On the 19th of June the oceangate submersible
began its descent to the Titanicās fractured remains here, in the north western atlantic. With a descent rate of 55 metres per minute
it would take the submersible 70 minutes to reach its destination. With each passing minute the equivalent of
5.3 atmospheres of pressure would be added to the subs hull. By the time it reached its target depth the
weight of 366 of earthās atmospheres would be attempting to crush it. Applied to just an area a little larger than
an A3 piece of paper, thatās equivalent to the thrust of a Saturn V F1 engine. Pressing in from all directions. An hour and 45 minutes into the dive. At the bottom of the Ocean. 3800 metres down. With this immense pressure bearing down on
its hull. The oceangate submersible lost contact with
the surface. We now know the submersible imploded, a sudden
catastrophic collapse. A tragic accident, however any composite material
engineer could have predicted this failure, and they did. I worked as a composite design engineer and
completed my masterās thesis in composite failure prediction. So, letās dive into the questionable engineering
decisions that Oceangate made that led to a tragic accident. With that pressure comes some extreme design
challenges. Oceangateās Titan submersible consists of
two titanium end caps, one with a large acrylic window, joined to a filament wound carbon
fiber reinforced epoxy hull. [REF] Inside the submersible is pretty barebone. Some screens that are fed data from cameras
from the outside. The four electric thrusters are controlled
with, from what I can tell, a third party gamecube controller. Many people are focusing on this part of the
design, but thatās the least of my concerns. We will be focusing on one design aspect of
this submersible, the composite hull. Carbon fibre composites arenāt really known
for their compressive strength. They work best in tension. Great for airplanes that are pressurised from
the inside. Where the pressure inside the fuselage works
to expand the circular cross section, putting the fibres in tension. For a submarine, the pressure will work to
compress the hull, placing the fibres primarily under compression. This immediately set off alarm bells in my
mind when I heard of the missing submarine, so I began digging into their justification
for using the material. Oceangate chose this carbon fibre composite
primarily to benefit from its natural buoyancy. These types of subs actually want to be as
close to neutrally buoyant as possible. Meaning the weight of water they displace
weighs about the same as the vehicle itself. Minimising the energy needed to rise or sink
in the water. This means to surface in an emergency they
donāt need power, they just drop ballasts that make them positively buoyant and they
just float to the surface. The carbon fibre composite can be lighter
and thus helps achieve this neutral buoyancy target. Typically submarine hulls are made from steel
or more recently titanium, but in order to achieve the desired buoyancy they need foam
outer layers. OceanGates CEO Stockton Rush, who was inside
the submersible stated that they wanted to skip this foam layer because it added to costs. That isnāt necessarily an evil thing if
the composite is up for the job. This is where things get iffy, oceangate had
no idea whether it was up to the task or not, and we know this because they admit in their
own blog post justifying their decision to not test their vehicle with a regulatory body. [REF]. The now removed blog entry read: Most major marine operators require that chartered
vessels are āclassedā by an independent group
Classing assures ship owners, insurers, and regulators that vessels are designed, constructed
and inspected to accepted standards. Classing may be effective at filtering out
unsatisfactory designers and builders, but the established standards do little to weed
out subpar vessel operators The vast majority of marine (and aviation) accidents are a result
of operator error, not mechanical failure. As a result, simply focusing on classing the
vessel does not address the operational risks. Now, I would have thought this wouldnāt
need pointing out, but the fact this glaring red flag has been written on their own website
for everyone to see, and several extremely wealthy and successful people didnāt seem
to think it was an issue seems to suggest otherwise. Perhaps most submarine failures occur due
to operator error precisely because they have undergone rigorous testing and certification. The comparison to aviation is also just a
wild can of worms that we have very recent catastrophic accidents to compare to, where
manufacturers willfully circumvented regulatory procedures. These arenāt procedures created as some
kind of unnecessary inconvenience to inventors. They are very useful guidelines and testing
procedures to prove you have not missed some catastrophic failure mode in your design,
and thatās exactly what happened. One failure mode is unique to composite materials
