There's a documentary about it on Netflix and the impression I came away with is that, while there are fundamental engineering problems associated with a carbon fiber design, they could have probably overcome them in one way or another.
The problem with oceangate is that their CEO was an arrogant narcissist who thought he knew better than everyone, and if anyone stood in his way he would explode with anger at them and fire them. It was a company with absolutely no culture of safety and a cult of personality where people were punished for being honest. The CEO knew about the problems and still somehow believed, to his core, that everyone else (including hard data!) was wrong. He believed in his own infallibility so deeply that it killed him
I've heard both assertions. I tend to believe that Carbon Fiber is a fine material to use.
This submersible used untested techniques. They didn't adhere the layers together properly and apparently never bothered to X-ray the tube as that would have shown at least some of the defects. It also seems like there were other design issues with how the tube was paired to the ends.
Most importantly, the deaths were caused by negligence during operation and maintenance. They had the data showing when the hull was damaged on the previous expedition, but either never did their due diligence and analyze it or ignored the results. Even during their last expedition, they may well have avoided death if the alarms had been heeded.
EDIT: to answer the people who seem skeptical, there are companies making carbon fiber vessels that have successfully gone much deeper than those Titanic dives. We're still in the learning stages with the technology, but we'll eventually find the combinations and standards that can make it safe to use (at which point, it may become better than our current solutions). Until then, maybe we shouldn't be shoving people into damaged experimental vessels to see what happens.
The Coast Guard report section “5.6 Insufficient Understanding of Carbon Fiber Material Properties for Deep-Sea Applications” addresses your arguments.
Yes. It can be safe. The problem is that its crystalline structure can fail instantaneously without any ability to detect beforehand. In this case the sub was likely improperly manufactured and improperly stored and damaged from previous dives and from transport. The company “planned” to inspect but as no non destructive testing was possible, they didn’t bother.
There is a YouTube channel that anaylzes the core problem in depth. Compression vs. tension is really a red herring because in a closed convex structure compression somewhere is tension elsewhere. The real problem is the carbon fiber maxtrix was wapped around the epoxy filler without tension like paper mache. So it had insufficient strength and non homogeneous strength. The sub was built up like an onion. Concentric layers of carbon fiber epoxy thermoset. I think it was something like 5 layers. Anyway because the layers were not wrapped tight before curing there were ripples in the surface of each layer. Subsequent layers were applied after sanding down high spots and applying a wrap of double sided adhesive tape between each layer (no joke). So not only were the carbon fibers not pretensioned but also they were cut in hundreds of spots. This is somewhat like if one were to pour layers of reinforced concrete by throwing a bunch of loose rebar in a hole, pouring concrete over it and then cuting pieces of rebar that stuck up before applying the next layer after putting a layer of plaster over it. For carbon fiber composites and concrete to be strong tension bearing elements need to be able to bear tension. If they are loose in the matrix or cut the composite will not be strong. Thus carbon fiber was not the problem but rather its manufacturing process. Anyone who has ever done drywall joints or autobody can understand the problem. It doesn't take an engineering degree to understand that if you wreck the tensile components of your composite it will be much less strong than if the composite is laid down properly!
>I tend to believe that Carbon Fiber is a fine material to use.
For deep underwater?
Apart from the series of stupidities you go on to list, I'd love to hear your reasons as to why?
I'm a carbon f bike rider, even down to carbon spokes and I do not trust the material, knowing that pressure, or force, applied in the wrong direction will make it crack!.
As for carbon in a circle...no way.
I think it's not ideal in the same way that plastics don't belong in an automotive engine bay and concrete doesn't belong" in tension. Add a little bit of fancy chemistry or some steel and fancy math and they both work fine for cheap.
With care and engineering trickery CF in a submersible (compression) probably can work. They still managed to make a few good dives with it despite comically bad decisions in just about every key area. The manufacturing process was primitive, the QC basically nonexistent and procedures didn't make any allocations for the materials (they beat on the thing like it was made of steel). Imagine what a well funded company with experience in CF, robust QC and careful operating procedures could do.
A submersible constructed of carbon fiber went to depths that many metallic submarines and submersibles cannot.
If somebody constructs a submersible and then tests it to 5000m and finds it fails on the 200th run after exhibiting for the past 50 dives bad acoustic data. Wouldn't you think it's fine for them to take people on the same designed submersible that's only done 100th runs and still has good data?
