Earlier quoted context omitted.
The Guardian is reporting the submersible as registered in the Bahamas
A place known for tight regulations
As the proverb goes, even a broken vise grips tightly when there are enough journalists in the workshop.
Why isn't Titan classed? (2019)
131–140 of 302 posts
Re: Why isn't Titan classed? (2019)
#132Earlier quoted context omitted.
That’s pretty wild. The operator was able to tell when they were going deeper based on the sound of the carbon fibers cracking in the hull.
These sort of sounds occur even in metal (steel/titanium) submersibles.
Navy subs literally deform while diving. If you tie a string tight from one bulkhead to another (from left to right, not front to back), as you dive, the string will go slack and you can tug on it. Destin (smarter every day) demonstrates this in one of his submarine videos.
Re: Why isn't Titan classed? (2019)
#133Earlier quoted context omitted.
The first space shuttle launch was crewed. It ended up with a ~2% failure rate. The Titan made about 50 dives. So, from a reliability perspective, on par with the shuttle. I posit that half the people on HN would volunteer for a hypothetical next shuttle flight without thinking twice.
The shuttle did something nobody had done before and was viewed as a genuine step forward in human capability. It was also over 50 years ago and had to rely on technology of the time - uncrewed tests were much harder to perform. This wasn't a particularly ground breaking vehicle in terms of capability and was taking paying tourists...
It also wasn't built with parts from camper world and cheap Xbox controller knockoffs.
NASA actually had a strong focus on safety. They just went about it the wrong way, calculating safety ratings backwards.
Considering the pressure vessel of this sub was only meant to handle 1300m as per another article, the way it survived 50 dives at 4000m is pretty amazing though.
Re: Why isn't Titan classed? (2019)
#134Re: Why isn't Titan classed? (2019)
#135Earlier quoted context omitted.
The craft survived several launches - that proved it can do it. Whether it can do it reliably / survive fatigue accross repeated cycles is a different question. Imagine we'll find out as the investigation progresses.
James Cameron gave an interview where he claimed the carbon fiber hull concept was tested by a team competing to get down to Challenger Deep at the same time his team was - and the concept failed in testing. He also claimed many within the deep submersible community wrote letters to OceanGate warning them their plan was flawed and would result in catastrophic loss. Specifically, the failure mode was delamination. I c…
Challenger Deep is exponentially more difficult than this - 10km Vs 4km so over double the pressure.
While it may still be an entirely unsuitable material for 4km, not being suitable for 10km doesn't prove that.
Re: Why isn't Titan classed? (2019)
#136Earlier quoted context omitted.
Their reasoning is fundamentally flawed. > The vast majority of marine (and aviation) accidents are a result of operator error, not mechanical failure. As a result, simply focusing on classing the vessel does not address the operational risks. Aka "classing doesn't mitigate all problems, so we're not going to do it at all"
Also: the reason most accidents are due to operator error and not mechanical failure is because the requirements exist in the first place. "Why do we have laws against slavery? It's not like anyone actually owns slaves. Seems pretty superfluous, so let's just get rid of it!"
Re: Why isn't Titan classed? (2019)
#137> They [inspections] do not ensure that operators adhere to proper operating procedures and decision-making processes – two areas that are much more important for mitigating risks at sea. As a former tall ship captain: No Shit. Ships stopped sinking when we started requiring inspections and design rules around stability and watertight compartments. We largely eliminated a common failure mode, designer error, through…
Their reasoning is fundamentally flawed. > The vast majority of marine (and aviation) accidents are a result of operator error, not mechanical failure. As a result, simply focusing on classing the vessel does not address the operational risks. Aka "classing doesn't mitigate all problems, so we're not going to do it at all"
[dead]
Re: Why isn't Titan classed? (2019)
#138Earlier quoted context omitted.
> Although, couldn't they just leave it at the bottom for a month and see if it implodes? No, cyclic stresses are a different animal altogether. But considering it's just a matter of attaching ballast to sink it, dropping ballast to raise it, there's nothing preventing cyclic testing vs. static @ max depth over the same duration. It seems obvious to me that you'd want to burn through a few test hulls characterizing t…
This is a really good point... from what I've seen they estimated the strength with Finite Element Analysis in Solidworks, and went for a ~2x margin of safety. There seems to have been no attempt to experimentally determine the expected number of load cycles to failure, they only considered the theoretical case of a perfectly flawless composite with no wear and tear.
Is 2x abstractly reasonable in this context? My [probably flawed] understanding in contexts such as hoisting is that safety margins of 5x are considered a bare minimum. Even crappy "Don't use this to lift things" chain is sold with 3x margins.
Re: Why isn't Titan classed? (2019)
#139> Another simple risk mitigation step we take, that we believe to be unique to OceanGate is that we draw a small vacuum on the inside of the sub at the start of each dive. This step verifies the integrity of the low-pressure O-ring seal and eliminates the risk of leaks I wonder what that low-pressure o-ring is sealing. I assume the vacuum would only simulate a one atmosphere differential, so that o-ring must not be s…
One thing I'm curious about, as someone who knows nothing about the engineering of these things... why wouldn't anyone building something like this choose to over-pressure the sub once people were inside it and it began descending? Wouldn't 2 atmospheres inside represent a 50% reduction in the pressure differential on the hull at depth?
Re: Why isn't Titan classed? (2019)
#140Earlier quoted context omitted.
The engineer who worked on it said it would provide only milliseconds of warning before the hull collapsed. He was promptly fired.
Just enough time to hear the "Bu" from "Buzz"
I had to check if sound travels fast
enough. Just about, yes. Half a millisec to go 1.5m.