Since my last post, I have concluded my technical internship aboard the R/V Atlantis. Now that I’m back home, I can take some time to update my blog and tell the story of Alvin Dive operations.
Departing Dutch harbor on June 15, we set sail further west along the Aleutian chain.
Arriving at our first dive location on the 15th a few miles off Bogoslof island, my job was to arrange the science basket by installing and moving around push cores and bio quivers, attaching Niskins, and securing bio boxes. I would meet with the Alvin Pilots frequently, getting feedback on equipment position and making changes to ensure the instruments were in optimal positions for the robotic arms to access.
The morning of the 16th at 5:30am, we started completing the first pre-dive checklists of the expedition. My role as a mechanical technician that morning was to top off all of the compensated volumes on the vehicle. These are oil filled volumes that enclose various critical systems including the main junction boxes, battery contactors, and solenoids. There were 3 main types of oils that I would top off: bray, carnation, and hydraulic. Topping off these volumes included plugging in a portable pump sprayer, with the desired oil, into one of the the fill ports on the vehicle and connecting a drain bottle to the opposite end of the system. I would then lightly pressurize the system, monitoring the fluid entering the drain bottle, ensuring there were no air or waters pockets within the system. This process was repeated for each of the 14 main oil compensated volumes on the port and starboard side of the sub.
My morning tasks would vary by day. Sometimes I would polish and inspect the windows while other days I would spend most of the pre-dive making basket adjustments, ensuring all the sample collection devices were arranged how the science team and pilot preferred.
Next, we would roll the sub out onto the back deck, and install the drop weights. These six weights are the main form of major buoyancy adjustment. All six attached allows the sub to descend fast, release two weights to achieve neutral buoyancy, and release an additional two weights to ascend to the surface. The last two weights are reserved to allow additional weight loss, in case extra buoyancy is needed to resurface. These weights are installed using specially designed hand carts that lift them using a hand-crank style forklift mechanism.
Deploying The Submersible
After all pre-dive checks are completed and signed off, the sub is attached to the LARS (launch and recovery system). The sub is attached to the LARS by several points: a tail line to prevent rotation, a main line wrapped around a titanium T-shaped lifting point, and a large hook that actuates downwards, locking into the lifting T. The pilot and scientific observers enter the submersible, and the hatch is sealed. Two divers are positioned on top of the submersible, and the vehicle is lifted off the deck of the ship. Once the vehicle is over the water, the main line is tightened, allowing the hook to release the vehicle. The main line then lowers the vehicle into the water. Once the sub is floating, the swimmers detach the main line and the tail line, allowing the sub to drift away from the ship. After some final checks, the basket support lines are removed, and the sub is ready to dive. The work boat picks up the swimmers, and the sub floods its ballast tanks, allowing the vehicle to begin sinking.
Recovery Operations
After the science dive, we would stage the deck for recovery one hour before the sub surfaced. This included ensuring the tow line was ready to be deployed, and laying out various tools such as drills used to loosen the subs panels and drain bottles for fluid inspection.
The recovery would begin by first lowering the work boat into the water off the side of the ship. The work boat then cruises ahead of the ship to meet the Alvin sub as it surfaced. The boat drops off two swimmers who prepare the vehicle for recovery. When the vehicle is ready to be picked up, one swimmer stays on the sub while the other swimmer boards the work boat. The boat drives back to the ship and positions itself behind the Atlantis, as the ship slowly approaches the sub. We then lower the rear lifelines and prepare to throw the tow line to the work boat. Passing the tow line to the work boat was sometimes my role during the recovery. Once the sub was halfway past the ship, I would toss the heavy rope and floating hook to the work boat. The heavy rope attached to the center-back of the ship would pay out line, and I would monitor the amount of line remaining while communicating with the recovery coordinator. The work boat then intercepts the submersible as the tow line swimmer dives off the work boat, attaching the tow line to the back of the sub. The swimmers then deploy a sea anchor, a sort of underwater parachute secured to the submersible. This allows the sub to be held in tension behind the ship as it is reeled in like a big fish. Once the sub is directly behind the ship, the tail line is lowered and attached to the sub, soon followed by the main line. The sub can then be lifted out of the water and the swimmers dive off the side of the sub to be recovered by the work boat.
One of my frequent jobs was to remove the tow line from the back of the sub after it had been lifted over the deck and as it was being lowered. I would then immediately move into post dive tasks.
Post Dive
Once the sub landed on deck, the Alvin team and I would move in with pins to secure any remaining weights, install life lines, rinse down the sub with fresh water, and place protective covers over the windows.
During the majority of post dives, I would sit beside the sub right after it landed on deck and check every oil volume for traces of water intrusion. I would plug a waste bottle into 19 different oil volume drain lines, one at a time, and inspect for water or abnormalities. During this time, the scientists and pilot climb out of the sub and are welcomed by an applaud from the crew and science team. We then roll the sub back into the hanger and finish an extensive list of post-dive inspections and tasks. My usual job was working the scientists. I assisted in removing various equipment and samples from the basket, so the scientists can begin their analysis and packaging of specimens.
This formed the pattern that most days followed with the occasional excitement where I would be asked to repair or inspect components that had failed during the dive. These tasks meant anything from reinstalling damaged mounting brackets on the science basket to disassembling and re-compensating large brushless thruster and hydraulic motors.
The 18 day science expedition proved to be a big success! Despite several dive days being canceled due to weather conditions, we were still able to accomplish nearly all of the 13 dives we set out to complete.
Keep an eye out for one more blog update describing the post cruise activities including preparing the Alvin for its next few months of rest and even the non-work related adventures I was able to go on while in Alaska.
