A U.S. submarine struck an underwater mountain last month, the Navy says | Hacker News Reader

A U.S. submarine struck an underwater mountain last month, the Navy says

npr.org

139 pointsnradov198 comments

The article references a similar fate experienced by the USS San Francisco [1].

I find seamounts somewhat fascinating; it's so odd that immensely huge features like these are still not yet charted. The Muirfield Seamount [2] is a good example. The surrounding water is 5km deep, but the mount reaches until about 20m under the surface, as an unlucky ship found out.

[1] https://en.wikipedia.org/wiki/USS_San_Francisco_(SSN-711)#Co...

[2] https://en.wikipedia.org/wiki/Muirfield_Seamount

Don’t submarines detect echos? When I walk into a room eyes closed, I know whether it is big or not, furnished or not depending on how the ambient noise gets reflected. Surely the sea must be full of noises and even a black spot of noise should be perceivable?

Especially since detection sensibility hs gotten so high with new tech that countries don’t try to hide anymore, but they try to produce fake sounds in other places in the ocean to disturb the detection.

Detecting echoes requires that they’re running active sonar, which announces their presence to everyone and somewhat ruins the raison d’être for submarines. Running passive they can detect surface ships, but not mountains per se.

To further clarify, unlike the ships of WW II, today US subs mostly exist for a nuclear second strike capability. The strategy assumes the enemy doesn’t know where all the submarine nukes are, so they’re guaranteed to face nuclear retribution if they initiate an attack.

This isn’t true, and, as the article states, this submarine is specifically a fast attack sub. It attacks other submarines and ships. That’s still related to nuclear deterrence, but not in the way you’re saying.

> today US subs mostly exist for a nuclear second strike capability.

I understand that you say “mostly”, but it is not quite true. There are many other mission types US submarines serve.

There are US submarines which provide nuclear second strike capability yes.

There are US submarines which carry land attack cruise missiles. These are mostly used to surpess enemy air defences.

There are US submarines clearly optimised for “special missions” such as insertion of special force units or taping underwater cables.

Then there are US submarines designed to hunt other submarines.

For example the USS Connecticut is a Seawolf-class nuclear powered fast attack submarine. Nuclear powered means that the energy used to propel it forward and power its systems come from a nuclear reactor, it doesn’t necessarily means that it has nuclear armed weapons. ( Some might think that I am stating the obvious here but it is surpisingly common to confuse the terms “nuclear armed” and “nuclear powered”. ) In any case she does not carry the kind of nuclear armed ballistic missiles one would associate with a second strike role.

I know it's not very economical, but perhaps someone could start a submarine cruise? You get some vacationers, use a relatively large submarine so they have some measure of comfort, then sonar your way around a pre-planned public route. Then you have navigational data and sonar scans you can release to the world. Or, even better than releasing (the bankers say to themselves), selling the data.

Why bother even going anywhere? It's a sealed box without windows—who'd know the difference?

can we have some port holes?

Sure. You can see plenty of black water all day long.

Submarines are notoriously bad places to be. The navy actually sets very long enlistment terms for its submarine crews, because the re-enlistment rate is extremely low. Even with nuclear reactors submarines are cramped, noisy, and unpleasant. Removing the weaponry might make it suck less, but it’s not gonna be “luxury”.

Surface soundings or a towed array are vastly more economical.

For uncontested waters, yes. The problems start when one military starts trying to make charts in waters claimed by another country. That tends to become a bit of a problem.

Sure, but if you're conducting the survey from a submarine you're 1) very nearly as detectable (the sonar is pinging like mad, China likely have hydrophones throughout the region) and 2) as noted, your consts, complications, and vulnerabilties have gone up markedly.

Given circumstances, something like a drone ship might be a better option. Slightly less detectable, cheap, and can be deployed in quantity if desired.

https://youtube.com/watch?v=9XoTAvcKgOE

Toward the end of the video (beginning about 4:30) the VP of ocean mapping talks about bathymetry as a major future mission. I note that whilst the surveyor craft has an international-orange sail as the other droneships, the body is battleship grey. I suspect there may be alternatively-liveried mission sails as well.

More on that here: https://www.saildrone.com/tag/bathymetry

Connan seems to be USN Ret.:

https://www.crunchbase.com/person/brian-connon

In fact, I'd put reasonable money on that being a chief mission consideration for the technology. Drop a bunch of these in bad weather --- they'll make good coverage, and it's going to be difficult as heck to get out, spot them, and take countermeasures.

Give it a grey paint-job and maybe drop some radar-absorbing material on it, and they'll be fairly stealthy.

There's no other way than sonar to detect things like mountains underwater?

That's interesting. Seems by now we might have something else that does that. A way to use sonar that obfuscates the source of a ping, underwater lidar, submarine drones, something?

What signal would you send that isn't detectable by anyone but you?

An array of tactile antennae/feelers?

now you’re thinking like a catfish! i like it

Entertaining the idea of a probe sticking out the front led to a realization. The problem is you're never going to stop in time if you're at speed. You need to know well in advance that something's there.

Perhaps a sound signal that's a copy of something naturally occurring, e.g. by sea animals.

That came to mind for me too.

Fleet of small scale autonomous drones? Bonus points if they're water soluble.

The generally accepted way to detect large geological features underwater, if you're not a survey ship (moving slowly, running multiple loud sonars, etc.) is to have and use accurate navigation charts.

Wretched shortcomings in that regard seem well-accepted as the cause of the USS San Francisco's mishap.

Doesn't look nearly as much damage as to USS San Francisco though, the idea of the Connecticut having hit a container seemed more likely to me.

