Sunday, June 5, 2011

Perhaps a Game of Tug of War Is All the Cable Needs

I woke up in a remarkably still bunk. I came out to the staging bay to find it bustling with hard hats and life vests. Behind them was a noticeable dearth of white caps and sinusoidal forms. Overnight, the squall had apparently found somebody else to harass and left us to deploy the TAAM in relative stability. Everyone had leapt at the opportunity of calmness and I was already late though I arrived at the party ten minutes early. Someone had pressed play on the scene from yesterday and we were off.

My official title in this operation was “Instrument Stager.” This means that I helped Cammy prepare the instruments to hand to Jefrey and Dave, the assemblers.  My box of instrument parts and I stood off to the starboard side of the A-frame trying to maintain the balance between close enough to hand something to Dave but far enough away to not trip Dave or get too close to heavy moving objects and wires under tension.

The first to go swimming was the anchor, followed shortly by the acoustic release and the inductive modem. These parts hung over the stern from the end of the jacketed wire rope, which was unspooling from the winch.  Simultaneously, a neon green communications cable that runs parallel to the black wire but carries no load was unspooling. Once the anchor hung ten meters below deck, the first yellow duct tape marker appeared on the black wire. This was the first of ten instrument markers that Dave, Jefrey, Nicholas and I attached to the wire two weeks earlier at snug harbor.  When the marker reached waist height, the winch was stopped.  Cammy handed Jefrey the thermistor and I handed Dave the clamps. Dave and Jefrey stood at the very edge of the back deck bolting the clamp to instrument thus sandwiching the jacketed wire rope. A cable spacer was then attached on either side of the instrument to keep the black and the neon green cables together but untangled.  The wire was then lowered another 10 m to the next instrument marker and the pattern continues through 30 m, 50 m, 100 m, all the way up to 200 m where the thermistor array ends. Then came the acoustic modem, followed shortly by 5 lengths of chain hosting three glass balls each. These fifteen glass balls in yellow casing are the source of buoyancy for the mooring as well as a thing of beauty hanging from the A-frame. Unwieldy on deck and quite heavy, once they are suspended in the air they waver and spin like plump yellow weather vanes against a blue sky.  In order to attach them, the weight of the anchor had to be transferred to A-frame momentarily while the glass balls’ chain was shackled and hoisted up to carry the load.  The cherry on top of the mooring was the second acoustic release that was to be triggered once the mooring was within 100 m of the seafloor.  With the cherry shackled in, the whole mooring was lowered through the water column over 4.7 km, giving us a brief repose in which to eat. The instruments indeed ended up center stage, so I feel my title earned.

At 1100, the anchor was approaching the bottom so it was time to prepare the deck box that transmits the acoustic signal to the releases. We waited for the green light after setting the hydrophones to the right frequency and uncoiling some particularly stubborn cables – at this point I am specially trained in taming cables so not even a knotted hydrophone cable can make me blink. The ship navigated the mooring to the correct position and the winch adjusted to the right depth then it was time to release.  Lowering the hydrophones overboard, we sent a loud zing through the water hoping to feel the decreased tension on the wire in response to the release. The wire remained tense. A second and third zing went travelling down. An enthusiast fourth and fifth were tried and somewhere between the sixth and seventh the release finally got the picture and let go. The anchor went barreling down to the seafloor taking with it the thermistor array to the chagrin of the yellow balloons.

The wire, now with just the release on the end, took another couple hours to come back up.  Once it got within 100 m of the surface the tension on the wire was not sufficient to wrap back on the winch properly. The solution to this problem involved no fiber optic cables or batter packs, no modems or thermistors, no computer code in Matlab or Dreamweaver, but simple, Newtonian physics. Most of the muscle on the ship grabbed a pair of gloves and pulled as hard as they could on the wire as it pulled back. A string of ten people on the quarterdeck playing tug of war with the winch provided tension enough to spool on the wire. The ten people rotated through until almost everyone on the ship had rusty brown streaks on their hands. I maintain that I could not take part because I couldn’t find any gloves. Feel free to believe me.

Before the TAAM mooring deployment was even finished, the observatory deployment began. The observatory was wheeled out to center stage where it underwent some last minute lashings and documentation. All the handles that Jason was going to have to pull to release the bungees and remove the ADCPs’ hard hats were inspected by the Jason team.  Just in time for pizza dinner, Jason, Medea and the observatory jumped in. They headed through the water column with the last piece of the puzzle in hand. Most of the puzzle is already laid out on the seafloor – the AMM, the camera, the J-box, and the TAAM mooring – and we’re all hoping that that one edge piece that’s always hiding under the corner of the rug decides to appear on the table top tomorrow.

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