TARGET 2: DELTA ROCKS

SATURDAY, 03.14.09

1547: Days 25-27 (March 11-13)
Well, I guess my plan to get back to a daily schedule on these reports was something of a failure. There are a couple reasons for it, but the biggest would be we had what was easily the best target of the trip so far. You’d think this would be a reason for crowing from the rooftops, but it doesn’t really work that way.

First, let’s take a look at the girls and their progress. Mary Ann was working with a new set of transducers and had shown some noise in one channel. Before sending her on a second mission with these transducers, we switched them over in order to diagnose what was causing the noise. Perhaps a little explanation as to the three basic components of the sonar system might be useful here.

The transducers basically look like two long black boxes, and are roughly three feet long and perhaps three inches square. They are, for all intents and purposes, plain black boxes. They have no moving parts to speak of, and there is a single plug in the back of the unit with a cable connector. The transducer is the sender and receiver of the sonic energy used to make the imagery for analysis. The other two components are the junction bottle and the cables that connect the two. The J bottle is a titanium cylinder about six inches across and perhaps a foot long. The junction bottle services both transducers and serves as the intersection between the sonar and the larger platform, or vehicle. They comprise the junction. A failure in sonar can be attributed to any one of these three components: bottle, cables or transducers. All three are subject to the immense pressure the vehicles work under. When there is a problem with the sonar, the best way to isolate the problem is to simply switch the transducers to the opposite sides of the vehicle. If the same problem shows up on the other side of the record, we know the problem is with the transducer since the cables have not been moved. This proves whether the transducer is the point of failure.

How much pressure is ‘immense pressure’ you ask? Good question. Let’s put it into real life terms. A 2009 Mazda MX-5 Miata weighs 2,480 pounds. Take three of these two-door convertibles, stack them on top of each other and then concentrate that weight over any single square inch of the system, and you have a good idea of the pressure the system must be able to perform under. At 5,100 meters, here are 7,446 pounds of pressure pushing down on every square inch of the vehicle, or 7,446 pounds per square inch. The face of the sonar is 114 square inches, which means that just one sonar face — looking out into the ocean — has the equivalent weight of 342 Mazda Miatas pressing down on it.

The entire transducer has 2,546,532 pounds of pressure on it at 5,100 meters, which is the equivalent of 1,026 Japanese convertibles pushing in on it from all sides. Every single surface inch of the vehicle, in and out, has this same kind of pressure acting against it. Imagine the difficulty designing something to withstand that! Truly, it is easier to design spacecraft than it is to fabricate equipment that can take the immense pressure of the ocean depths. The exterior of the vehicle, in its entirety, has about 8,190,600 pounds of pressure on it, which is the equivalent of 1,820 1972 Cadillac Coupe DeVilles, or 3,302 Miatas or 4,200 ‘71 Ford Pintos pressing in on it. I threw the Pintos in there just because the idea of 4,200 Pintos end-to-end excites the pyromaniac in me: tap the one at the rear, and you got yourself one serious daisy chain of explosions. Ya gotta get your fun where ya can when you’re at sea. Anyway, that’s a heck of a lot of pressure, huh?

So, let’s get back to Mary Ann. She went in on March 10th for a survey of box 9a, was recovered 24 hours later on the 11th at 2200. The problem had moved to the other channel. We knew then the issue was within the transducer itself, and that the cables and bottle — which had not changed — were good because the other transducer’s data looked okay and remained unaffected by the change. We made some adjustments and put her back in the water at 0156 on the 12th. While we are suffering some interference in one channel of her data, the static is only in that single channel and only 50 meters in from the outer limit of the record, so we can adjust her survey and overlap to get full coverage. We set her on a 350-meter range scale, but planned the survey with a 300-meter range plugged into the survey and a 100-meter overlap. We are seeing everything down there and seeing it well, with the higher frequency giving us lower range, but higher resolution. A good target will stand out. Mary Ann was recovered from her survey of 10a at 0130 on the 13th. She went back in that morning at 4 a.m. for a survey of the rest of box 10a and part of 11a and recovered this morning 0335. She is currently on survey, finishing up box 11a after launching at 0622 this morning (technically day 26, the 14th).

When last we left Ginger, she was down to one spare transducer and had been failing transducers with regularity. This has not changed. She is currently working with the last two functional 75/410 transducers aboard the ship. The last transducer went in her the other day when the latest replacement failed for the same reason, as far as we can tell, as the previously installed equipment — the depth. They stop working at around 2,000 meters on the way down, and then start back up when they hit that same depth as they return to the surface. This is like watching a healthy, albeit clumsy, person go quickly blind. In essence, we have seen our primary capability decline consistently over the last two weeks, this after being plagued by other frustrating failures and technical difficulties.

My last report was an update on the morning of March 11th, indicating Ginger was recovered and had good data. This information turned out to be faulty. The sonar analyst on duty at the time did not do a sufficient job of checking out the data, he only made a cursory look and declared it sound. When his replacement came on some seven hours later, he found we had suffered degradation in the port channel data and we aborted Ginger’s mission. She came to the surface, had her current transducers switched and undertook a single lane, diagnostic survey that evening into the morning of March 12th. When she came back up, we confirmed the transducer was failing. The last remaining low frequency transducer was mounted, and since there was nothing left to use to replace another failure, we decided to send her out for a full mission. As to our efforts to get replacement parts, I will fill you in on those in a later report.

Plane-Shaped Rocks

Finding a hot target…

The one good thing that happened during Ginger’s mission on March 11th is that she came back with a smoking hot target in her one good channel of data. We have established criteria for target ratings, and we submit a report to Ted Waitt when we have a target we wish to re-image. The vehicles can be programmed to break off, change their depth and sonar frequency, and run a search grid over a suspected target. We were very excited about this. In the midst of all of our breakdowns, it is sometimes easy to forget it is only going to take one sortie — one mission that happens to be in the right place — to make this operation successful. Spirits rose as we did the initial analysis, and though those high hopes faded somewhat over the next few hours as we looked more carefully at the target and compared it to some of the larger geology in the region, there were still hopes we may have finally sighted our quarry. The target showed some very definitive shapes and also gave off indications of debris.

When Ginger was put back in the water, we planned a mission for her that would take her first into box 10a to clean up a missing lane, and then have her run back into box 10b for a survey in opposition to her failed survey of the day before. This would put her good sonar looking into the channel that had been corrupted earlier. At the end of her trip she would finish her lines, drop down from 30 meters to eight, switch to high frequency sonar and break out the most impressive and powerful tool in her arsenal — her camera — to shoot some 2,000 2.2 megabyte black and white photographs.