The USS Connecticut weighs about 10k tons. A container weighs maybe 10 tons. That sort of collision might or might not even cause damage. But by the law of inertia, the sub would, in even the worst case scenario, barely slow down and you wouldn't have 10 injuries.

The USS San Francisco was going maximum speed. The Connecticut can do 35 knots but judging from the injuries almost certainly wasn't.

As anyone who has hit a deer in their car can tell you, that’s not how momentum works.

A deer weighs maybe pounds 100 lbs. A car weighs maybe 3000 lbs for a 30 to 1 ratio. That sub weighs 1000 times more than a container. That is how momentum works.

If you hit a 10 ton object and _any_ of the collision is inelastic, that is a tremendous amount of momentum to dissipate. It might not change the speed of the sub much, but it could still cause a lot of damage to the hull which could then injure sailors inside.

Wouldn't the submarine sink if the hull was so deformed that it damaged 10 sailors?

Not if the majority of the damage to the sailors came from them being unexpectedly bounced around the corridors. If they weren't expecting it, they weren't strapped in or otherwise secured.

That all depends on the cross section of the impact area. If you'd hit the container in a corner (extremely unlucky) then that would be highly annoying. But subs are made to survive pretty strong impacts, including using the conning tower to ram through ice layers. They're immensely strong compared to regular vessels due to the kind of forces they are exposed to when diving deep.

Depends on the deer. Mule Deer here that you can find the front yard of your house can be 200-300lbs. And depends on what you mean by, "deer". Are you think about reindeer? Elk? MOOSE? Hitting a moose is gunna be a bad day.

Why would someone refer to a moose or an elk as a deer?

Deer, Elk, and Moose are all part of the Cervid or deer family.

Also, in various parts of the world, the names are commonly used for different specific animals, which can be confusing. What's called a Moose in say, Sweden is called an Elk in Britain. But what we call elk in the US are a different species entirely. Elk in the US are another name for the red deer species, which was once considered merely a subspecies.

Not sure about what deer you've been around - but the deer family have hit definitely weighed about two or three times that.

Saying I've remembered since I started driving: If it's a deer, hit it, better than hitting a tree. If it's a moose, hit the tree, better than hitting the moose.

Total ratio is only relevant if you want to know how much the sub/car slowed down. Kinetic energy is more relevant if you want to know the physical damage sustained.

If you shoot a bullet at a tall wall and a shorter wall, the bullet hole will be the same.

Alternatively, a deer will still ruin the front end of a car with 1000X the mass.

The energy of the impact will be 1/2mdeltaV^2 either way.

I recently hit a deer while going about 60-65mph in a fairly heavy campervan (3 100amp AGM batteries + ~30 gallons of water storage and other gear).

It did $10k worth of damage to my front end.

Deer ended up 150-200 feet away in a ditch.

I barely felt it.

Yeah, and if the deer went through your windshield you likely would have been seriously injured. The relative size of the object to the vehicle doesn’t have to be large to cause significant damage or injuries. Just because you are big doesn’t make you invulnerable.

You're certainly right but still missing the point. The 10 injuries were most likely not due to a vulnerable part of the sub. They were likely due to a sudden change in the sub's motion, which wouldn't have occurred had they hit a container.

There a reason why vehicle crash testing is done with a vehicle of comparable weight. If the tests of a Mini Cooper were done with your camper van, there's no way they would get a reasonable safety rating.

It's not the mass difference that matters, but how rapid a momentum transfer your structure can survive.

You have underestimated the weight of a loaded cargo container by more than 50%.

That's a maximum weight, typical containers are maxed out volume wise long before they are maxed out weight wise unless they carry large amounts of steel, and this particular container would have to have been floating submerged which puts a pretty low upper limit on how much it could have weighed.

If a shipping container is partially submerged, I think you should include the mass of the water that is included in the shipping container. Assuming a neutral buoyancy, this would put the upper limit of mass at around 42 tons.

this is the correct methodology (though I dont know shipping container sizes beyond estimating ship heights as 10ft times the number of containers.

First the container is sealed and it will float. At that point, it will be a hazard to surface navigation, and the Coast Guard, the Navy, ..., will try to recover them or sink them. Or the shipper will.

Once the seals break down, the container will become heavier than water, have negative buoyancy (Archimedes Principle), and sink. As it sinks the pressure will increase and any remaining air will be squeezed out and it will sink faster.

Also, there really aren't that many containers lost overboard (1,382/yr on average) and few are not recovered. There are a lot more sea mounts, about 14,500.

> it's so odd that immensely huge features like these are still not yet charted

The fact that this was in the South China Sea makes me wonder if the reason it's uncharted is that the Chinese recently created it; for some time they have been building artificial islands in the South China Sea in order to claim that entire body of water as Chinese territorial waters. (It's outrageous that this doesn't get a lot more international attention; it's as if the United States started building artificial islands around the boundary of the Gulf of Mexico in order to declare all of that to be US territorial waters. Imagine the outcry.)

The South China Sea issue does get a fair amount of attention.

It is very unlikely that this is the cause of the Muirfield Seamount. They would have had to artificially create an underwater mountain taller than Mount Rainier to do so. The surrounding water is 16,000 feet deep.

Inconceivable. And I do know what that word means.

There was this a while ago, in a region not that far away.

[1] https://www.volcanocafe.org/japan-the-fukutuko-oka-no-ba-eru...

[2] https://www.ladbible.com/news/news-ghost-ships-brought-up-fr...

Also other recent volcanic activity in Japan, with news about volcanic ash from underwater volcano blocking harbors.

Maybe similar things happened there, not so visible, and weren't charted because of that, being new?

