The Tartan

By Balambal Suryanarayanan

RMS Titanic might have sailed her final voyage on April 15, 1912, but her spirit continues to burn with a ferocity enthralling and intense, for reasons that may vary across people’s hearts. For me, that reason was Rebecca, the hauntingly enigmatic title character of Du Maurier’s “Rebecca,” for everything you knew about her was what you heard from the people who thought they knew her. Like Rebecca, the Titanic had crafted an indestructible identity of her own, one that time wouldn’t dare to ruin. Standing large and magnificent, sailing through the waves that murmured, possessing their tunes under her hull, flying through the winds with a fascinating confidence, and embracing death on her own terms, she struck intriguing shades that piqued our minds to seek her out. And boy, did we do it, leaving more curious minds to pick up on the things we knew to let them trail behind.

Through this frenzied search to intimately understand the Titanic, if there’s something I can admit to with unwavering certainty, it’s this: We all love stories. Stories that entwine themselves through the thin lines of tragedy, hope, heroics, and danger. This is a love that has obviously tied me to pen this tale of a heartbreaking engineering catastrophe of the Titan submersible that unfolded last year on June 18 in the Atlantic Ocean, 500 meters from where the Titanic rests. With the OceanGate hearings shedding light on why the implosion unfolded, we’ll shift our magnifying glasses to poke holes into the hows. 

Submersibles aren’t supposed to implode, because it contradicts the purpose of their design: to navigate the deepest seas by withstanding the extreme pressures of those environments without signing their demises, especially through deadly catastrophes where physics walks out of the chat. The fundamental equations of hydrostatic pressure give the total pressure P = P₀ + dgh. With the atmospheric pressure at the surface (P₀) standing at 101,325 Pascals (Pa), density of water (d) at 1029 kilograms per meters cubed, an acceleration due to gravity (g) of 9.8 meters per second squared, and a depth (h) of 3.800 meters where the wrecks of the Titanic lie, the total pressure the vessel has to withstand rounds to about 38 million Pa. And if Lochridge’s observations about Oceangate’s Cyclops II (renamed Titan) being a lemon hold true, then the submersible will not have been able to withstand this huge pressure, thus setting forth an implosion.

And the simulations of Dr. Ronald Wagner, an engineer at Siemens attest to this theory. A linear analysis of the carbon-fiber-reinforced plastic (CFRP), the material used for building Titan’s pressure hull green flagged it as suitable to withstand approximately 40 million Pa of pressure. However, his non-linear analysis that would help understand the operation of a submersible under extreme stress, like in deep-sea water by studying the material strength, geometry, and their combined ability to withstand pressure deep within the ocean birthed several anomalies. The design of submarines, for ages, had to deal with a trade-off between weight and strength. For a submersible to float in water, its buoyancy exerted by the water on the submersible must exceed the weight of the submersible (downward force). In any submersible, four components play a significant role in contributing to the overall buoyancy and weight: the hull (responsible for structural integrity and providing buoyancy), ballast tanks (control of buoyancy by water intake or expulsion), payload (instruments and other critical equipment), and passengers. To achieve operational stability, the buoyant forces of these components need to balance with their weights. 

A major portion of the deep-portion submersibles have spherical titanium hulls counterbalanced through syntactic foam in water, attached to the external frame. This adds to their weight and might limit the number of passengers taking them to travel underwater. However, Stockton Rush, the CEO of OceanGate, felt that when one was setting on an ocean expedition, it was important that “they did not do it by themselves” and encouraged his designers to transform the hull into cylinders. However noble this idea might seem, Dr. Ronald Wagner’s simulations revealed that despite the lightness of carbon fiber and its advantage of stronger strength than titanium, its material buckling pressure for underwater conditions is worse than titanium, standing at an uncertified 42 million Pa against a buckling pressure of 57 million Pa, which according to Wagner, is a “terrifying close gap” which can open up three failure modes: window fracture, carbon-fiber cylinder fracture, and titanium-CFRP interface fracture, which was simply glued together , as stated by certified underwater expedition leader Rob McCallum.

When the window fractures, it sends the debris to the cylinder, damaging it. However, when pressure increases, the enhanced stresses on the interface of the titanium ring and CFRP pieces fracture the CFRP piece first. The hoop stress (σ) on Titan from deep waters could be given by the thin-walled pressure vessel equation which dictates the hoop stress to be much less than the tensile strength of the material used for the purpose of resisting the bursting effects from the application of pressure. 

