With the impressive array of professions and credentials represented in the great Sigforum, where are the deep submersible experts ? We've got aviators, physicians, engineers, warriors, businessmen, maybe even some astronauts for all I know. The deep submersibles people must be members of a very small worldwide community, so small that the chances of having one of those people in our little forum would be like winning a lottery. My guess is also that those people may not have the types of personalities that would enjoy explaining exactly what did, or what could not have happened, given the evidence seen, and unseen, so far. My guess is the world has orders of magnitude more astronauts than deep sea explorers and engineers, maybe that is the problem here, notwithstanding the generally shallow and incompetent level of investigative journalism that seems to pervade the world today.

quote:

Originally posted by kkina:
but why would implosion happen at all? That single atmosphere of pressure inside the vessel wasn't doing much in the first place. At the moment the port breaches, pressure begins to increase and equalize, taking more and more stress off the hull.

Because the sub is being crushed at 6,000 psi at that depth. If anything in that pressure vessel ruptures, it's over as fast or faster than the video I posted. Either everything works or it doesn't.

quote:

Originally posted by parabellum:
acrylic

They should have gone with transparent aluminum.

some perspective....

max pressure per SAAMI for 12-gauge 2¾" service load is 11,500 psi.

So a good part of the way to a shotgun going off upon implosion, I guess. Only a much larger "chamber"

Not a mechanical engineer, but does that seem like a fair comparison, even though this is an implosion as opposed to explosion?

quote:

Originally posted by DanH:

quote:

Originally posted by kkina:
but why would implosion happen at all? That single atmosphere of pressure inside the vessel wasn't doing much in the first place. At the moment the port breaches, pressure begins to increase and equalize, taking more and more stress off the hull.

Because the sub is being crushed at 6,000 psi at that depth. If anything in that pressure vessel ruptures, it's over as fast or faster than the video I posted. Either everything works or it doesn't.

Simulation in slow motion.

quote:

Originally posted by honestlou:
They should have gone with transparent aluminum.

The debris brought ashore on Wednesday appeared to include at least one titanium end cap, the sub's porthole with its window missing, as well as a titanium ring, landing frame and the end equipment bay, according to BBC science correspondent Jonathan Amos.

https://www.bbc.com/news/world-us-canada-66049789

I was in St. John's NewFoundland in 2017 for a conference. I recognized it instantly from the pictures of pieces beign offloaded.

quote:

Originally posted by honestlou:

quote:

Originally posted by parabellum:
acrylic

They should have gone with transparent aluminum.

They tried, but their science guy did a little to much LDS back in the 60s.

i still struggle to understand the design, but these 2 pics from oceangate.com help





don't know why it looks blue thru the viewport, was just interested in capturing where the bolts were

The blue window is a reflection of the blue of the water column.

quote:

Originally posted by DanH:

quote:

My thought process is the whole thing is under X pressure. If the acrylic viewport shatters, at that moment, the whole thing is still under X pressure. I’m guessing, but I don’t believe the external pressure on any other part rises which is why I’m guessing the carbon fiber tube wouldn’t collapse. What I think happens next is the rebound from the implosion pops the end caps off, but because the tube is way stronger in tension, it survives the rebound of the implosion.

Just a WAG on my part.

Not even close. Carbon fiber is not a flexible material. It does not bend, it shatters. This is what happens in an implosion from the opposite side:



Even if this disaster was made from steel, there is an immediate pressure imbalance leading to what happens in the video, except the carbon fiber would shatter into billions of pieces leaving the top and bottom metal caps.

Take the barrel in the video, cut a hole in the top 25% of the diameter of the barrel and plug that hole with a plastic plug. What happens now? I bet the plug gets sucked in and the rest of the barrel is undamaged. Now replace the cylinder portion of the steel barrel with a carbon fiber tube of equivalent strength. Again, I bet the barrel remains undamaged.

The fact the titanium parts of the Titan look good implies that my thought process is a least partially true. Parts that held up to the pressure in the first place didn’t get destroyed.

The actual carbon fiber part of the composite is very flexible and will not shatter. Even encapsulated in cured resin, I don’t believe the resulting composite shatters.

