If the implosion force was anywhere near what Scott Manley calculated the CF hull could very well have shattered from that.
As far as removing the viewport I would think bringing up debris as is without modification would be essential to an investigation.
Again, I'm just speculation based on info that could be false.
Pissing in the dark and they keep moving the toilet.
Me too, it's just an interesting thought experiment. I'm just running through the course of events in my head. If the port failed and imploded, you get a highly pressurized (from the POV of the inside of the sub) 22" column of water shooting into the sub, with some acrylic shrapnel. But from the POV of the CF Pressure vessel, what is happening is internal and external pressures are rapidly
equalizing. Unless there's an autoignition of the air (and there's no fuel to cause that) there's no way for the interior pressure of the CF vessel to exceed the exterior vessel. It IS a very quick and dynamic change in loads, but it's a very quick removal of loading, which I don't think would result in a bunch of CF shreds everywhere. There would be bigger pieces, which the divers have said they don't see.
The tiny shreds that they do see, combined with the pretty clean, undamaged titanium parts really make my thing that it was the CF cylinder that failed. I've been reading about delamination coupled buckling failure (or snap buckling) of composite shells on deep sea pipelines, which seems a really plausible failure mode for this sub. But as you say, we're really just giving our best guess here from incomplete info.
That does look like some sort of O-ring groove on the flange surface. At work, we have one compressor that can go up to 1400 psig. The higher pressure flanges use those O-ring style seals. Ours are ANSI class RTJ flanges if I remember correctly. I think the sub would need to go to higher pressures than the flanges at the link.
https://www.texasflange.com/products/flange-dims-weights/rtj-face-dimensions-and-flange-tolerances/
The 6000psi and 10000psi hydraulic systems I've worked on sealed the flanges that way. Well machined flanges with a groove in one or both, and an expensive, dimensionally accurate O-ring in the groove. Seal material has to be matched to the fluid in the system.
https://www.tu-lok.com/6000-psi-sae-flange.htmlAlso, removing the viewport by ROV tools would be extremely difficult. If there was any way to get that piece up without doing that they would, in addition to wanting to recover the viewport itself.
I think the implication was they got the dome to the surface as it was, and may have removed the port there or on deck for easier lifting and handling in air. But again, It was just speculation I saw based on the flange being gone, and the flange mounting surface seeming to be undamaged. If the port did go into the sub the question of where are the bolts and retaining flange is a good one.