As engineers, we are always looking for materials that are new, manufacturing methods that increase productivity, and, well, anything that gives an “edge,” especially in today's competitive world.
But how much of that engineering is real, and how much is a hope or gut feeling, or simply hubris? Whenever faced with such questions, one could do well to review the lessons from history.
There are many lessons to learn from but it seems these are often forgotten or ignored. The most recent example that comes to mind is that of the tragic loss of the tourist submersible Titan. There is a clear logic of failure to heed the lessons of others and basic engineering facts.
So, what are the basics? Well, quite simply, it is when designing or engineering something new, there are several principal procedures that must be fully understood and explored before embarking on a project. This becomes paramount if such a project is carrying people, whether crew or passengers.
When people are added into the mix of being transported, the stakes for failure become higher. Ergo, the engineering must follow a very clear and prescribed sequence of events to mitigate any possible events that may occur or can be identified as a source of failure, and verified by a third party as much as possible.
In the case of Titan, the objective of OceanGate was simple. Stockton Rush, the co-founder of OceanGate, stated that his initial vision was to, “give humanity greater access to the ocean.” This vision centred on the acquisition of a fleet of four to five deep-ocean submersibles, each engineered to reach depths of 6,000 metres while accommodating up to five passengers.
The strategic intent was to enable these submersibles to be deployed globally without reliance on a dedicated mothership.
So, with such grandiose ambitions, one would assume all measures necessary to ensure correct design and engineering will be followed. The report by the US Coast Guard (CG1788361) into the tragedy lays all such basics that should have been done but were ignored. For example, Boeing was engaged to investigate the design premise and what is required to achieve the scope. All sounds good so far engaging Boeing, an independent third party.
In terms of the material choice; the report identifies Titan’s pressure hull was constructed using carbon fibre, a material chosen by Mr Rush for its “impressive” strength-to-weight ratio.
While the strength-to-weight ratio was a considerable advantage, the use of carbon fibre in deep-sea environments remains unproven, unlike the case with materials with established safety records. There are currently no recognised national or international standards that approve of the use of carbon fibre pressure hulls for submersibles.
Boeing said that, “for a thick-walled cylindrical hull made from reinforced carbon composite, the required wall thickness would be about 9.3 inches [240 mm]…However, an open-hole structure indicated a negative margin of 83 per cent, necessitating over 32 inches [810 mm] of wall thickness”.
Boeing's report continued: “This structure will need to be carefully inspected for manufacturing defects such as porosity, voids, inclusions, and FOD [foreign object debris]."
The report also discussed buckling, indicating that thin-walled tubes under external pressure are vulnerable to compressive loads that may cause buckling. The feasibility study also found that a carbon fibre hull was technically possible, but it identified several critical challenges, including manufacturing defects, bonding issues, and thermal stresses during curing.
So, given the warning signs from an independent third party expert on the not-so-straightforward nature of the design, what actually occurred?
Despite Boeing’s recommendations for additional testing and process monitoring, OceanGate’s final design featured a reduced hull thickness, excluded key CFRP structural elements, and failed to implement NDT or advanced modelling, leaving significant uncertainties about the submersible’s integrity.
At some point, the design and manufacturing process should have stopped and headed the warnings from third-party experts on the design and manufacturing using a novel material and method of production for a submersible. Instead, the people at OceanGate continued with their plans and ignored the independent advice, which eventually led to the tragic event with the loss of Titan and all five individuals on board, including Stockton Rush himself. The events leading up to the loss were all predicted and well-documented, but were simply ignored.
Why is this important and why should we always follow well-prescribed design and manufacturing norms, rather than ill-informed “gut feeling,” for the glory of pushing the limits?
Well, take conventional ship design and building, with more of an emphasis on the building. When using conventional isotropic materials, like metals, the mechanical properties are well documented. In such a case, designing for “failure” becomes an exercise in simple mitigation and compliance checks against well-documented industry standards.
What about the manufacturing? That, too, is a mature industry with well-proven do’s and don’ts. Couple that with the fact that creating a structure from flat sheets of metal requires many disciplines and many skilled hands and knowledge to achieve the desired result. Simply placing sheets of steel or aluminium and several welding sets next to a shed along with drawing sheets for construction does not magically produce a boat merely because the "raw" materials for construction are there.
The welders, for example, must be highly trained and must have passed several tests to demonstrate a measure of compliance to ensure that the final weld of a structural joint is sound and not just once, but each and every time a weld is made. These skills take time.
Similarly, the plater needs to be trained in how to manipulate the raw flat sheet to become a shape that is, when offered up the hull framing, within tolerance gaps (for weld strength and fatigue), being stress-free and without defects and score marks that would otherwise become the sites of crack initiation. Again, it is another highly critical and time-consuming skill to learn.
When building to class approvals, the whole process becomes even more prescriptive to ensure a consistent level of quality is achieved to satisfy the requirements of class rules. Bear in mind that class compliance is the bare minimum, not the gold standard that many seem to think it is, and it at least acts as a first base of quality compliance and an independent third-party check.
If we now look at the same ship design and building through the lens of the latest kid on the block, large format additive manufacturing (LFAM) or 3D printing, can we say all the lessons learned from failures and known measures of compliance are being made? There are many new products on the market lauding the benefits of LFAM, of which there are indeed many, and yet such products tend to be small and simple, and any form of “failure” in connection with these, whilst being unfortunate, is not catastrophic, unlike that of Titan.
In this rush to 3D print anything for an “edge,” is the baby being thrown out with the bath water? In the case of small drones often with a single use operational profile, failure doesn’t really matter; drones are to be used at least once, anyway. But now we can see small rigid inflatable boats (RIBs) coming onto the market, and yes, these are carrying people, the same enthusiastic people that felt the need to dive to the depths.
Are we engineering for failure in the same way as OceanGate, which blinded by hubris because of the novelty factor? Designing and building vessels that carry people, whether using conventional materials and methods or deviating into manufacturing using the latest 3D printing, carries the same burden of responsibility and duty to safety.
For example, can these RIBs state such safety and means of compliance are satisfied, when the entire manufacturing process is wholly inside the digital environment where interrogation becomes somewhat difficult? Where do the independent third-party checks come into this process?
New materials and methods of construction are always welcomed, but let us not ignore the principal foundations upon which all this engineering has been successful, lest it become engineered to fail.
