> Ocean floor topography also helps identify underwater hazards
You think the ocean is mostly empty, until your nuclear powered attack submarine runs into a previously uncharted (or incorrectly charted) submarine mountain
On 8 January 2005 at 02:43 GMT, San Francisco collided with an undersea mountain about 364 nautical miles (675 km) southeast of Guam while operating at flank (maximum) speed at a depth of 525 feet (160 m).
military submarines do not as a matter of practice run around in general navigation pinging things, because that kind of defeats the purpose of hiding where you are
The passive sonar from their own prop noise would easily show a mountain. There is a reason about 30 people were demoted due to the incident. Bottom line is they weren’t paying attention to their sonar.
Passive sonar shows "things making noise". It doesn't show things that do not make noise.
Mountains do not, as a general rule, make noise, and do not show up on passive sonar.
In addition, when running at flank speed the efficiency of passive sonar is greatly degraded by flow and machinery noises.
The way a submarine avoids running into seamounts is a combination of very good maps, very good dead reckoning, (IIRC) gravitational anomaly detection (tied to more great maps), and if all else fails high-frequency (short-range) active sonar. It's a really interesting system! But I don't think passive sonar ties into it.
Mountains do make noise when they reflect the sound your prop makes. I took the gp to refer to that. Whether you can use that for collision avoidance, no idea.
There's a few problems with this. For one, your prop noise is going to be almost entirely masked directly ahead of you, because there's a whole submarine in the way. Isolating "sound of our propellers from in front of us" from "our propellers behind us" is certain to be extremely difficult if it's not completely impossible too.
I've got no idea where jcampbell pulled their information from, but I've never seen anything to even suggest it's possible to use your own prop and machinery noises like that.
There's a whole series of highly classified inertial navigation units used in aviation and submarine applications. The ones for use above the ocean's surface have many DoD applications in a theoretical GPS-jammed environment in warfare against an equal-tech adversary.
I've got no clue about the downvotes either. Maybe because the first version of the comment was a little snarky, and didn't include how submarines actually avoid crashing into things?
I believe there have been successful experiments to detect underwater mountains by their gravitational pull, but I don't think it's an operational system type thing. https://ieeexplore.ieee.org/document/5345843
and also, I wanted to mention another submarine navigation technique that the Soviet Russians pioneered. I thought it was called Crazy Ivan but I just looked that up and that's Soviet Russian submarinery, but not this one. The idea is to carefully map the ocean floor features in a particular area, and water currents, and know your boat well, and use that information to "blindly run a route" at high speed. I'm not an expert but something like, when submarines are traveling at speed, stuff like sonar (at least the quiet kind) is useless because of all the turbulence around the boat, so the Russians figured out they didn't need to be stealthier to evade US subs in the Baltic, they just needed to know where they were and then go fast. The goal was to get to the open sea were it's easier to get loast in the vastness. Maybe these Navy subs were trying something like that.
What do you propose? Any sonar-equivalent involves broadcasting (in this context, broadcasting nearly continuously). Any broadcast makes it trivial to locate you.
Submarines go to great lengths to be as quiet as possible so that the acoustics of the engine, ship, etc. can't be caught in a microphone. Any sort of EM radiation is child's play to trace compared to that. The content of the message and the frequency of the message don't matter - any sort of signal means you can be monitored and your location determined.
The threat model isn't a torpedo, it's knowing where the enemy's subs are (and aren't). "There's a sub within half a mile of this point" is likely 90% as bad as "there's a sub exactly here" for most missions.
While water motors are not exactly my area of expertise, I would also expect that drone/torpedo motors are significantly louder than submarine engines and that launching or recovering a drone is itself a fairly noisy event that exposes the sub to traditional acoustic tracking.
Sure, all valid issues. It for sure would expose the general vicinity.
In terms of noise, keep in mind that submarines have all sorts of concessions already. A diesel-electric sub is quieter than a nuclear sub, but it has to surface every two days or so to get air to run its very noisy diesel generators.
I think a battery powered electric drone should be far quieter than any sub technology we have (steam/nuke is loud, diesel is louder). The quiet systems we have are all electric and therefore have limited energy capacity.
Is detection of EM radiation really that easy? Broad parts of the EM spectrum are heavily attenuated by water - this is what makes underwater comms difficult.
Sure. You can transmit the sonar from a different location. A hidden sub could send out a drone to make the sonar pings from a different location. You'll be giving away the location of the drone, rather than the sub. There's still an issue around detecting that a sub is in the general vicinity, of course.
or more conventionally, you build a fleet of oceanographic survey ships which operate in the open navigating international waters, collecting vast data sets of bathymetric information... obviously not perfect yet.
there is also the danger that a drone emitting sonar pings may be indistinguishable to a third party from a live torpedo, and makes it look like you're preparing to attack somebody you really don't want to start a war with (China, etc).
