Watching the video, Rush really comes off like an arrogant prick who didn’t even know what he didn’t know, and with no sense of risk management whatsoever.
And wherever did he come up with the idea of glueing titanium end caps to a homemade carbon fiber cylinder in the first place? Why not connect them to a titanium cylinder instead? It seems like the engineering involved with a titanium pressure hull is a lot simpler, along with not worrying about how to connect dissimilar materials.
It is. It is also much costlier. Rush was all about being “cost effective” to use his own words, aka cheaping it out. Triton submersibles cost several million even on the low end (10’s of millions on the high end). No one seems to know exactly what Rush spent building the Titan, but it was almost certainly a lot less than that.
Right, it just seems like a false economy to me. Joining dissimilar materials together is much more complex, as is designing and fabricating a pressure hull out of a material (carbon fiber) that has never been used before in that application. Increased complexity generally means increased cost. I suppose the corollary to this is that it doesn’t cost as much to do the complex thing poorly. Which seems to be the case here.
Not quite true. As Scott Manley pointed out, the US Navy fielded just such a sub–titanium endcaps and all–rated to an even greater depth than the Titan:
https://irp.fas.org/program/collect/auss.htm
The AUSS vehicle is designed to operate as deep as 20,000 feet. It is 17 feet long, 31 inches in diameter, and weighs 2800 pounds. The center section is a cylindrical graphite epoxy pressure hull with titanium hemispherical ends. The hull provides the central structure and all its buoyancy—no syntactic foam is used. The free-flooded forward and aft end fairings and structure are of Spectra, a nearly buoyant composite.
As has come up in the thread before, the light weight of CF is an advantage here as a pure metallic hull would likely need a buoyancy aid like syntactic foam.
The Titan was just a shitty design with shitty construction. There’s nothing wrong with CF+titanium in principle. Nor is there anything wrong with saving money in principle–Toyotas are more reliable than Audis.
The key thing is that you have to be competent, or at least be able to seek out competent people. And Rush was not.
As you say, the AUSS is the product of competent design–two particular elements of which I would note:
It is an unmanned vehicle; it need not meet the safety requirements for human transport.
The interface between the endcaps and the hull is different–the Titan’s endcaps were epoxied directly onto the ends of the hull. The AUSS’s endcaps attach to titanium coupling rings that fit over the circumference of the ends of the CF hull. The mechanical coupling system is designed to protect the hull from splitting and to accommodate differences in expansion and compression between the two different materials.
In other words, the engineers of the AUSS were specifically aware of the interface issue, made as much allowance for it as possible in the design, and still didn’t send people down in it.
There have been several video clips of Rush saying, in different ways, essentially “they said it couldn’t be done, but I did it”. Yes, Rush, you did, but you shouldn’t have.
yep - and throw in a healthy dose of:
“they say it would not work, yet it did” (so who is the fool now?)
of course it did work, until it didn’t.
@wolfpup thanks for that video!
The Titan had separate coupling rings as well. You can actually see one of them sticking out at an angle in the video I linked above in the largest debris section. Presumably as the material was shoved in that direction, the internal forces sheared off the retention mechanism (bolts?) in some fashion. The other ring seems to have drifted farther away.
Clearly the design was still insufficient but it wasn’t due to a lack of an extra ring. Possibly they needed much more depth in the groove that the CF cylinder end fits into.
It’s certainly true that the AUSS wasn’t man-rated, but they had dozens of dives under their belts and they probably could have come up with a human-qualified version given the lessons learned.
I rewatched the assembly video, and I had remembered it incorrectly, so thank you for the correction.
I didn’t find specific dimensions on the AUSS couplings, so it’s hard to compare them. The documents I found suggest a rather more meticulous process of attaching them on AUSS Mod 2 than is evident from the Titan video, but who knows? (The documentation does make clear that they were well aware of the interface issues and went to great lengths to mitigate them and test the hull.)
Seems hard to get less meticulous than a few guys on ladders daubing epoxy on with paintbrushes, but I suppose I don’t know what the AUSS guys did. I’d think that would guarantee bubbles and other defects. I think I’d want to put it through a vacuum chamber at least, but the warehouse they were doing that in didn’t seem that well equipped.
I can’t find any details on methodologies for AUSS, but I feel like its perfectly reasonable to assume it would have been a much more rigorous, controlled and clean build than OceanGate’s Three-Freds-in-a-Shed approach. They weren’t even controlling dust and contamination - the rings were glued on to the cylinder in a shed with the doors and skylights open and the wind wafting through it.
In every video I see on Youtube, Stockton is always saying
Safety gets in the way.
That’s too expensive.
I suppose to be fair we should consider that he could have been hamming that all up for the cameras.
On the other hand, the front fell off.
Ha! ISWYDT
The AUSS, being a Navy project, would have had access to the knowledge, experience, and more important, equipment and facilities of the military at large for working with both titanium and composites. There is absolutely no way OceanGate could have matched the experience and equipment available to the USN. Or, for that matter, the budget - while the Navy does have a budget for projects being a part of the US government it had/has a LOT deeper pockets than Stockton Rush ever did.
Deeper than the Titanic?
Most definitely yes.
Absolutely - and very probably a more deeply ingrained ethic for best practice.
I don’t think this article has been linked. It has the video of the wreck taken by the unmanned submersible used by the USN or USGC.
Both of the titanium end-pieces are intact.
The sea bottom around the wreck is scattered with the pieces of the carbon fibre.