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This feels off, though. We may be at the point where it is hard to keep any particular thing quiet, sure. But we are also at the point where it is rather easy to park a ton of things around that are very easy to keep quiet until we want a lot of noise.

That is, if you are going to first principals, I have to ask why you don't have a ton of unmanned drones down there. Literally remove the need to move somewhere for the people on board.

Communicating with the drones is nearly impossible.

Missed this thread, apologies. I would take "nearly impossible" to be akin to "very expensive." Which is not to say that any of the difficulties just flat go away. But you don't necessarily need long range communication.

I now realize the other thread is taking my point to be that this is trivially doable. That was also not my intent. My point was simply that "reducing to first principals" is a bit silly if you are going to maintain the requirement that you have a big enough vehicle to sustain a crew. Even a minimal crew imposes some massive design constraints that you don't necessarily have if you reduce the problem down. (In general, oddly, I meant my comment mostly as a criticism of "first principals" thinking on this. Too many of those analyses bring in base assumptions that are often invisible to the people arm chairing it.)

> Missed this thread, apologies. I would take "nearly impossible" to be akin to "very expensive."

I’m certainly no expert, but I don’t think that’s the case here. Radio waves don’t penetrate water that far. Communicating with an untethered vehicle deep underwater is impossible. At the surface, trivial.

I would include dropping tethers to many places as part of a viable plan?

Though, to your point. Not trying to be an expert or to second guess any expertise out there. I was really only meaning to question the "first principals" idea of reducing it to something that still requires radio waves to penetrate deep into the water. There is no need to keep the idea that it has to remain in radio contact with something far away. You would want it to be able to establish contact, and there will be prioritized methods to do that based on plenty of other variables. Not trivial, mind. But there is already nothing trivial about going underwater.

Trying to do what you’re proposing without being detected (the primary use case for military submersibles) is what is essentially impossible, since communicating via sound is of course doable - and also would entirely compromise their purpose.

Hooking to previously unhooked tethers (or keeping drone like submersibles tethered over long periods of time), or communicating via radio underwater is just not practically useful. Like ‘tens or hundreds of meters’ type limited range, when kilometers is typical ‘close’ range.

The reason why crews are required (except for limited research/investigation use cases), is because of these communication issues.

We are likely comparing different scenarios, then? I'd assume defense has a different set of requirements from infiltration.

To be sure, you need a lot more flexibility for defense that projects farther than you can put a stake in the ground. (Well, tethers in the water, here.) But I would assume you could almost certainly invest in and build both?

Not really, no.

If the opponent knows where all the defense equipment is, they can often bypass or destroy it in a first strike too.

And any common tethering point is not only a weak link (since it’s fixed), but a way to find every piece of equipment that interacts with it (since it has a easy to find location).

The exception maybe purely passive equipment, like SOSUS microphones. But drones are going to make noise when operating, and they’ll point to the tethering point - and every other tethered drone even if it’s not yet operating.

The deep ocean is the definition of the ‘dark forest’ problem.

The passive suggestion is basically exactly what I had in my brief imagination. Would have somewhat obvious points of failure that you would have to fortify in somewhat obvious ways. Much like any fence technology on land.

But this discussion is largely silly; as you are arguing against it as being some sort of perfect proposal. I thought it was quite clear I don't even really mean it as a serious proposal. Just as one that goes against "first principals" being some sort of golden blessing that is bound to get good results.

The responses have been to my original comment that the whole idea is silly, essentially. Because these first principles are fundamental physics limitations.

You seem really intent on ignoring these fundamental issues. It’s like trying to argue that habitats on the moon should try to ignore that the moon has no atmosphere.

We can, but why?

And if you didn’t want arguments, well this is obviously the wrong crowd hah.

What is the argument, then? My point is that it seemed off because it was still trying to force a way to find stealth for large containers that have to move. Remove the need for large and movement, and you get different constraints. No need to rely on "fundamental physics limitations" to point out that it will be difficult.

