There's a transcript going around allegedly from the fatal dive. You may have seen it. While waiting for my tea to cool down I watched an engineer comment on it. He claimed that the reported depths show that the craft was descending far too fast, which is consistent with the transcript being a fake. (Or that his estimates were naive--"descend fast at first and then more slowly when you get close" is a plausible approach.) Perhaps ship-to-craft questions were mainly for crew health and not for information, but if I had a hand in the design there'd be as much telemetry monitoring on the craft as the bandwidth would carry; you'd hope they'd not need to ask the crew for wattage numbers. Granted they sometimes lost communications, so the bandwidth wouldn't be great, and a relay system would be quite difficult and expensive to build and position.
So, if you could only send a few numbers, what would they be? Depth and a summary hull health value?
The business about ascending very slowly after dropping the ballast doesn't seem to make a lot of sense. If they succeeded in dropping all the ballast they should be as on buoyant as on the previous trips. The devil is in the details, of course, and I don't know what was in the tail cone--I figure it was just for streamlining and let water in freely. But just based on the crude schematics google shows me, I suspect the slow ascent isn't true and the transcript is fake.
But while listening to the engineer, it occurred to me that cracking and hull failure could begin non-catastrophically. If the seal at one side leaks just a bit, and water seeps in at an edge to begin to delaminate the outer half mm or so of the carbon hull, it might crackle quite a bit. There was some (unfortunately) unknown safety factor in the hull design, so I assume they could lose a bit of the outside and live. There were edges at the endcaps, but also at every perforation. If delamination aggressively peeled up sheets of the outer hull, could those bits puncture or otherwise interfere with the operation of the systems outside? I can't think of a good reason why the power should fail without a short or a severing. Assuming the power did fail this time. It did fail on earlier tests.
Though--the batteries were where? I find the schematics online to be less than useful. If they were outside, and since they had battery problems before, it sounds like they had an issue with protecting the batteries.
At the scale of fractions of a mm I don't think the difference between a round hole through the hull and a flat edge at the endcap makes much difference to delamination of the glue layers. I'd guess that it was harder to verify the seal on a small perforation than on a big flat edge, though the big one has more edge to worry about.
Once again, I don't find the detail I'd prefer--but what goes through those perforations, and is it robust against a small leak compressing the contents?
I assume they designed the parts so that the titanium caps would compress by almost the same amount as the carbon/epoxy body. This was a custom carbon-fiber mix, so I doubt that whatever I find online for bulk modulus is going to be relevant--and the body's compressibility won't be the same along the axis as it will "squeezing the can". (Plus the bulk modulus value changes with pressure) If the cap and body compress differently, the joints between the two get stressed as the body bows in or out.
Just trying to chase some low-hanging fruit gets me into nit-picky research details. I assume those "50yo white guys" are familiar with these things--and charge accordingly.
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