Updates From Sea | Cruise 2007
January 14th
By Eric Simms, Education Outreach Coordinator
Diving to the Deep
The deep sea is a challenging environment for humans to explore. Crushing pressures, complete darkness and very cold temperatures make it impossible for us to visit far below the surface without the help of technology. One of the most important pieces of equipment here aboard the R/V Atlantis is the Deep Submergence Vehicle (DSV) Alvin. For over 40 years Alvin has safely carried scientists to the deep sea and back, allowing them to observe and sample our planet's least explored environment in person.
What does it take to get Alvin safely in and out of the water at sea? We spoke with Alvin pilot Mark Spear, who shared a typical Alvin dive day schedule with us.
Photo © 2007 E. Simms
Alvin Dive Day
5:30 a.m. All of the Alvin pilots and pilots-in-training (P.I.T.'s), review their assignments for the day. They will rotate turns as Pilot for that day, Surface Coordinator, Launch Coordinator, or one of the four Swimmers that help launch the sub in the water. Each person carefully follows part of a 13-page checklist (depending on their role that day) to ensure that Alvin is ready to enter the water safely. In spite of the early hour, there is a flurry of activity in Alvin's hanger.
7:00 a.m. The Pilot for the day takes a break to eat breakfast and grab a shower, while the Launch Coordinator makes sure that the sub hatch is greased and the ballast weights have been added. Alvin is moved from its hangar on the deck to the rear of the stern of the boat (back) where it will be deployed.
7:30 a.m. The Pilot for the day enters the sub and does a final check to make sure that all systems are functioning properly.
7:45 a.m. The two other passengers, typically two scientists, enter the sub and the hatch is closed and sealed. Every fifth dive the observer position is reserved for one of the P.I.T.'s so they can get direct experience observing and assisting with operating the sub. The support boat Avon is deployed off the starboard (right) side of the ship and moves behind the Atlantis where the Alvin will enter the water. The sub, with two swimmers on top, is deployed off the stern using a rope about 6-inches thick to lift the 35,000 pound sub using the ship's large A-frame.
Photo © 2007 Eric Simms
8:00 a.m. Alvin submerges and slowly begins its descent to the bottom, and the Avon and Swimmers return to the Atlantis. The Surface Coordinator tracks the position of the sub from the Top Lab (an area of the Atlantis' bridge), checks-in with the Pilot every half-hour, and makes sure the Alvin and Atlantis stay close to one another.
9:30 a.m. The sub reaches a depth of ~2500 meters, drops half of their ballast weights, and those on board begin the tasks outlined in the dive plan. Before each dive, the chief scientist and other senior scientists on board decide what needs to be accomplished and discuss the plan with the Alvin pilots.
Six hours later, 3:30 p.m. When the work on the bottom is complete, the Alvin Pilot signals to the Atlantis from the bottom that they are prepared to begin their ascent to the surface. He drops the remaining ballast weights to lighten the sub, and the sub begins its ascent.
4:30 p.m. Just before the sub reaches the surface, the support boat Avon is launched from the ship and positions itself to meet Alvin.
5:00 p.m. Alvin reaches the surface. The Swimmers dive from the Avon and swim to the Alvin to escort it to the stern of the Atlantis, where they secure the sub to the A-frame rope. The A-frame lifts Alvin onto the stern where it is secured on its cradle on deck. The passengers and Pilot exit the sub, and the sub is then returned to its hangar. The Alvin Pilots and P.I.T.'s make sure that all the systems on Alvin are properly shut down, and that sensitive areas (e.g. portholes) and instruments on the sub are protected.
Photo © 2007 E. Simms
5:30 p.m. The Pilots and P.I.T.'s enjoy a well-earned dinner.
6:00 p.m. The day's not over. Alvin's Pilots and P.I.T.'s complete a 5-page post-dive checklist to put the sub to sleep for the night, including changing any sampling gear and instruments needed for the following days dive. When all is set for the next day, the pilots call it a day.
Click here for a slideshow of Alvin
Weather
Weather conditions and sea state are critical factors when deciding whether or not Alvin can be launched for the day. If the swells are too large, or the wind is too strong (above 25 knots), the dive will be postponed until better conditions are available. But it's not just about the conditions in the morning - the pilots must also factor in whether the conditions will be good in the afternoon when Alvin must be retrieved. Not only could the sub be damaged as it is lifted from the swells, but the passengers, swimmers, and people on deck could also be placed in jeopardy - safety is the top priority! In fact, the first scheduled dive of this cruise was postponed because of high winds, but conditions have been good enough the past two days to make successful dives.
Maintenance
Keeping Alvin in excellent condition is also a top priority for safety and reliability. Alvin follows a strict schedule of maintenance between every cruise; every 3, 6, and 12 months; and undergoes a complete overhaul every 5 years. All the parts on Alvin have been replaced and upgraded over the years, including the installation of a titanium pressure hull (the sphere that holds the pilot and scientists) in 1973.
You can learn more about the history and operations of Alvin on the web http://www.whoi.edu/marops/vehicles/alvin/.
