Black wind

“Autonomous Underwater Data Recovery Vehicle.” A state-of-the-art self-propelled sensing unit, Audry contained a side-scan sonar, a magnetometer, and a sub-bottom profiler, all packaged into a torpedo-shaped casing that was simply dropped over the side of the ship. The combined sensors provided the capability to seismically map the seafloor for natural or man-made objects, as well as peer beneath the seabed for buried anomalies. The fish-shaped sensor could skim above the seafloor at a depth of five thousand feet, propelled by a powerful battery pack, which eliminated the need for a lengthy and cumbersome tow cable.
    As the Sea Rover approached the search area, Dirk assisted Sum* mer in downloading the search parameters into Audry’s navigatiot| computer.
    “We’ll use the side-scan sonar only so we can run wider search! lanes,” Dirk instructed. “If the I-411 is out there, we ought to be able| to see her sitting up off the bottom.”
    “How large a search grid?” Summer asked as she tapped instructions into a laptop computer.
    “We have only a rough fix from the Swordfish, so we’ll likely have plenty of ground to cover. Let’s set the initial search grid at five by five miles.”
    “That’s still within range of the data relay system. I’ll do a quick systems check, then we should be ready to deploy.”
    As Audry’s software program was reconfigured, the Sea Rover dropped a pair of self-positioning transducers into the water at either end of the search grid. With built-in GPS satellite receivers, the transducers would relay underwater navigational guidance to Audry that would enable the vehicle to run a precise back-and-forth grid pattern several dozen feet above the seafloor. Audry in return would upload packets of data to the transducers at periodic intervals, detailing the sonar’s search results.
    “Ready with the winch,” a crewman’s voice shouted.
    Dirk gave the thumbs-up signal, then he and Summer watched as the eight-foot-long, lemon-colored survey vehicle was lifted out of a rack on the rear deck and lowered over the side railing into the water. A white plume of spray from the tail indicated that Audry’s small propeller was churning, then the grips from the winch were let go. Lunging like a thoroughbred out of the gates at Santa Anita, the torpedo-shaped vehicle surged down the length of the Sea Rover before submerging under a wave and into the depths.
    “Audry has some legs on her,” Dirk noted.
    “She’s undergone a recent modification and is now capable of running her surveys at a speed of 9 knots.”
    “At that pace, she may not give me much time for my favorite part of the search.”
    “What’s that?” Summer asked, a quizzical look on her face.
    “Why, having a beer and a peanut butter sandwich while waiting for the results,” he grinned.
    While Audry motored back and forth down neat imaginary lanes a hundred feet above the seafloor, Summer monitored the vehicle’s progress on a computer display aboard the Sea Rover. At twenty-minute intervals, a digital data upload was wirelessly transmitted from the transducers to the ship, where further electronic processing converted the binary data bits into a graphical image of the sonar readings. Dirk and Summer took turns scanning through the images of the seabed, searching for linear or angular shapes that might signify a shipwreck.
    “Looks like a pepperoni pizza,” Dirk mused as he studied the rock-strewn bottom, seeing odd-shaped boulders that threw off round shadows against the flat backdrop.
    “Don’t tell me you’re hungry again,” Summer replied, shaking her head.
    “No, but I bet Audry is. What kind of mileage does she get on a tank of battery acid?”
    “The batteries for high-speed operation are only designed to last eight hours. We never run her past seven hours, though, to make sure she has enough juice to propel herself from deep water to the surface. She’s been in the water now about six hours,” Summer said, glancing at her watch, “so we’ll need to call her back for a battery change within the next hour.”
    A pop-up window suddenly appeared on the computer screen, signaling receipt of the latest data upload.
    “Only one more file to go till we’ve covered the first search box,” remarked, standing up from his computer console chair and
    stretching his arms. “I better identify the boundaries of the next search grid. Can you take a look at the next data feed?”
    “Sure, I’ll just go