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Titanic tourist submersible goes missing with search under way

bbc.com

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Re: Titanic tourist submersible goes missing with search under way

#611

Post by mardifoufs »

jacquesm wrote: post #597
mardifoufs wrote: post #349

Earlier quoted context omitted.

Composites can be tested. Not as easily as metals can be, and it involves a lot more software analysis and even AI, but it's still possible. I work on flaw detection/segmentation with ultrasounds -and I have not directly worked with metal scans so I can't exactly compare- but we can already get some pretty good results with the right probes and scanners. The other major issue is that NDT on composites needs more care…

How does that work? Shouldn't the device be certified for such an application?

Yes! Sorry if I wasn't clear enough. I meant that they use the devices because they are compliant and certified for carbon composites. I just wasn't sure since the devices are usually not for a single purpose so it's hard to keep track of all certified use cases from my PoV.

But sometimes they are! We have a few scanners specifically for pipelines and even robots for wind blades, yet even then the probe usually uses the same detection technology (ultrasounds, eddy currents, etc). The magic happens on the signal processing side when it comes to the difference between the scanners, and the trend is towards multipurpose all in ones. Our most recent industrial scanner has an FPGA that is explicitly there to allow for extensibility so that it fits most applications. FPGAs have been used quite often in the field but usually merely to implement some specific signal processing, not to be extensible!

I'm rambling here but my point is that some devices can be used for pretty much any application (the Omniscan for example), process specific devices are more for large scale industrial workflows! The probes can be the only thing you need to change to use the same scanner to do stuff as varied as hydrogen poisoning analysis on steel to composite flaw detection on windblades!

Here is an example, again with the Omniscan :

https://www.olympus-ims.com/en/scanners/aerospace-wind-blade...

Re: Titanic tourist submersible goes missing with search under way

#612

Post by [deleted] »

londons_explore wrote: post #134
svnt wrote: post #127

Earlier quoted context omitted.

I found the (wireless, $30) game controller: https://www.amazon.com/Logitech-Wireless-Nano-Receiver-Contr... and this from a review: “Pretty good controller, fits in hand comfortably and is compatible with anything I throw at it in a Debian linux environment. The conductive pads are extremely low quality though as I've had to replace them 3 times in the 2 years Ive been using it. For a Logitech product I expect bette…

So it's possible this sub is stuck turning in right only circles deep underwater because the left button has broken...

[deleted]

Re: Titanic tourist submersible goes missing with search under way

#613

Post by numpad0 »

wnkrshm wrote: post #494
numpad0 wrote: post #485

Earlier quoted context omitted.

I was imagining a round door in the middle of the hull, like a submarine hatch, but it looks like the entire front dome comes off and that’s the “hatch”. If so, can’t they just make the front a giant screw and add handles to both sides?

The dome shape is a structural necessity to withstand the pressure, like in a soda can. Else you would need more material, more material means more weight, more weight means more bouyancy required which again means more weight etc. It's like designing a spacecraft but with different constraints.

But it's withstanding pressure(called external pressure, yesterday I learned), so can't they just have a clean, stepped flange to mate and to prevent slipping off, plus a simple lock to prevent unintended disengagement?

Re: Titanic tourist submersible goes missing with search under way

#614

Post by stickfigure »

erik_seaberg wrote: post #504
stickfigure wrote: post #125

Earlier quoted context omitted.

I think you have unreasonable expectations. Off-the-shelf components may be more reliable than custom developed products (especially since you can afford a backup or two). Also, with respect to emergency ballast - cheapness is a virtue. You're supposed to drop it in an emergency, and hesitating because "I don't want to lose my expensive weights" could kill you. This is a consideration for recreational scuba too, inst…

Does a submersible like this only drop ballast weight in an emergency, or every time they’re ready to go home? I know submarines tend to use diving planes and pneumatic ballast tanks (flood with water, or inject air to push water out), but I don’t know if that’s an option down at 400 atm.

I heard an interview this afternoon on NPR with David Pogue (the bbc guy who filmed a ride). He said there are 7 different ways of surfacing, including several that do not require electricity and don't even require consciousness. For example, some of the ballast is attached by mounts that dissolve after a certain number of hours in water (presumably less than 96).

Re: Titanic tourist submersible goes missing with search under way

#615

Post by yetanotherloser »

jacquesm wrote: post #598
yetanotherloser wrote: post #531

Earlier quoted context omitted.

The advantage of testing pressure vessels with water is that the failure mode is usually less bad than gas (because it doesn't expand through any breach like gas does). Unfortunately a sub is the opposite of a pressure tank (the pressure is on the outside) so you need a pressure bottle bigger than the sub to test it in. I don't think these are common or easy to come by.

