Titanic tourist sub missing

[The Man]

Yes, I think that is right. Thus, conical windows, hatches, and such function because the pressure only pushes them tighter, without distorting them or the hul.

Hans

For them it does, due to that cylindrical shape but for the planed edges of the CF pressure hull not so much. This was bad however you slice it, the very pressures of the outer titanium shells puts a delaminating stress on the CF pressure hull. Again, autoclaving in production might have reduced interlayer shear stress but not eliminated it. With out it, it’s a crescant waiting to be ripped apart.

I continue to be completely disgusted.

ETA: To try to explain, it’s the difference of a solid body of material (like the outer shells) and one composed of layers (The pressure hull) Both endure stress and strain, the latter being the important part. How strain moves things under stress, if in opposition that’s a shear stress, like scissors or shears, so some of the layers of the pressure hull, because it's a composite move in opposite directions. A solid hull has stronger intermolecular forces to resist such shear stress. However, the very CF construction makes those layers susceptible to shear stress and thus delaminating (layers separating from each other). Once that happens structural integrity is compromised.

 

[Andy_Ross]

Well, I am, and I can tell you its not an unreasonable suggestion.

Pound-for-pound, titanium is the strongest and least flexible metal on the planet - tungsten is the outright strongest. Now in theory carbon fibre has the potential to be as much three times stronger than titanium... that is why SpaceX initially considered using it for BFR (Starship) construction. However, once the alignment of the stressors departs from the alignment of the fibres, its strength drops dramatically - by the time the stressor alignment is 45° from the fibre alignment, carbon fibre has become about three times weaker than titanium.

I'm not sure what grade of titanium OceanGate used to build this thing, but to put some figures on the above...

Density (gm/cm²)
Grade 9 Titanium - 4.5
Carbon Fibre - 1.6

Ultimate Tensile Strength (MPa)
Grade 9 Titanium - 530
Carbon Fibre - 600 @ 0° and 90°, 110 @ 45°

Young Modulus* (GPa)
Grade 9 Titanium - 100
Carbon Fibre - 70 @ 0° and 90°, 17 @ 45°

* elasticity

To summarize, If what you say is correct, that the carbon fibre hull slotted into the titanium pressure dome (and if the carbon fibre hull was manufactured as a wound CPV) then that could be a weak point. If, as you suggested, the carbon fibre compressed more than the titanium, then in the area around that joint, the stressor alignment could start to be more misaligned with the direction of the fibres. As the pressure pushes down at right angles to the fibres.....

1. a small "ring" area just inboard (behind) the slot, flexes inwards.
2. the pressure is now pushing at an angle to the direction of the fibres at that point
3. this makes the hull weaker at that point.
4. goto 1

-- Repeat until the strength around that ring is so badly compromised that it collapses.

But proper design would mitigate this surely?

 

[Andy_Ross]

One last comment. I worked in a electrical coal fired power station. There was enormous pressure in the pipes and equipment.

To join them there were bolts almost side by side around the flange. A red-hot heating rod was put in a hole in the center to expand the bolts. They were then tightened by two men using a 3-meter bar on the spanner.

We were instructed that if we heard a whistling sound indicating a leak, we were not to run our hand over the pipes to feel for the leak. One man did this with a hole less than the diameter of a human hair and it neatly sliced all his fingers off like butter.

Superheted steam is frightening.
In a ship's boiler room or machinery space you use a spanner or similar implement waved carefully in front of you if you have to move around looking for a suspected leak.

 

[smartcooky]

But proper design would mitigate this surely?

True, but do you think Titan was a "proper design"? And even if so, do you think that design was properly implemented?

 

[Foster Zygote]

True, but do you think Titan was a "proper design"? And even if so, do you think that design was properly implemented?

A Boeing engineer pointed out a couple of issues in some video showing a technician apparently cleaning one of the titanium rings, presumably in preparation for the epoxy application. The first thing was that as he was wiping the ring with a cloth in his right hand, he was resting his bare left hand on the ring. The second was that the mating surfaces appeared to be glass smooth, with no mechanical or chemical etching to help the adhesive bond to the surface.

 

[MRC_Hans]

For them it does, due to that cylindrical shape but for the planed edges of the CF pressure hull not so much. This was bad however you slice it, the very pressures of the outer titanium shells puts a delaminating stress on the CF pressure hull. Again, autoclaving in production might have reduced interlayer shear stress but not eliminated it. With out it, it’s a crescant waiting to be ripped apart.

*snip*

Ah, but I fully agree.

The takeaway from this, in as much as that ought to come to a surprise to anybody, is that you can make low-cost designs and you can make innovative design, but if there are serious safety concerns, you can't do both:

Either you save by using well proven standard components (if such exist in the deep-sea business) and -methods, or you try and test every new idea you implement.

Hans

 

[TurkeysGhost]

Haters gonna hate.

https://en.wikipedia.org/wiki/OceanGate,_Inc.

The company has been around since 2009, has worked with University of Washington and NASA on its submersible designs, and has been operating subs since at least 2015. The Titan sub they just lost has conducted several visits to the Titanic, starting in 2021.

This seems less "amateur-hour clown show" and more "submarine expeditions are risky".

