an array with very tight and numerous beams that operates at high frequency and the submarine is very close to you, you may get this sound-shadow effect. But under more realistic conditions diffraction and the wide beam size compared to the target (both in the horizontal and vertical planes) make this a highly impractical method of detecting submarines.
Unfortunately it's a myth, sound diffracts so it won't block out any sound unless you're within just a few metres. Also, your bearing resolution with passive sonar is low enough that you wouldn't notice it anyway (at 1km, a beam-on Kilo-sized contact takes up 0.0012°)