I would say that is different. A steel part will make sounds as it rapidly flexes under pressure or temperature cycling, but those sudden movements can be withi

I would say that is different. A steel part will make sounds as it rapidly flexes under pressure or temperature cycling, but those sudden movements can be within the "endurance limit" of the material, and not lead to fatigue or failure. The hull sounds they were hearing in Titan were likely snapping of carbon fibers (based on the linked video above), which means a permanent reduction in strength each time it happens. DeepFlight Challenger, the unused submarine that pioneered this type of design, was intended only for single use: "But the company that built DeepFlight Challenger has told The Telegraph it refused to back the project, insisting the submarine was suitable for only one dive and could not be reused because of the pressure on its structure at such depths." "The problem is the strength of the vessel does decrease after each dive. It is strongest on the first dive.” https://www.telegraph.co.uk/news/science/science-news/11291994/Sir-Richard-Branson-quietly-shelves-Virgin-submarine-plan.html https://www.telegraph.co.uk/news/science/science-news/112919...