They turned the titanic submarine into a video gameðŸ˜ðŸ˜ðŸ˜ pic.twitter.com/gupwgy02X6
— 🦂 (@uhlayyynuh) June 29, 2023
eric76 said:It does give an idea of the relative strengths of each material and how they fail. What I found most interesting is how the carbon fiber shredded as expected rather than deforming.Mathguy64 said:eric76 said:
Hydraulic Press testing Carbon Fiber and other materials
I wonder how many people would watch that and still use carbon fiber for the hull.
Except that's not really how the hull was loaded. It was under a radial compression around the outside of the cylinder. The longitudinal compression would have been greatly reduced by the titanium dome end caps.
The question is what happens to the tubes when you squeeze inwards all around? What is the crush pressure of each?
What I would have liked to see is for them to have built some number of identical hulls, load them with sensors, encase the hull in a net to collect the pieces and then lower it into the ocean collecting data until it collapsed and then return the pieces to the surface to inspect. Call that depth "crush depth".
Then do the same, but to some percentage of the "crush depth", keep these at that depth for a day, then bring them back for non-destructive examination of the materials. And then repeat a number of times. If they remains intact after a number of trials, call that "never exceed" depth.
And then set a "maximum manned operating depth" at something less than "never exceed" depth.
The percentage of crush depth to use and the margin between "never exceed" and "maximum manned operating depth" should be determined before testing, not to be played with after the "crush depth" is found. Otherwise, the temptation is to fudge the percentage to allow you to go to the depths you want to go to.
Yeah, but they threw all that out the window when they went with a carbon fiber hull, didn't they?yawny06 said:eric76 said:It does give an idea of the relative strengths of each material and how they fail. What I found most interesting is how the carbon fiber shredded as expected rather than deforming.Mathguy64 said:eric76 said:
Hydraulic Press testing Carbon Fiber and other materials
I wonder how many people would watch that and still use carbon fiber for the hull.
Except that's not really how the hull was loaded. It was under a radial compression around the outside of the cylinder. The longitudinal compression would have been greatly reduced by the titanium dome end caps.
The question is what happens to the tubes when you squeeze inwards all around? What is the crush pressure of each?
What I would have liked to see is for them to have built some number of identical hulls, load them with sensors, encase the hull in a net to collect the pieces and then lower it into the ocean collecting data until it collapsed and then return the pieces to the surface to inspect. Call that depth "crush depth".
Then do the same, but to some percentage of the "crush depth", keep these at that depth for a day, then bring them back for non-destructive examination of the materials. And then repeat a number of times. If they remains intact after a number of trials, call that "never exceed" depth.
And then set a "maximum manned operating depth" at something less than "never exceed" depth.
The percentage of crush depth to use and the margin between "never exceed" and "maximum manned operating depth" should be determined before testing, not to be played with after the "crush depth" is found. Otherwise, the temptation is to fudge the percentage to allow you to go to the depths you want to go to.
Or, and I know this is a revolutionary thought…people could just follow the engineering rules and guidelines put forth by certifying third party agencies, like ABS, DNV, Lloyds, for design and construction.
Yup. And now because of someone ignoring sound science and killing his passengers, the five countries investigating the incident will probably pass some sort of onerous regulation that will affect law abiding people minding their own business with no plans to take tourists down to the Titanic.yawny06 said:
That is the point, exactly. This was not a failure of industry standards. It was a failure to follow them. We don't need new test methods to prove what we already know.
cbr said:
I've seen a lot of 'wow, i can instantly see that that was an idiotic idea' issues with this sub, but let's go back to day 1.
Why the **** would you try to use cf for the sub? Its not cheaper. Its not appropriate. Its not proven. By the time its 5" thick i doubt its even lighter, and why would you put weight as a significant criteria in a submersible?
I use a lot of cf in my race car, but thats in low stress, high surface area applications where weigh is the primary goal.
bonfarr said:cbr said:
I've seen a lot of 'wow, i can instantly see that that was an idiotic idea' issues with this sub, but let's go back to day 1.
Why the **** would you try to use cf for the sub? Its not cheaper. Its not appropriate. Its not proven. By the time its 5" thick i doubt its even lighter, and why would you put weight as a significant criteria in a submersible?
I use a lot of cf in my race car, but thats in low stress, high surface area applications where weigh is the primary goal.
In interviews he gave he stated he used CF because of the proposed shape of the vessel. He needed it to be cylinder shaped to hold 5 adults which was necessary for their business model. He claimed building it entirely out of metal would have made it too heavy for them to manage.
I am under the impression that they were trying to be "innovative".yawny06 said:
That is the point, exactly. This was not a failure of industry standards. It was a failure to follow them. We don't need new test methods to prove what we already know.