Maybe they were saying haha we know where you patrol

That seamount was above water until the end of the Younger dryas, and the 100+ meters of sea level rise that came with it. Perhaps it was once a coral reef?

The Monroe Doctrine doesn't count?

What do they teach at MIT ?

Your comment reminds me of that scene in The Hunt for Red October managed to slip away from a chasing torpedo--the Russians had "hyper-accurate" maps of the underwater terrain and knew exactly when to turn from the torpedo's path...

Same same recall. But is it real though.

If you saw it on the big screen or the internet, its real.

The sub movie Hunter Killer applies this as well.

As far as I know, the South China Sea is pretty geologically active. So it's possible the seamount got created since the last good mapping

The sort of geological activity needed to create a large seamount (especially within mere decades) would be obvious to any country with a few seismometers.

Geophysicist here. No, SCS does not have any active volcano in the ocean basin. The last volcanic activity is around 6 million years ago.

Oh cool, then maybe you can explain why someone said that the it was due to a "dangerous grounds miniplate"? I thought the contention was the bed of the SCS was a thin plate that formed mountains quicker because it moved faster because it was smaller? So maybe the seamount moved?

I'll admit I'm pretty ignorant here, and could have been mislead. Or maybe it's all true and the answer is still "yeah, it only takes 100 millennia, not the usual much longer"

An interesting aspect to the story is that it looks like China forced the Navy to disclose details the accident publicly accusing the US of a cover up.

https://www.military.com/daily-news/2021/10/29/china-accusin...

I was worried it was a collision with a Chinese vessel. Communication was poorly handled by the Navy.

"US Pacific Fleet released a press statement on the submarine incident five days after the collision occurred on October 2, delaying its release because of operational security concerns. China has capitalized on that delay, suggesting it is suspicious."

Public notice within 5 days isn't too bad given we are talking about a strategic asset.

Yes, you are right, especially under normal circumstances. In this case it allowed a window for China to take advantage of the delay in releasing the information and use it for their own PR spin.

5 days also makes sense for a cautious quiet transit to a major port.

More info

https://www.thedrive.com/the-war-zone/42954/uss-connecticut-...

The mountain is in the South China Sea, a leading focus of the US Navy. We learn something about the state of underwater mapping from the fact that even in the South China Sea a mountain wasn't mapped.

Why can't satellites map the topology using something like RADAR (though likely using other frequencies), which I believe is done on land? Is there no technology that will penetrate water sufficiently? Is it a physical limit of electromagnetic energy and water?

I assume it hasn't been done by satellite because otherwise we wouldn't have unmapped mountains, and because the same technology could help find submarines, taking away their stealth and eliminating a nuclear deterrent.

Radar does not penetrate through brine water. Other remote sensing techniques have such poor resolution that they are relatively useless for this task. Unfortunately, sonar based bathymetry is really the best tool for this task and that means you have to run around with a surface ship mapping out the sea. As you can imagine the Chinese are not a big fan of American ships doing that in waters that they claim to be theirs.

> sonar based bathymetry is really the best tool for this task and that means you have to run around with a surface ship

Why can't it be done from a plane or satellite? I can imagine answers (e.g., sound doesn't travel as well through air), but does anyone know?

> the Chinese are not a big fan of American ships doing that in waters that they claim to be theirs

I'd be surprised if that stopped the US in this circumstance. They regularly conduct operations in the South China Sea.

Sound doesn't transmit well at all between air and water in either direction. It just bounces off. You can't hear what's going on underwater when you're out of the water and you can't hear what's going on above water when you're underwater.

How do anti-glare coatings on lenses work? Could something similar be devised for the air-water interface?

Sure. You just need to apply your anti-glare coating to the world's oceans.

I mean for acoustic waves. Alternatively/similarly, could an aerial sonar waveform be matched to the ocean surface waves to cause constructive interference below the surface, and destructive above it? Would it be possible to recover the reflections afterward?

https://en.wikipedia.org/wiki/Anti-reflective_coating

> Layer thicknesses are chosen to produce destructive interference in the beams reflected from the interfaces, and constructive interference in the corresponding transmitted beams. This makes the structure's performance change with wavelength and incident angle, so that color effects often appear at oblique angles.

Water isn’t air? Even air can become opaque.

Sound doesn't travel as well through the air, but it still does. The primary reason that you can't do it from the air is that the surface of the ocean is a big irregular reflector of acoustic energy from the air, so the overwhelming majority of the energy will be lost. It just would never be practical.

It might be possible to use airborne gravity gradiometry to map seaborne mounts. I'd never considered that before, but I see no reason to think it wouldn't work.

I'm finding it hard to believe that satellite and/or local gravimetry would entirely miss an underwater mountain.

The kind of sensors you can put on a plane or satellite simply can’t penetrate seawater effectively. It absorbs radar, dissipates heat and light. Sonar sound waves in air mostly just bounce off the ocean surface.

This is why submarines are so stealthy and therefore militarily useful. As long as they stay quiet they’re almost impossible to detect without using relatively short range active sonar.

The air / water interface makes it impossible to get any useful sonar data from an aircraft. Some military helicopters carry dipping sonar that they can temporarily lower into the water, and specialized aircraft can also drop sonar buoys, but those are designed for detecting submarines and are mostly useless for bathymetry.

The US Navy does regularly operate in the South China Sea. In fact the USNS Mary Spears oceanography research vessel was there recently, presumably gathering bathymetry and other data.

https://www.marinevesseltraffic.com/vessels/USNS-Mary-Sears-...

Thanks.

