This discussion concerning the trapped air inside the Lusitania is both valid and relevant to a similar discussion regarding the Titanic. In both cases the knowledge of how trapped pockets of air dramatically lose volume when compressed. When an air pocket is pulled down 100 feet, according to the figures it would only be 1/8 of its original volume. These calculations indicate that extreme pressure forces within the hull, currently thought to be a contributing factor to Titanic's breakup at or near the surface, in actuality reveal that any such forces are short lived. For instance, a 1,000 cubic foot pocket of trapped air, once pulled down to a depth of 100 feet would only displace 125 cubic feet. So as the vessel sinks lower, the air trapped within it has approximately the same upward force, 62,430 lb. but concentrated in a smaller area. This may seem like enough concentrated force to rip steel compartments apart, however what about the weight of the water that has leaked into the ship and is pushing back in equal and opposite directions? Isn't the weight of the water on the other side pushing back equally and thus negating the forces of the trapped air?

It you consider the entire volume of the Titanic to be equal to her 52,000 Ton displacement, this works out to be 1.66 million cubic feet of air. Big deal! If the ship is sinking, and only one half of it is filled with air, then there is an "air bubble" trapped and pulling upwards with 26,000 Tons of force. Actually, this force is reduced by appx. 15% because of water buoyancy, leaving us with 22,100 Tons pulling downward.

How much steel did the Titanic have in cross section to resist this downward force? If we take Titanic’s 9 decks at ½” thick plus the two bottom 1” bilge decks, this represents an area of 92ft x12 in/ft. x 6 ½” total cross-sectional steel thickness, which equates to 7,176 sq. inches of steel. How much stress is on the steel: 22,100 tons/7176 in2 = 3.1 tons per sq. in. or 6,160 lb. per sq. inch.

How much force does it take to pull steel apart in tension? Laboratory testing of an actual piece of Titanic taken from the wreck yielded a value of 64,000 psi. This means, that in a worst-case scenario, the stresses imposed on the steel decks s of the Titanic would have been only 11.2% of the rated strength of the steel, and I have not added in the sides nor the structural beams beneath the floor nor the 18” bilge keels on either side nor the 3” x 3” steel keel along the bottom. Therefore, I have yet to see any kind of valid explanation of what caused this steel ship to separate into individual pieces.