What I don't understand is, if it imploded, why didn't the boat hear the implosion? Surely that would be really loud. Louder than the 15 min audio ping that the boat is normally listening for.
Was interested by this comment and wanted to note a few things. The Titan is significantly smaller (in terms of length ~1/10th the size although obviously displacement is the real measure)[1][2]. And the depth of the implosion is about 4x deeper[1][3]. So there are things that could definitely affect the sound signature.
Yes, and as far as I can tell it's not even certain that what was picked up from the San Juan was an implosion. But on the other hand, the Polar Prince was sitting right on top of the Titan listening for pings, and apparently it didn't hear anything.
I'm not suggesting anything nefarious, I'm just hoping someone who understands these things better than I do comes along.
The ocean is not a homogenous mass. As you go down you can measure temperature, pressure and salinity changes. These all individually and together affect the speed of sound in the water. Given the right circumstances a layer can form which bends the sound waves away from an observer. It is possible that they couldn’t hear the implosion precisely because they were on top of them. Perhaps they could have heard the implosion better if they were off to the side a few kilometers, or if they would have had a hydrophone dangling to the other side of the layer. More info on the layer. [1]
This perhaps also can explain why they routinely lost contact with the sub during dives. (And normalisation of deviance explains how they become okay with that. [2])
I'm speculating, but their ping detector may have had a filter for the frequency they were interested in. A low frequency explosion could easily have been ignored.
The size is irrelevant, the energy released is significant either way and definitely beyond the thresholds of hydrophones. During the USCG press conference today it was stated that the implosion made a significant soundwave as a result of the implosion, and I think in the coming weeks we'll hear reports of findings in regards to hydrophones which picked up the noise.
I don't know. But sea water isn't a homogeneous medium as far as sound propagation is concerned. There are layers of changing salinity, temperature etc and these can effectively cut off sound propagation. Submarines (used to?) depend on such effects to avoid detection.
Also, would the implosion necessarily be that loud? It would be like crushing a large tin really. Maybe blends in with background noise.
My guess would be that the Oceangate ship ignores everything that it's not 'expecting' to hear. I don't really know anything about deep sea exploration, but having general purpose microphones in the water seems like a bit of an oversight to me, given the marginal cost of having them.
So many things about this venture were not really considered. I am terrified that this guy was an aerospace engineer. It feels like he threw the book about engineering safety out the window.
The big one is designing the sub to travel to 95% of the expected maximum depth, leaving a 5% margin of safety. I was taught to aim for a margin of safety of (I think it was) 50% back in the day. Operating so close to the safe limit for the sub is appalling. That doesn't even include all the other warning signs about the design that were brought up.
The missing beacon on the sub, in case of loss of radio contact, is another standout. No consideration given for loss of power or anything. Consideration of contingency plans is so important.
A minor one that is really indicative of the overall attitude is drilling screws into the carbon fiber hull, possibly exposing the hull to stress fractures from both the screws and the constant weight of holding a monitor. It's... just a silly thing that could have been avoided. I'm not saying those screws are why it failed, but if you can use an adhesive to hold your monitor in place, wouldn't you rather do that then by drilling directly into the hull keeping ~100 atm of ocean out of your face?
It just makes me so sad for so many reasons. It definitely could have been avoided...
> The big one is designing the sub to travel to 95% of the expected maximum depth, leaving a 5% margin of safety.
Wouldn't a a 5% margin of safety mean the sub was designed to survive at 105% of the trip's expected maximum depth? 95% sounds like the opposite of a margin of safety.
Some people saw that they had affixed things to the inside of the craft. There is almost assuredly an inner liner that is not structural that these were attached to. Just like an airplane.
> The big one is designing the sub to travel to 95% of the expected maximum depth, leaving a 5% margin of safety.
Sorry, but this does not follow. I believe you are confused about the fact that the Titan was designed to go down to 4,000 meters, and the Titanic lays at 3,840 meters.
And because 3,840 is so close to 4,000 you believe they had no safety margin. Do I understand you well?
But the thing is when you design a submarine which can go down to 4,000m you don’t design a hull which instantly implodes at that precise depth. You add a safety margin on top of your design requirement and that is what you design for. And then using calculations, simulations and tests you convince yourself that your submersible is still safe even at that extra safety padded depth.
I’m not saying that this is how they designed it. After all it seems their engineering culture was deficient in several ways. But you simply can’t conclude that they had no safety margin because they dove close to their design limit.
Safety factors are in terms of the yield stress. So, if they had a safety of factor of 3, this means that they should be able to withstand 3x the expected stress. Pressure is linearly related to depth, so it should have been designed for 12,000 meters with a reasonable safety factor like that. Of course, this doesn't take in to account sharp impacts, which, especially for carbon fiber, dramatically change the strength requirements.
Some ballpark typical numbers for safety factor: spacecraft ~1.2, airplanes ~1.5, automobiles ~3
Yes but you also don’t want to operate so close to the safety margin. If you need to travel to 3800m, you design a sub to safely withstand 1.5x that. And then agreed that yes it should not implode right if it were to reach that depth. At least this is how I remember learning it, which I admit was a long time ago.
I think I’m misinterpreting what “rated for 4000m” means. My impression is this is the maximum safe depth the sub is capable of reaching without damage. And that they are bring it regularly to 95% of that depth.
My understanding of safety margins, as I was taught, is that one should design such that you have a safety margin of 1.5x the intended use case. In other words, for 3800m expected frequent usage, it should be able to reach a depth of 5700m.
Alvin, for example, can reach a depth of 6500m.
But you’re right, we don’t know what that 4000m means, really. I’m just assuming it means safe depth without damage.
I would be surprised if the supporting vessel would have heard (were they listening?) or recognised that. Probably from the data from other hydrophones somebody will write an article on this sooner or later.
I can't imagine it was loud: vessel was tiny, and the energy will reduce at the order of 3 quite a bit at 4 km distance. I can imagine it would be detectable with the right equipment and that this equipment is installed in the Atlantic.
Turns out the Navy heard it, based on a WSJ article. They started actively listening when notified that contact was lost, and shortly after they picked up what sounded like an implosion or explosion.
"The Navy began listening for the Titan almost as soon as the sub lost communications, according to a U.S. defense official. Shortly after the submersible’s disappearance Sunday, the U.S. system detected what it suspected was the sound of an implosion near the debris site discovered Thursday and reported its findings to the Coast Guard commander on site, U.S. defense officials said. [...] The Navy said it shared its findings Sunday with the Coast Guard, which led the search, U.S. defense officials said. " https://www.wsj.com/articles/u-s-navy-detected-titan-sub-imp...