Now, if the pressure from the water was approximately 38 million Pa, the radius (r) of the hull was 8.3 by 5.5 meters, and the thickness was five inches (0.127 meters), then the hoop stresses would be 1241.7 million Pa (σ8.3) and 822.8 (σ5.5), values that are much larger than the tensile strength of the CFRP. Stockton Rush’s claim of buying the carbon fiber at a discount from Boeing past its shelf life makes the matter regarding the tensile strength worse, for this would mean that the hull already was way more brittle than a new CFRP, battling loss of strength and failing at battling any extensive pressure. This failure to hold against the water’s pressure was confirmed by Lochridge through his examination of the material’s cross-section, which revealed “signs of delamination and porosity,” which if tested frequently, might come apart. Lochridge’s reports detailed glue detaching from the seams of ballast bags, mounting bolts at the risk of rupture, spreading galvanic corruption of the different metals employed for its construction of the rings, highly inflammable flooring, and snagging thrusting cables — factors that defy what physics dictates to keep a submersible afloat. 

Andreas, a safety manager, took to X (formerly known as Twitter) to explain that a sphere offers the best atmosphere for coping with tremendous pressure. In the Titan’s case, the sphere was stretched to a cylinder through a carbon fiber by making a groove into the titanium which would allow the glue joints to not break from the stress offered by water, which was a masterstroke by Rush, according to Andreas. However, as carbon is not a homogenous block but composed of carbon fiber layers, the glue that holds them is not strong despite their extensive strength. This would mean that as the titanium ring’s lip that rests on the edge of the carbon tube adds to the pressure from the water, carbon fiber would start ripping apart between its layers where it is the weakest, resulting in a phenomenon known as delamination. As the layers give way with the force from water and titanium acting on the edge, a crackling sound is heard. This was reported extensively by Rush and his friend, Karl Stanley, and confirmed by Lochridge.

John Ramsey, the lead designer of Limiting Factor, a successful submersible designed by Triton Submarines, confirmed Andreas’ theory. “With titanium, there’s a reason it clears the multiple pressure tests it is subjected to, for it strengthens under repeated stress,” John Ramsey shared. However, with carbon fiber, it’s the opposite, and as it delaminates steadily over every cycle, there is an unpredictability in overshadowing when it might break off completely, causing a catastrophic implosion. Stockton Rush’s advertisements of Titan being unsinkable was hauntingly parallel to RMS Titanic’s claims, and his attempt to prove it through multiple trial runs weakened the carbon fiber further, ending in a disaster in its manned run. 

The most awful part comes with its operation through PS3 controllers, which Rush christened “his innovation,” experimenting with Bluetooth (a blunder, according to McCallum, for submersibles were wired in addition to Bluetooth to ensure that they were always in contact with the operator), keeping the submersible void of failure sensors, and not letting DNV classify his submersible were a differently disastrous tale to tell, one that might conclude with an ethical violation lesson to spell. The last straw came with utilizing acrylic as a viewport for a submersible that was designed to take an extreme-depth sea tour. Despite its elevated transparency, its strength decreases with increasing pressure, and due to acrylic’s creep, it can start deforming over time, eventually weakening, and cracking completely. Deep into the sea, the temperature is just above freezing limits, a risk factor for the brittleness of acrylic which adds to the damage. Cyclic pressure can introduce micro-cracking, and to withstand extreme pressures, an increase in the thickness of acrylic might be favorable, but presents a trade-off with structural malfunctions of the submersibles. And according to Ramsay, the risk rating is directly proportional to twice the depth the submersible is looking to explore, and Titan’s viewport had a rating that was one-third of the Titanic’s depths. So why is this crucial? When Jerry Stachiw, the acrylic viewport expert, and his team worked through understanding implosions, they would apply the pressure fast enough to cause the implosion, assign a conversion factor, and evaluate a safe diving depth. For example, if a sample imploded at ten hundred meters, and one applied a conversion factor of five, the depth rating for the submersible would be two hundred meters. This would mean that acrylic would never be safe to navigate through twelve hundred meters, and Rush, as an aerospace engineer, should have known better than calling the conversion factors that help determine the risk rating of a submersible “safety factors,” according to Ramsay. 

In the end, these engineering design flaws would result in a disastrous implosion. The irony wasn’t lost: The passengers took their last voyage to witness the debris of a ship that took its last breath as a consequence of cutting costs in its development. The only consolation through this tragedy lay in a fact that psychologists, neuroscientists, and physicists agreed on together: the sequence leading to the events of the Titan’s implosion took 13 seconds to unfold, and it takes exactly 13 seconds for the brain’s nociceptors (pain receptors) to process what caused the pain. This meant the passengers would have taken their last breath without allowing time to understand or witness what caused the disaster to unfold. 

Our hearts go out to the victims and their families as we remember them in the wake of this tragedy.