August 1, 2006
August 1, 2006
Aug 7 2006, 01:55 AM
Group: TREC Team
Joined: 19-July 06
Member No.: 39
August 1, 2006
In the early morning, Peggy and Matt had deployed five more seismic instruments by helicopter. The total number of instruments on the ice was now at twelve.
Kevin called to wake me up at 7:00. I was first on the morning wake up list and I told him to hold off on getting anyone else up just yet. It had been an incredibly long day. Since midnight, Kevin and Chase had made the rounds of the cage and the guns and everything looked in good shape and ready for our second deployment of the cruise.
Chad a Coast Guard MST, had made some adjustments to the towing lines and it was felt that the cage would tow better than the first attempt. Larry was in the Aloft Com communicating with the bridge and looking for some open leads and "softer" ice.
By 8:30, everyone was ready to go. Chief directed the safety brief. He noted the changes made to the towing arrangement and assigned each person to their deck duties. The start up progressed nicely until Steffen started the number 2 compressor. The diesel engine was not running properly and as a result, we didn't have a backup system to operate the guns properly if the first compressor failed. By lunchtime a solution had set to be found for the engine problems. After about an hour of trouble shooting, the engine was running properly and we were one step closer to deployment.
Air Gun Damage
At 1:00 everyone was on deck ready to put the cage in the water. Compared to day one, moving the cage from on deck, attaching to the A frame and positioning the cage over the transom worked smoothly. Repositioning the tube farther aft on the deck improved the process dramatically.
Once in the water, we changed the tag line positions a number of times to make sure that no ropes crossed and that they were secure to the ship. The cage towed straight behind the ship unless the bridge used thrusters or rudder to adjust the course quickly. When thrusters or the rudder were used, the currents of water were directed right at the cage causing it tip and lift to one side or the other. We requested that the bridge minimize thruster use and prepared to ramp up to fire the guns.
The whole complex system was working well. The cage was towing nicely and the guns were firing correctly. Dale gave me a radio so that I could listen to and communicate with the bridge and the gun controllers in aft con. About twenty minutes into the deployment, we hit heavy ice. Large chunks were coming from under the ship and banging into the cage. More ice was floating over the top of the cage. To maintain the ships course through the ice, the bridge had to use thrusters.
The whole combination caused the cage to twist considerably and occasionally the corners of the cage would come up out of the water. Our biggest concern was if the guns were to come out if the water and fire. If they fire in the air rather than the water, the energy released can blow the gun apart. I was monitoring the cage and guns from the aft fantail, when all hell broke loose.
A huge truck size piece of ice moved up and under the cage buoying it up at the same time the thrusters started. The added together pushed the cage up so that three of the guns were out of the water. I pushed the talk button on my radio and yelled "Guns out of the water" as I ran behind the A frame support. A second latter, a gun fired in the air. I could see it fire over the corner of the hydraulic rams. Fortunately gun did blow apart. Mark in the aft con shut down the guns and Steffen took care of bleeding the air from the guns. In less than a minute we had gone for smooth sailing, to scrambling to recover the cage and guns. By the time we had the air in the guns vented so that we could bring it up on deck, the cage had twisted nearly 180 degrees.
The streamer was hanging by a broken eyelet that we had welded to the cage and wrapped in rope to protect the streamer as it was let out. We tried to cut the rope with a knife on the end of the pole, because we could not bring the cage on deck until the streamer was reeled in on deck. By 4:55 we had gotten everything back on deck.
When we final got the cage on deck a three-foot ice ball balanced on the bottom cage rails. The streamer had only one functioning channel, and the gun mount bolts were bent and stretched by the ice.
The evening was devoted to coring. We started coring at the first site at 7:30. The big bertha corer capable of taking a 30-foot core was used. The first location produced a short core of about three feet. Larry selected a second site about six miles away. This time we would use a piston corer. The guys from OSU assemble the corer for deployment as we headed to the new site. We started toward taking our second core at midnight.
|NSF Acknowledgment & Disclaimer||Time is now: 25th August 2016 - 03:13 PM|