Everything is a consumable in the long run. They didn't have data on what Titan looks like before a failure. Although in hindsight the acoustic data looks really bad, the issue really is just the specific design didn't have a known lifespan. A submserible without that defect is going to be a lot safer.
Trek 2100. The first carbon fiber bike affordable by upper middle class people.
Their trick was pre-formed carbon tubing glued to aluminum lugs. Sound familiar?
Good, because they had a massive recall because the carbon at the joinst started to chip and crack. Member of our club had to call a friend to come get him because his top tube came apart fifteen miles from town. Took em a while to replace it too. Eventually he ended up on a Serotta (Titanium with extra metalurgical tricks to make it lighter still).
I've linked this elsewhere in thread, but here's testing results from a US Navy pilot project for carbon fiber unmanned subs. It looks like this found it pretty viable.
What's the issue with CF in a circle? My bike is mainly CF (mainly just brakes and drivechain are metal) and of course that means CF wheels which I think are great (CF means that you can have deep section "aero" wheels without much of a weight penalty).
When carbon fiber rims were new we still had not transitioned to disk brakes. You had to keep an extra eye out for misaligned brake pads to make sure they weren't dragging on surfaces not meant for friction contact. Now they make more sense. But also different loads on a wheel under braking than before, but also more like a wheel under acceleration, which is torsional force on the other side of the axle and pointed the opposite direction.
You don't need to watch Netflix series. There is a transcript of entire conversation between Stockthon and David Lochridge where the former scolds the latter for taking his safety concerns outside of company and firing him:
>Not at all, because carbon fiber is better compression than tension. And that's what nobody understands. It's completely opposite of what everyone else says. Everyone's, oh, carbon fiber can't handle compression. They're full of shit, and I've proven they're full of shit. If you want to see that, you take a look at the third scale model that we tested.
Jesus Christ, I met people like him in previous jobs when I worked in Aerospace. Don't need to know nothing but a giant ego and connections to get a job managing engineers.
Carbon Fiber just isn't suited for submarine type of loads. It really doesn't like being compressed, and it tends to give you no warning before snapping.
This isn't the first carbon fiber submarine, although it is the first manned one. The US Navy tried out an unmanned model in the 80s, and got much better results- they were expecting at least 1000 successful dives before stress fatigue was an issue.
Here's a detailed report on it. Pages 32-33 has their take on material analysis, probably the most relevant to this failure
It’s the unpredictable nature of failure that’s at issue here. For unmanned subs it doesn’t matter if 10% of failures occur well below the expected lifespan but that’s a huge issue for manned subs.
I'm not even sure it's the first manned carbon fiber submersible.
Deepflight Challenger [...] is the first deep-diving sub to be constructed with a pressure hull (central tube portion) of carbon fibre composite, built by Spencer Composites for HOT. Its carbon fiber design would later influence the tube for the sub Titan,[12] which imploded...
"""
Based on testing at high pressure, the DeepFlight Challenger was determined to be suitable only for a single dive, not the repeated uses that had been planned as part of Virgin Oceanic service. As such, in 2014, Virgin Oceanic scrapped plans for the five dives project using the DeepFlight Challenger, as originally conceived, putting plans on hold until more suitable technologies are developed.
"""
Being manned is a major difference. Humans need a lot of space. Pressure grows with volume, which is cubic, but the hull grows with area. You can also submerge components in oil, which is much better at resisting pressure than air.
Pressure doesn't grow with volume. The exterior design pressure is constant. The stress on the wall scales linearly with the diameter. Making submarines bigger actually makes it easier because the buoyancy scales cubically with the volume while the weight scales linearly with the perimeter, so the larger the submarine the thicker the walls can be.
There’s several kinds of scaling involved, once the radius increases enough thicker walls are less efficient than internal bracing.
It’s impractical to build something like an Ohio class submarine that can reach the bottom of the Mariana Trench when you also want multiple internal compartments in case of damage.
Internal bracing is to resist buckling. You need it as your cylinder gets longer (as military subs tend to be), but has nothing to do with the diameter. It's also good for torsional strength, which is not really a concern for a pressure vessel but is important for a ship that's going to be in the actual ocean. But for just resisting pressure, once your diameter exceeds 20 times the wall thickness, the relationship is linear.
You can get better efficiency with multiple spherical pressure vessels joined together over a cylindrical vessel, as spherical pressure vessels better distribute the loads than cylinders. This is done in some particularly deep diving military subs, which are then surrounded by an unpressurized cylinder for hydrodynamics.
