4 ms·

Non-expert, pure speculator here: I cannot help but think of the Titan submersible and its minor flaw in the hull that slowly became more and more of an issue w

by bt1a 2y ago

Non-expert, pure speculator here: I cannot help but think of the Titan submersible and its minor flaw in the hull that slowly became more and more of an issue with each dive and pressurization cycle. I wonder if the 'untenable' leak rate that isn't agreed upon is the rate at which an accelerated and catastrophic runaway event occurs?

themaninthedark 2y ago
There was no "minor flaw" in the Titan submersible. It was a very bad design[1], using substandard material[2] in new and untested ways[3] with poor assembly practices[4]. It was fatally flawed from the start. 1 - Asked about the carbon composite used in Titan’s experimental design, Cameron said, “It’s completely inappropriate for a vessel that sees external pressure.” He went on to say that carbon fiber is very helpful when used for applications subject to internal pressure, like scuba tanks. But, he said, “for something that’s seeing external pressure, all of the advantages of composite material go away and all the disadvantages come into play.” 2 - Another possible "shortcut": https://www.latestly.com/world/titan-submersibles-hull-was-apparently-made-of-expired-carbon-fiber-says-report-5224751.html https://www.latestly.com/world/titan-submersibles-hull-was-a... "Expired" bare carbon fiber might be ok; expired prepreg is likely not ok. And I still can't get my head around the apparent mixing of prepreg and wet winding resins in the same laminates. That article says Boeing has no record of ever selling oceangate composite material. So either he got it for free (Dumpster diving?) or it came from someone else. Maybe some guy in a parking lot: My boss told me to deliver this stuff to Boeing but they wouldn't take it because its expired, I'll sell it to you cheap. 3 - "Thickness, he says, was estimated using micromechanics, and then verified with finite element analysis (FEA).”. >Wonderful. That sort of maybe can work for tension stresses, but can be highly unreliable for compression loading 4 - https://www.youtube.com/watch?v=4PUTbK5AqY8 https://www.youtube.com/watch?v=4PUTbK5AqY8 : >For such a critical joint I see some questionable prep work >in the video. >-Bare hands touching the bond surface. >-Solvent wiping used instead of caustic degreasers. >-Poor wiping technique >-no surface profile/grit blast immediately prior to fixing. All sources are from commenters on: https://www.eng-tips.com/viewthread.cfm?qid=508005 https://www.eng-tips.com/viewthread.cfm?qid=508005
dotnet00 2y ago
It's important to remember that the pressures involved are very different. The ISS pressure vessels only have to hold 1atm in, and not several atmospheres out.
- bebop 2y ago
  To reinforce this point, it is around 375 atmospheres at the titanic. The deep sea is a crazy place.
- jcranmer 2y ago
  Equally important is that the ISS is under tensile load (the cylinder is trying to explode), while a submersible is under compressive load (the cylinder is trying to implode).
  - rbanffy 2y ago
    It's just 1 atm. You can't even say it's trying seriously.

by bt1a 2y ago

themaninthedark 2y ago

There was no "minor flaw" in the Titan submersible. It was a very bad design[1], using substandard material[2] in new and untested ways[3] with poor assembly practices[4]. It was fatally flawed from the start. 1 - Asked about the carbon composite used in Titan’s experimental design, Cameron said, “It’s completely inappropriate for a vessel that sees external pressure.” He went on to say that carbon fiber is very helpful when used for applications subject to internal pressure, like scuba tanks. But, he said, “for something that’s seeing external pressure, all of the advantages of composite material go away and all the disadvantages come into play.” 2 - Another possible "shortcut": https://www.latestly.com/world/titan-submersibles-hull-was-apparently-made-of-expired-carbon-fiber-says-report-5224751.html https://www.latestly.com/world/titan-submersibles-hull-was-a... "Expired" bare carbon fiber might be ok; expired prepreg is likely not ok. And I still can't get my head around the apparent mixing of prepreg and wet winding resins in the same laminates. That article says Boeing has no record of ever selling oceangate composite material. So either he got it for free (Dumpster diving?) or it came from someone else. Maybe some guy in a parking lot: My boss told me to deliver this stuff to Boeing but they wouldn't take it because its expired, I'll sell it to you cheap. 3 - "Thickness, he says, was estimated using micromechanics, and then verified with finite element analysis (FEA).”. >Wonderful. That sort of maybe can work for tension stresses, but can be highly unreliable for compression loading 4 - https://www.youtube.com/watch?v=4PUTbK5AqY8 https://www.youtube.com/watch?v=4PUTbK5AqY8 : >For such a critical joint I see some questionable prep work >in the video. >-Bare hands touching the bond surface. >-Solvent wiping used instead of caustic degreasers. >-Poor wiping technique >-no surface profile/grit blast immediately prior to fixing. All sources are from commenters on: https://www.eng-tips.com/viewthread.cfm?qid=508005 https://www.eng-tips.com/viewthread.cfm?qid=508005

dotnet00 2y ago

It's important to remember that the pressures involved are very different. The ISS pressure vessels only have to hold 1atm in, and not several atmospheres out.

bebop 2y ago
To reinforce this point, it is around 375 atmospheres at the titanic. The deep sea is a crazy place.
jcranmer 2y ago
Equally important is that the ISS is under tensile load (the cylinder is trying to explode), while a submersible is under compressive load (the cylinder is trying to implode).
- rbanffy 2y ago
  It's just 1 atm. You can't even say it's trying seriously.