Titanic tourist sub goes missing sparking search

[Akimbo]

Anyone know why they built it out of carbon and titanium in the first place?

Deep submersibles are extremely weight critical, meaning the weight to displacement ratio. Just like a diver, they need to be neutrally buoyant. The greater the design depth, the thicker the hull wall has to be for a given material.

The weight and displacement of every screw and length of electrical cable was tracked during the design process, even in the 1970s. That was really labor intensive before solids modeling and finite element analysis software became affordable and usable without months of training.

Very expensive and bulky syntactic foam must be added once the components (hull, batteries, systems, etc) and crew weigh more than the water displaced. That increases the power (batteries) and propulsion requirements creating a cascading effect on the cost and size of the boat.

Another problem is dry weigh. The heavier and larger the boat, the more complex and expensive the handling system becomes. At some point the machinery to get the boat in and out of the water in reasonable open sea conditions makes it difficult to impossible to use a vessel of opportunity — a vessel that can be leased around the world. A dedicated ship and professional crew is an enormous expense unless you can keep it busy (making money) most of the time.

Leased or owned vessels aside, the costs continue regardless if you have to wait for better weather/sea conditions in order to get the boat in and out of the water. This is a HUGE cost justification to design the handling and sea keeping capacity of the vessel to handle higher seas. This issue alone has nearly replaced manned submersibles with ROVs in science, military, and industrial applications.

All this is why the great majority, if not all, the hulls for greater depths are spherical. Spheres are the most efficient geometry for equal distribution of hydrostatic forces. The wall thickness has to increase around hull penetrations for electrical connectors, hydraulics, viewports, and hatches. This makes it critical to do the best engineering and machining job possible to make the strength around all these penetrations as equal as possible to the rest of the hull.

Very small deviations from the "perfect" sphere makes huge differences in the engineering calculation — meaning radius, wall thickness, and material homogeneity.

 

[Manatee Diver]

Anyone know why they built it out of carbon and titanium in the first place?

Buoyancy, Rush said that building the hull out of anything else would require expensive buoyancy foam to counteract the negative buoyancy to bring it to neutral with the ballast installed. But Carbon Fiber is light enough that the air in the hull alone would be enough to make it neutral.

 

[Akimbo]

With all the money at Stockton Rush's disposal, why not charter onto existing subs instead of a haphazard build? Or hire people in the field to assist his own endeavor?

One word answer: H-U-B-R-I-S

I suspect it was more a matter of operating cost to make the business plan work than hubris. Hubris certainly came after the conclusion that they needed a cost-effective boat and handling system for the tourism application.

 

[lowwall]

Another Billionaire bites it. https://www.cnn.com/2023/06/26/business/james-crown-obit/index.html

Risky business being a Billionaire.

James Crown, a billionaire businessman who held several leadership roles including board member of JPMorgan Chase, died Sunday in a racing accident in Colorado.

Crown, who also turned 70 on Sunday, died in the single-vehicle crash after colliding with an impact barrier at Aspen Motorsports Park in Woody Creek, Colorado

Heavy is the foot that bears the Crown.

 

[Gone for diving]

I suspect it was more a matter of operating cost to make the business plan work than hubris. Hubris certainly came after the conclusion that they needed a cost-effective boat and handling system for the tourism application.

First step in building a sub of any kind
Is to have a good pressure vessel.
After that simpler the better,

Rush's quote about
Everything can fail, but if your hull is ok you still can get to the surface because of the extra features,
is fairly true,
Problem is the hull didn't survive, so everything else is moot,

He obviously believed in the hull being strong enough. (unless he was suicidal),

 

[wetb4igetinthewater]

He obviously believed in the hull being strong enough. (unless he was suicidal),

This is a question that will obviously never be answered, but on what basis did he believe his hull was strong enough?

 

[Wookie]

This is a question that will obviously never be answered, but on what basis did he believe his hull was strong enough?

It made 23 trips?

 

[wetb4igetinthewater]

It made 23 trips?

And what was the determined point of stress failure? I'm not a materials person, and I didn't stay at a Holiday Inn. I may know the person who supplied the carbon fiber, but I'm pretty sure he's not going to talk about it.

Everything fails at what point. The question is, what is the probability of failure over time? There's a reason why after 5 years subs are supposed to be completely taken apart, inspected, and then reassembled.

 

[Akimbo]

This is a question that will obviously never be answered, but on what basis did he believe his hull was strong enough?

It made 23 trips?

And what was the determined point of stress failure?

Commercial and military aircraft are tightly regulated based on flight hours and sometimes takeoff and landing cycles, largely due to material cyclic fatigue. The last 10 minutes of this video discusses it.

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[HalcyonDaze]

It made 23 trips?

I thought it was only 13 prior Titanic dives, not counting shallow test dives in Puget Sound and deep dives in the Bahamas. Were there 10 test dives?