And yes, as you add in more constraints, you get more difficulties. So, if you want completely clandestine deployment, that will be far harder. But nobody would be surprised to learn that a military base has lots of latent defenses. Why would this be any different?

> I have to ask why you don't have a ton of unmanned drones down there. Literally remove the need to move somewhere for the people on board.

https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_...

It's extremely hard to communicate long distance underwater, especially to do so discreetly.

You presume it has to be incredibly long range? I'd be surprised if that is necessarily the case. Could also flat out do cables to many of them at rest.

Is it fool proof? Almost certainly not. It doesn't have to compete with perfect, though. Just with what we have right now.

> You presume it has to be incredibly long range?

No. But you seem to presume engineers working on underwater communication are brainless morons.

No, I presume most of the press is brainless morons when it comes to talking about what the military is likely doing.

I assure you, you realize very quickly that most of military procurement are also brainless morons when you have to talk to them.

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.

Ha! Fair. I should have scoped my statement largely to arm chair quarterbacks on the internet. With the full understanding and endorsement of what that implies about my contributions! :D

> You presume it has to be incredibly long range?

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.

This is assuming I think you have to have radio communication with the drones at all times? I'd assume more that you have tethered trenches scattered throughout the ocean that you care about and can dispatch an absurd number of drones at will. No need to keep them moving on a regular basis. My general thought there was more that keeping an absurdly large fleet of mostly inactive drones a bit more hidden is almost certainly easier than keeping anything in motion and constant communication hidden.

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?)

> It's extremely hard to communicate long distance underwater, especially to do so discreetly.

How does existing submarine cable infrastructure carry communications to subs?

Low-frequency AC current in the shield, data picked up magnetically?

ELF

https://en.m.wikipedia.org/wiki/Extremely_low_frequency

Sound waves. Acoustic waves travel much farther and there are transmitting stations underwater.

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...

I did notice the bit in the Wikipedia article where they mention the US station isn't used for submarine comms anymore. Thanks for the higher quality info.

If you're launching a fleet of drones, discretion is probably not a major concern.

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.

Drones that sound like, act like, or maybe look like whales, might be the answer. If the adversary can't tell if its a whale or drone, likely to force them to waste a lot of resources and/or ammunition.

It's a compelling picture, but it seems like it would be rather harmful for real whales, and if chances are it's a drone rather than a whale, several actors might choose to fire regardless and find out later. Not that whales are the only option to mimic, but whatever is chosen had better be common enough to make the drones rare by comparison, and stay that way.

Jellyfish might be a nice option when conditions permit...

Don't whales communicate across oceans with moans?

Pretending to be a whale doesn't seem like a sound principle to me. Subs don't follow the migratory paths of whales, as far as I know. Now, we just look for whales that are out of place and send a drone out to check.

Maybe you're right though, that overwhelming the signal pattern, similar to how SDI/Star Wars was deemed moot.

Reminds me of that old joke about then-modern stealth fighters having the radar cross section of a bird, with a reply stating that if they saw a bird going at mach 0.8 they'd fire some missiles at it.

I have a vague memory that nobody knew how high some birds flew until military radar got good enough to see them.

They sent up an interceptor aircraft to check out what was flying up there, rather than missiles.

https://en.wikipedia.org/wiki/List_of_birds_by_flight_height...

Americas obsession with nuclear propulsion is a large part of the problem. You can’t switch a nuclear power plant off. It’s always making noise and vibrating. These these subs are always noisier than electric units which can be totally off and totally silent, emitting nothing.

It’s politics that demands the glamour of a huge nuclear fleet. For stealth nuclear power which makes noise constantly and is nuts radiation is an inferior choice.

How much of the detection is detecting the affect a large object moving (or holding a stationary position in a current) has on water (displacing it, wake etc) vs the object itself?

This is like spotting soldiers wearing camouflage by following their muddy footprints?