(I'd upvote you but for some reason votes don't stick, on comments and stories: When I reload the page, the arrows return, as if I hadn't voted. flag/vouch behaves normally. Perhaps a mod will read this.)

Votes typically take a few seconds to resolve, possibly longer under load. HN's JS indicates them immediately when you're on the page.

Check your profile's upvoted comments / posts link (https://news.ycombinator.com/upvoted?id=wolverine876&comment... -- that's private for you only) to see if your upvotes have been registered.

If not, drop a line to hn@ycombinator.com as I suspect they'll be interested.

Thank you. No upvotes in 2 days via that link and I'm not that stingy! I upvoted your comment just before I wrote this.

I'm confirming either no upvotes (or at least balanced ones) on my GP comment above.

What browser are you using? We changed hn.js a few days ago to use the Fetch API - I wonder if this is related.

It's probably not a configuration you test against (and almost certainly not worth testing against), both an unusual and an old browser used for compatibility with something else.

  Tor Browser 8.5.5
  - built on Firefox 60.9.0 ESR
  NoScript 11.2.11
  - ycombinator.com is 'trusted', which has always
    been sufficient for voting to work

So I'm not filing a bug report, so to speak, but if it helps you track down something useful:

* It happened once before, I think sometime in 2020 (sorry I don't recall more precisely), and it likely would have been in the same browser. I forget what fixed it but it went away eventually. Possibly it was just restarting the browser, which I can try if that will help (but that will lose the current state, of course, and Tor Browser deletes a lot of the current state on a restart; it may create a new profile).

* The top comment on my upvote page is this one from 2 days ago: https://news.ycombinator.com/item?id=29062312

* I don't know the precise times of my comments, of course, but if you see I was commenting then I was very likely voting (though my voting slowed a bit in the last day or two when I noticed they weren't registering).

* I just upvoted your comment at 22:44:07 UTC

I think the problem is that our JS now does this:

  fetch(url);

where it used to do this:

  new Image().src = url;

... and that seems to breaking a few edge cases of older browsers.

Can you try collapsing a comment somewhere and then refreshing the page to see if it stays collapsed? If it doesn't stay collapsed, that's another sign that fetch() calls aren't making it to the server.

> Can you try collapsing a comment somewhere and then refreshing the page to see if it stays collapsed?

I tried a few times on a couple pages, and they don't stay collapsed after refresh.

EDIT: Using another browser on this computer, I just logged into HN, and upvotes and collapsed threads seem to stick. I upvoted your comment (i.e., the parent to this one I'm writing) at 00:27:49 UTC.

This browser (another old and unusual one, but much more recent):

   Brave Version 1.25.72
   - built on: Chromium: 91.0.4472.101

It looks like you managed to upvote https://news.ycombinator.com/item?id=29101929 - did you do anything different to get that to work? e.g. different browser or turn JS off?

Yes, different browser. See my edit in the GP (which seems to have crossed on the wire with your comment).

I reverted the change for voting and collapsing. Does it work now?

Yup, both upvoting and collapsing work. Thanks! Though I wouldn't want to be the edge case that stands in the way of an update. I can workaround it pretty easily.

Another user had emailed to complain of something similar. Where there are two there are probably many, so I think we can leave it this way—it's no big deal. One question though: do 'hide' links on stories work, e.g. on the front page or /newest? I suspect they probably won't, because I didn't revert that part of the change.

> One question though: do 'hide' links on stories work, e.g. on the front page or /newest? I suspect they probably won't, because I didn't revert that part of the change.

I've never used that feature so I don't know what's supposed to happen ...

1. On /newest, under a story, click "hide"

2. Story disappears, stories beneath it are renumbered, an additional story appears at the bottom of the list.

3. Reload page (F5)

4. Hidden story reappears

EDIT: Also, I just noticed that when I upvote a story, the points displayed under the story don't increment until I reload. For all I know it's always been that way, but at the moment, of course, I'm a bit more attentive. Not a problem for me, but maybe useful for you.

> As you can imagine the Chinese are not a big fan of American ships doing that in waters that they claim to be theirs.

Why does anyone (besides China) care? Nobody in that region recognizes those claims.

> Why does anyone (besides China) care? Nobody in that region recognizes those claims.

China has power, military and economic, and thus can't be ignored. If Fiji claimed a region of the Pacific, it wouldn't matter (in this respect).

>> Why does anyone (besides China) care? Nobody in that region recognizes those claims.

> China has power, military and economic, and thus can't be ignored. If Fiji claimed a region of the Pacific, it wouldn't matter (in this respect).

It isn't ignored, but that doesn't mean those claims are recognized. The US (at least) takes actions to specifically show that:

https://en.wikipedia.org/wiki/Freedom_of_navigation#Freedom_...

> It isn't ignored, but that doesn't mean those claims are recognized.

Agreed. The GGP was asking if anyone cared. People certainly care about the claims, even if they don't recognize them.

Because China happens to have nukes, probably.

A good techno-thriller might be some group of hackers nab the Chinese bathymetry database, which then finds its hands in some war hungry US general

Yes, water is a very excellent RF attenuator at all frequencies. Acoustic waves travel quite far in water, especially in the ~1 kHz range. Making loud sounds isn't something you want to do when you're somewhere you're not supposed to be though. If a mountain isn't making any noise then it's going to be difficult to know that it's there.

Electromagnetic energy doesn't penetrate water, at least not enough of the right wavelengths to be useful for mapping. The US Navy and NOAA do sea floor mapping using sonar. But it's a big ocean and some areas haven't been covered very well.