You make some good points there.yawny06 said:
The industry standard and certification process would not allow for carbon fiber to be used at all.
I will give you an example. If you write a weld procedure for use in a DNV certified design, it must be to DNV standards, reviewed, and certified by DNV. Not only do you have to write the procedure to the standard, you have to weld a coupon and do all of the appropriate non-destructive and destructive testing. If you were to use a non-qualified electrode (that is, a normal standard electrode used for welding that is not qualified by DNV) then you must do additional testing on the electrode itself to get it qualified for use in the weld procedure. Those are the rules and the process. There is no wiggle room and that is just with a weld procedure and doesn't even touch on what must be done with a full design and the materials used in that design. And, as I have said earlier, that is my experience with topside equipment, not vessels or submersibles.
What they did would never pass any certification process without extensive testing, and even then it still may never have been approved. They viewed those design rules as a means to prevent new entrants into the industry and decided to ignore pretty much everything that has been learned in the design of submersibles. The guy thought he was smarter than everyone else, which is also why he didn't want to hire "50 year old white guys" who likely would have told him he was wrong.
Stockton Rush was smart enough to get a degree in aerospace engineering. It seems that his mistake was assuming that this knowledge would apply to undersea vessels. That it's just like flying, but down.Quote:
What they did would never pass any certification process without extensive testing, and even then it still may never have been approved. They viewed those design rules as a means to prevent new entrants into the industry and decided to ignore pretty much everything that has been learned in the design of submersibles. The guy thought he was smarter than everyone else, which is also why he didn't want to hire "50 year old white guys" who likely would have told him he was wrong.
Stat Monitor Repairman said:
Anyone see this alleged text message transcript between the support vessel and the sub?
They might have had their first indication of a problem 19 minutes before the implosion.
Said they got an alarm on the system that acoustically monitors the hull for cracks. Then decided to make an emergency ascent. Sounds like they somehow did some emergency procedure that released the skids. The vessel didn't respond like they expected.
Then they released more ballast which involved putting all 5 people to one side until ballast fell of hooks.
Sound like they were hearing the hull cracking and trying to figure out what to do.
cbr said:
Apparently metal hulls require expensive buoyant coatings.
https://www.compositesworld.com/articles/composite-submersibles-under-pressure-in-deep-deep-waters
But as i expected the math doesnt ad up. Cf is about 20% of the weight and half the compression strength in some applications. So the weight difference was likely marginal especially given that only one component of many was cf. a full ti vessel would have been much lighter and stronger. Steel much cheaper and not that much heavier.
It looks to me like there was no sound case for cf other than virtue signaling or trying to seem smart. Likely they drummed up a fat cf sponsorship.
Yes, but apparently weight was a driving factor until it's in the water.ABATTBQ11 said:cbr said:
Apparently metal hulls require expensive buoyant coatings.
https://www.compositesworld.com/articles/composite-submersibles-under-pressure-in-deep-deep-waters
But as i expected the math doesnt ad up. Cf is about 20% of the weight and half the compression strength in some applications. So the weight difference was likely marginal especially given that only one component of many was cf. a full ti vessel would have been much lighter and stronger. Steel much cheaper and not that much heavier.
It looks to me like there was no sound case for cf other than virtue signaling or trying to seem smart. Likely they drummed up a fat cf sponsorship.
Buoyancy isn't about weight. It's about density and displacement.
NDE of CFRP or the bond at the CFRP / Ti dome interface isn't hard. You can do ultrasonic or x-ray. Gaps due to delamination would easily show up. Hell, they could automate it in 2 degrees of freedom making passes axially and around the circumference with a simple jig.bmks270 said:NASAg03 said:
Okay here's my POV after working 5 years designing deep sea robotic vehicles for Nauticus Robotics. My experience includes a trip to WHOI to study their latest ROVs and apply to our vehicles. Our last vehicle was rated to 3000m. There were not humans involved, precisely because designing ANY deep sea vehicle is hard. It's a more challenging environment than space, and as such, we're trying to replace humans deep sea because of the cost and risk.
All of our vehicles were flooded, and only specialized electronics were placed in very expensive titanium pressure housings using American material stock, fabricated in America, with high quality metals. All were machined from single stock of material, pipe or billet. Why? Because any void can cause an immediate failure.
Any electronics with pressure-rated components were flooded with oil, and pressure compensated. Slightly positive pressure ensures oil is pushed out of the system so that no seawater gets into the electronics. We place water sensors in all electronics so that if they get wet, the computer will immediately know and bring the sub to surface before housing is completely flooded.
Most housings are pressure-assisted seals, and only need enough fastener preload to set the seal. After that, water pressure assists the seal until the metal flanges compress and transfer the load.
