(CNN) — Few man-made movable buildings are bigger than a fashionable cruise ship, however even these giants of the ocean generally need somebody to lend them a hand to get to port.

So what do you do when one in all these giants of the ocean is unable to transfer by itself energy?

You name a ship-carrying ship, or, to be extra exact, a “semi-submersible heavy transport vessel,” such because the Boka Vanguard.

Constructed in 2012, the 275-meter-long Boka Vanguard is the most important ship of its type. Typically it transports giant offshore oil and gasoline buildings, however often it will likely be known as on to to carry different vessels — corresponding to occurred with the Carnival Vista again earlier than the pandemic.

The Carnival Vista is the second largest in Carnival’s fleet, with capability for 4,000 passengers and 1,500 crew, and in July 2019 it wanted rescuing after experiencing a malfunction in Caribbean waters.

Cranes aren’t actually an possibility when you need to raise a 133,500-ton ship out of the water (the most important cranes on this planet raise about 20,000 tons), so the Boka Vanguard makes use of a reasonably completely different method.

Float-on/float-off

This peculiar-looking vessel has a flat, open central deck — utterly empty — with 5 giant vertical wall-like buildings protruding from its sides. The management bridge and the crew’s dwelling quarters are nested in one in all them, which is significantly bigger and taller than the opposite 4.

The ship’s awkward form hides a complicated system of ballast tanks that makes it attainable for it to grow to be semi-submerged, with solely the highest of the vertical buildings remaining over water. Different sorts of floating cargoes, together with entire ships, can then slide onto its deck to be correctly fixed. This is named the “float-on” operation.

Once the cargo has been secured on deck, the ballast tanks might be emptied for the Boka Vanguard to emerge once more from the water, lifting its heavy cargo upwards with it. It can then begin its journey similar to some other ship. When it has arrived at its meant vacation spot, the method is reversed. This is the “float-off” stage.

“We simply take advantage of Archimedes’ law to lift some massive cargoes,” says Michel Seij, international engineering common supervisor at Boskalis, the Dutch firm that owns Boka Vanguard. You may keep in mind the Archimedes precept from the “Eureka!” story — any physique submerged in fluid is acted upon by an upward pressure, with a magnitude equal to the load of the fluid displaced by the physique.

The oil and gasoline business

Boskalis ships, for instance, have assisted within the transportation of two US Arleigh Burke Class destroyers after they had been each broken in two separate collisions with service provider ships in Asian waters in 2017, USS Fitzgerald (DDG-62) and USS John S. McCain (DDG-56). Although on that event it was not the Boka Vanguard, however two smaller semi-submersible heavy raise ships, the Transshelf and Treasure respectively.

Ship-carrying is not among the many commonest assignments for one of these ships. The bread-and-butter work is transferring platforms and heavy gear world wide’s main offshore oil and gasoline fields. But you by no means know.

In the case of the Carnival Vista, the need to name within the Boka Vanguard arose when the ship’s propulsion system malfunctioned and the one dry dock within the area wasn’t out there. An various resolution had to be discovered.

“We were called in at short notice, but we managed to dispatch the ship quickly. It took a couple of weeks for our ship to get to the Caribbean from Europe and another week to take care of all the necessary arrangements. What followed was a very smooth operation and the cruise ship was safely transported to Freeport, Bahamas. During this operation part of the cruise ship’s crew remained on board,” says Seij of the Carnival Vista dry-docking operation.

The Boka Vanguard will not be solely the most important ship of its type, making it attainable for it to comfortably comprise the 325-meter-long Carnival Vista inside its construction, but it surely will also be used as a transferring dry-dock, making it attainable to conduct upkeep on the ship whereas underway or in port.

This was the case with the Carnival Vista, a clockwork operation assisted by a number of smaller vessels, that has offered us with mesmerizing footage of the entire sequence.

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