> Why can't satellites map the topology using something like RADAR

If you were close enough, say in a plane, you could do something to cause a soundwave to propagate through the water. Say you fire a femtosecond laser pulse or blast it with an ultrasonic pulse. You could then, probably, use a second laser to pick up the reflections as disturbances on the surface. Otherwise you're probably stuck, since RF doesn't propagate well through a conductive fluid. Submarines can communicate somewhat using very, very low frequencies of electromagnetic energy, but the problem with that is the resolution at those wavelengths would be very, very poor.

The best bet at this point in time is probably to just make a bio-mimicing, underwater drone and map under the surface. If you were really clever, you'd just hook some electrodes into a whale's brain and make it carry your mapping payload, using whale sounds to map the ocean floor. Not very nice thing to do to a living creature, but we've done very bad things in the name of national security before.

The best bet at this point is to just tow a powerful side scan sonar behind a surface ship, as has been done successfully for decades. No need for any overly complex Rube Goldberg schemes.

I'm talking about areas where you need to covertly surveil the seafloor(say, in waters near China). Of course you wouldn't need any of those schemes for a normal mapping operation.

Civilian geophysicist (but not an oceanographic one) here. This is my best understanding:

As others have posted, above surface based propagating EM techniques won't work because seawater is conductive.

Acoustic waves are probably the best way to map bathymetry, but that requires active sonar. The subs don't use that because it gives away their position. Surface mapping (sidescan sonar) in the area is probably the best viable technique to do the job, but geopolitical concerns make it impractical.

Aside from sonar, gravity and magnetostatics could in principle be used to find seamounts. But both suffer from a fundamental problem that "upward continuation" decays short wavelengths exponentially faster than long wavelengths. In other words, to horizontally resolve a seamount with a characteristic length of (say) 10km you'd need to fly no higher than 10km. That rules out satellites. What's left are airborne and surface based surveys, which face the same geopolitical issues as sidescan sonar.

Give all of that, you might as well do the sonar survey, as long as you can solve the geopolitical problems.

Gracias.

> above surface based propagating EM techniques won't work because seawater is conductive

Dumb question: My very poor understanding is that the EM images are created by objects reflecting the energy back to the sensor. Is the problem that the water's conductivity will spread the EM in every direction or otherwise cause it to behave unpredictably?

> "upward continuation"

It's mostly that the inbound energy doesn't even reach the reflector. An optical analog (yes, yes, EM true) would be trying to image something well behind a mirror.

"Upward continuation": both gravity and (after certain manipulations) magnetostatic surveys obey Poisson's equation. The characteristic (Green's) function has a 1/R decay. If you will allow me another optical analog, upward continuation is closely analogous to a detailed image being convolved with a 1/R blurring function. That's the heart of why I (roughly) say you can only resolve stuff of characteristic length R by observing/measuring from below a height of R. Higher than R, and the short wavelengths are completely attenuated, and you lose ability to resolve them.

Thank you; that makes some sense!

There are no geopolitical concerns which prevent the US Navy from doing side scan sonar bathymetry in the international waters portion of the South China Sea. In fact they do this on a regular basis. But they haven't covered the whole region yet.

Which does kind of beg the question, why did a fast attack sub hit an uncharted seamount? (If that is indeed what happened. Maybe it was "user error" in which case it sucks to be the sub's captain and sonar operator.)

> There are no geopolitical concerns which prevent the US Navy from doing side scan sonar bathymetry in the international waters portion of the South China Sea. In fact they do this on a regular basis.

China, a powerful country, says it's their territory and threatens those who disregard it. Many think it's the most likely place for a US-China war, besides Taiwan. That's a geopolitical concern.

The US chooses to handle it in a certain way, including by operating in the area. The US says that legally there is no concern. But that doesn't preclude a geopolitical concern.

I think it’s not just possible but done[1], I do wonder why it still happened though. Maybe maps were outdated or resolution is not ideal?

1: https://www.esa.int/ESA_Multimedia/Images/2012/05/Mapping_th...

That radar is actually measuring the sea height. Sea height (on average) more-or-less defines the geoid (the height of an equipotential surface) over the oceans. That ignores sea height disturbances due to winds, currents, tides, etc. The geoid, in turn, is sensitive to local mass distributions. So yes, "it has been done", but the result is nowhere near the resolution or interpretability of a sonar survey. Still, it would greatly surprise me if the military _wasn't_ already using the technique. So, if there were interpretable results from the technique, I would personally expect the Navy already had them...

Why is SCS US’s business? No I’m not from 50cent army.

Generally the U.S. leads a coalition of western nations that protect international shipping via freedom of navigation exercises. So if some country like India declares it owns the Indian Ocean, or China declares it owns the SCS, or Egypt announces it owns the Mediterranean, then the U.S. (and other nations like the U.K., France, etc) will sail through the area as well as acommpany shipping traffic to demonstrate that, no, these are really international waters that anyone has a right to use, and that no one can claim for themselves.

This is an important and useful exercise in order to keep important shipping lanes free. This is critical to the functioning of the global economy, on which the U.S., U.K., and other nations depend. It is in their interest to ensure that no nation claims ownership of these global transit routes.

Great answer, and I think there are much broader reasons too:

International order is fundamentally anarchy. There is no power - no world government - that can enforce order (the United Nations is just an association, a place where sovereign countries can meet and make arrangements with each other). If the order breaks down, if 'might makes right', then international wars start; wars are bad or catastrophic for everyone. WWII was so destructive that the victors worried that the world could not survive another one (one reason they started the UN and what became the EU) - and that was 75 years ago. The 'US-led rules-based international order' strives maintain an order based on rules (laws), not on might.

(Yes, this is all very simplified; motives and actions are not so simple.)

