Watch The USNS Big Horn Refuel Two Ships At Once

The USNS Big Horn Henry J. Kaiser-class fleet replenishment oiler with room to tote some 180,000 barrels or jet fuel or oil. But she doesn't just carry it around for fun; the idea is to use this fuel to help resupply ships that are already underway, and this recent video from the U.S. Navy shows just how that process works, and with two ships at once, no less.

It's straightforward, but sort of surreal to watch what with all the firing of hauling lines, and pulling in of cables so small you can barely even see them. 

What you see here is an "alongside connected replenishment" (CONREP), specifically the process of getting the hose from the tanker ship to the receivers by firing a messenger line that serves as the bridge that other hoses or lines will use to travel across the gap between ships. 

What you don't see is the monumental difficulty of just keeping the ships in formation. Not only is it difficult to keep such a huge vehicle headed in a very, very precise direction on a moving sea, but having one or more ships very close to yours while you are trying to do it makes the feat even tougher. 

As detailed in this wildly in-depth explanation from the Federation of American Scientists: 

Replenishment at sea demands the very best of helmsmanship from both the guide and approach ships.As the two ships close each other, the hydrodynamic forces will both change and increase noticeably. At a replenishment speed of 12 knots, a one degree course variation will move the ship 20 feet sideways per minute.Replenishment at sea involves an extended period of time where two ships are in close proximity while at relatively high speeds. Any problem at all, either external to the ships or internal to one or more of the ships, can require an immediate and timely disengagement. The Captain of either ship can initiate an emergency breakaway procedures if there is a maneuvering problem or an unsafe situation is developing.

It doesn't always go off without a hitch. In 2012, four sailors on the USS Harry S. Truman were injured when the line from a replenishment vessel parted during the refueling process.

Just something to think about the next time you're loath to swing by the gas station.

http://www.popularmechanics.com/military/navy-ships/a21401/watch-the-usns-big-horn-refuel-two-ships-at-once/