The pressure-assisted front "hatch" on Titan isn't the big issue. That's typical and a low risk item. The acrylic window is the higher risk item, as plastics creep, age, and change more with time, pressure and UV exposure than most metals. The biggest issue is the composites...which also have plastic involved.
We use composites for our unmanned subsea vehicle, but only as unpressurized vehicle structure. I've never seen any one use composites for a subsea pressure housing. That applies to ROVs and AUVs. Making a human-rated composite pressure vessel is unheard of.
Even using them for internal pressure, such as COPV, they typically have a metal liner to prevent leaks and are still leak-before-burst designs. You can't get that with external pressure, as any leak in the structural walls typically is catastrophic.
The mating seal between the Ti end caps and the composite cylinder is an adhesive bond, which isn't a big deal as it looks like the end cap has a flange that transmits axially load into the cylinder and the adhesive isn't that structural. However, the issue with this design is, any uneven loading on that flange can cause localized failures, ripples, and delamination of the composite, most likely internally due to the pressure distribution. This results in high stress regions that will avalanche since it's in compression.
My guess is that's what happened. After a few cycles, the internal flange lip of the composite cylinder wall delaminated due to higher-stress from the dome. Depending on post-dive inspections (if they did any), the delamination might not have even been detected at STP due to relaxing of the joint.
I'm curious what kind of NDE they did after fabrication and every dive, and what areas of the sub they inspected. I'm also curious if they did any leak monitoring or stress measurements during missions at high criticality regions.
It's 5 inches thick carbon fiber.
It's not easy to inspect.
The engineer who wanted do scans of the structure was fired.
I saw a video about it last night. If real, the crew would have had a scary last few minutes in this world.Stat Monitor Repairman said:
Anyone see this alleged text message transcript between the support vessel and the sub?
They might have had their first indication of a problem 19 minutes before the implosion.
Said they got an alarm on the system that acoustically monitors the hull for cracks. Then decided to make an emergency ascent. Sounds like they somehow did some emergency procedure that released the skids. The vessel didn't respond like they expected.
Then they released more ballast which involved putting all 5 people to one side until ballast fell of hooks.
Sound like they were hearing the hull cracking and trying to figure out what to do.
To his credit, the CEO drank his own "this is perfectly safe" Kool-Aid, and was on the sub himself. He took the ultimate responsibility for his corner-cutting. Unfortunately, he took other people with him.Quote:
If this wasn't happening, it's because the CEO didn't think it was worth the cost, not because it's hard. He was wrong and cutting corners in every way possible.
MarathonAg12 said:
There's a video game out where you have to explore the Titanic and find a certain amount of objects. If you run out of oxygen, it implodes.They turned the titanic submarine into a video gameðŸ˜ðŸ˜ðŸ˜ pic.twitter.com/gupwgy02X6
— 🦂 (@uhlayyynuh) June 29, 2023
This could go one of two ways...GMaster0 said:
I've been playing this video game and have been crushing it!!!
That IS how the sub was loaded, but only ONE of the ways.Mathguy64 said:eric76 said:
Hydraulic Press testing Carbon Fiber and other materials
I wonder how many people would watch that and still use carbon fiber for the hull.
Except that's not really how the hull was loaded. It was under a radial compression around the outside of the cylinder. The longitudinal compression would have been greatly reduced by the titanium dome end caps.
The question is what happens to the tubes when you squeeze inwards all around? What is the crush pressure of each?
The adhesive between the cylindrical hull and end cap didn't carry any shear stresses, other than internal due to water trying to press between the hull ID and the end cap surfaces.Stat Monitor Repairman said:
I still don't understand how that titanium ring was glued to the carbon fiber tube, and how that was expected to work.
That video above shows them painting on adhesive with a paint brush and lowing that ring on there.
It didn't look wasn't a press fit or anything. And it look like they did it with the expectation that adhesive would seal the joint between the ring and the hull.
As a layman looking at all this, it was was a success in a sense that it even worked once.
I'll give the guy credit for that. He made the most economical sub possible and dove it to the titanic several times.
But I think they underestimated the repeated stresses that this thing would have been under.
I also think they didn't properly account for thermoclines in the ocean.
Even on a surface vessel. If you hit a thermocline it can cause things to leak and malfunction.
I'm mainly talking about rubber o-ring seals and the seals on any kind of hydraulic rams in particular. They don't like drastic changes in temperature. You don't see this on land because temp change is gradual.
But if you hit a thermocline on the surface, you''ll sometimes see raw water cooled machinery and other auxiliary equipment develop leaks. Things that weren't leaking before will start leaking due to cold water causing rubber seals and gaskets to contract.
The point i'm trying to make is that this thing was held together with glue.
And that's lack of proper respect for the sea.
And that's the difference between being a professional mariner and somebody that thinks they can do something.
So it's telling that there were no professional mariners involved in this project.
