Is there any information on how control cables were routed through the hull to the equipment cluster on the back end? I’m assuming there must have been some cable gland somewhere.
You’re talking about cables that physically move motors and rudders, right?
My WAG would be that they’d they’re controlled by waterproof servos designed to withstand the pressure. Then it’s just a matter of either running wires through the hull, or probably more likely, a wireless signal.
This might seem like a nitpick, but I think “presumed” is doing a lot of heavy lifting here. It could be as simple as “we don’t actually know if there are or even could be some trace human remains mixed in with all this wreckage, so for now we’re just going to presume that there could be, and leave it at that until such time as close inspection confirms there’s no such thing.”
No, I was thinking of electrical cables, probably just data rather than power, but just wondering how they did it - consumer grade cables probably wouldn’t be good enough under the sorts of pressures this was subjected to - typically having voids between the conductors and insulation, and also having insulation that’s generally fairly soft and deformable.
I would expect, for example that if a typical Cat6 cable was run through the wall of a pressure vessel, even if the hole around the cable was sealed or potted, when subjected to very high pressure, the conductors inside the outer cable sheath would just extrude out like sphghetti.
I wouldn’t have thought wireless connections would work in this application as the equipment cluster was not designed to be watertight - and water flooding the space around the kit would attenuate any transmission severely
I think if you put an antenna on the inside of the hull and a receiver on the outside of the hull, there wouldn’t be much water in the way to attenuate the signal. However, carbon fiber is conductive - so maybe the hull would act like a Faraday cage, and block any radio transmissions anyway.
I think that was the whole point of using off the shelf stuff and bluetooth. Wireless. No holes for wiring bundles through the hull. Or as few as possible.
The pressure hull was intended to open only at the “hatch” itself, which I guess was the acrylic window itself, secured by “17 or 18” bolts. I thought that was strange reportage. Can’t they count?
Turns out, they would leave one bolt out at the top, something something about hard to get at, or “it isn’t necessary” or somesuch. Did they use a torque wrench?
What about the feed/vent for oxygen? I assume from reports the air tank was external; at very least, some air had to be pumped out or the pressure would go up quite a bit as they used 4 days’ supply of air. I don’t imagine that interior volume without resupply was providing 4 days’ supply.
This is true. I’ve potted assemblies in epoxy under vacuum to degass the epoxy, and insulated wires never stop bubbling. And that’s just 15 psi driving the leaking (though of course air).
I don’t think Bluetooth signals will penetrate any useful distance in water. Half an inch attenuates the signal by more than 60%
FWIW, my pool has an underwater light that came with a remote control. I don’t know what frequency it’s at, but it does have 1 ft long antenna, and with that, it has no problem communicating with the light from inside the house. So probably 5 ft through the air, then an external wall, another 30 ft through the air, then 10 ft through the water. It’s sending very little data though, just on/off/color signals.
You don’t use glands to feed conductors through pressure vessels. You you use bulkhead connectors. The connector has a solid ceramic disk bonded to the metal body. Copper stubs are embedded in the ceramic disc. You connect the inside wires to one end of each stub and the outside wires to the other end. This can be done by soldering or by a detachable plug. The metal body seals to the vessel with o rings or it can be welded around the edge of a flange. In practice the bulkheads are often mounted in round plates that are o-ring sealed to the vessel.
https://rovafrica.com/product/cobalt-series-bulkhead-connector/
https://www.lesker.com/newweb/feedthroughs/instrument_feedthroughs_mpc_doubleend.cfm?pgid=cf
When communicating through water, you need low frequency longwave communication to penetrate water’s RF opacity. So not microwaves (like wifi).
I have NO idea what was used but I could see Bluetooth being used if there was a tether to the submarine. Then you could use Bluetooth to send to a receiver on the tether just outside the hull then transmit that signal along the tether to the mothership. That way you could avoid poking some holes in the hull.
Of course, there was no tether on this sub so it doesn’t matter for this.
Thanks - that makes sense. I suppose the question is… Did they use those on thr Titan?
That’s if you want to communicate across the globe. Also, it needs a huge antenna on the submarine as well. Whatever they were using to manipulate control surfaces, I doubt ELF was involved.
Honestly, something acoustic would make more sense.
All I’m saying is that if you want to communicate electromagnetically through short distances of water, you can use
- moderately high-powered visible light (maybe lasers)
- low-frequency RF
- exotically (and impractically) high-energy EM like x-rays
Acoustics would work, but it would be very low-bandwidth to work reliably in the high ambient noise environment.
If the objective is to carry control signals through the submersible’s hull, would either need through-holes for cables or transducers/receivers on either side of a patch of the hull which is transparent to the chosen carrier energy.
With the amount of carbon fiber and the ‘churning effect’ of the instant compression I suspect the metaphor we are looking at is: tomatoes in a blender, the only point of contention is how many seconds of ‘pulse’ we have to work with.
I’m not sure Bluetooth could even be expected to work reliably through the hull if the two devices had their antennas stuck right to it on the insideand outside.
Of course that’s not to say they didn’t try some weird configuration like that. Best Practice was pretty much an offensive term to Rush, it seems.
However much it was we can be sure it was plenty.
I only just learned that the way they constructed the carbon fibre tube was to wind it onto a steel pipe perpendicular to the axis of the pipe, back and forth - there was no significant crossweaving of the material - it was wound like a coil spring over and over itself.
This means they made a structure that was just like a whole load of hoops stuck together to make a tube - this would, I think, make it very weak the moment anything happens that isn’t completely uniform; if it started to buckle, with no fibres running in the axial (or diagonal) direction, only the strength of the resin was there to resist the buckling.
I believe this does also imply lesser resistance to concertina-type crushing - as again, the lack of any longitudinal fibres allows the rings of fibre to slip over or inside one another, like the coils of a spring if it is overcompressed.