I have no idea specifically how loud it would have been. However with some probably-reasonable guesses, it looks like it actually would have been quite loud.
They found that a 10lb block of C4 exploding produced ~210db of underwater sound. If we use that sound level as an approximation of the implosion of 200 cubic meters of submersible, which seems not completely unreasonable, then we can use the inverse square law to calculate the perceived sound far away.
Halifax, NS is 1100km from the Titanic wreck. A sound that is 210db at 1 meter, is 89db at 1100000 meters. Boston is 1700km away; at that distance it would be 85db.
85db is really quite loud. You would be able to hear that, if you were underwater and paying attention.
If the implosion was instead, say, 180db, then it would have been 55db in Boston harbor. Still easily detectable by instruments.
For reference, when divers are performing construction using e.g. rock drills, those commonly reach 170db. The implosion of close to 200 cubic meters of air seems like it would produce a louder noise than a rock drill.
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).
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.
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.
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.
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.
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.
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.
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
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.
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.
Navy sonar equipment can hear so much more than you would ever expect. Sound travels very well in water. The navy has software that pretty much tunes all of that out, similar to how radar ignores things under certain speeds as it's just not interesting to them. However, if they want, they can see/hear the raw data. There's all sorts of Navy stories about what can be heard, and not all of them are untrue.
I worked at an aquarium for a while, and IIRC one of the exhibits discussed how a device equivalent to an average home stereo placed in the water in Japan could be easily heard on the coast of California.
Sound can travel MUCH further and fast underwater, so in the event of an implosion, it might create enough of a spike in hydrophones that is statistically significant. Also the experts might be able to analyze the signal's signature to confirm (or bet) it's an implosion.
Crossmatch that with the time of loss of communication and it's safe to assume that it's it.
Indeed, and moreover, the ability to detect underwater sound is probably aided by the lack of localized turbulence (wind noise in microphones) and the degree of sophistication sought after by navies due to the detection and counter-detection of military submarines.
Without any actual knowledge, I imagine that a ship or sub could be festooned with hydrophones, enabling it to detect faint noises, but also to determine their direction from phase information.
How do submarines commonly fail? Is the assumption of a violent implosion warranted?
I would think another failure mode could be water rushing in without the overall structure catastrophically failing, which would actually relieve pressure on the structure as it happened and be much less energetic.
It's hard enough to make a small hole that doesn't turn into a big hole under such pressure when you're trying to. Even harder for a small hole you're not expecting.
Just note that the body was experimental: while the hull indeed have a thick titanium body, it was mixed with (don't know exactly how and where though) carbon fibers, which are known to catastrophically break under pressure if there's even a microscopic impurity or damage. At least that's what the experts say. Carbon fibers is great for lightweight things that need to bend, terrible for things to be relied under pressure.
It was just the end caps that were titanium - the entire tube was just a 5inch thick carbon fiber wrap. In one of the videos with the CEO I saw him saying that he was a rule breaker because common consensus was that you shouldn't build a submarine out of carbon fiber and titanium.
I'd really like more detail on that tube's layup schedule.
Solid 5inch thick carbon composite OR a sandwich design with thick outer facesheets of carbon fiber? I suppose under that pressure not much would take the hydrostatic loads other than carbon, but that seems thick compared to everything I've seen made out of composites.
There are videos of them building it. From what I remember, they rolled carbon fiber around a cylinder, making the flat part of the cylinder. Then they mated two titanium half spheres to the end of the carbon fibre cylinder. This was done using some kind of "glue". Meaning that the middle part had no titanium.
I saw a bit of video where they showed the construction- it’s a few inch wide band of carbon fibre wrapped around an inner tube like a spool of thread until it reaches 5” thickness.
"The Spencer-built composite cylindrical hull either was repaired or replaced by Electroimpact and Janicki Industries in 2020 or 2021, prior to the first trips to Titanic."
And composite materials are basically threads embedded in glue. Threads can be extremely strong in tension. In compression, you have only the strength of the glue and the fiber/glue interface strength, which isn't a whole lot. Composite materials are in general poor in compression.
Crewed submersible hulls are always in compressive stress from the ocean outside. I can't fathom why somebody would choose a composite for a deep submersible hull. It's just asking for a buckling failure. Bad design choice, IMO.
It’s been a while since physics for me, but I was under the impression that this only really applies when pressure is greater inside the solid shape. In this case, it seems roughly equivalent to pulling a vacuum inside a soda can at sea level, which fairs quite poorly for the soda can, and I cannot imagine an unfortified sphere-ish shape performing better.
>Carbon fibers is great for lightweight things that need to bend, terrible for things to be relied under pressure.
Composite Overwrapped Pressure Vessels (COPVs) are fairly common in cases where a pressurized system needs to be relatively lightweight (e.g., spacecraft). To your point though, the failure mechanisms can be hard to model.
Take this with a grain of salt because I worked on the data acquisition side of COPV testing and not the engineering side, but my understanding is that while carbon fiber is strong in tension but weak in compression, epoxy is strong in compression but weak in tension. So the combination is thought to make a vessel strong in both.
Like evryone else I have no idea but I do know implosions tend to be pretty impressive events and can easily be supersonic generating a shockwave, so pretty loud!
I mean the thing was a tiny 7x3m cylinder located 700Km from the nearest coast...