Your drone would need to be really close to the sub to provide any useful information - so close that you’d definitely be exposing the submarines locations unless it was quieter than the sub. Which good luck with that.
Any active sonar would likely paint the submarine anyway too for any passive sonar listeners.
A mile is far, far too close then. A square mile of ocean is a VERY small search place compared to what they would start with.
And how would the drone know to 'flash the flashlight' where it was useful to the sub without the sub somehow communicating to the drone? Which would require the sub to emit something, or preprogram it before release.
Not to mention, unless the sub stayed in one place or somehow communicated with the drone, it would have to stay in one place to have any chance to recover it. Even then, odds of finding the hidden black spot on it’s own with inertial guidance aren’t great if it’s away for long.
If it was programmed into the drone when it was launched, just the drone coming to and from the sub would draw a giant red line to and from the sub. It would also severely restrict the sub - it either has to program in a path, in which case the drone will illustrate where the sub WILL BE shortly, or it has to do a one-off, in which case anyone could listen to/follow the drone back to the sub when it's retrieved.
Seems not very useful in practice, except as some kind of disposable thing during an attack for redirection or distraction.
A drone would be far less detectable than the sub itself when not pinging (the drone would have only electronics, no nuclear turbine), so that seems like a non-issue regarding detecting the drone while in silent running. Drones are a lot more quiet and harder to locate than nuclear subs.
A programmed path wouldn't illustrate where the drone or sub will be in advance so that's also a non-issue. You only know where the ping came from, at the time the ping was sent.
The drone could also simply surface and pick up new instructions from satellite.
I assume we will soon be moving en masse to underwater drones for reasons far beyond what's discussed here.
There are of course ocean based drones already, but they tend to be for surveillance and data gathering in general - like detecting subs. Not so much for navigation.
Autonomous ocean going drones have been common place for decades.
Fire and forget programmable torpedoes have been a thing for decades.
What makes no sense is trying to link them in some operational/controllable/recallable way to submarines which are trying to remain covert, as the communication channels give away the submarine or require them to do risky behaviors like surface for satellite comms.
So my point is, you’re not proposing anything novel where you seem to think you are, and where you think they are advantages are actually significant operational disadvantages based on actual submarine mission profiles.
1) active sonar plays havoc with marine life, and it’s not a problem that can be typically solved by shifting frequencies, as the frequencies used by certain species are used due to beneficial transmission characteristics.
Wartime sonar is so powerful it can literally kill or injure people or animals nearby in the water due to the over pressure pulse, so tends to be seen as dangerous and undesirable to use except in specific emergency circumstances.
Low energy active sonar is indeed used by a lot of folks, but due to #3, would likely have some economic issues.
2) sound can be listened to in the oceans over far longer distances than a useful return signal can be gleaned by the emitter, and tends to transmit unevenly due to factors that are difficult to impossible to predict or control like thermoclines, currents, etc. [https://oceanservice.noaa.gov/facts/sound.html]
Listeners to an active sonar emitter can identify the location of something using triangulation even 10-100x the distance the ‘pinging’ party could get a useful return signal. (See performance here [https://en.m.wikipedia.org/wiki/Sonar]. Think of it like shining a flashlight around in the dark. Folks miles around could see the pinprick of light easily, even if the flashlight wielder can see nothing out there, and it’s not bright enough for everyone else to see anything else either.
Listeners at 2x the distance would typically have the same clarity of view as the initial ‘pinging’ party within the area energized.
This also makes it easy to avoid for parties trying to hide. They stay 5x the distance from the active sonar, and they’re likely good, minus passive sonars listening for engine noises or whatever which are always a hazard.
And 3) distances in the ocean are huge. Much, much larger than you might be mentally modeling.
Outside of a harbor or port (which generally already have these systems), a hundred square miles of ocean is tiny.
The Atlantic Ocean is 41.2 million square miles, the pacific 63.8, and the Indian Ocean 27.
So covering any useful segment of a large shoreline can be nearly impossible economically, let alone a segment of the open ocean. Even if you wanted a sensor per 100 square miles over half of the ocean - say the most interesting/busy parts of the ocean, or approx. 70 million square miles, well, 700k drones are not going to be easy to build, maintain, etc.
For this reason, equipment tends to be carried by parties who might need it, and only deployed in areas they might need it, or deployed as fixed installations in very high value/interesting areas.
