P=1.01325*10^5+1020*9.806*5=151336 (Pa) =151.336 kPa
Since 1Pascal = 1.45 x 10(power of -4) lb/square inch
then P = 15.1336 x 1.45 = 21.94372 = 21.94b/sq inch
Submarines withstand pressure through their robust hull design, which is typically made from strong materials like high-strength steel or titanium. The hull is shaped to distribute external pressure evenly, minimizing stress concentrations. Additionally, submarines are built with a double-hulled structure or reinforced sections to enhance structural integrity. Advanced engineering and thorough testing ensure that they can safely operate at great depths.
Submarines require thick, strong walls to withstand the immense pressure exerted by water at great depths. As a submarine descends, the pressure increases significantly, which can lead to structural failure if the hull is not robust enough. Additionally, a strong hull helps protect against external threats, such as underwater debris or potential attacks. Overall, the integrity of the hull is crucial for the safety and operational effectiveness of the submarine.
A pressure hull is a strong, sealed structure designed to withstand external pressure while maintaining a safe environment inside, commonly used in submarines and deep-sea vehicles. It is constructed from robust materials, such as steel or titanium, and is engineered to distribute stress evenly across its surface. As external water pressure increases with depth, the hull prevents water from entering and protects the occupants and equipment inside from the crushing forces of the ocean. The design includes features like rounded shapes to minimize stress concentrations and ensure structural integrity.
Submarines don't have windows, at least not any that are used for viewing outside of the hull while submerged. They are used in some submarines as bridge viewing windows, but they're subjected to ambient sea pressure when the boat submerges, not direct sea pressure like the hull is.
The hull of the submarine will crush or give way if the pressure of the water is too much.
To prevent it from collapsing from the high pressure of the water outside while submerged. Roughly every 30 feet of depth under water adds another atmosphere of inward pressure on the hull.
Submarines have 2 or more hulls - the superstructure, which is the visible external hull you see, and the inner pressure hull, which contains all the primary equipment and houses the crew. The space between the superstructure and the pressure hull is where the main ballast tanks are located, as well as line lockers, access/weapons hatches, etc. The pressure hull is where the crew lives and works (and keeps on working...). The primary reason there are 2 hulls is that the pressure hull, while optimally designed for maximum sea pressure resistance, isn't designed for optimum speed and maneuverability underwater. The superstructure, built over the pressure hull, streamlines the boat and compensates for this, making modern boats extremely fast and maneuverable underwater. The best analogy is a thermos bottle, which has an outer shell (the superstructure) that protects and insulates the inner thermal bottle (the pressure hull). The Russians are known to use a double-layered superstructure on their larger boats, the theory being to insulate the pressure hull from a torpedo attack. The problem with that theory is that modern torpedoes don't need much proximity to severely damage or sink submarine, and any significant damage
All modern submarines are "dual hull" constructed. What you see on the surface is the outer hull, or "superstructure". The inner hull, where the main systems and crew are, is protected by the outer hull. Damage severity of either the outer or inner hulls depends on the boat's depth at the time. If deep enough, it doesn't take much damage to the hull, as sea pressure will be virtually unstoppable, even with the quick-reaction damage control skills of a submarine crew. However, if sea pressure isn't a factor and the flooding can be controlled, then it's possible to survive such a casualty. Again, it depends on the severity of the hull breach, and the depth at the time. Several modern submarines (my old boat included) have survived underwater collisions which produced severe damage.
They're not - they are pressurized upon submergence to maintain a positive pressure in the boat to detect any hull breaches. Any seal leak or breach, no matter how small, will immediately register on the boat's pressure board.
The simple explanation of the ability of a submarine to withstand deep sea pressure lies in the mechanical strength of the pressure hull. On modern military submarines (called boats by the crews) the pressure hull is make of steel (except in the case of a few Russian boats which used titanium). This steel basically forms a cylinder and keeps the pressure of the sea water at operating depth from crushing the hull. To gain a tactical advantage, the Russian Navy built some of their boats with titanium pressure hulls. These hulls were designed to allow greater operating depths, and, therefore, increased ability to "hide" beneath the sea. But as is the case with the steel hulls, the titanium hulls used the geometry (shape) and the mechanical strength of the pressure hull and all the fittings to keep the water out at test depth.
The pressure hull of a submarine must withstand the pressure of water at depth. Hundreds of pounds of pressure per square inch translates into many tons of pressure around a pressure hull. If that hull doesn't have the strength to stand up to this, the pressure hull will implode. Steel is a "known quantity" as far as metals. We've used it for a long time, and we have a good handle on its characteristics. Steel alloys are extremely strong, fairly easy to fabricate, and won't double the national debt if we use this metal to make a submarine pressure hull. Steel's weldability and its common availability make it a fine choice for submarine pressure hulls. It's really strong, too. That's a big plus. No one wants to be inside the pressure hull of a submarine when it fails.
All submarines have a rated "Crush Depth", the depth at which the hull will succumb to external sea pressure. While the actual depths for each class are classified, several submarines were lost during the Cold War to implosion events after major casualties. The most noted for the United States was the USS Thresher (SSN-593) which was lost during sea trials after she suffered a major flooding casualty. It was estimated she made it to within 100' of the surface before sinking to her crush depth and the bottom of the ocean.