I've been in the reverse, an autoclave large enough to hold an entire spacecraft. That was already engineering on a scale that defied my imagination considerably, doing the same at the level where an entire sub could be pressurized to 400 atmospheres is engineering on a different plane. I don't think you could do this any cheaper/easier than just strapping it to a tether and dropping it overboard in a very deep part…

Gosh, that's one big autoclave. As you say, a sub tank would be even more of a monster bit of engineering. They do exist for more normal depths but I'm not sure if there are civilian / rentable sub test tanks for this kind of ultra deep stuff.

Re: Titanic tourist submersible goes missing with search under way

#616

Post by jacquesm »

mardifoufs wrote: post #611
jacquesm wrote: post #597

Earlier quoted context omitted.

How does that work? Shouldn't the device be certified for such an application?

Yes! Sorry if I wasn't clear enough. I meant that they use the devices because they are compliant and certified for carbon composites. I just wasn't sure since the devices are usually not for a single purpose so it's hard to keep track of all certified use cases from my PoV. But sometimes they are! We have a few scanners specifically for pipelines and even robots for wind blades, yet even then the probe usually uses…

Super interesting work, thank you for the follow up. Some of my customers use stuff like this so it's nice to see someone from the supply side. It's interesting to think about the different kinds of defects. "Not like the rest" is a fairly easy kind of defect to detect, "Structurally different from the baseline" is a bit harder and a whole batch that is different in some important aspect is quite hard.

FPGAs are super powerful for applications like these, I see them used in plenty of sensors where flexibility and being future proof is a must so that you don't need to redesign the entire sensor for every variation on the theme.

Re: Titanic tourist submersible goes missing with search under way

#617

Post by wnkrshm »

jacquesm wrote: post #594
wnkrshm wrote: post #494

Earlier quoted context omitted.

The dome shape is a structural necessity to withstand the pressure, like in a soda can. Else you would need more material, more material means more weight, more weight means more bouyancy required which again means more weight etc. It's like designing a spacecraft but with different constraints.

It's pretty much the exact opposite of designing a spacecraft.

Then let me amend what I wrote: It's as difficult as designing a spacecraft, because you reach the limits of what materials that can be used can offer.

Re: Titanic tourist submersible goes missing with search under way

#618

Post by foobar1962 »

wnc3141 wrote: post #461
foobar1962 wrote: post #422

Earlier quoted context omitted.

> Can any engineers comment on whether that task is easier for a vessel exposed to compression (under sea) as opposed to vacuum (space)? I believe the pressure where the Titanic lays is 300 atmospheres. The pressure differential for the submarine is 300 - 1 = 299 atmospheres. A vessel in space will be have a pressure differential of 1 atmosphere to contend with.

I too am interested in this question, may I piggyback and add a question about whether the basic capsule shape is as efficient in negative pressure as it is in positive pressure

The design of pressurised aircraft is probably a good example to study.

Re: Titanic tourist submersible goes missing with search under way

#619

Post by BigWackenhut »

ciguy wrote: post #99

This section from their website is interesting: "Real-Time Health Monitoring The most significant innovation is the proprietary real-time hull health monitoring (RTM) system. Titan is the only manned submersible to employ an integrated real-time health monitoring system. Utilizing co-located acoustic sensors and strain gauges throughout the pressure boundary, the RTM system makes it possible to analyze the effects of…

It sounds a lot like marketing jargon to my ears. Not just the ridiculous name but the vague description- and obvious fact that even if it works it certainly isn’t bailing you out at depths where the craft is most likely to fsil.

I’m surprised those who paid to ride were not more atuned to this.

I don’t want to pick on Honda here, as a long time owner, but the name itself keeps reminding me of “Super Handling All wheel Drive” (SH-AWD)

Re: Titanic tourist submersible goes missing with search under way

#620

Post by tim333 »

belorn wrote: post #528
tim333 wrote: post #511

Earlier quoted context omitted.

People deal with potential gas cylinder failure by occasionally testing them at higher than their usual pressure. You fill them with water and pressure to say 350 bar rather than 300. At least that's what they do with scuba tanks. Even if designed well they can be dropped, corroded etc. Not sure it's practical to do that with subs.

Yes, that is what they do with steel and aluminum cylinders. After over pressuring them you measure how much the metal flex, and that way you get an indication of how much fatigue and thus risk there is with that cylinders. I am unsure if they do that with carbon versions. Do they flex with over pressuring, and is that flexing indicative to failure? If they do fail, is it like an explosion where the whole thing just…

Everest oxygen cylinders, made of titanium and kevlar usually sometimes get dropped off a cliff by accident, hit a rock and explode. Apparently they go off with quite a bang.

I'm not sure how they do routine testing.

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