Missing sub construction material

[Michael Chare]

The sub that went to see the Titanic and is now missing is made from carbon fibre.

The front wings on Formula 1 cars look like they are also made from carbon fibre and when there are accidents the carbon breaks into little bits unlike steel cars where the metal is generally bent into a different shape if there is an accident.

So I am wondering what might happen to this sub if it gets involved in a collision because of the currents near the Titanic or just suffers from the pressure. I presume that that if there is a failure it will be a catastrophic crack rather any kind of bend to the shape.

[jon]

I am surprised at the lack of safety equipment, where are the detachable floating beacons and echo transponders..?

[jon]

Surprised at the lack of safety equipment: No floating beacons, no acoustic transmitter..?

[Andy Burns]

But the cars are probably a couple of mm thick, AIUI the sub is 5 inches?

[The Natural Philosopher]

Yes. Carbon fibre is extremely flexibble and strong - much stronger than steel - and under stress is bends like a spring, it doesn't deform (plasticly)

But in the limit it delaminates and loses all its compressive strength You end up with shards and so on.

BUT in this case there seem to have been knocking sounds heard which suggest the sub is intact, but unable to rise

[GB]

Like a teenager in the morning.

[Spike]

There was a BBC TV news item last night that showed the interior of the tubular hull, which was smooth, had the standard submarine hooped reinforcement, and sounded metallic, especially when they were closing up before tightening the bolts.

I get from this that the impression that the pressure vessel is largely metallic, but the front dome with the viewing window might be composite.

I’m guessing that no-one on board knows Morse code, and they are randomly banging on the hull to attract attention, whereas SOS, QRZ, CQDX, or suchlike would be instantly recognisable.

[Andy Burns]

Opposite of what I read, the cylinder is hugely thick fibre glass, the front and back domes are metal (titanium?)

[Colin Bignell]

On 21/06/2023 14:08, Spike wrote: ..

The emergency protocol for a submerged vessel is to bang for three minutes, every half hour.

[Colin Bignell]

Carbon fibre reinforced plastic and titanium, according to the Ocean gate web site:

It all looks a bit Heath Robisonish to me.

[Spike]

I’ve looked at the video again, and the inside of the hull has what looks like a perforated metal lining. The outside of the hull seems to be a metallic cover. These are standard ways of protecting composite-material structures from the sort of nicks and dings that would otherwise compromise their strength. When you see the parts being mated prior to a dive, and the tools used, protection such as this is highly desirable. Looks like it is in fact a composite hull.

[Spike]

You might be interested in this item:

[Andy Burns]

here's what wikilies says

the wayback machine link to the original article seems to be playing up

[Spike]

Fascinating, thanks for the link.

[GB]

Apart from cost, what's the advantage of composite? Weight is not an advantage. So ...?

[soup]

Mmm lets see sub is 4Kilometres down gets into trouble so realeses the floating bouy it has to get 4Km straight up . But Ar 3 Km down the current is going east to west at X knots at two kilometres the current is going North to South at Y knots ... . You get the idea by the time the bouy has floated to the surface it may be miles from where the sub is. Ok you would know the sub is in trouble but you would have no idea where it was.

[Fredxx]

If you read the Wikipedia article:

"The problem is the strength of the [DeepFlight Challenger] does decrease after each dive", which I thought was from the carbon fibre fatigue issues.

Given a submersible takes extra weight that it can release to surface I too don't see the advantage of using light composites. Perhaps someone has done their maths and concluded an all steel hull with an all steel hull might be heavier than water if it was going to cope with such depths?

[Colin Bignell]

Most reports mention him raising safety issues, but without being specific as to what they are. It seems to be a mix of quite bright ideas, such as ballast weights held on with fixings that dissolve after

16 hours in contact with sea water, and primitive. An alternative way to shed ballast is for the passengers to move from side to side, so that the vessel tilts and different ballast rolls off the vessel.

[Colin Bignell]

It is probably easier to achieve neutral buoyancy with a lighter structure.

[SteveW]

The way bathyscaphes work is a small, spherical, thick, high-strength compartment, supported by a much larger, thin, buoyancy tank, filled with (nigh on incompressible) petrol. That allows a hugely strong and heavy crew compartment, supported by a relatively lightweight structure that is immune from pressure effects and cycling.