Invention Bubbles Friction Away

Blowing a bubble blanket under the hull of a large ship can cut down fuel consumption by 5-20%. This works because air offers less resistance than water. A few things must come together for this invention to function. The bubbles must be created fast enough to keep the bottom covered and kept in place as the ship cruises forward and, at the same time, the bubbles must not diminish the hydrodynamics of the propeller. Damen Shipyards Group, a Dutch firm that builds more than 150 ships a year, has found that bubbles trapped in specially designed hull cavities cut fuel consumption by about 15% on a 60-meter ship that carries cargo on rivers. Tests at MARIN, a naval-engineering institute based in Wageningen, also in the Netherlands, suggest air cavities can reduce a big ship’s fuel costs by as much as 20%. Here's more from The Economist.