Yes I think decoy drones will be critical to extending the useful lifespan of submarines, and perimeter drone defense critical to deep water.

But I think the Ukraine war has shown that shallow water navies are totally vulnerable to drones. So the purported numerical advantage of the current Chinese navy is basically worthless.

If course it is debatable if our deep water Navy can withstand missile guidance tech from the 1970s.

> Long term, I think silence is a losing strategy for the hider. You can hide with silence in the ocean because it’s so big.

This would also apply to low observability strategies for the atmosphere, no?

Perhaps lower observable atmospheric vehicles in general, autonomous or not, would mitigate mass freak-outs like NJ.

The sky has a very dark background though when it's clear out and you're looking up. Whereas the ocean is more "messy" and noisy.

> But as sensors become more sensitive, the ocean gets “smaller”.

is it not still possible to have 1 submarine and 9000 really annoying "noisemakers"? Smoke is a kind of camouflage. A constant smokescreen of sonar waves probably won't be fun for the whales...

The more sensitive detectors are, the more subject they are to spoofing, I'd think, since less noise is needed to look real.

If they are especially noisy wouldn't that make them incredibly easy to track identify and then disregard in addition to being so expensive that your country can't even afford to have healthcare?

There's another sub-distinction (hah) I'd like to make: Smoke versus decoys.

So instead of 9000 devices to blanket the area with noise so that the movements of the real submarine are hard to discern, you could have 90 decoys which are localized, and the real sub is "hiding in plain sight."

In other words, the difference between obscuring "where" versus "which one."

Except, having 1000 subs in Chinese waters (just as an example) doesn't help you. The point isn't just to evade being blown up, or which is the sub with weapons, it's also to evade detecting you were ever there or are there.

Of submarine missions, only one of them (special operations support) requires complete secrecy.

Subs with SLB/CMs or attack subs are perfectly fine with being known-in-AO but untargetable.

Which mirrors air, where MALDs/EW are a critical part of any mission in hostile airspace.

Yup, agree:

> The point isn't just to evade being blown up

Should have read "The point isn't always..."

Why not have thousands of sea drones that send fake signals.

If I had to guess, it would be gravity sensors that render submarines obsolete.

Can't hide mass.

Subs float in the water column by having the same mass as the water they displace.

The same density _overall_ but locally the density varies. Maybe there’s some way to use this for detection but I don’t see it.

Aye. Dipole and similar gross asymmetries.

I don't know about all the potential noise sources and how well any of them could be compensated for, but the raw sensory capacity of the best systems is at least enough to be worth considering the question.

Submarines have roughly neutral buoyancy when submerged; how will you detect the mass?

When a sub is submerged, by definition it is buoyant and therefore has the same average density as the surrounding water. Unless your gravity sensor is so sensitive it can detect the different densities on a per-cubic meter basis (or smaller).

just convert it from space and into time, duh. can't weigh time

Easier to detect the ferrous metal, given the size/strength requirements mean steel.

Magnetic anomaly detectors have been used since the WWII airship days. https://en.m.wikipedia.org/wiki/Magnetic_anomaly_detector

Related fact: the first Goodyear blimp was a repurposed ex-Navy submarine hunter, that likely had a MAD device fitted. You can see the restored gondola from it in the New England Air Museum.

> given the size/strength requirements mean steel

The Soviet Alpha, Mike and Sierra classes were built from titanium. Incredibly expensive but very deep-diving and invisible to MAD.

MAD has fallen out of favor. Detection range is very short so it really only works when the aircraft is low and the submarine is shallow. There are techniques to greatly reduce a submarine's magnetic signature. The P-8A doesn't even have a MAD built in.

Reflecting nothing can be as bad as reflecting a big bright 'ping'. Once you get to a certain level of stealth you have to essentially camouflage against an 'empty' background or you become a conspicuous absence.

Edit: I'm thinking more about visual camouflage here, though - maybe for sound underwater there's no point at which being quieter becomes a liability?