A few thoughts on the lost Titanic submersible

 "A wrong-doer is often a man who has left something undone, not always one who has done something." - Marcus Aurelius

I thought that it might be useful from the perspective of an ex-submariner and occasional social critic, to explain a few things that the news media won't be informing their viewers/readers about - or things that they would rather their readers forgot about.

Below: The ill-fated Titan submersible, under tow.

 Even at the relatively shallow depths at which military submarines operate, there is significant risk involved.  I've made several posts - without regard to nationality - about several of these tragic events over the years.  There has been significant loss of life on military ships, even outside of wartime.

I bear no ill will towards a sailor from *any* country who volunteers to serve their fellow countrymen under the sea, who meet their end in the depths of the ocean.  Links to a few of these posts are listed below.

• USS Thresher SSN-593
•  Submarine 361
• Losharik
• ARA San Juan
• Nanggala-402
• Kursk K-141 
• USS Scorpion SSN-589
• K-278 Komsomelets 
  

At the other end of the human behavioral spectrum is this:  Extreme Tourism.  This is the polar opposite of "service towards one's fellow countrymen".  Taking selfies while submerged next to RMS Titanic is one of the most incomprehensible behaviors that I can imagine.  

How does someone find enjoyment in visiting, knowing the fear that so many people experienced, watching one another die as the stricken ship sank?   Is it possible to dismiss the tragedy of over 1500 lives lost, and just enjoy the experience?  There are healthy levels of narcissism, and then there are these levels.

It's healthy and normal for people to travel and to enjoy new places and new experiences.  This is how we grow, learn to understand and respect other people's points of view - so that we can find ways to get along peacefully.  However, there is also currently a booming business in extreme tourism catering to the wealthy.  We have amateurs being assisted in summiting Mt. Everest, paying millions simply for the thrill of riding a rocket into space, or viewing the graveyard of RMS Titanic on a whim.   "Extreme tourism" does not seem like healthy activity.  How much can one really see of the Titanic in the deep from a tiny window, anyhow?  It's pitch black down there.  I'm slightly surprised that no "influencers" were along for the trip.  End of the criticism of our sick society.

There are also difficult engineering problems with going to great depths - which have long been understood.

 

Once you get below about 3300 ft (1000m), you are into the realm of non-survivability for any sort of problem.  At 1000m, the seawater pressure on the hull is 1450 psig, or 100 bar.  At this depth, a submersible better be as tough as a boiler steam drum, with thick high-quality steel walls.  Titanic lies at a depth of 12,500 feet - roughly 3800 meters down - so multiply all the above numbers by 3.8.  Pressure outside the hull will be 5500 psig (380 bar).  

The ideal deep-diving pressure hull should be spherical, so there are no straight sides for the pressure to bend inwards.  It should also be small, so that there is less surface area for the pressure to work against.  Lastly, it should be strong - of high-quality, tough metal  This should be titanium or very high quality steel alloy - and bear in mind that titanium alloy is incredibly expensive.  

This is where the problem for companies catering to tourists to visit RMS Titanic shows up:  Weight and expense.  To reach these depths, you need a very thick and strong metal hull.  If the hull is titanium, it will be light, but prohibitively expensive.  If it is steel, it will be expensive *and* prohibitively heavy.  

The physical weight of the submersible itself isn't doesn't cause much of an operating issue once it is in the water, but transport and handling of that weight does.  Any mother ship that could carry an appropriately robust steel submersible that seated five passengers would have to be massive - and expensive to operate.  That ship would also need additional specialized and expensive equipment to get that heavy load into and out of the water. 

Oceangate, the company that was offering these tours, likely could not afford to build the entire vessel from titanium, but they did find a way around the weight issue - and therefore around the expenses that come with moving that weight in and out of the water.  Their submersible was built from a light-weight tube of layered carbon fiber cloth.  Either end of the carbon fiber tube was sealed by titanium domes.  Access to the vessel was via the dome at the front end, which held a small viewing window.  

The appeal of this arrangement is that the submersible could be towed to the dive site on a barge by a small vessel.  The barge could be flooded, which would allow the submersible to enter the water.  Following a dive, the barge would be refilled with air.  All of this was only possible due to the carbon fiber construction of the hull of the submersible.

