Inside The World's Largest Semisubmersible Vessel
When a battleship needs repairs in the middle of the ocean, a semisubmersible vessel like the Dockwise Vanguard can provide offshore dry dock. The 902-foot-long and 230-foot-wide bowless Vanguard—the largest craft of its kind by nearly a football field—can submerge its deck below the waterline and move its above-water towers aside, allowing mammoth marine vessels to float aboard before the Vanguard rides back up underneath them. The Vanguard can carry 121,254 tons of cargo and another 7,716 tons of food, fuel, and supplies; that's almost double the payload of any such craft before it.
Because the Vanguard doesn't have a typical peaked bow, the entire 207,000-
square-foot deck is open for cargo: a few small crafts or a single huge one. The Vanguard can carry a structure up to 1,066 feet long, with the cargo extending over the Vanguard's stern and front.
In addition to the steering and lodging tower on the starboard side, four other structures—two aft and two along the perimeter as necessary—balance the Vanguard. These structures are movable, so the cargo can sit on the deck in any configuration.
PROPS AND THRUSTERS
The 27-megawatt engine works with two forward retractable azimuth thrusters and two rear pitch propellers. The Vanguard can make tiny adjustments as it approaches for a lift, and can plow through open ocean at a sustained 14 knots.
SUBMERGING CARGO LOAD
The Vanguard can submerge its deck 52 feet, so it can lift boats with a deep draft for offshore dry-docking, and release oil rigs into deepwater locations.
The trouble with huge tonnage on what's essentially a big spatula is the risk of structural collapse. Engineers designed the steel frame that supports the Vanguard's hull to handle 22 tons per square meter and 50 tons per square meter in critical areas. The side shell can support 99 tons per square meter.