Another Titanic Tragedy
On 18 June 2023, the deep sea submarine Titan, owned and operated by OceanGate Expeditions sank gently beneath the surface of the North Atlantic Ocean to commence the 3.8 kilometre (2.36 mile) journey down to world’s most famous shipwreck – Titanic. On board the Titan was the CEO of OceanGate Expeditions, Stockton Rush, as well as four paying passengers. One hour and forty-five minutes into the journey, as the Titan was nearing the Titanic, communication with it was lost.
A worldwide search, involving many countries, and ultimately costing many millions of dollars, began. So too did a worldwide media frenzy. It was reported the Titan had enough oxygen for the occupants to survive for three days. Could the rescuers get to them in time? How could the rescuers get them to the surface? What if they were already back on the surface, but were drifting somewhere in the North Atlantic? Speculation was wild and, at times, bordered on the absurd. When the US Coast Guard heard noises coming from the area of the Titanic (which could have been anything, but was most likely water current moving objects on the sea bed or within the wreck), commentators speculated that it might be the occupants of the submersible trying to tap out a message.
What no media commentators (either mainstream media or social media) talked about was the physics. While some people suggested that the Titan could have imploded, no one explained what the implosion would have meant – and why.
Because the book The Frontier Below had been released seven weeks before the OceanGate Titan went silent, I got many requests asking me to comment. I was surprised, because when I tried to explain some of the background as to what would happen in an implosion at this depth, people did not want to listen. Nor did they want to listen to how the shape of the OceanGate Titan was a major concern. A story of daring rescue attempts, while the Titan occupants bravely hung on to hope, breathing their diminishing oxygen supply, was far more dramatic.
So, for this article I am going to give a brief overview of the history of how we came to understand underwater implosions, and show why lessons that explorers learned hundreds of years ago, were ignored by OceanGate and Stockton Rush.
At this point I have to use the metric system because many measurements are based on water. These include temperature (water freezes at zero degrees and boils at 100 degrees), weight (one litre of water weighs one kilogram and 1,000 litres of water weighs a metric tonne) and volume (one litre of water occupies one cubic litre of space).
Water is heavy. Like anything subject to gravity, it is pulled down. Get a box or some sort of cube-shaped container with each side measuring 1 metre in length (roughly the size of a box sitting on a forklift pallet). Fill that box with water and it will weigh 1 tonne (in addition to the weight of the container.)
Just for the moment, let’s keep our cube-box empty and climb inside it and close the lid. We’re scrunched up, knees to our chest, sitting in a closed box. Now let’s try to push the box underwater. (We’ll assume it is watertight.) The box with us in it will float and bob on the surface because to get underwater it needs to displace a cubic metre of water, which weighs 1 tonne. Unless the person and the box weigh more than a tonne, it will continue to float, partly above water. To get it underwater, we have to put some weight in the box, or sling weight from the sides. When the box and contents weigh more than one tonne, the whole lot goes under.
Archimedes, the Greek mathematician, (Indiana Jones meets him in his latest movie) figured this out over 2,200 years ago when he sat in his bath and noticed the water rise around him.
Anyway, let’s take our cube-box, with us inside it, one metre under water. We are at a depth of one metre and we have a cubic metre of water sitting on top of us. That’s 1 tonne of weight above us. Do we want to ensure our box is strong and not going to be crushed? I think so.
Let’s take our cube-box down to a depth of two metres. Now we have 2 tonnes of water pressing down us. Three metres, 3 tonnes. Four metres, 4 tonnes.
If we managed to sit inside our cube-box and somehow get it down to that depth, that is 3,800 tonnes of weight pushing down on the top of the box. Yes, the box has to be strong and not have any leaks.
If we are getting a hollow vessel deep underwater we need to make the shell of our vessel strong or it will implode, which is another way of saying it will get squashed by water. This has been understood for hundreds of years. If you want to think about what an implosion would be like, take a blacksmith’s anvil and drop it on an egg. Then imagine you are inside the egg.
