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Volume is more like a tenth of that, I think? Maybe interior dimensions 2 meters diameter and 5 meters length gives around 16 cubic meters if my math is sane (Religion major, so go easy on me if not).

"not completely unreasonable" does a lot of heavy lifting here. I have zero intuition how the sound of an under water explosion of c4 compares to an implosion.

Your calculations might be wrong. If the distance is 1000 km (1M meters), and inverse square law is correct, then the sound would become 1M*1M = 1T times more silent. 1M times smaller is 120 dB less, and 1T times smaller is 240 db less, so the amplitude of sound should be at 210 - 240 = -30dB less than threshold of hearing.

Also, I wonder, if sound of explosions propagate that well, can one install multiple sensors to detect and map source of gunfire and artillery positions in realtime? (I hope I haven't disclosed NATO military secrets here).

You just invented ShotSpotter https://en.wikipedia.org/wiki/ShotSpotter

The sad part to ponder is most likely the team on the ship knew the sub was gone right when the communications was lost but kept the information to themselves.

Apparently they've "lost communications" in many of their other trips, which is why also hints at why they didn't raise the alarm for many hours.

From what I read and watched the company didn't take safety very seriously at all.

A former employee claims they were fired after brining up concerns about safety. The glass apparently was not rated for the depth required to see the titanic.

Which begs the question why there were no additional safety measures put in place after so many "skin of the teeth" trips making it back.

IMHO this was a get rich scheme the two founders spun up that went sideways. They spent the absolute minimum on safety and repeatedly cut corners on the sub in order to get it up and running, then charged people a ton of money to take a trip down deeper than the sub was clearly capable of going.

Look up "normalization of deviance".

Perversely, a bunch of near-disasters can reduce people's concern and make them less likely to demand fixes because "it did that last time too and everything turned out okay" is a powerful rationalization.

Yup.

Meanwhile, smart organizations have decades-ago stopped tracking (primarily) "Time-Lost Work Accidents" and replaced that with tracking "Close Calls".

I've seen prominent signs for "N Days Since a Time Lost Accident", and more recently "X Days Since a Close Call".

Sadly, it is so obvious that this CEO clown was doing everything possible to avoid experienced people ("not as inspiring to hire 50yo white guys as hiring young upstarts") so he could overrule any safety or redundancy concerns, firing people as soon as they raised things like "this porthole window is only rated to 1500m and we're going to 4000m", using cheap scrap scaffolding as ballast, and completely ignoring any kind of redundancy in case something went wrong. He seems to have gotten a just end, but his deceived customers didn't deserve that.

A good real-world example of the consequences of this normalization is British Airways flight 5390 [1]

  This problem extended far beyond this one individual, who was merely a symptom. The entire Birmingham maintenance facility, and perhaps British Airways more broadly, had a singular focus on “getting the job done.” If doing the work by the book took longer and jeopardized schedules, then doing the work by the book was discouraged. The shift manager who used the wrong bolts stated in an interview that if he sought out the instructions or used the official parts catalogue on every task, then he would never “get the job done,” as though this was a totally normal and reasonable attitude with which to approach aircraft maintenance. This attitude was in fact normalized on a high level by supervisors who rewarded the employees who most consistently kept planes on schedule. That a serious incident would result from such a culture was inevitable. The shift manager believed it to be reasonable to just “put on whatever bolts came off” and make a quick judgment call about what kind of bolts they were — not because he was personally deficient, but because he had been trained into a culture that didn’t consider this a flagrant safety violation.

[1] https://admiralcloudberg.medium.com/the-near-crash-of-britis...

Very few industries are safe enough to actually capture the "That could have been bad" events, that's what ASRS https://asrs.arc.nasa.gov/ does for the Aviation industry (there are equivalent agencies in various other wealthy countries e.g. CHIRP in the UK)

In the absence of a proper means to report "That could have been bad" as you say it can cause normalization. But it's understandable that you don't implement something like ASRS when you haven't solved most of your "That was bad" problems. If you regularly have CI failures due to the code not even compiling, "We need more unit tests" isn't top of the list of your problems.

I mean the CEO of the company is one of the fatalities so it's not like he thought and understood the sub was dangerous but was still willing to sell tickets to other people. We thought what is was doing was safe (obviously he was wrong) but he did have skin in the game.

I honestly see the company as a startup in idea. They couldn't afford to build a proper deep sea sub so they used the idea of new tech in the form of carbon fiber (which I'm assuming is way cheaper to form vs a titanium hull) and billed this as next gen. Everything that I read almost fits in the idea of "fail fast".

yes I believe in one interview the CEO said carbon fiber provides buoyancy but is much cheaper than syntactic foam, which other similar such vessels have used

"losing communications" could be a broad misunderstanding of Pogue's comments

https://twitter.com/Pogue/status/1671524465736335366

my "orders of magnitude" alarm is going off here. There's no way that the implosion of a fairly small sub is going to be heard in Boston even if underwater. Something doesn't make sense here.

Sound does travel extremely well in water.

http://resource.npl.co.uk/acoustics/techguides/seaabsorption... -- here is a quick calculator for sound loss by distance. I think actual geography is important too but from understanding whether or not it's hypothetically possible, it certainly looks like it.

For example, at the default inputs we see .061 db/km absorption. This is at 1khz. Higher frequencies attenuated more and lower frequencies less.

I have no idea what frequencies an implosion generates, but given that, a sound at 120db might still be 60db 1000km later. Certainly seems possible and in fact given what we have seen from the US Navy (detecting imploding soviet subs in the middle of the pacific ocean) it seems totally possible to me that this small sub could be detected if microphones were places in quiet spots offshore of the continental US and Canada.

I think we don't have enough information to rule out that this was detectable.