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Long-Running Underwater Robot Lost At Sea

Posted by timothy on from the all-mechanical-pincers-bury-the-dead dept.

this_boat_is_real writes "Somewhere off the coast of Chile a pioneering underwater robot named Abe lies in a watery grave today. The Autonomous Benthic Explorer was one of the first truly independent research submersibles, being both unmanned and un-tethered to its launching ship. While on its 222nd research dive on Friday all contact with the craft was lost, the Woods Hole Oceanographic Institution has announced."

3 of 132 comments (clear)

  1. Re:floaties? by Volante3192 · · Score: 5, Informative

    Touché, vulgar anonymous poster.

    The people that design these things are smart. Smarter than the average poster here in their field. If Joe Armchairengineer can think it up, I'm pretty damn confident that the engineers behind ABE thought of it too.

    In fact, from the WHOI release, there's this nugget:

    ABE was equipped with several independent systems to bring it back to the surface at the end of a dive or should a fault occur. The Melville remained in the vicinity to see if ABE had resurfaced, at first searching for ABE’s strobe lights in the darkness. Researchers tried to establish radio contact with ABE in the event it had surfaced, but attempts turned up nothing.

  2. Re:they where right! by Volante3192 · · Score: 4, Informative

    That, or the fact that 'benthic' is an adjective referring to the bottom of the ocean.

    http://www.merriam-webster.com/dictionary/benthic

  3. Re:floaties? by Solandri · · Score: 4, Informative
    It's been a while since I worked with the WHOI folks so my memory is a bit hazy. But generally these underwater submersibles come with:
    • A descent weight, used to make the craft negatively buoyant for the initial descent, then dropped to leave it neutrally buoyant.
    • An ascent weight, dropped at the end of the mission to make the neutrally buoyant craft positively buoyant.
    • A bladder which can be pumped with oil from a reservoir tank to fine-tune buoyancy.

    Air doesn't work because of the enormous pressure involved. A 3000 psi scuba tank could only inflate a balloon down to about 2000 meters. Below that, the water pressure is greater than that inside the tank, and opening the valve would result in water forcing the balloon into the tank, rather than air inflating the balloon. A 10000 psi high pressure tank would work at 5000 meters, but would only result in about a 30% increase in volume, meaning you'd need a very big tank to be able to raise the entire craft in a catastrophic failure. Furthermore, the air would expand as the craft rose, risking rupturing the balloon. That's why the buoyancy control uses an oil bladder - oil is relatively incompressible.

    Dropping the ascent weight helps raise the craft at the end of a mission. But usually they're relatively lightweight so you can attach them manually. The 17-inch glass spheres typically used to house equipment provides over 50 pounds of buoyancy. The failure of one of these spheres at a depth of 3000 meters (~4500 psi) would release (4500 psi) * 4/3 * pi * (8.5 inches)^3 = 1.3 MJ of energy. A stick of dynamite is about 2.1 MJ, so losing one sphere is pretty much guaranteed to cause all the other spheres to fail. If the remainder of the craft somehow survived all that energy release, the loss in buoyancy would overwhelm what buoyancy you'd get by dropping the ascent weight.