Robert Boyle, the 17th century scientist, studied how air compressed and came up with Boyles Law. Boyle observed that if you are in a diving bell underwater, then the deeper you go, the more the air is squeezed in to the upper part of the bell. As you come back to the surface, the air pushes down and the water level lowers. Air is ‘springy’ Boyle wrote. He also conducted experiments where he got empty drinking flasks (the sort of thing sailors kept their whisky or rum in) and made sure the lid was sealed tight. Then Boyle would tie a rope to it, and some added weight, then lower the flask underwater. He observed that when he brought it back to the surface, the flask was crushed, like a heavy weight had smashed down on it.
Diving bells remained open at the bottom for the next 250 years, so the air in them was compressed, rather than have the bell implode. The standard diving dress (hard hat helmet suit) was developed in the early 19th century and this supplied divers with compressed air from the surface, to stop their lungs being squashed. People became aware of the dangers of compressed air (nitrogen narcosis and decompression sickness, or ‘the bends’) and by the late 19th century were trying to make one atmosphere diving suits. A one atmosphere diving suit protects the diver from the surrounding water pressure.
Various ‘one atmosphere’ diving suits were tried and plenty of their inventors either died, or were crippled by the bends. What some people failed to understand was that you cannot partially protect a sealed vessel against water pressure. Go back to our cube-box. That is, the one in which we are sitting inside hoping it doesn’t leak or get crushed by the tonnes of weight bearing down on it. Our box has six sides. It is pointless if five of those sides are made of some strong material, like steel, if the sixth side is canvas. A hollow underwater vessel is a strong as its weakest point. Water surrounds it and presses from all sides. Think of a car tyre. It doesn’t matter how thick the rubber is, if there is the smallest hole in the tyre, air will escape and the tyre will go flat. A hollow underwater vessel is a bit like a car tyre, but in reverse. The pressure is on the outside, trying to get in. The smallest hole, or weakness, and it will find a way. So, one atmospheric diving suits were limited to depths of around 120 metres until improved lightweight materials were developed.
The breakthrough that took people deeper into the ocean was made by Otis Barton in the 1920s. He designed and built a bathysphere. Sphere is the important syllable, because Barton designed a hollow ‘ball’.
Over 2,000 years ago, the Romans understood the principals of supporting weight when they built arches to hold up aqueducts, bridges and large buildings. When outside pressure pushes on a curved surface, the surface is compressed on itself, becoming stronger. Barton’s bathysphere was a continuous curve, all the way around. He understood that any flat area would be weaker. Barton, along with celebrity naturalist William Beebe, were lowered to record depths in the 1930s, suspended on a cable on a winch. Their deepest dive was to 923 metres (3,028 feet) in 1934. After World War II, Otis Barton built another bathysphere (but called it a ‘benthoscope’) and, suspended on a cable, he went to 1,372 metres (4,500 feet). To ensure the hollow steel ball was thick enough not to implode, it weighed 6.4 tonnes.
In the 1940s and 1950s, Auguste Piccard and his son Jacques, as well as Frenchmen Georges Houot and Pierre Willm, developed bathyscaphes. These did away with the cable to the surface and, instead, suspended a steel ball under a float filled with petrol. (Petrol, or gasoline, is lighter than water and will not crush under the pressure.) The bathyscaphe Trieste, reached the deepest point of the ocean – the Mariana Trench – in January 1960. The depth is 10,900 metres (6.8 miles) – more than two and a half ties deeper than the Titanic.
With bathyscaphes, the hollow heavy steel ball, into which two occupants could squeeze, was made by pouring molten steel into a cast. They were extremely heavy and, as a consequence, the float above the sphere had to be large, because petrol has a specific gravity of approximately .75. (It’s 25% lighter than water.)
The principles of getting a bathyscaphe to go down and up are as follows: Get the bathyscaphe in the water so that it is positively buoyant, i.e. it will float to the surface. Then add extra weight to it in such a manner that you can jettison the weight whenever you want. This is usually done with electromagnets on the outside of the hull. The occupant in the sphere turns on the power, magnetising the electromagnets. Extra weight clings to them. The extra weight pulls the submersible underwater, taking it to the depth required. When the occupant turns off the power, the extra weight drops off, and the submersible – now positively buoyant – returns to the surface. There’s a built-in safety factor, because if there is any loss of power the weight will drop off.
