Tourist submersible visiting the Titanic is missing Part 2 68

[hpaircraft]

...No other application is even close to that of a deep sea sub hull...

Except maybe the Advanced Unmanned Search System (AUSS) deep sea sub hull?

...The center section is a cylindrical graphite epoxy pressure hull with titanium hemispherical ends. The hull provides the central structure and all its buoyancy---no syntactic foam is used...

Huh. Sounds kinda familiar.

https://irp.fas.org/program/collect/auss.htm

Edit add: I'm guessing that this is the technical paper that Spencer used as the starting point for their hull design:

https://www.researchgate.net/public...r_the_Advanced_Unmanned_Search_System_Vehicle

...The AUSS Mod 2 pressure-hull assembly, consisting of a wet-wound graphite-fiber epoxy composite cylinder capped with adhesive-bonded titanium coupling rings, and closed off with titanium hemispherical bulkheads...

If that's so, it could be that they didn't account for scaling factors as they sized their barrel up from 31" x 65" to 66" x 98".

 

[SnTMan]

Tethered. I guess it's the only way to transmit high quality data. So 2 1/2 (or more) miles of wire after all. My mind boggles

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[dik]

From what I read, with the significant issues of CF construction, there has to be a rigourous quality control program in place. No matter how accurate your analysis is, the QC is far more significant.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

How does 'one way' CF accommodate the large compression forces from the end hemispheres?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[TugboatEng]

Yes, this should have been made from rings that allowed for radial orientation of the strands and not as a cylinder.

 

[JStephen]

The video used above kept mentioning "one-way" carbon-fiber, while other information has said they had longitudinal and hoop in a 1:2 radio, if I remember right.

Since the submersible failed, there is obviously room for criticism of whatever design went on. But I've not seen anything really that indicated how sophisticated that analysis was. So this may have been the "code monkey" approach, or experts in the field, or anything in between, from what I can see.
For a metallic tube with hemispherical ends with internal pressure, the analysis would be fairly simple and straight-forward.
But throwing in bucking/ external pressure, thick-walled, composite, significant temperature changes, fatigue evaluations, joint/glue design, bolted-joint design, plus an acrylic window- each one of those adds another layer of complication, and it'd be easy to get lost at some point if you weren't really on top of it all. And on top of all that, you have the instant-death-if-it-fails aspect.

One thing I've seen mentioned numerous times is the window only being rated for 1300m. That seems to be confused with the window only being adequate for 1300m, which is entirely different. IE, rating the window for deeper may have involved more testing or more analysis, but wouldn't necessarily have changed the window, either.

 

[SnTMan]

JStephen, you left out "lack of significant NDE"

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[dik]

It doesn't matter very much... the whole enterprise is an excellent example or 'bad engineering' or 'non-engineering'. It's because of my exposure to 'bad engineering' when I first started that I don't wear an engineer's iron ring.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[MechinNC]

I would give credit to OG if they took a prototype of their submersible to a deep part of the ocean and did like 100 dives to test depth (what ever that is) and preferably took it on last dive to failure. Then the next boat would have some cred.

Not clear at all what type of test protocol was used, we shall see when reports come out.

 

[waross]

There were claims that the hull was laid up in both directions, but it may have been replaced with a cylinder laid in only one direction. The craft was repaired. The repair may have involved replacement of the carbon fibre cylinder.


--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Demented]

https://www.heraldnet.com/news/titanic-in-reach-as-everetts-oceangate-works-with-nasa/

Monday, March 9, 2020 5:34am

EVERETT — A hoped for visit to the Titanic has been years in the making, but OceanGate now wants to reach the world’s most famous sunken ship with some help from NASA.

The Everett-based company is working with the federal space agency to build a submarine that’s strong enough to survive the pressure of those kinds of ocean depths.

OceanGate first planned to study the Titanic in 2018, but its submarine was hit by lightning. The team tried again the next year, but it didn’t work out because of complications.

With the extra time, the company did more testing and realized the vessel wasn’t strong enough for multiple trips to the sunken ship, almost 4,000 meters under the sea, or about 2½ miles.

They needed a stronger material, OceanGate CEO Stockton Rush said.

“We had talked to NASA in the past, and found out they had a need for this advanced technology,” he said. “It’s one of the thickest structures ever made of carbon fiber. They are also looking to go to the moons of Jupiter and Saturn, and that’s likely going to require advanced materials to be able to melt through the ice and explore these watery moons.”

NASA is using the carbon fiber material to build the vessel’s hull, or the outer part of the submarine. Manufacturing is expected to begin in a few weeks at the Marshall Space Flight Center in Huntsville, Alabama.

Later, the submarine will be assembled in Everett. OceanGate’s headquarters are on Craftsman Way, on the waterfront. About 25 people work there.

In a way, OceanGate and NASA are helping each other.

“NASA can only do this kind of contract work where it sees advantages to advancing technology and there isn’t really a commercial alternative,” Rush said. “We will be paying NASA for the work, and NASA will get access to this technology, so we get a pretty good rate and they get a lot of data.”

The submarine, called Titan, is about 5 feet in diameter and roughly 10 feet long, with enough space for five people to fit inside. The design is similar to another OceanGate submarine, called Cyclops 1.

