The famous Titanic Submarine got crushed due to pressur, how comes the Titanic itself is (more or less) still in one piece?
In: Physics
The Titanic filled up with water as it sank. The hull itself is quite sturdy. The problem with a submarine like the Titan is that it wants to keep surface pressure air inside so that the people remain alive.
A submarine has crushing water pressure on the outside and surface pressure air on the inside. This creates a massive pressure differential that wants to equalize, and the air is highly compressible and cannot push back against any ingress or hull failures.
A sunken ship has water on the outside *and* water on the inside, so there’s no pressure difference.
Various sealed bits (bottles, lightbulbs) and watertight bulkheads probably did rupture when the ship originally sank, but the main structure of the ship itself was already ruptured and filling with water when it went under.
The fact that the Titanic was full of water instead of air was kinda the original problem.
The ship wasn’t sealed.
If you have an empty water bottle with the cap on and pull it down into a pool then the water pressure will compress the air inside, reducing its volume and crushing the bottle. But if you have an empty water bottle with no cap and lower it into a pool it will just fill up with water. Water inside and water outside will have the same pressure and there is no net pressure on the bottle to make it deform. It will not crush.
The same thing happened with the Titanic. It was mostly full of water as it sank so there was nothing trying to crush it.
The sub got crushed because there was waaaay more pressure outside than there was inside. When the Titanic sank, it wasn’t sealed, so there was just as much pressure inside as there was outside. The pressure *difference* is what causes an implosion.
The submarine was a pressure vessel – the inside was kept at a low pressure so that humans could survive in there, while the outside was feeling the massive pressure of the deep ocean pushing in. Very little pressure inside, lots of pressure outside, means that if the materials weren’t strong enough, they’d crumple in and get crushed.
The Titanic, since it wasn’t made to go underwater, was open – water got inside of it, causing it to sink. So as it went down, the pressure inside and the pressure outside stayed the same. Lots of water pushing in from the outside, but also lots of water pushing out from the inside. Which means no net pressure on the steel of the hull.
When the ship was sinking, if there were any watertight compartments inside, they would have crumpled as they went down, just like a submarine. But the ship itself was never watertight, so it wasn’t subject to those forces.
Pressure itself does not cause such damage. It is the pressure difference which does damage. In the case of a submarine the inside is atmospheric pressure while the outside have huge pressure. So there was a huge difference in pressure across the hull. The Titanic was not sealed. Water could flood into every space inside the ship and increase the inside pressure at the same rate as the ship was sinking. So there were never any pressure difference between the inside and outside.
There were however a few sealed compartments inside the Titanic. Things like coolers, sealed tanks, etc. Most importantly the steam boilers on the ship were sealed to contain the pressure inside them during normal operation. Some of the boilers exploded on contact with water as rapidly cooling steel which have been super heated by the coal fire weakens the steel. But some of the boilers were cold enough to survive most of the way down to the bottom where they did implode, just like the submarine. We can still see the damage caused by the boilers imploding on the ocean floor.
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