From what I've heard/read, and from what I know about submarines operating at those depths, I have to assume that, most probably, all the occupants of the sub are dead.
Many scenarios are plausible. A catastrophic failure of the pressure vessel, followed by implosion, is one possibility. A fire on board that led to the crew being overcome by smoke inhalation is another. An imbalance of gases in the air in the sub is yet another.
At the depth at which the sub was operating, there isn't much room for error. Unfortunately, it appears that this particular sub had many possible design flaws.
I'm guessing there a crack/implosion or their oxygen system/rebreather failed and everyone passed out.
I don't think it had a "rebreather". I could be wrong. If the gases weren't managed properly - the carbon dioxide levels, for instance, that could lead to loss of life. If the oxygen levels rose too high, that could lead to an electrical fire, similar to the one that killed the Apollo 1 astronauts.
I think there would be ways of dumping ballast and surfacing even if power were lost and I'd think back communications gear would be available especially for the surface.
Apparently, the designer made a design choice to restrict communications available between the sub and the surface, because he didn't want to be bothered by demands for status updates from the surface while he was pootling around in the sub.
On a previous solo dive in the sub, communications with the surface were lost in a similar way, which is probably one reason why the surface crew didn't immediately panic when communication was initially lost. Instead, they waited about 10 hours before raising the alarm.
It sounds unimaginably terrifying. I’ve read that if/when found, the vessel would need to be opened from the outside. Apparently, the entire crew is dead-bolted inside which means they can’t “break out” if it surfaces. There's no mechanism inside of the sub for the crew to open on their own if/when it emerges.
That's correct. But even if there was a fire on board or something like that, exiting the sub at 4 km under the surface would not have been an option, even if there was some facility for opening the hatch from inside.
Time is truly of the essence for this rescue mission.
There are very few companies/agencies that have the necessary technical capabilities to mount any kind of rescue mission at the depth of the Titanic. I would guess that there simply isn't enough time to get the necessary equipment onsite and save the crew, now.
Otherwise they could have snagged on something and lost power or the ability to communicate but I think this scenario is the least likely.
I think communication was lost at around the time the sub was meant to release the weights it was using to cause it to descend - when it would have been approaching the ocean floor. It is possible that the sub could have got snagged after that, of course. But maybe something went wrong on releasing the weights.
The third is that they are on the surface and no one has located them and I agree that would be hard to do.
Possible they are on the surface, I suppose, but it seems the less likely possibility to me.
However, I have to assume that the submersible, when on the surface, would have access at least to portable radios or EPIRB units.
I don't think we can assume there was any communication gear on board, other than the telemetry link (which obviously failed). I'm not sure if voice communication was even available.
What I don't know (anyone here know?) is whether radio waves could get through the thick carbon fiber shell or the titanium end plates.
If the sub was, in effect, a Faraday cage, the answer would be that radio cannot not penetrate the hull.
I tend to think that if they have been on the surface all this time that they would be able to at least use some backup radio but maybe not? Even if they are on the surface, they are bolted in and will still run out of air soon.
It is not clear whether an actual test of how long the air supply would last with five people on board was ever made. Some people apparently did some theoretical calculations, but was any real-world testing done for this scenario? It is not clear. Similarly, as far as I'm aware, no actual testing was done to see whether the sub would withstand the pressure at the depth of the Titanic. There was a previous successful dive to a significantly lower depth, but that doesn't necessarily prove anything.
Everything still points to catastrophic issues (external or internal) from the initial communication loss given all that has followed otherwise they would be on the surface and they don't seem to be.
The communication loss was more or less expected, based on the experience with previous dives of this sub. The question is: what
else could go wrong? What was actually done to test whether the sub could safely operate at the depth they sent it to?
This structure didn't seem to be tested a lot and they may not be taken into account material fatigue.
Right.
Given the immense pressures it may be that the hull could stand this environment for a few cycles and then just fail.
Yes.
On paper it's supposed to be good to 14,000 feet ...
That's a theoretical prediction. If I understand correctly, it has never actually been tested at that depth, let alone with 5 people on board.
Obviously, this will be a tragedy if five people have lost their lives due to deficiencies in design and testing.
