What is the difference between a submarine and a submersible?
A submarine refers to an underwater vehicle that is largely independent and has power reserves to help it depart from a port or come back to the port after an expedition.
Meanwhile, a submersible an underwater vehicle, which is generally smaller in size and has less power, so it needs to work with a ship in order to be launched and recovered.
How was the Titan submersible operated?
Titan is made of carbon fibre and titanium, and weighs 10,432 kilograms.
It is capable of going 4,000 metres undersea, and moves as fast as three knots per hour (5.56 kph).
Based on images from the company website, there is space for five crew members to sit on the floor, though not stand.
While there is a small porthole window at one end, below 1,000 metres no sunlight reaches the ocean so the submersible would have to rely on its own lighting.
It’s pressure vessel was made of a combination of titanium and composite carbon fibre.
This is somewhat unusual from a structural engineering perspective since, in a deep diving context, titanium and carbon fibre are materials with vastly different properties.
Titanium is elastic and can adapt to an extended range of stresses without any measurable permanent strain remaining after the return to atmospheric pressure.
It shrinks to adjust to pressure forces, and re-expands as these forces are alleviated.
A carbon-fibre composite, on the other hand, is much stiffer and does not have the same kind of elasticity.
We can only speculate about what happened with the combination of these two technologies, which do not dynamically behave the same way under pressure.
But what we can say almost certainly is that there would have been some kind of loss of integrity due to the differences between these materials.
A composite material could potential suffer from “delamination”, which leads to a separation of the layers of reinforcement.
This would have created a defect which triggered an instantaneous implosion due to the underwater pressure.
Within less than one second, the vessel — being pushed down on by the weight of a 3,800m column of water — would have immediately crumpled in from all sides.
The company has explained that “off-the-shelf” technology helped make it easier to replace parts.
While it may sound strange that a submersible on such a high-risk expedition was operated with a gaming-style controller, the fact is that such devices are also used by some drone operators, navy personnel, and robot operators.
Game controllers are cheap, easy to buy in bulk, designed to be intuitive, and respond quickly to the users’ hand movements.
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