Ah, thank you both! That makes sense.
Titanic tourist submarine missing 6-19-2023 (Debris field found, passengers presumed dead. 06-22-23)
fair point.
Finally made it through the thread, in time to have missed all the good discussion. Going to leave this here anyway…
Maybe the issues weren’t obvious to the average “Titanic tourist” or “explorer”…I bet plenty of people got a good-natured chuckle out of seeing that much-maligned controller, without a second thought about environmental or cycle testing.
Reading about the certification process for underwater vessels and their componets made me think of my line of work - commercial grade dedication of parts for use in backup generators in nuclear plants. Long story short, when nuclear plants need replacement parts for their generator sets, pretty much the only solution now is to dedicate commercial parts. This is a rigorous process of inspection, functional testing, material verification, and sometimes seismic testing. We’ll even do environmental and cycle testing if it’s determined that there’s no justification for extending the original qualification – for example, if the part in question has undergone more than a few simple design changes, or if we’ve had to purchase a completely different part. And the slightest change to a part – even something as simple as a different type of coating used on a bolt – starts a whole new process of intensive research to find out if it’s still suitable for safety-related service. Purchasing some bolts or valves that look just like the ones you might find at the hardware store** is fine, but we’re going to test the hell out of them before they’re released for shipment.
**(No, we don’t buy from hardware stores; we go direct to the manufacturer or through authorized distributors. We have bought a certain item from an auto parts store, but only because the manufacturer stopped talking to us. It’s a fun business!)
Interesting info. Thanx
I don’t understand why they tried to use titanium and composite material together. the materials aren’t going to expand and contract at the same rate so each dive cycle is going to stress the materials where they are joined. I would expect micro fractures that get worse over time.
Maybe an engineer can explain how they would inspect such a vessel for signs of damage.
Credit where credit is due, though, his comments in the video are on point and a pretty solid summary of known facts and when they were known, and it’s to his credit he didn’t give that interview four days ago, when it became clear to him (for very good reasons that weren’t widely published) that the submersible’s occupants were almost certainly dead.
Even so, I don’t think it’s surprising that rescue efforts were set to continue until exhaustion (of breathable atmosphere + a suitable fudge factor) or discovery of wreckage. Having personally participated in search and rescue efforts for people who were known, within minutes of disappearing from a ship, to be all but certain to be *dead, no one in their right mind is going to call that search off until “all but certain” approaches something like mathematical certainty based on survivability calculations in a best case scenario, assuming the person didn’t die within minutes of disappearing (as everyone fully expected).
*I may or may not have made an off-hand comment once along the lines of “Whatever, we all know this guy is dead. We should just go home.” without realizing the Captain was standing right next to me. Oops…
CNN has a story about a father and son who were supposed to be on this trip, but canceled out of concern for safety. The story is embedded in CNN’s peculiar “live updates” format and I don’t think it’s possible to link to it, but these are the key quotes. I have to say that I read this with a certain amount of skepticism, as it’s easy to say in hindsight “I knew all along that it wouldn’t be safe”, but I’m willing to believe that they had legitimate safety concerns based on actual evidence they were seeing.
A father and son gave up their seats on the Titan submersible just weeks before the fatal implosion after they had safety concerns about the craft.
Jay Bloom and his son Sean said they were both worried about the submersible and its ability to travel deep into the ocean ahead of the planned voyage. Their seats ultimately went to the father and son who were onboard when the vessel imploded, Shahzada and Suleman Dawood.
“I saw a lot of red flags,” Sean told CNN’s Erin Burnett on Friday evening after he was shown a video of tour organizer Stockton Rush walking through the submersible and its features.
Jay shared a text message exchange between him and Rush — the CEO of the vessel’s operator, OceanGate Expeditions — where Rush offered the spots on the vessel for the May expedition.
Rush then flew out to Las Vegas in March to try and get Jay to buy the tickets. Jay noted that Rush flew in on a two-seater experimental plane he built.
“He has a different risk appetite than I do,” Jay said.
Both Jay and Sean said Rush brushed off questions and concerns they had with the submersible.
“He had so much passion for the project that he was blinded by it,” Jay said, “He didn’t look at the things that I saw and that others saw that were problematic because it didn’t fit his narrative."
That must have been a very not fun day for you. Did you escape with no more than a death stare?
If they truly did have seats booked but gave them up, that’s a pretty good indication of their sincerity, I would think.
Sorry for the hijack but … “to try and”? Maybe this is why the story seems dubious to you.
Actually, nothing happened, except my own pet sense of embarrassment.
You need some kind of junction if you’re going to have a window at least. It should be possible to engineer things robustly. Still, I agree that this is a likely failure point.
Another failure point is with delamination of the carbon fiber. In tension, delamination is undesirable but not immediately catastrophic, since the tension will tend to pull the two parts together. But in compression, the parts will buckle out from each other. Even the tiniest defect would propagate catastrophically after some number of cycles.
I daresay a good commander knows when to be oblivious to the follies of his underlings.
I wondere if it was a Van’s.
I sang it at karaoke last night. Then my friend sang yellow submarine.
read the mod note; NM!
You seem to be suggesting that carbon fiber was probably a bad choice for the main body of the vessel, which now appears to be the prevailing opinion. It probably didn’t help (as noted in post #672 earlier in this thread) that the carbon fiber mats were rejects from Boeing that one supposes Rush got at a big discount.
No wonder there is now speculation that OceanGate will be seeking court protection from anticipated lawsuits, and I suspect it will soon cease to exist.
There are lots of titanium / composite interfaces in airplanes. Precisely because compared to other metals, titanium is an especially good thermal fit for composites. There are still issues with these interfaces, mostly pertaining to a weird sort of corrosion / deterioration as I understand it.
IANA engineer, but inspecting composite airplanes for damage impact is a painstaking process with ultrasonic probes scanning for voids and delaminations invisible at the surface, plus skin surface analysis, sometimes done with lasers, to identify small dents that represent evidence of prior significant impacts. In all, the aerospace maintenance industry is still struggling with doing this cost effectively at production scale with the requisite confidence that a clean bill of health isn’t merely a bunch of overlooked faults.
I would phrase it a bit more carefully than that. CF has some qualities that make it an excellent choice for this application: namely, a high strength-to-weight ratio. And in fact the hull did work successfully a number of times.
The issue with CF in general is that it has poor inspectability. The tools for non-destructive testing and so on are just not at the same level as they are for metals. Which is why they’ve taken so long to get into aviation. The tools are getting better, though.
And what we have here is an entirely new mode of operation, where the dominant forces are for compression. So the lessons from aviation are basically useless. The hull was in completely uncharted territory, and being used in a way where basic engineering intuition says it might have problems.
I think CF is absolutely the right choice for a modern unmanned experimental sub. It will probably fail, and you can use that information to design something better. CF designs are highly sensitive to the method of winding, for instance. Could delamination be avoided with a winding technique where every layer fully interlocks with multiple adjacent layers? Maybe. Try it and see what happens. Just not with humans onboard. You can put humans on after you’ve tested the design with a few thousand cycles and proven that you can hit a cycle limit far higher than what you’re rating it for.
Upon hearing that OceanGate’s offices are closed indefinitely, I thought of the employees. (They’re ‘local’ to me, for a given value of ‘local’.) Open sources say there are 47 of them. It’s got to be quite a shock to suddenly discover you’re out of a job.