A simple example is when Iraq invaded Kuawait in the early 1990s. They had the might, so they took it. The US, openly stating they would maintain international order, drove them out of Kuwait. To reinforce the point, they did it according to international law, and with a coalition of international partners.

China seizing the South China Sea is a serious threat to that order - what will China seize next? If the only way to stop them is to fight a war - if there is no rules-based way to do it - the world and the people in it are in big trouble. So the US and allies (which is not only western, but democracies all over including Japan, India, etc.) work to undermine that claim.

A good reminder that we know less about what's happening under the surface of the ocean than we do about LEO and near space.

A different commenter mentioned airborne gravity gradiometry to map seaborne mounts. It definitely would work up to a point. It would tell you "there is more mass here", but there are different ways to interpret that information. A gravimetric map is not a map of land contours, but of the density of the geologic column below.

That said, nearby masses (not below the sensor) also can influence the results. When doing gravimetric surveys on land, nearby buildings can have sufficient mass to influence the readings, so certainly a nearby seamount would also influence readings.

Theoretically, a gravimiter inside of a submarine could be used to detect nearby masses. Which might or might not be a seamount you're about to run into. It would be like having automatic collision brakes on a car that could be misinterpreted based on ambiguous interpretation of sensor data. You'd want to get it right.

For some background reading, I found this short write-up online about interpretation of gravity data -> https://sites.ualberta.ca/~unsworth/UA-classes/224/notes224/...

I know of one gravity gradiometer technology developed by the US Navy for submarines that was de-classified and commercially deployed in airborne gravity (gradiometer) surveys. That happened in the '90s, and (as of about 2010 or so) the technology was adapted and actively deployed in Australian mineral exploration. The mining technology was named "Falcon" and the BHP was the mining company that deployed it. I have been out of that game for a decade, so for all I know the tech has changed corporate ownership a few times, but it definitely exists.

You are absolutely correct. There are many, many ways to interpret such gravity information -- most involving solution of ill-posed inverse problems. I have my personal favorites, but so does every other working potential fields geophysicist.

I used to be a research ship tech years ago and did a lot of shipboard gravity surveys on Navy ONR contract. Which kind of dates my geophysical work :) Sure could cover a lot more are on with a plane! I also wrote software to do 2.5D forward modelling for a geophysical consulting business.

FALCON is a different beast than the shipboard gravimeters.

Shipboard gravimeters are -- in effect -- extremely well damped/shock absorbed/sprung/mechanically isolated standard spring-stretching gravimeters. Essentially the same idea as Lacoste-Romberg machines from post WWII. The damping is to ameliorate the accelerations from the ship moving through the ocean. Similar systems are flown in aircraft, but they both face the same exact problem: How the hell do you get rid of the background accelerations to measure something akin to a geological signal?

Falcon is a gradiometer. There are accelerometers at the end of a spinning arm -- at least that's my mental picture. Perhaps it's a flat plate with two sets of accelerometers at 90 degrees from each other to measure two gradient components simultaneously? In any case, it is designed to "reject the common mode" between the paired accelerometers. If that rejection is done "successfully enough", the difference in the accelerometers' readings samples the spatial gradient of the gravity field at that place and time. A whole lot of ingenious engineering, a lot of on-device processing, and a lot of data massaging afterwords yields an estimate of the local gravity gradient. It's a very impressive piece of kit, and my hat's off to whoever dreamed up the idea in the first place -- even if it was buried under security classification prior to release in the '90s.

Yea we used old L&R ones on the ships. GPS receiver was $60k and we only got 2-3 hours of semi-ok GPS per day, but also recorded speed & heading, used some early satnav systems with fixes once in a while, and ranging navigation from custom transmitters on shore. Lots and lots of post processing of the nav to try and use it to correct the gravity data. It was pretty crude.

I always wonder if the whales laugh at submarines for swimming around blind (not using active sonar).

One of the more interesting thing over the last 10 years that I've been reading about has been the amazing amount of volcanic activity that is ongoing under the oceans. Not as photographic as crushing a community on an island, none the less mountains are growing out of the ground at an astonishing pace under the sea.

If an island appears in the middle of international waters, who gets it? Is it finders keepers?

I believe most of these islands formed by volcanoes are temporary and they are claimed by the ocean very quickly.

https://www.quora.com/International-Law-and-Legal-Institutio...

I find it kind of crazy that the ocean isn't mapped out like most of the roads in the world are with street view. I get that sonar isn't stealthy and is not great for marine life, but considering the budget and capabilities of the U.S. military, I'm surprised they haven't gotten that over with as its own mission.

Some companies are trying some pretty cool tech

https://youtu.be/eR8TQ2rXTbE?t=119

Dang read up on USS San Francisco briefly and ran across this tidbit about sonar, dang.

> For those who dont know how tremendously loud it is. It can be used to kill enemy divers if they are near your ship. It will rupture your lungs at 200 Db and hemorrhage your brain at 210 Db, sonar operates at 235 Db ... also affects sea life

The ocean's real big.

Maybe they should try using google earth

If it were just marine life the Navy would certainly be willing to press the sonar button.

The problem is that navigation-quality sonar gives away the position of the submarine, which is the polar opposite of what the Navy has submarines to do.

Shipping lanes do exist, and are quite heavily traveled. They're marked on nearly all nautical maps in bright pink and even have their own rules/laws, and a lot of areas even have radio beacons to help ships into ports from many miles out. These "super highways of the sea" are very well marked and mapped.

Outside of major shipping lanes there's almost zero economic reason to map the areas immediately outside of your own economic zones

It’s common to over estimate human capabilities. Perhaps “holywood” tends to exacerbate that.

