The Oceangate story is so much worse than we thought

In reply to Duke :

We need a clapping emoji. 

Toyman! said:

The googles says "There have been 18 fatal accidents involving submersibles since 1915, resulting in 835 deaths."

That's an average of 7.6 people per year. Using that metric, 2023 was better than average. 

I would be interested to see the accident rate strictly for research submersibles since then. I bet it's a lot lower, especially if your numbers include wartime casualties and military submarine figures...

codrus (Forum Supporter) said:

Pete. (l33t FS) said:

(given that they thought a material that is weak in compression would be a good idea for a submersible, in the first place, this is not really that surprising)

Apparently the carbon-fiber-with-titanium-end-caps design was based on a US Navy submersible called AUSS.  That one was unmanned; but it had a pressure hull for bouyancy, went deeper than the OceanGate one did, and they did over a hundred successful dives in the 90s before retiring it.  So perhaps the core idea isn't a crazy as everyone makes it out to be now?

 

AUSS was significantly smaller in diameter had no view ports and was likely not made with expired materials and glued ends. If you don't need to accommodate a human and breathing gasses you can do a ton more reinforcement on the inside. I trust the US military to build a AUV and I trust that they did not put a human inside it for a reason. 

1988RedT2 said:

I keep asking myself, how do people still consider this event relevant today?

The reason it is relevant today is that the public hearings into this cluster are ongoing this week and next week. That is why we are now seeing wreck footage, why the truth of the original venture is coming out, and why the things that have been investigated are now coming to light. 

Yes, too much regulation is stifling to innovation.  Testing of the original hull design for the Titan showed that it was inadequate for the specified working depth. Then, they had to replace the first hull because it de-laminated. The next one was built by a different method done so by different contractors, and the new method was untested. Then, they re-used the mounting rings and titanium domes from the old hull. 

Mr. Rush at this point was basically hitting Murphy with a 2x4, daring him to do something.

That type of ignorance borders on the criminally negligent, especially since so many SMEs in the field warned Rush about it years prior. 

2.4 miles beneath the waves is the last place you want to be "innovating" without spending millions on R&D and unmanned testing first.

I'm still scratching my head about the darned ratchet strap... can somebody suggest a reason why that was there?

In reply to SV reX :

Im betting it held skids or some external gear on.  Normally you would bond that on, but given other shortcuts taken...

Wonder if it can be found in other pictures before failure? Might give a hint

SV reX said:

I'm still scratching my head about the darned ratchet strap... can somebody suggest a reason why that was there?

It's not on the pressure vessel, that's the fairing for the tail. So while it's a really bad look, it's not a serious problem in itself. I don't see it in any of the pre-implosion pics.

z31maniac said:

In reply to Duke :

We need a clapping emoji. 

Here you go:

👏

Still chugging through this, it has the usual slowness of content as with any other livestream.  But there are interesting tidbits.

One thing that I find interesting is how they turned a negative into a positive.  I remember seeing an interview with one of the clients who was glowing about how the submersible was so small and so much had to be done that the people who paid to dive were tasked with certain jobs and given little titles.

ITV:  They were called crew and not passengers, because the standards of safety are much higher if you have passengers.

Pete. (l33t FS) said:

ITV:  They were called crew and not passengers, because the standards of safety are much higher if you have passengers.

Why do I have a hard time being surprised by this?

Hard to remember if this video has already been linked...

Yahoo.com: Coast Guard releases video showing Titan submersible wreck at bottom of Atlantic

Also hydraulic press vs various tubing. It's interesting how the carbon fiber fails.

And, another video

In reply to VolvoHeretic :

Cool vid to be sure, but that carbon fiber sample looks to have been made with a focus on aesthetics rather than structural strength. In addition, we don't know what adhesives were used in manufacture or how it was cured.

In reply to myf16n :

Fare enough. I know nothing about carbon fiber and for some reason, there are virtually no videos of destructive testing of it. You would think that over the years, someone would have made a video of a driveshaft or maybe a wheel spun to failure.

How about one more video in regards to OceanGate? Also, note to self: Never name anything that ends with "Gate".

In reply to VolvoHeretic :

I have torn apart a CF driveshaft. Maybe I'll post pics. No need for a video. But that won't tell you anything about using it under compression. Composite pressure vessels are very common in containing high pressure, but then it's basically under tension. 

In reply to Keith Tanner :

So, I suppose it's not a good idea to built a mini sub out of my 500 gallon steel propane tank?

In reply to VolvoHeretic :

Nothing wrong with it as long as you keep the depth at a point where the propane tank is rated. For steel, compression and tension strength is pretty similar.  

But, as for using anything, you have to know what it's rated for.  It won't go all that far down, it seems that the tank runs nominally at 200psi, which would be under 500ft of depth.  

In reply to alfadriver :

A 2 liter soda bottle can handle 150psi internal pressure, but it can crush just from sucking on it with wimpy meat-lung vacuum.

What is strong to internal pressure is often weak to external pressure.

In reply to Pete. (l33t FS) :

Very true, but steel tanks are reasonably equal.  

In reply to alfadriver :

Have you watched Mythbusters and the rail car tank?  14.5 psi...

I understand the pushback on rules and regulations, but the rebuttal is to remember that they are most commonly written in blood. 

alfadriver said:

In reply to Pete. (l33t FS) :

Very true, but steel tanks are reasonably equal.  

No.

Steel, as a material, reacts roughly the same in tension vs compression.

Shape of the material determines how it will react to positive or negative pressure deltas

Streetwiseguy said:

In reply to alfadriver :

Have you watched Mythbusters and the rail car tank?  14.5 psi...

Was that rail car intended to carry pressurized gas, or was it just for something like oil? If the latter, it wouldn't be designed for much pressure differential of any sort. 

wearymicrobe said:

AUSS was significantly smaller in diameter had no view ports and was likely not made with expired materials and glued ends. If you don't need to accommodate a human and breathing gasses you can do a ton more reinforcement on the inside. I trust the US military to build a AUV and I trust that they did not put a human inside it for a reason. 

I'm not saying that the oceangate design was sound -- clearly it wasn't, or it wouldn't have failed.  And yup, they appear to have cut every corner there was, skipped all the safety testing, etc.

It's just that we suddenly have a thousand armchair experts talking about the limits of carbon fiber and how the very idea of using it to hold out external pressure deep under water is crazy and nobody with any sense would ever do it.  And yet, 40 years ago (an eternity in the composites industry!) it was a core of a very successful USN design.

Keith Tanner said:

Streetwiseguy said:

In reply to alfadriver :

Have you watched Mythbusters and the rail car tank?  14.5 psi...

Was that rail car intended to carry pressurized gas, or was it just for something like oil? If the latter, it wouldn't be designed for much pressure differential of any sort. 

I guess I'm making some assumptions, but I think you could seal a rail tank car up, apply one bar of pressure internally, and have a very successful pressure vessel.  The failure from internal pressure has to stretch and rupture the tank.  External pressure just changes the shape of the tank,  bends the material and collapses.  The steel tank likely would just bend, but still be sealed.  My thought is that carbon fiber would be more likely to fracture, based on what an F1 track looks like following a visit to the wall.