Black Sea 2007, Day 9
Let talk a little bit about undersea operations.
There are many types of undersea vehicles. They all have their ups and downs. There are subs, but they have a limited time on the bottom which equals a limited range. And there are robotic vehicles that can go forever, as long as things don’t break, or there isn’t a long transit between sites. Either way, if the vehicle has a manipulator to pick up samples (rocks, sea life, sand, etc) there is a limited amount of room for samples.
That’s fine for a manned submersible, but really stinks for an ROV that’s working properly. So, scientists and engineers being as smart as they are devised what’s called, an “elevator”. An Elevator is a platform that is fitted with both flotation devices as well as lead weights, that’s dropped to the sea floor long before the vehicles are launched. This gives the ROV pilots a “Platform” to place samples on, to empty out the containers on the ROV. Once the elevator is filled with samples, instead of bringing the whole ROV back up to the surface (which takes a lot of time away from searching and collecting), a command is sent to the elevator, the elevator drops its lead weight, and the flotation devices bring it to the surface. The elevator is brought on board and the scientists can have their samples. This is how its supposed to work.
Now, if you were one of the people that received a daily journal entry through e-mail back in 2005, when my father and I were on the Ronald H Brown, you might remember how elevators work. AND you might remember we had problems with that elevator. For those that are new to our blog or don’t remember, let me refresh your memory. Back in 2005, our first expedition with Dr. Ballard, we went to the Atlantic Massif, which is a ridge line in the middle of the Atlantic Ocean. We had the typical complement of Herc and Argus, and we used elevators. Of the two we sent over the gunwales, we only ever got two back. Not good. Especially since these things are not terribly cheap. They run on the line of about $20,000.
What happened then was, we threw the thing overboard and the transpoder that tells us where it is turned off (OR was never turned on, we’ll never know). We had a pretty good idea where it was, it was just a matter of finding it. We checked all of the ocean floor as best we could. We never did. So, in a move of desperation we sent the signal that tells the elevator to drop its weights. Once that happens you circle around the ocean looking for it. We never did. Sigh.
THIS time, when we threw the elevator over the side, the comment made when the transponder woke up was, “Well, we’re doing better than when we were in 2005!” So, we waited until it was time to bring it up, sent the signal out for the elevator to drop the weights, and.....Nothing happened. Double sigh.
But this time we knew where it was. So, we put Herc and Argus over the side and found the elevator. Now, in years past when this has happened there’s been a lot of debate about what to do. When the transponder receives the signal to drop the weights, what it actually does is connect a battery to ground through a very thin wire. When the thin wire heats up, because of the electricity flowing through it (for all those not technical people, think of how a light bulb works AND how delicate it is), the wire breaks. This wire is holding a lever in position to hold up the weights. When it breaks, it releases the lever that releases the weights. Unfortunately it hasn’t had a good track record with us.
So, there are two options: reach the manipulator into the elevator and cut the line or grab onto the elevator and recover the vehicle. If you cut the wire with the manipulator inside the elevator, there is a great possibility for the elevator to rise before you’ve moved the manipulator out of the way, so that option is very rarely used. I’ve been told sometime before we were part of these expeditions that they did find the elevator and grab onto it. Then when you get to the surface you can cut the wire, because the elevator is already on the surface and has no place to go.
Well, having some idea of the problems that could occur the smart engineers that they are put a pull string that was 12 feet long on the thin wire, so if this happened they cut break the wire from a good distance away. So far I’ve been setting up the story that made last night another “interesting” night.
So, as you can figure we found the elevator with Herc and Argus, pulled the string, and watched the elevator rise. Start your clocks at 7:30 pm. The elevator is much lighter than the vehicles, so it reached the surface quickly. To retrieve an elevator you launch a small boat, clip a rope to it, drag it to the main boat and haul it up with a winch. We knew we were in trouble when we heard they needed to get the second small boat to retrieve the first boat and the elevator. It seems the first boat got the tag line snagged in their prop. Now, what I haven’t told you is that these boats don’t have any outboard motors or props, per se. They have jet water drives, like the personal water crafts and jet skis. So, the crew sucked 100’ of rope into the impeller, disabling the boat. Oops!
When they went to retrieve the second boat, they had to lift it over the satellite dish, missing it by INCHES!!!!!!! Needless to say our satellite guy, Mike Durbin, survived, as he had his heart restarted. It seemed to the crew a heart-stopping moment, either way, we won’t be putting the boat back in its original holder.
posted by DaveandBrian @ 8:18 AM
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