Even with a spherical sub the diameter impacts a lot of things. For example a large sphere sees significantly lower pressure across the side facing the surface than the side facing the sea floor.
At the depth of the titanic to see a 1% variation in pressure between the top most and bottom most points of a sphere, the sphere would need to be 40 meters in diameter. For context, the pressure vessels of the largest submarine in the world have a diameter of 10.9 meters. Note that pressure at a given depth varies due to things like temperature fluctuations, ocean currents, and even variation in Earth's gravity. Further, the walls of pressure vessels distribute the load - any variations of the pressure get averaged out. It's the same principle as a dome - every element of the sphere is pushing against the adjacent elements and resisting being pushed by those adjacent elements. At the size scale where this is no longer the case, you're not building a pressure vessel. If you're making a dam or a hollow column going down into water, or perhaps a massive dome on the ocean floor, you would need different equations. Even for a submarine you may be concerned with things besides pressure resistance, like collision or sea keeping, as previously stated. But from a pressure resistance standpoint the diameter to wall thickness requirement holds equally true for small exploratory subs and the largest military subs.
A sphere is a great shape for dealing with such forces but it’s just a more complicated system. Rotation can cause metal fatigue, openings get more complicated, etc.
> For context, the pressure vessels of the largest submarine in the world have a diameter of 10.9 meters.
Few subs can reach the titanic at 12,500 feet, at more common crush depths and especially non spherical geometries it’s very much worth considering. Subs often dive and surface at a significant angle.
Carbon fiber is actually a pretty good material for submarine type loads. Submarines have to balance their need for an extremely strong hull with the need for buoyancy. For a given size, to make your hull stronger, you must make your walls thicker, which makes you heavier. The only options are to make the sub bigger, increasing the internal volume, or making the hull out of something with a better strength to weight ratio, or more accurately a better strength to specific gravity ratio.
In carbon fiber composite, it's actually the epoxy which provides the compressive strength, and while it has very good compressive strength, the real advantage is its very low density. It is only just barely denser than water, so you can make your hull extremely thick with essentially no loss in buoyancy. Carbon fiber does fail catastrophically, but they could have just made the hull so thick that they were never getting anywhere near the failure point. Further, since carbon fiber is built up in plied layers, you don't have the same sorts of processing limits as with thick metal plates.
The basic concept of Titan was sound, it was just horribly horribly executed. With their flagrant violation of basic engineering and safety practices, they would have killed people no matter what they made their sub out of.
"Isn't suited" is a stretch. They still managed to make a few good dives with it despite comically bad decisions in just about every key area. Imagine what a well funded company with experience in CF, robust QC and non-laughable operating procedures could do.
It's not ideal on a first pass analysis in the same way concrete can't to shit in tension yet with a bunch of carefully placed steel and number crunching magic it works great. I think they proved that CF has the same potential. A more serious attempt could likely work in some capacity.
There's been a vibe shift. A cult of personality around an arrogant narcissist who fires people for publishing hard data when it contradicts him is apparently what a lot of people seem to want right now.
> The problem with oceangate is that their CEO was an arrogant narcissist who thought he knew better than everyone, and if anyone stood in his way he would explode with anger at them and fire them. It was a company with absolutely no culture of safety and a cult of personality where people were punished for being honest.
Sounds like someone else that's been in the news these last few months.
> The problem with oceangate is that their CEO was an arrogant narcissist who thought he knew better than everyone, and if anyone stood in his way he would explode with anger at them and fire them.
There has to be a point at which you go "fuck it" and stop working for such a guy, even if you haven't been the target of his temper. I lasted 9 months at a company that had a CEO who wasn't explosive, but toxic in so many ways. His company had a 90% staff turnover over any given 18 month period, primarily everyone outside of senior leadership. If senior leadership had stopped propping him up, and quit that company would have been dead and buried far quicker. Thankfully that company wasn't involved in anything that could endanger anyone's lives.
The problem with oceangate is that their CEO was an arrogant narcissist who thought he knew better than everyone, and if anyone stood in his way he would explode with anger at them and fire them. It was a company with absolutely no culture of safety and a cult of personality where people were punished for being honest. The CEO knew about the problems and still somehow believed, to his core, that everyone else (including hard data!) was wrong. He believed in his own infallibility so deeply that it killed him