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Woods Hole Oceanographic Institution Loses Deep Sea Vehicle

Posted by samzenpus on from the davy-jones's-locker dept.

First time accepted submitter Mr D from 63 (3395377) writes in with news about a WHOI vehicle that has been feared lost. "On Saturday, May 10, 2014, at 2 p.m. local time (10 p.m. Friday EDT), the hybrid remotely operated vehicle Nereus was confirmed lost at 9,990 meters (6.2 miles) depth in the Kermadec Trench northeast of New Zealand. The unmanned vehicle was working as part of a mission to explore the ocean's hadal region from 6,000 to nearly 11,000 meters deep. Scientists say a portion of it likely imploded under pressure as great as 16,000 pounds per square inch."

2 of 93 comments (clear)

  1. Ob. Slightly Scientific Comment... by ThatsDrDangerToYou · · Score: 4, Informative

    Years ago (not saying how many!) I worked with a university program specializing in autonomous underwater vehicles. Their designs made the submersibles nominally buoyant so that when they lost power they would eventually surface. For deep sea applications I'm sure it's more difficult.. If it were crushed, then I imagine all bets are off.

    1. Re:Ob. Slightly Scientific Comment... by Solandri · · Score: 3, Informative

      These vehicles typically use glass spheres (containing air) for buoyancy. We also experimented with a ceramic "foam" - basically millions of tiny hollow glass beads glued together and molded to fit into unused portions of the vehicle. They're more reliable, but don't provide as much floatation for a given volume. Any equipment and electronics you have on board has to go inside the larger glass spheres, so you always have some of those aboard.

      The founder of Benthos gave us a lecture on the tech. When one of them implodes, the energy released is the ambient pressure at depth times the volume. This is why you can't simulate an implosion in a tank - the moment the implosion begins, the pressure drops, and the energy release stops But at depth, the water simply fills in any lost volume with more water at the same pressure, and the energy release continues until the entire volume of air is crushed. The smaller sphere in the link (13 inch or 33 cm diameter) has an air volume of about 15 liters. At 9000 meters, the pressure is 90.57 MPa. So its implosion releases 1.36 MJ - about as much energy as 2/3rds of a stick of dynamite. The glass spheres which implode basically revert back to sand. You can imagine how much more energetic it is if something as large as a submarine implodes.