The Titan Submarine: How On Earth?

Well, the more I hear about the lost Titan Submarine, the more question the sanity of those operating it and those signing away their life to travel in it.

There are several issues concerning the sub. I'm sure the operators and builders had the best intentions, but just looking at videos of the hull being built gives me pause for thought.

Let's just look at that hull construction. 

The main part of the hull is a carbon fibre cylinder, with a five inch hull thickness.

This cylinder is then capped off by titanium domes, one with a perspex viewing port. The domes are fixed to metal collars glued to the ends of the carbon fibre cylinder.

Knowing high pressure vessels like I do as a layman, I do wonder if that glue can withstand the pressure of 6000psi. How did they verify the consistency of the seal? 

I do know the owner of the sub has taken it down to 3000m to test it, but I don't think it has been as deep as this dive before.

According to this article by the hull's builder, the designed service pressure is 6,600 PSI or around 4000m.with a safety margin of 2.25. Also the design parameters called for a hull thickness of less than 5 inches, but they rounded up to give it a better safety margin.

So the hull and the titanium end caps can withstand the pressure, but can that glue joint? I'm no high pressure composites expert, but hopefully there was something done to provide a better mechanical seal at extreme pressures and the glue itself wasn't the only thing holding back those 6000psi.

The other risky fact is that there is no releasable hatch. The occupants of the sub are sealed in from the outside. so if for example, the sub didn't implode or get stuck at the bottom and surfaced without mating with its carrying sled, there was no way for the occupants to exit the sub. For instance popping a hatch located above the waterline and making a call on VHF, or in an extreme emergency where they surfaced several miles from the mothership: popping an EPIRB emergency beacon.

Nope, those people are sealed in and doomed to float until the air ran out. 

So many modes of failure, it's no wonder the owners made occupants sign a very clear disclaimer before being taken on trips. 

As a sailor, I know about and rely on  secondary and even tertiary systems when at sea. For instance if there is no wind for the sails, not just relying on one engine, but having a backup, albeit smaller engine to get you home just in case the main engine fails. It may be slower, but you will get home. Even having bloody oars on the boat can prove useful in an emergency.

The same for communications: the main VHF is backed up by a small walkie-talkie and if necessary an emergency antenna you can hoist up the mast to get better range. 

Buoyancy: most deep water boats have positive buoyancy built in, such that the boat will float normally, if it is holed then it will still float and then if the hull is further compromised like it starts to break up, you have the option then to transfer to a liferaft. 

Always three options: Primary, Secondary and Tertiary. 

I get the impression from all that I have heard about this sub is those principles have been compromised. Not something I'd be happy about when travelling to somewhere there is very little chance of being rescued 

Basically the "experimental" tag excuses the need to adhere to basic tenets of safety. I understand the use of that tag in US aviation. It allows owners to avoid the strictures of certified aviation and basically do their own maintenance and be liable personally if anything goes wrong. 

Most people would prefer the certified route to ensure any work done on the aircraft was up to a certain standard. Some that can't afford certification and go down the experimental route to save money, but still follow common sense safety and maintenance schedules. 

Then there are people that don't do maintenance and cut corners and see safety as a hindrance or don't see the need at all. They are the people that deliberately crash aircraft for money, fame, or internet clicks, or skimp on maintenance, seize the engine and crash the plane, the ones that take off and land in the most serious of weather conditions, or just ignore any safety margins until there is no margin. Those people gladly put others at risk with a jaunty smile and are the people you really, really need to identify before you get into any vehicle they own.

.UPDATE.

It seems I was wrong saying that the sub hadn't been on deep dives before. It had been on a number of dives previously. But of course there are no methods available to easily check the consistency of the carbon fibre tube. Most are destructive: test the vessel to pressure and then take core samples to see what the damage is to the carbon fibres in the matrix.

As far as I'm aware there is no non-destructive test available.

Also it's now apparent that the sub imploded with the loss of all the people on board. My condolences to their families.

Is too early to know for sure, but it looks like there were issues with the sub before it imploded. Evidence shows the sub descending more quickly than the planned rate and an attempt to abort the descent and surface failed. No idea why yet, but possibly flooding of a module in the rear machinery space of the sub causing it to not be as buoyant as planned. Hopefully any investigation will shed some light on the cause of this disaster.