Sonobouys from helicopters, sonar arrays on ships or submarines, fixed sonar installations at harbors, ports, clandestine passive sonar arrays near expected strategic areas off coastlines, etc.
4) clandestine bandwidth is very limited.
VLF has VERY low bandwidth (depending on frequency), so low even voice transmission is generally not practical, and it still has limited penetration into water. As far as I am aware, it’s used the equivalent of submarine texting (at best), and the submarine still has to come quite close to the surface. ELF can work at operating depths, but communication is one way, and bandwidth is in the ‘bits per minute’ range [https://en.m.wikipedia.org/wiki/Communication_with_submarine...]
ELF antennas are measured in miles and use the earths crust.
Sound in the ocean has weird transmission effects. If your quiet ‘whispered’ data gets under a thermocline, it could go 100s of km and you would be none the wiser. If it didn’t, it might go just meters. Distortion at high frequencies also makes it difficult to transmit much data this way unless the listener is close.
You’d want some kind of mesh network ideally though, as whatever node the sub is near would not be one the sub would want to approach if there was a potential enemy contact nearby, as it’s drawing a giant target on them.
If one way, that could be useful - however that also means the crypto better be really good, as one compromised node would turn the array into an enemy asset to hunt your subs, and the passive listening and mesh network model would mean you’d need to be transmitting all potentially interesting data all the time.
> 2) sound can be listened to in the oceans over far longer distances than a useful return signal can be gleaned by the emitter, and tends to transmit unevenly due to factors that are difficult to impossible to predict or control like thermoclines, currents, etc. [https://oceanservice.noaa.gov/facts/sound.html]
This sounds exactly like the kind of thing a top secret military program would know how to do with a few petaflops of calculating power, a network of linked microphones, and a complete survey of the area. At least to ranges that would be very surprising to someone outside of that program.
But yes, anything some rando on hn thinks of in five minutes has been thought of and dismissed or thought of in detail and had problems said rando didn't think of worked through.
> you’re not proposing anything novel where you seem to think you are
I haven't suggested any novel ideas at all. I'm only pointing out something that should be obvious.
This conversation started when someone asked whether it's possible to use sonar without giving away a sub's location. It is possible. That's really all there is to it.
They're in a place where there is no lights and no sound. You have to emit something whether that be in the form of sound or in the electromagnetic spectrum in order to receive a reflection back and emissions remove stealth.
Not to mention that sonar is highly disruptive to many forms of sea life as it's incredibly loud.
the only thing I could possibly think of are receive-only apparatus like magnetometers, which are themselves used by low flying aircraft and surface ships to locate submarines. And likely of very limited value in underwater navigation unless you're in a research submarine literally hovering a few meters above some rocky metallic outcroping on a seamount.
Or something thermal sensor based, there's rumored to be systems that submarines can use passively to follow and track other submarines by the waste heat put into the water.
I'm not sure how practical they are for mapping but the sensitivity of some such sensors is so outrageous you can definitely measure well beyond a few meters of distance.
You seem generally very knowledgeable about this environment and I'm by no means an expert in the SQUID, but the way I understand it it's effectively a magnetometer with sensitivity down to about femtotesla scale. Clearly that could in principle pick up the magnetic effects of many objects well beyond a decimeter, even with consideration of the field rapidly declining with distance.
The main problem in using it, as I understand it, is rather that picking up everything the sensor could detect would usually result in an unmanageable deluge of unwanted information, and it's a normal operation context to filter the signal for distance so as to not pick up too much interference from equipment, staff, etc.
But personally I don't see any reason it would be impossible to arrange it to band-pass instead of low-pass in that filtering.
I suspect the real purpose of the Poseidon nuke torpedo is to avoid the difficulties of detecting subs by over-pressuring an enormous area all at once, like fishing with dynamite
I'm just the right age to have learned about the enormous potential of deep sea mining by being taught about it in grade school! we were gonna vacuum up manganese nodules!
I was the right age to learn about the enormous potential of deep sea mining by reading Willard Price. Actually, looking at when Underwater Adventure was written, I could have been born any year and still learn about it by that method.
I'm talking about when it was breathlessly added to the school curriculum at the time the Glomar ship was being built.
So I was saying something like "I read about leaked story of Moses parting the Red Sea in the newspaper!"; yes, you're right, anybody can learn about Moses from the Bible.
Likely to inform and fuel the Rare Earth mining already being done on the ocean floor. Take for example off the West Coast of North America: https://www.cbsnews.com/news/rare-earth-elements-u-s-on-side...