https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_...
It's extremely hard to communicate long distance underwater, especially to do so discreetly.
A coded sonic pulse could have exceptionally long range. Sure your enemies would detect it, about half a second before they detect the drones.
A more practical concern is simply temperature and how long the drone's power supply can survive in the cold ocean.
Jellyfish might be a nice option when conditions permit...
How does existing submarine cable infrastructure carry communications to subs?
Low-frequency AC current in the shield, data picked up magnetically?
Contrary to the other reply, ELF is not used and is impractical: https://en.wikipedia.org/wiki/Project_Sanguine
For VLF you can drag a very long antenna behind you, but most submarines just launch a buoy with a normal antenna to the surface and a fiber connection to allow them to stay below the surface.
https://www.navalnews.com/naval-news/2022/04/communication-a...
Is it fool proof? Almost certainly not. It doesn't have to compete with perfect, though. Just with what we have right now.
EM waves fall off exponentially inside a conductor like saltwater. A 1 kHz wave has a skin depth of 8.75 meters, vs the Virginia class' 10m width. A signal from the front to the back of the submarine would be attenuated by 10 million times.
Note that this is in addition to the normal problems with antennas. Your home router transmits at <100 mW. Say you spent a ton of money and made a super sensitive receiver that could operate from 140m on the low SNR of your router. In order to receive the same power at 140m on 1 kHz, you would need a 1 megawatt transmitter. It would be dumping 60% of its power in the first 8.75 meters of water. Not quite enough to boil it, but not far off.
That's your first problem. The second problem is that the wavelength of a 1 kHz signal is 299.8 km. Antenna effectiveness also falls off exponentially with size, and the smallest antennas are maybe 10% of the wavelength. A 1 km antenna does not work well for 1 km, and even then you have to let out a buoy with a long cable- which is how current submarines do it.
The third problem is that if the drones are 10s of km or less away from the sub, there's no point. That means you know where the sub is. The problem is knowing where to aim active sonar or drop depth charges, not aiming.
Is it necessarily a good idea? Probably not? I was only poking at the "first principals" taking the assumption of constant radio communication as a given. Why? We don't even assume that for submarines with people on them.
Which, yes, we have people there so that they can think and respond with situational awareness to events. And I'm fully agreed that we don't want to jump straight to AI to replace people completely. But I also don't know why you wouldn't build a bit more smarts into deployments? And fully expect some of this to happen. (Realistically, I'm largely describing what science fiction used to imagine mine fields are like in the ocean?)
No. But you seem to presume engineers working on underwater communication are brainless morons.
There's a big disconnect between the military and actual engineering. Yes, that one magic Xilinx part is cool, but you don't need to blow $10k extra on literally everything you buy. They suffer buzzwords and fads the same way everyone in civilian C suite does.