US Navy is a mess, 3.5B submarine that is one of only 3 active in its class is now out of commission.

They also imply human error, especially bad considering the Bon Homme Richard was lost due to bad fire fighter training. Billion dollar accidents seem to be becoming common in the Navy. At this point I really have no confidence in the US military considering the performance during the Afghanistan withdrawal. The performance is pathetic considering the budget they have

Billion dollars accidents will become more and more common because billion dollars ships will become more and more common.

Accidents happen, risk management will never end that.

Propublica has a fascinating series on the failures of the modern Navy: https://features.propublica.org/navy-uss-mccain-crash/navy-i...

I don't know why I'm still shocked by things like this, but I am.

> The Navy installed touch-screen steering systems to save money.

> Ten sailors paid with their lives.

Well, to be fair, they decided to go with the Virginia class as a replacement after only three.

US military considering the performance during the Afghanistan withdrawal - that's pure DC leadership and not a reflection on the actual troops.

>that's pure DC leadership and not a reflection on the actual troops.

true, but the fact the Pentagon has been filled with liars for decades isn't a positive sign. And nobody has paid any consequences for the failure, not a single person fired or punished. Having lions led by sheep isn't a consolation, the results are still the same

Major changes aren't going to happen until something really bad happens, and by then it might be too late to matter

which ended up not really being cheaper

This assertion is interesting.. Even before inflation, the Seawolf cost per unit was higher than 774, and it was nearly double in inflation-adjusted terms. You could argue that the Block V VAs are closer to catching up, but at this point in the program it's better understood as an SSGN (which, ironically, is now out of style just as it's starting to be built.)

Besides this, everything about Seawolf screams expensive, which can't be said about VA.

Why are ssgn outdated?

It's a 5.5B submarine actually

>only 3 active in its class is now out of commission.

There's potentially even worse intangible costs. Chinese military watching rumormills are alleging that Russian and Chinese forces were monitoring the multi-carrier exercise that Connecticut was part of, may have isolated the subs acouistic signiture and are poring over old sonar records to identify past Seawolf class activity. I'm somewhat skeptical, but PRC has been absolutely saturating region with anti-submarine warfare assets especially when US conducts exercises in the region.

> PRC has been absolutely saturating region with anti-submarine warfare assets

While the US has been saturation the region with submarine warfare assets.

Are there GIS / mapping software where you can fly through sea mounts with water off? Maps of ocean floor would be amazing to explore in MS flight simulator.

http://onemanz.com/wp-content/uploads/2016/03/ocean_floor_ma...

If it's big enough to hit, how does it avoid any of the onboard high-tech high-budget detection systems?

I understand the oceans are massive. But if there are 100,000 if these "structures" wouldn't there be better prevention? This are world class and world beating war ships, eh.

https://www.youtube.com/watch?v=dqDqvKYDv9M

I wouldn't read too much into what they say after the fact, and resign to the fact that we'll never know what actually happened.

Isn't there some sensing system that works within roughly the inertial envelope and is mostly or even theoretically undetectable outside of it? You'd think the subs would have it.

Shouldn't a submarine have some sort of system in place to warn about or prevent collisions? It seems like human error has to be a pretty large factor here.

What is the (covert) sensor for this system?

And yes, human error is a prerequisite for this to happen, and in no small amount.

A system like what, precisely? Keep in mind that such a system needs to ensure that a submarine remains almost impossible to detect, which is the whole reason this type of platform exists in the first place.

Large whiskers like a cat

There's a public effort to get it all mapped:

https://seabed2030.org/

Would it be unusual for a sub to be traveling in a poorly mapped area? Seems they would only follow well known trusted underwater pathways

US spy planes over South China Sea likely surveyed nuclear fallout of sub collision, observers say

https://www.scmp.com/news/china/military/article/3154476/us-...

"That mountain had it comin'" replied the driver of the submarine...

"It wasnt there when I checked the mirrors before reversing"

Aren’t there maps?

Only where you go and record data to create said maps.

Sonar systems have not mapped the entire sea floor, and as others have pointed out, sonar is the main effective way to create such a map.

and running sonar in enemy waters is not exactly a good idea :)

True, though they are very important for continued and safe commerce in said waters. If you have any kind of ship-based commerce passing through waters, you want good charted data, and you want that data made public for the safety of ships coming and going.

It's worth pointing out that regular, non-military ships do run into uncharted seamounts too. A good example is the discovery of the Muirfield Seamount, which happened when a ship in what charts said was water over 5000 meters deep ran into it. The top was only 16-18 meters below the surface.

See https://en.wikipedia.org/wiki/Muirfield_Seamount

Well, now the map of that area has one mountain on it.

Charts. Yes, and arguably that's part of the problem. If everything is just 'charted', you lose sensitivity to the things that are old or low resolution because it's all on the same chart.

Reminds me of this urban legend story:

This is the transcript of a radio conversation of a US naval ship with Canadian authorities off the coast of Newfoundland in October, 1995. Radio conversation released by the Chief of Naval Operations 10-10-95.

Americans: Please divert your course 15 degrees to the North to avoid a collision.

Canadians: Recommend you divert YOUR course 15 degrees to the South to avoid a collision.

Americans: This is the Captain of a US Navy ship. I say again, divert YOUR course.

Canadians: No. I say again, you divert YOUR course.

Americans: This is the aircraft carrier USS Lincoln, the second largest ship in the United States' Atlantic fleet. We are accompanied by three destroyers, three cruisers and numerous support vessels. I demand that YOU change your course 15 degrees north, that's one five degrees north, or countermeasures will be undertaken to ensure the safety of this ship.

