Saturday, January 2, 2010

Sea Snow

This morning when I walked up to the bridge for coffee I was almost convinced we were out at sea. Except for Horsburgh light to the east and a strip of shore to the west the horizon was nearly unbroken in all directions. Still we are only 5 miles from Malaysia at the mouth to Singapore Strait. In the last six months since returning from Bermuda on a schooner this is the furthest I have been out to sea.

We are repairing another shallow water fiber optic cable that has been down for the better part of three months. The water is only 30 meters deep but the currents here roar and the full New Year’s moon hasn’t been helping. Fast currents mean that our Remotely Operated Vehicle has limited windows for working on the bottom and that when it is down the visibility stands a good chance of being completely clouded.

Swift currents also mean that when maneuvering the ship to recover or lay cable the three azipods and one bow thruster will load up the generators and try to shake the ship apart. To avoid this the Dynamic Positioning Operator, normally the Captain, Chief Mate or First Officer, will line the ship parallel with the tidal stream to reduce engine load.

After spending the last six years on commercial seagoing vessels I am endlessly fascinated to watch this ship maintain position in 3 or 4 knots of current to within sub meter accuracy. Even when a swell is running down the strait and the ships bobbing from side to side the engines instantaneously respond to every external force in a complex, diesel fueled, mechanical balancing act.

This of course is accomplished through the use of Global Positioning Satellites 24 of which are constantly circumnavigating the earth. Using a minimum of four satellites at a time still isn’t sufficient for our positioning needs. In addition to the satellite signal we subscribe to a paid differential correction propagated from a number of geostationary satellites over the equator. This differential corrects the majority of error within the GPS constellation providing an accuracy good enough to drill for oil or pick up cable in water that is miles and miles deep.

While there are free differential corrections available to any enabled GPS, or DGPS, the paid service is much more reliable than shore based radio beacons or the WAAS/EGNOS/MAAS satellite systems. That reliability allows the DP operator to focus almost exclusively on retrieving the cable and relaying it exactly where it is supposed to go.

Something else that has been fascinating me lately is watching the camera feed from the ROV as it surveys the cable before and after repairs as well as cutting and gripping the cable for retrieval if need be. I have always been intrigued by what lives and grows and drifts about under the surface of water and there is no place in the world I love more than under the ocean. Seeing a live view of what’s beneath our hull as we work up cables, which happen to encourage marine growth, is mesmerizing.

There hasn’t been anything too impressive lately, corals and fish, a ray or two and the always swirling sea snow, but I still know it’s better than television. Add to that the suspense generated when the ROV operator is working two manipulator arms to cut and grip a section of cable and I’m right entertained.

Tonight before the moon rises there will be a clear view of the stars. To the west where Singapore, Johor and hundreds of anchored ships are the clouds reflect an orange glow but at this range it’s not enough to smear the heavens. The wind has been steady day and night and the water never stops flowing one way or the other past the hull. The crew is working twelve’s until cable operations are complete and now it is time to sift through another chapter of Patrick Obrien’s Post Captain without imaging Russell Crowe in the lead role.

1 comment:

  1. any way you can get some screen grabs off that feed?

    ReplyDelete