Essex's belt armor, protected decks, and machinery

Essex was the largest of the three carrier designs, but its 33-knot speed fell between Shokaku's 34.5 knots and Implacable's 32.5. It carried substantial protection, including a quoted 2.5- to 4-inch belt and 2.5 inches of armor at hangar-deck level. Another 1.5-inch protective layer lay at the fourth deck. Special treatment steel (STS) contributed protection and helped hold the hull together after damage. Eight Babcock and Wilcox boilers supplied machinery rated at 150,000 shaft horsepower.