Canadians: This is a lighthouse. Your call

Copied from here:

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

Not a bad lesson to keep in mind in life: sometimes you're a lighthouse that has to deal with a ship, which is frustrating. And sometimes you're the ship, and you should learn from those mistakes.

lol! Great urban legend, you're right. I remember hearing it back in the 90s!

https://www.snopes.com/fact-check/the-obstinate-lighthouse/

great link! thanks

I don't know if it's fake, but I've heard this clip and the encounter is with Spain: https://www.youtube.com/watch?v=xkx0MxK-Yl4

Similarly dramatized in this video:

https://youtu.be/ajq8eag4Mvc

It is funny, but isn’t it kind of a maritime rule or law that a smaller vessel always gives way to a larger one? So it makes sense they would say that really.

> isn’t it kind of a maritime rule or law that a smaller vessel always gives way to a larger one?

The more maneuverable vessel needs to give way.

No. According to international maritime law ships propelled by engines give way to ships under sail. There are no specific rules for sizes, so theoretically if a triple E class Maersk containership catches up to your dinghy powered by a 5 hp outboard it has to give way (because it approaches from behind).

That's mostly true but there are limited circumstances where there sailboat would be the give way vessel.

The Swedish rules I learned as a boy in a dingy included that leisure craft yield to commercial, regardless of propulsion.

I take my boating leisure so seriously that I pay myself for every trip. Now move.

Yep. As a boy in the UK, "Steam gives way to sail, but don't try it with the Isle of Wight ferry."

In a restricted channel that isn't the case. If you see a triple E coming at you and you're in a dinghy, it will be in a channel and you will want to skedaddle; even the bow wave could swamp you. Usually it will have escorting tugs to shoo you away. But I've been in a sailboat and had Coast Guard machine guns pointed at me and ordered to leave the SF shipping channel because an LNG tanker was a mile or two away.

OTOH, I've been yelled at by Red and White tour boats who were hugging the shore for current relief. That's all nice but I did have right of way and maintained it.

> I've been in a sailboat and had Coast Guard machine guns pointed at me and ordered to leave the SF shipping channel

Why on earth is American law enforcement so braindead macho?

Does anybody think this is acceptable?.... To do something so stupidly dangerous as pointing a gun at somebody? Why do you tolerate this?

Here in Blightly, I guarantee such behaviour would lead to prosecution of those involved. (And I wouldn't be surprised if the yacht crew first moon the ignorant coastguard whilst quoting COLREGS).

https://www.imo.org/en/About/Conventions/Pages/COLREG.aspx

COLREGS, Rule 9, Narrow Channels, (b) A vessel of less than 20 meters in length or a sailing vessel shall not impede the passage of a vessel which can safely navigate only within a narrow channel or fairway.

The CG was correct if a bit rude.

Depending on how far out, you might've still been under the inland rules.

Not that my pedantry changes anything - sailboat still comes below "vessel restricted in its ability to maneuver" and you gotta give way all the same.

"...Helge Ingstad believed the vessel calling them to be one of the oncoming vessels they were tracking on radar. Assuming the tanker, slow moving and with its bright deck lights obscuring its navigation lights, to be part of the shore installation,...":

https://en.m.wikipedia.org/wiki/HNoMS_Helge_Ingstad_(F313)

Your comment reminded me of one of the funniest ads ever that involved the German coastguard:

https://m.youtube.com/watch?v=gmOTpIVxji8

Reminds me of this one: https://www.youtube.com/watch?v=cUEkOVdUjHc

Hey, I know this ain't Reddit - but gosh darn you folks make me proud! Both of those links were to the exact videos that I came to my mind as well, and in the same order. Thank you.

This is hard to believe, what really did they hit or what hit them in that region is anyone's guess now.

I wonder how did this really happen? I mean, mountains don't move, at least not the the timescale of a submarine's motion: 1. Don't submarine use some form of radars to figure what's around then and where are they headed? 2. Assuming there were radars, were there no alarms or were the alarms ignored?

Submarines often don't use active sonar as that sonar could give away the presence and location of the submarine.

> Don't submarine use some form of radars to figure what's around then and where are they headed?

No. Radar is basically useless under water (many submarines do have surface search radar available, but that wouldn't help), and while they have sonar it breaks stealth and is usually used tactically, and with a very specific cause, not as a continuous interrogation of the environment.

Also active sonar deafens nearby sea life. Running around with it on constantly would be an ecological harm.

There are several circumstances where submarines don't actually use their sonar. They have it, but a submarine that is pinging is easily identified / tracked.

The underlying question is why they were in an area that hadn't been adequately mapped.

When evading, sometimes you have to leave the safe zone. OpFor will probably be familiar with safe operating areas and limit search zones. Would a USS Captain risk the boat by leaving uncharted areas to avoid detection? Just an idea of why.

> Don't submarine use some form of radars to figure what's around then and where are they headed?

No. When submerged they rely on navigation charts (with higher than normal bathymetric details), passive sonar, and their navigation instruments. A submerged submarine blasting out active radar and sonar to determine its position wouldn't be very stealthy.

Not every part of every ocean has complete bathymetric details. Seamounts don't necessarily move but undersea volcanos can grow in size significantly in short periods of time. A change in a few meters height can make last year's chart inaccurate today.

Just to add to what others said. If a submarines uses its sonar enemies can hear it. They can also save the subs unique signature and then use it later to identify it. You don’t want an enemy to know where and who you are.

It is pretty easy to run into a sea mount when active sonar isn't on. All it takes is misinterpreting a chart or an inaccurate chart.

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