OceanGate plans to visit the Titanic in 2021 from July to mid-August. A typical dive is around 12 hours long.

Along with researchers, anyone interested is invited to come along and may buy tickets to join the expedition. Proceeds fund the missions.

The group would stay on a ship for eight days at a time, above the wreck site in the Atlantic Ocean, nearly 400 miles from Newfoundland, Canada.

Once at the Titanic, researchers expect to take detailed photos, and scan the ship with lasers and high definition sonar.

“One of the questions that needs to be answered is how quickly is the wreck decaying, what’s its current conditions and how quickly is it going to disappear into the sea?” Rush said.

OceanGate also hopes to study the debris field, where personal belongings may be scattered, and marine life. Around 300 different species are unique to the wreckage, Rush said.

The Titanic sank during its maiden voyage, in April 1912. It was making its way between Southampton, England, and New York City. About 1,500 people were killed.

The luxury marine liner was 882 feet long, 92 feet wide, with space for 3,547 passengers.

Because OceanGate only wants to look around, the company doesn’t need permission to visit the site. However, officials know about their plans. Titanic’s location was first discovered by Robert Ballard in 1985, and photos were later taken by remotely operated deep-dive vehicles.

Rush and his team hope to go back every summer to see how the Titanic changes each year, and make that information available to other researchers.

There’s no set time frame to continue the trips, just until “people stop wanting to go,” Rush said.

Stephanie Davey: 425-339-3192; sdavey@heraldnet.com; Twitter: @stephrdavey.

 

[rodface]

An article from 2022 that names several companies that were involved in building the Titan's second hull (the one involved in the incident)?

https://www.nwyachting.com/titan-of-industry/

All of OceanGate Inc.’s submersibles—there are currently four including Titan—are developed out of the company’s homebase at the Port of Everett, with testing and research dives often taking place in nearby Possession Sound. Local partnerships abound: OceanGate collaborated with NASA on some of the technical aspects of Titan, but they also leaned on the experts at Boeing and the University of Washington Applied Physics Lab during fabrication. Toray in Tacoma produced the carbon fiber composite material for the submersible, Janicki Industries out of Sedro-Wooley did all the machining work, and then the UW stepped up again to help OceanGate test the pressure vessel at their School of Oceanography. “It’s really unique to have all these companies and resources available to us here locally,” says Rush. “It’s been a great community to work with.”

Well first hull? Second hull? It's all quite confusing.

What is certain is that this video shows a very different manufacturing process from the "wet" one shown in more widely-distributed video:

https://www.facebook.com/watch/?extid=NS-UNK-UNK-UNK-IOS_GK0T-GK1C&mibextid=2Rb1fB&v=745914473825135

 

[rodface]

That Herald article implies a very high level of collaboration between MSFC and OceanGate. Was it all complete bollocks out of Stockton's mouth? I think NASA has stated that they "consulted" on it, correct?

Edit to add: if this was really all out of a single source and was not verified with NASA, that seems like quite lazy journalism.

 

[dik]

From another thread, I just realised that the non-uniform radial compression stress will create shear stresses with the CF matrix. How is CF with shear? Is the longitudinal compression stress created by the end domes uniform or does it vary across the cross section?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[blakmax]

More questions about manufacture:

1. The composite cylinder was tape-laid onto a metal mandrel. Did the manufacturer undertake regular compaction as the structure was built up? Usually, composites are compacted regularly as the thickness is added. That was trapped air can be extracted, minimising void content.

2. What resin was used and how was it cured? My experience with composites is that thick laminates are susceptible to thermal runaway with a risk of spontaneous combustion. Maybe they used room temperature curing resins, which in itself has inherent dangers.

3. Given the thickness, they would almost certainly have used a zero bleed pre-preg, which also risks high porosity.

Regards

Blakmax

 

[LittleInch]

I went back and had a look at the original videos of construction again like this one

https://www.youtube.com/watch?v=WK99kBS1AfE

The lack of connection between the shell and the titanium ring is unreal. Basically less than 50mm insertion of the CF shell into a C shaped end with very thin inner and outer cylinders. I just can't see how this survived any outings, not to mention 7 or 8.

As to the design itself, who knows what they did? I do suspect a bit of undue reliance on computer says Yes...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

A few atm will easily push the ends on. More to worry about is heating up under the sun while on the surface. Underwater camera housings only have O-rings.


Wall stress: 55,000 psi compression-
Long stress: 29,000 psi compression
Max shear +/-13,000 psi
(neglecting radial stress)

Does not seem excessive. I think it will be a defect issue.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[dik]

More technical stuff on CF.

https://www.youtube.com/watch?v=6LcGrLnzYuU

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

They seem high to me considering they are compressive stresses. I have no background in CF technology. The earlier post I just made seems to think there are general problems with the method.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[LittleInch]

Does CF "bruise" n the same way GRP does?

I.e. no surface damage visible, but deeper layers get broken and create weaknesses?

My issue with the end ring / dome connection to the CF pressure dome is where different materials react differently in terms of reaction under the huge loads it experienced and temperature changes, but about 50mm only is contained within a joint. Any damage within that joint or right at the stress concentration point at the end would have been very difficult to see / repair or monitor I believe. The analysis might all be ok, but the devil is in the details of the connection.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.