This assessment hasn't aged well

 

[MRC_Hans]

A Boeing engineer pointed out a couple of issues in some video showing a technician apparently cleaning one of the titanium rings, presumably in preparation for the epoxy application. The first thing was that as he was wiping the ring with a cloth in his right hand, he was resting his bare left hand on the ring. The second was that the mating surfaces appeared to be glass smooth, with no mechanical or chemical etching to help the adhesive bond to the surface.

The use of adhesives is a science in itself, and aircraft producers have brought that science far. Not without some expensive lessons.

Hans

 

[Andy_Ross]

True, but do you think Titan was a "proper design"? And even if so, do you think that design was properly implemented?

No and even if it was properly designed it was never put up for third party scrutiny or testing.

 

[Myriad]

A Boeing engineer pointed out a couple of issues in some video showing a technician apparently cleaning one of the titanium rings, presumably in preparation for the epoxy application. The first thing was that as he was wiping the ring with a cloth in his right hand, he was resting his bare left hand on the ring. The second was that the mating surfaces appeared to be glass smooth, with no mechanical or chemical etching to help the adhesive bond to the surface.

Others have opined that the adhesive application should have been done in a clean room. (Sorry, I can't provide a cite, it was a couple of the many articles about the Titan that I've read.)

 

[TurkeysGhost]

Others have opined that the adhesive application should have been done in a clean room. (Sorry, I can't provide a cite, it was a couple of the many articles about the Titan that I've read.)

More know-it-all regulators trying to stifle innovation.

Move fast and break things!

 

[MRC_Hans]

More know-it-all regulators trying to stifle innovation.

Move fast and break things!

Yes, this can work. But try not to be inside the things you break.

Hans

 

[TurkeysGhost]

Yes, this can work. But try not to be inside the things you break.

Hans

Silicon valley brain tends not to work great when you're interacting with physical forces that can turn the human body into jelly.

But yeah, this galaxy brain guy piloting his death trap does give us a bit insight into his mental state. Hard to say this guy was cynical since he believed in the tech enough to put his own life on the line. Idiotic, but respectable in some way, though roping in other people into his deathtrap is harder to admire.

 

[IsThisTheLife]

What's become quite clear is that Rush was a person who liked to bask in admiration, and he wasn't going to get too much of that ego-stroking from grizzled old pros hence his preference for hiring "inspirational" "young" people instead.

ETA >> One has to suspect another (unspoken) rationale; cost. Experienced professionals are expensive, young neophytes are (much) cheaper. However, there are any number of aphorisms in engineering (and other) circles, such as; If you think hiring professionals is expensive, try hiring amateurs.

 

[IsThisTheLife]

The rationale behind the design (if you can call it that) was facile almost beyond belief - ALL submersibles which have gone to this depth and beyond have had spherical crew cabins, Rush (or whoever) apparently thought;

" ... if you, like, split that sphere in half, you can just put a tube between the two halves, and CF is, like, really, really strong ....."

 

[Dr.Sid]

The rationale behind the design (if you can call it that) was facile almost beyond belief - ALL submersibles which have gone to this depth and beyond have had spherical crew cabins, Rush (or whoever) apparently thought;

" ... if you, like, split that sphere in half, you can just put a tube between the two halves, and CF is, like, really, really strong ....."

Well pipe with halfdomes is standard solution for shallower diving subs basically since day one. Typically with ring stiffeners, sure, but it is well understood geometry. That's not the issue.
The issue is combination of materials, together with likely sloppy manufacturing process, and certainly sloppy way of operating the vessel.

 

[Foster Zygote]

Others have opined that the adhesive application should have been done in a clean room. (Sorry, I can't provide a cite, it was a couple of the many articles about the Titan that I've read.)

I've seen that stated by a number of sources as well. I've seen some others express dismay that they were applying the adhesives by hand because of the inconsistency that introduces.

Lack of clean facilities (from an industrial standpoint), lack of autoclave, lack of robotic application of adhesives...

Rush wanted to do this on the cheap, and was, in his own mind, too cool to fail.

 

[IsThisTheLife]

Well pipe with halfdomes is standard solution for shallower diving subs basically since day one. Typically with ring stiffeners, sure, but it is well understood geometry. That's not the issue.
The issue is combination of materials, together with likely sloppy manufacturing process, and certainly sloppy way of operating the vessel.

"Shallower diving subs"? What relevance do they have? Are you really going to give any credence to Oceangate's assertion that no other deep-water submersible has been built with anything but a spherical cabin because of 'conservatism'?

 

[jeremyp]

This assessment hasn't aged well

It's almost amusing reading the naive comments we* all made on the first few pages before we had the facts we have now.

*Yeah, I know: you called it right with the very first post.

 

[jeremyp]

I've seen that stated by a number of sources as well. I've seen some others express dismay that they were applying the adhesives by hand because of the inconsistency that introduces.

Lack of clean facilities (from an industrial standpoint), lack of autoclave, lack of robotic application of adhesives...

Rush wanted to do this on the cheap, and was, in his own mind, too cool to fail.

In 500 years time, online etymology dictionaries will have entries for "the job was rushed" saying "back in the 21st century a man named Stockton Rush made a submarine..."