in deep sea applications. Some of the first evidence we got for it was
glass fibre reinforced deep sea piping. Itās called snap buckling, or delamination
coupled buckling failure mode. For thin walled pressure vessels the failure
mode is simply buckling, where the pressure simply caves the entire wall in, but here,
because the wall thickness is so large to deal with the immense pressure of the deep
sea the failure mode gets more complicated. This failure mode is characterised by delamination
of the internal layer of the pressure vessel, basically the inside of the pressure vessel
suddenly peels away from the rest of the wall, leading to catastrophic failure of the overall
structure. The exact mechanisms of the failure mode are
not entirely well understood, as stated in this 2022 research paper titled āA Review
on Structural Failure of Composite Pressure Hulls in Deep Seaā. [REF] It states, in its conclusion āinvestigations on this subject have remained
at theoretical level. There is still very little research in this
area in recent years.ā So, I am assuming whoever engineered this
pressure vessel did at least the same level of research as a YouTuber who wrote a script
on the subject in two days. They must have at least been aware of this
problem. A failure mode like this is going to be exacerbated
by gradual damage incurred through cyclical stresses, like those experienced when diving
to the depths of 4000 metres and resurfacing again. They have done that at least 50 times with
this vessel, without ever fatigue testing it. Per their own admission they did not undergo
industry standard classifications, but they did do their own classification test. One test, stated on that blog post once again. āA licensed marine surveyor will witness
a successful dive to 4000 metres, inspect the vessel before and after the dive, and
provide a Statement of Fact attesting to the completion of the dive test plan.ā That is simply not adequate. Anything undergoing repeated stress cycles
like this needs to be fatigue tested. Like the test airplane manufacturers do on
wings where they flex the plane's wings thousands of times on the ground. They designed this thing essentially with
computer modelling with no real world testing. Composite materials are incredibly difficult
to model in computer software. Composite materials are far more complicated
than homogeneous materials like steel, where the material properties are the same in all
directions and in all regions of the material. Composites are composed of fibre bound together
by a matrix material like epoxy. If we were to zoom into a small cross section
of this, we may see something like this. Some fibres, some of them could be touching
without any matrix between them, some could be spaced further apart, and there can also
be empty voids that the epoxy didnāt manage to fill. We can simulate a small section like this
independently to help analyse some failure modes, such as delamination. However if we want to zoom out and test a
larger section we often need to average the material properties in some way or else the
simulation will take too long to run. My own master thesis tried to combine the
two by embedding a fibre and matrix cell within an averaged composite material. There are specialised softwares that can model
different fibre orientations, but they are still very much an estimation. You need to back this up with physical testing. Something OceanGate didnāt do. There are more signs of incompetent use of
composites. For a critical structure like this, I would
very much recommend curing it in an autoclave. Thatās basically a pressurised oven that
helps push those voids I mentioned earlier out of the epoxy resin. Autoclaves are expensive, and can be difficult
to find ones large enough to fit something like this, but itās nice to not have air
bubbles in a pressure vessel keeping you alive. However, it wasnāt used for this pressure
vessel. It was simply bagged and cured, a cheaper
alternative. Spencer Composites was commissioned to make
the composite hull and their CEO was interviewed back in 2017 in a compositesworld article. He seems very aware of the immense design
challenge he was handed, and he does mention that the porosity of the cured pressure vessel
was assessed to be less than <1%. āLess than 1% voidsā doesnāt exactly
inspire confidence. Is it 0.99% or 0.0001% porosity? Thatās exactly the type of defect thatās
going to increase the risk of snap buckling as voids can be propagation sites for delamination. The blog post goes on to dismiss classification
tests as unsuitable for innovative designs, which is just complete narcissistic nonsense. This isnāt innovative. They have just made the pressure vessel from
a carbon fibre composite, using known manufacturing practices, and started charging rich people
250,000 dollars to risk their lives in it. Innovation would be creating that pressure
vessel and testing it. Figuring out the causes of snap buckling and
