Scrutable

I don’t think it’s too harsh to suggest that whoever designed it should face losing their professional accreditation.

Grumble wrote: Fri Jun 23, 2023 5:54 am I don’t think it’s too harsh to suggest that whoever designed it should face losing their professional accreditation.

The CEO of the company was the pilot of the submersible.

jimbob wrote: Fri Jun 23, 2023 6:58 am

Grumble wrote: Fri Jun 23, 2023 5:54 am I don’t think it’s too harsh to suggest that whoever designed it should face losing their professional accreditation.

The CEO of the company was the pilot of the submersible.

So he lost his accreditation and his integrity (literally).

jimbob wrote: Fri Jun 23, 2023 6:58 am

Grumble wrote: Fri Jun 23, 2023 5:54 am I don’t think it’s too harsh to suggest that whoever designed it should face losing their professional accreditation.

The CEO of the company was the pilot of the submersible.

I’m talking about the designer. Did the CEO design it as well?

Awww, I'm crushed by this news

Grumble wrote: Fri Jun 23, 2023 5:54 am I don’t think it’s too harsh to suggest that whoever designed it should face losing their professional accreditation.

If they had any.

In the mid-90s, being seconded to what is now the CMA, I had the opportunity to visit the nuclear submarine construction works at Barrow-in-Furness, while the Trident subs were in mid-construction. They were the largest ships in the navy at that time. I think the construction hall was not big enough to hold a complete ship, final assembly had to be done on the slipway. Also, building the interior structure inside a complete enclosed shell is not practical. So they were being built in relatively short sections, giving good access inside the ring-shaped sections of pressure vessel to build the interior structure. The pressure vessel was later welded together in numerous sections.

They explained how the pressure vessel shrank materially in size when the sub dived deep. So you had to build much of the internal structure as a self-supporting structure resting on the base, so that you could leave a space gap between the pressure vessel and the internal structure, to provide for that contraction.

The biggest and most basic mistake in engineering is to build something insufficiently strong. It was surely the first consideration of the designer. This sub had been down to 4000m repeatedly, and so appeared to be strong enough. But we recognise that pressure vessels used over time can fail gradually through processes such as fatigue, stress corrosion, etc. Repeated compression on that kind of scale would be a large challenge to the internal structure of the material it is made of.

I would suspect that fibre-glass would have less fatigue resistance than, say, a suitable type of steel. One would expect it to compress more than a steel pressure vessel does. So maybe the error here is to build something that doesn't have much longevity to repeated dives, but suffer fatigue fairly quickly. Someone suggested that the thickness of the fibre-glass seems less than commercial equivalents. Maybe that redundancy is related to fatigue resistance.

Another failure point could be the attachment of the metal ends to the fibre-glass cylinder.

IvanV wrote: Fri Jun 23, 2023 10:13 amAnother failure point could be the attachment of the metal ends to the fibre-glass cylinder.

I'm not saying it's automatically the wrong thing to do, but using materials that react in differing ways to heat and pressure is a recipe for stress concentrations when designing something designed to exposed to significant changes in heat and pressure.

EACLucifer wrote: Fri Jun 23, 2023 10:41 am

IvanV wrote: Fri Jun 23, 2023 10:13 amAnother failure point could be the attachment of the metal ends to the fibre-glass cylinder.

I'm not saying it's automatically the wrong thing to do, but using materials that react in differing ways to heat and pressure is a recipe for stress concentrations when designing something designed to exposed to significant changes in heat and pressure.

Exactly. It is bad enough with our power transistors (of whatever type) and we only have almost solid devices - copper or aluminium on silicon or GaN chips placedbon copper and covered with epoxy mould compound.

I'd say that about half the problems I've encountered have been related to thermo-mechanicsl stresses in these devices - the largest of which are just over a square centimetre.

All at ambient pressure, but with temperature cycling between -55⁰C and+175⁰C

Designing dome ended cylindrical pressure vessels is a standard undergraduate engineering exercise.
The tricky bit is the junction between the cylinder and the domes, they have different curvatures so everything being equal the cylinder tends to shrink more under pressure than the ends, which leads to added stresses at the junction.
So you make the dome ends slightly thinner, but then you have a transition to make between the different thicknesses for which you have to use use a concave parabolic chamfer. Now add different materials with different Young's modulus and you have a huge mismatch with possibly sliding contact or added stresses if one deflects more than the other.