I have watched a few videos of various objects made of various materials being crushed with a hydraulic press. It’s a rabbit hole. There’s one where combination wrenches from various countries get tested and some break, some bend, but the US made one breaks the test apparatus. Anyway, of the materials I saw tested, glass shatters, hardened steel shatters, the stuff Titans viewport was made from shatters, but carbon fiber composite does not. Not in a single one of the half a dozen videos does carbon fiber composite shatter. Fracture along the layers, yes. Bend and then break, yes. Carbon fiber cylinders crushed from the sides, flattened and cracked, yes. The ones showing tubes of carbon fiber composite being crushed from end to end are amazing. They show the carbon fibers separating from the resin and not breaking at all. Just the resin failing, but again, no shattering.



Maybe the shattering thing is temperature dependent. Here’s a picture of a failed carbon fiber composite pressure hull:


"This is the carbon fiber pressure vessel following its implosion test, showing the delamination of its walls.” Link

Not shattered into a billion pieces.

quote:

Originally posted by trapper189:
Take the barrel in the video, cut a hole in the top 25% of the diameter of the barrel and plug that hole with a plastic plug. What happens now? I bet the plug gets sucked in and the rest of the barrel is undamaged. Now replace the cylinder portion of the steel barrel with a carbon fiber tube of equivalent strength. Again, I bet the barrel remains undamaged.

You don't get it at all. The vehicle is being crushed at all times from ALL directions. It's not being mashed from only 1 direction like something would be in the air or on the ground or a hydraulic press.

quote:

Originally posted by DanH:
…It's not being mashed from only 1 direction like something would be in the air...

Actually, in the air, like the barrel in the video you posted is exactly the same thing. It’s the external air pressure surrounding the barrel being applied equally on all the surfaces of the barrel that causes it to implode.

I added a picture at the end of my post above. I get it.

What do you think happens to the barrel of a plastic plug like I mentioned is put into the top?

quote:

Originally posted by DanH:


You don't get it at all. The vehicle is being crushed at all times from ALL directions. It's not being mashed from only 1 direction like something would be in the air or on the ground or a hydraulic press.

Not only is there pressure at all points on that composite cylinder, but also on all points on the two titanium end caps.

Another way to look at it would be that the two end caps are likely sufficient to handle the pressure. They cylinder has to withstand not only the pressure all around trying to collapse it, but the pressure from the two end caps trying to meet in the middle like a pair of cymbals. I'll guess it wouldn't take much of a compromise in the cylinder to bring those two titanium end caps together. Think about standing on a empty beer can and tapping the side.

Likely yet another reason deep submersibles are spheres, so the pressure is acting on all points equally.

Right, stuff breaks at the weakest point. I questioned the cylinder shape many pages back and said it seemed to me that it should have been thicker in the middle. The barrel implosion video DanH posted demonstrates this very well. Where does the barrel fail? In the middle where the cylinder has the least support.

The failure point can be changed. You could put a thick ring of steel in the middle and move the least supported point to two places: between the ring and each end. Those parts would collapse and the ends would get pushed towards the ring.

Switching gears, I think the investigation will show the Titan failed in design and/or execution. It’s not a failure of the materials used, or a lack of knowledge of how to use use those materials. People went 35,797 feet deep in 1960. It’s niche field, but there’s certainly a body of knowledge that shows how it can be done. Nothing that happened with the Titan will advance that body of knowledge. This was a human failure and let’s face it, people have been doing stupid shit for a very long time and if history is any indication, people are unlikely to stop doing stupid shit.

I'm no engineer. But I agree with some of the above. A failure in the middle of the tube seems to make the most sense.

I'd think a porthole failure would cause such a violent pressure change. That even that would cause failures down stream in the design. Cracking or failures in the body.

I don't see a porthole blowing out at that depth and water just rushing in and filling up. With those kinds of pressures any failures I'd think would be extremely violent.

I've stayed out of this conversation, but I will just leave this. The inventor and CEO of Ocean Gate assembled a kit built aircraft, a Glasair III. I've built several homebuilts, including assisting on an Oshkosh Grand Champion Lindy winning Glasair III. I saw and inspected Rush's handiwork on *his* Glasair, and although he offered a ride in it... I declined. Most kit built airplanes are reasonably safe, as they go together like erector sets - but the builder has free reign on the components, wiring, mechanical bits lifted from production certified GA aircraft, etc. I haven't declined many rides or first fights of homebuilts, but I wasn't getting in Rush's bird N78G. By the way, primary structure is fiberglas, not carbon fiber.

Blast from the past....