Scientists hope to remain underwater for most of the day, but a limiting factor is available power. Alvin's manipulator arms use an especially large amount of it. And it may take the sub's batteries several dives to completely charge up near the beginning of a cruise. When it's time to return, the pilot will drop enough weights to make Alvin more bouyant than its surrounding water. As the weights settle to the bottom, the submarine begins to rise at a rate of 29 meters per minute. When it reaches 200 meters from the surface, the top lab communicator notifies the bridge. In response, Chiljean sounds the ship's whistle - the signal for Atlantis' bosun Wayne Bailey to again lower the Avon.
With two swimmers aboard (three if one is in training), the Avon's cockswain slices and chops through the waves as the runabout races in front of the ship to encircle where Alvin is believed to be hiding. "Three people, sometimes four, are exposed to the ocean," noted Chiljean. After the sub's red sail punches through the surface, the swimmers dive towards it and climb aboard, one of them installing a telephone link to talk directly to the pilot. While all this is going on, the bridge watch is nursing Atlantis forward to meet and barely pass Alvin by.
On Saturday Patrick Hennessy, one of the ship's three "able bodied seamen" (AB) - an official merchant marine rating - moved the joystick controlling the jet-like thrusters that actually steer the ship with the aid of computers- there being no rudder nor wheel. Meanwhile, first mate Erica Iseminger, Chiljean's second in command, watched Alvin through her binoculars and monitored the radar. And Chiljean called for pinpoint changes in heading and rate of speed. "Two eighty two, 50 percent," the captain said quietly. "Two seventy eight, 75 percent..."
The ballet continues as Atlantis inches forward past the tiny, fragile-looking sub, maneuvering to put Alvin just-so behind its fantail A-Frame. As a DSL team member there tosses a towline into the water the swimmers retrieve it and tie it to Alvin. At the same time, one swimmer throws out a bag-like sea anchor to hold Alvin in place between it and the increasingly taut towline. That sets the stage to reattach the braided rope and raise Alvin back on deck. Pitching seas can make that job difficult for the swimmers and deck personnel alike, with Alvin still swinging in the A-frame after it lifts above the water, as divers and pilot inside grow disoriented. That's why Alvin dives are cancelled when winds reach 25 knots, Chiljean said.
"I don't accept that anything should go wrong," added Williams later. "Everybody's operational philosophy is that there isn't any 'good enough.' It doesn't matter if it's the first dive or the last. It should go perfectly...For us there is no compromise. It's got to be that way. Lives are at stake."
Going down in Alvin
When Nooner's and Cann's dive reached the edge of the mountain's eastern hanging wall last Saturday, the outside water pressure was 4,322 pounds per square inch. Up on the top lab, Williams described what goes through his mind as a pilot when he looks out Alvin's 3 ½ inch thick viewports at the bottom of a rock wall to see "boulders the size of houses" or even "the size of the ship" in the sub's floodlights.
Fig. 3. One of Alvin's viewports, still covered to protect the acrylic viewport.
He starts guesstimating what is above him, outside the visual field of viewports or range of video cameras, he said. "It sinks in that those boulders started out above our heads and rolled down." And when a scientist asks him to pry a promising rock specimen out of such a wall, Williams must quickly weigh cause-and-effect: "Is that rock the only thing that is holding back a boulder the size of the ship from crushing the submarine?"
For one week now, scientists have been viewing various parts of the massif from inside Alvin. They emerge showing the strains of spending hours cramped in a chilly confining titanium cage, the mixed feelings of gained and lost opportunities, and the exuberance of going where none have gone before them. After dinner they report on what they saw, or didn't see, at a science meeting around a map-covered table in Atlantis's main lab.
The first two dives, by Karson and Schroeder on Nov. 21 and and Kelley and John on Nov. 22, did not move as far as planned up the craggy south side. Battery power was one limitation. And while Karson reported that his geocompass was working well, several of the rocks he used the instrument on stubbornly resisted removal by Alvin's manipulator arms. Kelley described "fantastic outcrops" at their dive site, but no geocompass, let alone navigation or video cameras, to use on them. "It was like driving around at night with Volkswagen headlights," John added.
Alvin: History and Launch | Alvin Recovery | Under the Sea | Dredging