Titanic Mistakes

"Safety is just pure waste, I mean if you want just to be safe don’t get out of bed, don’t get in your car, don’t do anything. [...] The submarine industry is obscenely safe because of all the regulations." The author of these prophetic words is Richard Stockton Rush the 3rd. He had a bachelor degree in aerospace engineering (1984) and an MBA (1989). He died on 18th of June, 2023 in a submarine designed and built by his company Ocean Gate, in defiance of all norms and principles of the industry. To avoid the obscene safety of the competitors, he decided to ignore any certification process, all warnings sent to him in writing by most submarine experts against the solution he chose for the Titan submarine: the hull made of Carbon fiber cylinder with two caps of Titanium. "This Carbon fiber hull is a huge thing, the Carbon fiber has been used for autonomous underwater vehicles but never anything as large as what we are doing. Some work was done by the Navy decades ago and the[ir] determination [was] that you can’t use composites, but that was not using aerospace grade manufacturing and the kinds of controls that go into making units that are used on planes as primary structure. So, a lot of the arguments against Carbon fiber in submersibles were very similar to the arguments against using composites in aircraft, and having built my own plane, fiberglass plane 30 years ago and still flying it, I realized you can do it, you just have to do it right, and that is the big advance." (Stockton Rush inverview with Teledyne Marine, 2018).

The analogy between submarines and aircraft is all wrong. Aircraft materials are exposed to tensile forces mainly, whereas submarines are exposed to compression forces. Some materials are strong for tension (like composites), others are strong for compression (like concrete). The pressure cycle of the body of an aircraft goes from zero to 0.8 bar from the inside, whereas a submarine going at 4000 meters down withstands pressure cycles from zero to 400 bar from the outside. So carbon fiber is successful in aviation because it does a different thing. James Cameron, the Oscar winning movie director and deep ocean explorer, explained this eloquently: "Carbon fiber is completely inappropriate for a vessel that sees external pressure. Carbon fiber composites are used very, very successfully for internal pressure vessels, like scuba tank, and you can get two or three times more than what you can get out of steel or Aluminum for that type of pressure bottle. But for something that is seeing external pressure, all of the advantages of composite materials go away and all the disadvantages come into play. So if you are using an uniform material like steel, or Titanium, or ceramic, or acrylic, you can do computer modelling with a high degree of accuracy and confidence. The second you start doing Carbon composite or any kind of composite materials, you are introducing two materials that are in contact with each other, the filament itself, and then the epoxy matrix that it sits within. And at that point you have degradation failure." (CNN interview with James Cameron, Anderson Cooper, 23 June 2023)

The Titan submarine made 6 dives in 2021 to the Titanic wreck, and 7 dives in 2022. These successful dives gave confidence in the design, but this was misleading, since the enemy in this case was materials fatigue (by Carbon fiber delamination). It is a process which needs more cycles until a catastrophic failure. Due to its lack of certification, the submarine was not authorised to operate, but it did this in international waters, outside the jurisdiction of Canadian or US coast guards. The 1st dive in 2023 was on June the 18th. The dive started at 9 am. At 11:47 communications with the submarine were lost and in the same time the navigation locator was lost. This simultaneous failure made the experts believe in a tragic collapse of the submarine under the pressure. The prediction was unfortunately confirmed by the remotely operated underwater vehicles, which found the debris of the Titan near the debris of the Titanic.

Stockton Rush was aware that all other experts were opposed to the Carbon fibre solution and he came with a shocking palliative innovation: he filed a patent on a real time acoustic monitoring system used on the submersible to detect the onset of delamination in the carbon fiber hull prior to a catastrophic failure. It is like building an airplane with wings of questionable strength, and include microphones in the structure to listen to the noises of cracks. When you hear the noises, you land immediately, before the wings fall off. Rush was confident that his system provided enough warning time to surface the submarine immediately. As a matter of fact, the submarine wreck indicated that it imploded while going up, not down, so the noise was detected, but most probably it was loud enough to be heard without sensors.

This patent with the sensors reveals another mistake of the Titan: the lack of understanding of the hazard the submarine was facing, the catastrophic failure. How long does this structural failure take, from the moment the first noise can be sensed? The structural analysis for static loads in the elastic domain is straightforward using finite element, but the structural analysis of a structural failure is much harder. Even without calculations, a submarine implosion is a loss of stability type of failure, so a sudden collapse. There is hardly any warning before it kills everyone on board.

Stockton Rush is not the only representative of the experimentalist trend, where innovators call themselves disruptors. My aerospace engineering students are also attracted by the idea to throw overboard theory, mathematics, regulations, and safety, and focus of practice, experiments, and fast progress. In a survey from 2019, almost all my students wanted less theory in their studies, and more practice. I have great difficulty in making the case for mathematics as the basis of aerospace engineering. My students admire youtubers who present experiments. For example, there is one young influencer in aerospace engineering who tested 200 different shapes of propellers for a quad-copter, until he found the best shape. To many young people today, it is more fun to 3D-print 200 innovative shapes and play with them, instead to use higher ?mathematics and aerodynamics to find the optimal shape for the propeller. Experimentalists are encouraged by leaders such as Elon Musk, who does not mind a ruined launch operation to prove the flat launch pad idea wrong. However, Elon Musk has a strong team of experts in the classic meaning of the word, who use mathematics and physics to model the space vehicles in the design process. Elon Musk projects this image of an experimentalist and a disruptor, but he does not defy safety and regulations, and listens to the experts (at least half of the time). Unfortunately, young people enthuse and take inspiration just from this exceptional side.

The science of making submarines made no real progress in the last 50 years. The Navy was right in assessing that composite materials are wrong for submarines. The problem when you design a submarine according to all regulations and use all this rich experience, there is nothing exceptional in it. We are driven by the number of clicks we generate, unfortunately. The Ocean Gate experiment generated a huge number of clicks and continues to do so in the aftermath of the implosion.

My own lessons from this outstanding accident are simple and I hope my students get them right:

·???????Safety is not a waste. Investing in safety is probably the best financial investment imaginable.

·???????Obscenely safe could be shortened to just safe and it is the opposite of hazardous or dangerous. ?

·???????Regulations are not made to kill creativity. On the contrary, they distill the lessons learned from past experiences, to empower creativity and protect creators from known traps.

·???????Engineering is a science. By definition, a science is based on mathematical models. Experiments are part of this science in complementing theory, not replacing it.

·???????Old school principles may be non-sensational or downright boring, but progress does not mean to trash them.?