By the 1960s, people began to build deep sea submersibles using syntactic foam instead of petrol. Syntactic foam (a polymer filled with tiny hollow spheres) has a lower specific gravity than petrol (and therefore greater buoyancy), so the float to bring the steel spherical cabin back to the surface became smaller. At the same time, titanium spherical cabins replaced the old cast steel cabins. Deep sea submersibles became smaller. The first was the American Alvin, developed by the Woods Hole Oceanographic Institution in the 1960s.
The first, and most important function of a deep sea submersible (or Deep Submergence Vehicle – DSV) is not to implode, and thereby protect the occupants from the water pressure. Its second most important function is to get back to the surface. After that, the priorities should be an ability for the occupants to get out unassisted once they are on the surface, because they may have drifted a long way from where they went under. And other functions include the ability to allow the occupants to breathe, and an ability to communicate with a surface vessel.
But the two most important functions – not imploding and being positively buoyant – were revolutionised by the introduction of titanium spheres (or cabins) for the occupants, along with syntactic foam.
Using the current combination of materials (syntactic foam and titanium) the sphere holding the occupants is limited to a diameter of about 2 metres. Much bigger, and the shell becomes weaker. A hollow titanium sphere with a diameter of 2 metres can squeeze in two people. Maybe, three if they are smaller and on very friendly terms.
All this brings us to the OceanGate Titan submarine. Stockton Rush, the CEO of OceanGate wanted to take passengers to the Titanic. Obviously, the more paying passengers he could take on board in a single trip, the more money he could make. Originally, he purchased a cigar-shaped – or cylindrical – submersible, previously used by a marine research organisation. Because of its shape, it was able to accommodate five people. It had a viewing port at one end and, because the viewing port was like a single eye, Stockton Rush called this submersible Cyclops I. The Cyclops I was only rated to a depth of 500 metres.
Realising the potential of a submersible that was capable of carrying five people at once, Stockton Rush began building a submersible with the same shape at the Cyclops I, but with a stronger hull to resist pressure at greater depths. The problem was the shape. He needed a cylindrical shape with flat sides and unlike spheres, flat surfaces are more prone to buckling in under pressure or weight.
Stockton Rush’s submersible, which he initially called Cyclops II, was built with titanium ends, but the wall of the cylinder in the middle was made of carbon fibre strands. This allowed it some flex. But repeated pressure on a flat sided cylinder made of carbon fibre, weakens it. Under flexing, the strands of carbon fibre separate.
Initially, Stockton Rush told people who worked in the deep submersible industry (and who were alarmed at what he was doing), that he was going to have the submersible independently tested by engineers, to certify that it could safely go to the depths of the Titanic. But he never did.
To highlight the fact that he was taking people to the Titanic, Stockton Rush changed the name of the Cyclops II to Titan. Commencing in 2018 he made some test dives in the Titan. After a number of dives, the carbon fibre hull was shown to have weakened and Stockton Rush replaced it. That’s when he started taking paying passengers to the Titanic.
There were plenty of people willing to pay a quarter of a million dollars to get a glimpse of the world’s most famous shipwreck. After a couple of successful trips to the Titanic, with passengers on board, Stockton Rush commenced the fateful dive, with four passengers, on 18 June 2023.
After the previous dives however, the carbon fibre hull was most likely weakened. Strands of carbon fibre would have separated with each dive. There is no evidence that the hull was examined or X-rayed before the 18 June dive. One hour and forty-five minutes into the dive the OceanGate Titan was approaching 3,500 metres. It dropped weights. That means the Stockton Rush was preparing to slow the descent because he was nearing the Titanic, or he was instigating an emergency ascent – either way, we’ll never know. Next the tracking and the communications were lost. Tracking and communications run on separate power sources. Losing them both at the same time is not a good sign. Next, an implosion was heard.
The blacksmith’s anvil had dropped on the egg. It was all over in a millisecond, but the media nonsense was just getting started.
The Frontier Below is published by William Collins, and is the first book to give a complete history of the 2,000 year human quest to reach the bottom of the ocean.