This is a nice Gif of a railway tank imploding which shows what happens, note the ends remain intact. https://gifer.com/en/ywW

Oof.

Rich people do like to get litigious so expect a lot of passing the buck

Boustrophedon wrote: Fri Jun 23, 2023 12:35 pm Designing dome ended cylindrical pressure vessels is a standard undergraduate engineering exercise.
The tricky bit is the junction between the cylinder and the domes, they have different curvatures so everything being equal the cylinder tends to shrink more under pressure than the ends, which leads to added stresses at the junction.
So you make the dome ends slightly thinner, but then you have a transition to make between the different thicknesses for which you have to use use a concave parabolic chamfer. Now add different materials with different Young's modulus and you have a huge mismatch with possibly sliding contact or added stresses if one deflects more than the other.

This is a nice Gif of a railway tank imploding which shows what happens, note the ends remain intact. https://gifer.com/en/ywW

And it happens that quickly (it's not sped-up footage). So if the sub did suffer from a catastrophic failure it likely would have been a mercifully swift death.

Martin_B wrote: Fri Jun 23, 2023 1:41 pm

And it happens that quickly (it's not sped-up footage). So if the sub did suffer from a catastrophic failure it likely would have been a mercifully swift death.

Stability failures are always quick with little or no warning.

Boustrophedon wrote: Fri Jun 23, 2023 2:13 pm

Martin_B wrote: Fri Jun 23, 2023 1:41 pm

And it happens that quickly (it's not sped-up footage). So if the sub did suffer from a catastrophic failure it likely would have been a mercifully swift death.

Stability failures are always quick with little or no warning.

Mercifully swift after 2 days of the air running out, knowing they would probably die.

ETA The media is now blaming people for being ghoulish and seeing the tragedy as entertainment when of course the media has been using it as clickbait and winding the drama up as high as they can.

Swift to the point they wouldn't have known about it, I understand they'd be dead before the brain was able to process the signals from the pain receptors.

I think the USN believes it happened early on though... at the 1h45m point in the dive when they lost contact, at least that's what they say correlates to their underwater listening.

Anyway, perhaps now the news could pivot to the many other non-billionaires dying every day due to more serious issues than incredibly high risk leisure trips going wrong...

Guess what Boris' latest DM column is about. I can't read it, I want to enjoy my evening.

TopBadger wrote: Fri Jun 23, 2023 3:03 pm Anyway, perhaps now the news could pivot to the many other non-billionaires dying every day due to more serious issues than incredibly high risk leisure trips going wrong...

Well, you could go with Hundreds of migrants don't drown, as an upbeat update to yesterday's story that thirty or more did drown. https://www.bbc.co.uk/news/world-europe-65995796

Lacks billionaires and schadenfreude so not really front page material.

I just took one for the team. FFS, it's one of the most amateurish bits of wordsmithery I've read in a long time.
Have a good night.

So what was doing the knocking then?

There might be a clue here.

Opti wrote: Fri Jun 23, 2023 6:15 pm There might be a clue here.

There was an Ignobel Prize for research into that.

Of course, it could also have been Jason Momoa

You only have to look at the Deepsea Challenger that James Cameron used to go to the bottom of the Challenger deep or the DSV Limiting Factor both of which have dived 4 times as deep as the Titanic, they make the Titan look cheap and shoddy, both were built, tested and certified to the appropriate standards.

https://en.wikipedia.org/wiki/DSV_Limiting_Factor

https://en.wikipedia.org/wiki/Deepsea_Challenger

Boustrophedon wrote: Fri Jun 23, 2023 2:13 pm

Martin_B wrote: Fri Jun 23, 2023 1:41 pm

And it happens that quickly (it's not sped-up footage). So if the sub did suffer from a catastrophic failure it likely would have been a mercifully swift death.

Stability failures are always quick with little or no warning.

I recall working on pressures in food cans and sitting with an evacuated A10 can in my lap. When it collapsed - with no warning - the flat ends met like a pair of pincers closing, fortunately upwards

Tessa K wrote: Fri Jun 23, 2023 2:55 pm ETA The media is now blaming people for being ghoulish and seeing the tragedy as entertainment when of course the media has been using it as clickbait and winding the drama up as high as they can.

Coincidentally, ghoulish is the word that sprang to mind for people taking tourist jaunts to a site where over 1500 people died.

I mean, they might have gone there in a spirit of respectful homage, as one might go to a first world war battlefield, or for the archaeological research. Mmm.