advancing material science for all mankind. This is profiteering, not innovation. To eliminate all doubt that this company has
willfully ignored standard safety practices. This court case from 2018 was brought against
oceangate by a former employee who was fired shortly after raising concerns about the composite
hull. Stating not enough was done to check for delaminations
and voids. Oceangate argued that the technology to check
for voids and delaminations in a composite this thick did not exist, and instead they
would use their acoustic monitoring system, which essentially listens for the sounds of
fracture to predict failure. But this is what a carbon fibre composite
fracture curve looks like. Itās a cliff edge. Sudden catastrophic collapse. An acoustic monitoring system like this is
akin to setting up a camera to warn you thunder is coming. You will see the lighting before the thunder,
but the time between them is minimal. Pure safety theatre. It gets even worse. On one test dive in the Bahamas, a submersible
expert could hear the cracking with his own ears and warned Stockton Rush that it was
a sign of damage accumulating. Stockton, once again, chose to ignore an expert's
advice. So this acoustic monitoring system was purely
for marketing purposes. To give customers, who donāt have the engineering
background to see through it, a false sense of security. I would attribute this to malice and greed,
but Stockton Rush chose to pilot this death trap himself. As the Hanlonās Razor goes:
Never attribute to malice that which can be attributed to stupidity. There is this growing trend in engineering
of moving fast and breaking stuff. Mostly driven by one overconfident CEO who
has, to be fair to him, succeeded in revolutionising an entire industry with that ethos. That incriminating blog post even mentions
SpaceX, Blue Origin and Virgin Galactic as bastions of innovation for this move fast
and break things mantra. Virgin Galactic too have blood on their hands,
with their 2014 in-flight break up, which was attributed to inadequate design safeguards
and poor pilot training, along with a lack of oversight from regulatory authorities. This attitude is dangerous, and this wonāt
be the last story of wealthy narcissistic CEOās putting lives at risk. When a doctor is negligent to the safety of
their patients, they are liable for malpractice, but the impact their incompetence has affects
one patient, when an engineer neglects their responsibilities it can affect hundreds, thousands,
maybe even millions of people. We need more people like David Lockridge,
the employee who was fired for raising concerns over safety. The very first video on this channel stated
our mission. To inspire the next generation of engineers,
but itās more than just inspiring engineers, we need engineers going into the most impactful
industries. To solve the largest problems facing our civilization. Youāve probably heard a lot of career advice:
āfollow your passionā, ādo what you loveā, ātake the initiativeā, etc. etc. But a lot of the advice out there doesnāt
take into account the best available evidence we have for what actually makes for a high
impact and fulfilling career. Today's sponsor, 80,000 Hours is a nonprofit
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This is a very credible overview, not a clickbait video and provides some interesting viewpoints from someone who has studied composites. Real Engineering calls the RTHM system "safety theater."
They also bring up another one of Rush's illogical statements:
According to this logic, I could go down in a tin can, as long as I'm focusing on safe operations. The safety illogic was on the Oceangate website for all to see.
Failure enalysis engineer here. I am not particularly knowledgeable in composites failure (my main field is machine components failure, which usually involves only metals and some elastomers), and I've found this video very interesting and highly educational. Probably one of the few actually giving some added value.
For who wants to go a bit deeper into the topic of snap buckling failure mode, here's the link to the article he's citing:
https://www.mdpi.com/2077-1312/10/10/1456
MDPI is an open access journal, so the article is free to read and download.
That was a fascinating watch. Thanks for sharing!
Fascinating and enlightening. Thank you.
Great video, my favorite quote:
It perfectly aligns with how Jerry-rigged this Sub and every qualified opinion was dismissed despite there was a research paper with common failures of carbon fiber under pressure
Wow. Really well done and a high level in-depth explanation of what happened. Thanks!
There's nothing new here, though I've watched a lot of videos. It's all about money. You'd think Rush was a billionaire like Musk, Bezos, and Brandon. His net worth was only $10 million. He spent half of his money building this thing. No wonder it was done as cheap as possible and was tested by dropping paying customers down into the abyss.