 The submersible had previously made 12 successful dives to Titanic, and there was no reason to believe that this dive would be any different than the previous dives.  In lieu of frequent Ultrasonic Testing of the walls of the pressure vessel walls, the vessel was equipped with a real-time stress monitoring system that the owner believed would give advance warning should the hull begin to fail.  Unfortunately in this instance, the carbon fiber may have suddenly failed due to brittle fracture, with little advance notice.  It's not currently known what component of the submersible caused the implosion.

 Carbon fiber has some benefits:

1. It is inexpensive compared to other materials of similar strength
2. It is lightweight, which is very attractive if the item needs to be transported

Carbon fiber also has some disadvantages that are not immediately obvious

1. It has never been used as a structural material for high-stress salt-water undersea use
2. Is not typically used in compressive stress applications. 

To be honest, it's impressive that this submersible was even able to reach RMS Titanic.  This was a very innovative approach to getting the task accomplished.  The use of lightweight material allowed an inexpensive submersible barge to bring the lightweight ship on site.  There was minimization of the use of titanium alloy, which further brought the cost down. 

That said, there are a lot of questions revolving around the safety of the operation.  The more we learn about it, the sketchier it seems to get.  There is an excellent Wikipedia article that describes a lot of the reservations that many outside engineers had about the project, of whistle-blowers and lawsuits, and specifically about using carbon fiber as hull material.  Obviously even the most minute void or delamination of the hull could significantly weaken it, and at 5500 psig, water would certainly find its way into any defect, potentially fatally weakening the carbon fiber fabric.

As a point of comparison, have a look at a fiberglass tank where I work.  This of course is not a deep-sea diving five inch thick carbon fiber pressure vessel.  Nevertheless, it has microscopic pores that allow water to seep out of it, even though it is under no pressure whatsoever.  This seepage has happened since the tank internal and external surfaces were re-coated. 

Speaking of sketchy activities, the earliest news reports about the accident all explained that contact with the vessel had been suddenly lost 1-1/2 hours into the dive, and that they had 48 hours of air remaining, and that "Banging noises could be heard".  Thus we were treated to the media spectacle and drama of a dogsled run to Nome, Alaska to provide the village with life-saving serum.  Except in this current event, the entire story was fabricated bullshit.

Not one of these articles mentioned that the sound of the hull imploding had been registered by the US Navy ocean monitoring systems.  And no one who knew the truth said a thing about it, including James Cameron.  From the linked article:

James Cameron, director of the 1997 blockbuster film Titanic, told CNN's Anderson Cooper that he called some of his diving connections and "tracked down some intel that was probably of military origin" to confirm his hunch of an implosion on Monday.

"Then I watched over the ensuing days this whole, everyone-running-around-with-their-hair-on-fire search," he said. "I just feel terrible for the families that had to go through all these false hopes that kept getting dangled as it played out."

One of the fascinating things I read about a rapid implosion at great depth is that the air inside would become super-heated in a fraction of a second.  This makes sense - it's how diesel engines work.  Compressing air heats it up - in a diesel engine, it heats up enough for fuel oil to spontaneously ignite when injected.  

At the depth the submersible was lost, sudden hull failure would compress and heat the air inside to thousands of degrees in a millisecond.  Quite likely, the hull caved in at greater than the speed of sound, and nobody even realized what happened.   

One of the things that struck me was a reporter asking whether there would be an attempt to recover the bodies.  Would they even bother if these people weren't billionaires?  Nevertheless, deep-sea remote tools were sent down, and some wreckage has been recovered.  

Below: The front titanium dome, now minus window.  Underneath that, a section of the tail, which was not part of the pressure hull.

Once you get a few tens of meters below the surface of the ocean, there is not a lot of forgiveness for design flaws or other human error - and the deeper you go, the less forgiveness there is, until there is no forgiveness at all.  

Maybe this event is simply more of the sort of hubris that caused RMS Titanic to be lost in the first place. 

UPDATE July 15, 2023:  There is an alleged leak of the transcript of the failed expedition.  Below is a video with a great explanation.