The following log was written by MBARI engineer Tom O'Reilly as he participated in the deployment of the MOOS Science Experiment.
Saturday, July 15, 2006
Expedition to Shepard Meander
Last week we attempted to deploy the MTM-4 Science Experiment in Monterey Canyon.
These blog entries describe the cheap thrills, the nausea and the ecstacy we experienced during the expedition.
Here's a shot of the usual suspects on the aft deck of the R/V Western Flyer. From left to right: Andy Hamilton, Larry Bird, Ed Mellinger, Tom O'Reilly, Mark Chaffey, Bill Ussler, and Kent Headley.
|The MTM-4 mooring rides the waves off the bow of R/V Western Flyer, 100 kilometers west of Moss Landing, one week after being deployed from the R/V Point Sur.
The mooring looks deceptively small against all of that ocean – but the
solar panels are about seven feet tall. Meanwhile, preparations are made to
dive to the base of the mooring with ROV Tiburon.
|Kent and me with ROV Tiburon. Tiburon will attempt to plug a seafloorcable into the 4 kilometer vertical “riser” cable that extends from the sea surface to the seabed. Tiburon is a “remotely operated vehicle” – she carries no crew. Rather, the pilots remotely control Tiburon from a control room aboard the Western Flyer; a 2-mile-long umbilical cable connects Western Flyer to Tiburon, providing power and communications to the ROV. The vehicle fairly bristles with lights, cameras, robot arm, science instruments, and other gear.|
|Charlie and Larry prepare to mount the seafloor cable spool onto Tiburon. The first 100 meters of cable is steel-jacketed; the remaining 2000 meters is covered in Kevlar.|
From the ROV control room aboard Western Flyer, pilots “fly” Tiburon using joysticks and computers. Images from Tiburon’s video cameras are displayed on large monitors.
|A crane lifts Tiburon off the deck, and the “moon pool” doors unfold. It’s a long way down through those doors –the seafloor lies two miles below the ship, and Tiburon will take over two hours to descend. The silver and orange spool of seafloor cable is visible hanging underneath Tiburon. Once on the bottom, Tiburon will plug one end of this cable into a connector at the base of the
mooring, then unreel about 2.7 kilometers of cable along the seafloor
to the edge of the canyon, where the first science station -“the BIN”-
will be attached. The orange floats attached to the side of the vehicle
provide added buoyancy to compensate for the weight of the cable spool.
As Tiburon unreels cable on the bottom, the pilots will periodically release
the drink - and on the way down to rendezvous with the mooring anchor.
On previous attempts to deploy this mooring, we encountered extreme
nastiness at the base of the mooring, and so we have extensively
redesigned the cable and mooring anchor. What would we find this time?
Sunday, July 16, 2006
Laying cable and dropping the "elevator"
|O'Reilly here, your deep sea guide. You're probably wondering "What's with the hard-hat?" Well, I actually wanted to be the Indian Chief, or maybe even the Policeman, but I guess the Construction Worker will hafta do. Heh - just kidding.|
is a schematic picture of the system we are attempting to deploy; note
that the vertical and horizontal scales have been drastically reduced
in order to fit the entire picture on one page; the cables involved are
actually several miles in
length! I've been using this cartoon for several years now during
presentations - now it is time to actually deploy the real thing.
|Tiburon descends through Western Flyer's moon pool, and two hours later reaches the seafloor at a depth of 3,200 meters; no sunlight reaches these midnight depths, but Tiburon locates the base of the mooring on sonar, and closes in. Then Tiburon’s powerful floodlights and HDTV camera reveal the mooring’s base, sitting quietly on the ocean floor at the edge of Shepard Meander. Contrary to our worst fears, the mooring base and cable look beautiful. Even the rattail fish hovering above the float looks reasonably attractive. The mooring anchor consists of eight train wheels. The vertical “riser” cable extends more than two miles from the top of the yellow float to the sunshine far above. The loop of orange cable on the front of the float provides a plug into the riser cable. Tiburon's next task is to plug the seafloor cable into this connector, which she does without a hitch. Tiburon now slowly heads toward the science site, 2.7 kilometers to the north, paying out cable as she goes. However after traveling a few hundred meters, we detected a break in “optical continuity” – the optical fibers in the cable had broken! Tiburon retraced her path and found a nasty kink in the cable – much like a cheapo garden hose exhibits when you pull too hard on it. Tiburon pilots had to cut the cable and return to the surface. Fortunately we had brought a spare cable with us, and dove the next day to try again. This second attempt was, er, quite exciting. Almost immediately the cable snarled horribly after coming off the reel – but the pilots used incredible ingenuity and dexterity to untangle things, using the vehicle’s robot arm! Six hours later, Tiburon reached the science site, and dropped off the spool on the bottom in preparation for the next day’s climactic operation, and came back to the surface.|
|Mark Chaffey performs final checkout of the seafloor science station - aka “Benthic Instrument Node” or “BIN” - on the aft deck of Western Flyer. Science instruments are attached to the titanium sphere, which contains the computer, power system, and other electronics. The yellow cables wrapped around the base will be plugged into the seafloor cable by Tiburon, forming a real-time network that extends from the deep ocean to the sea surface, into low Earth orbit via Globalstar satellite and back to Moss Landing – providing the “data highway” for MBARI’s ocean observatory.|
|The team prepares the BIN for deployment on “the elevator”. The elevator transports payloads too heavy to be carried by Tiburon; the elevator and it’s payload will be dropped over the side of the ship and free fall to the seafloor science site. After rendezvous with the elevator, Tiburon will pick up the BIN, and untie steel weights attached to the bottom of the elevator; the suddenly-buoyant elevator then “rockets” to the surface for recovery by Western Flyer.|
|The elevator and its payload are swung out over the stern of Western Flyer, and lowered into the ocean - the elevator is released and free-falls two miles to the ocean floor.
Where the winds sleep
|These pages are dedicated to the Tiburon pilots, an elite group of incredibly skilled and dedicated individuals, the true heroes of this deployment.
Pilot Knute Brekke at work aboard the R/V Western Flyer.
|Three hours after the elevator is dropped, Tiburon closes in on the elevator and its payload resting on the seafloor.|
|Tiburon moves in with her robotic arm to remove the BIN from the elevator.|
|Tiburon carries the BIN to the science frame, 50 meters away.|
The BIN and its instruments installed on the frame, ready to begin acquiring science data.
In sand-strewn caverns cool and deep,
Tiburon returns to the now-vacant elevator; the ROV pilot used the manipulator
arm to loosen a knot that secured 50 kilograms of steel to the elevator
- the suddenly-buoyant elevator then "rockets" to the surface, for
recovery by the Western Flyer. One last tug on the line... that's got it!
The next morning, we turned on the system power via radio modem aboard the Western Flyer, and data from the deep sea began flowing back to shore!