Probing Deep Waters
Analytical apparatus is taken to extremes

-- by Richard Mandel

Designing equipment for scientific research means creating a product that will be exposed to unique situations. Experiments on the space shuttle must tolerate the hard vacuum of space and the onslaught of micrometeorites, and research at a facility like Argonne National Labs may involve ultra-high precision components that will be exposed to high energies and radiation. Scientific study is still exploring phenomena on the bottom of the ocean, in pressures and temperatures not unlike the surface of bodies in our solar system.

UD chemist George Luther works with needle-like electrode sensors for deep-sea research.

One of the items actively being investigated is in the realm of volcanic vents more than a mile down in the ocean depths. These vents are not only spewing out a rich mixture of sulfurous compounds, but have been found to harbor a rich array of micro-organisms. These creatures are highly specialized, since at that depth there is insufficient light for photosynthesis -- instead, some are using the hydrogen being generated to provide the supporting energy for their life-cycle. Other organisms literally can eat rock -- they are consuming local minerals as a food source, a mechanism that could be of interest to industries involved in mineral processing, among others. To look for these organisms, scientists study the "fingerprint" of the compounds suspended in the water.

Analysis at the source

In the earliest days of water analysis in oceanographic research, water samples were taken from the target site and analyzed on-board the survey ship. During the '80s, a flow-injection system was developed and used that could be sent down to the desired point. The miniature lab was able to detect levels of oxygen, silicates and total H₂S as the water sample was pumped through the working chamber.

More recently, University of Delaware chemist George Luther worked with Donald Nuzzio, president of Analytical Instrument Systems, Inc., in Flemington, NJ, to develop a more flexible system. The equipment they assembled worked from the basis of electrochemistry, where small variations in voltage can be read like a spectrograph of light, providing markers that correspond to the presence of specific substances.

Constraints

There were two primary factors involved in the design of this package: the working environment for the sensor, and the method of delivering it.

A sensor wand at the end of one of ALVIN's manipulator arms takes measurements at a hydrothermal vent.

As mentioned before, the volcanic vents are more than a mile down in the ocean, which translates to pressures of more than 200 atmospheres being exerted. The temperature at the vent opening can be 300°C, although the surrounding water provides enough of a thermal sink that the temperature drops to 25°C at a distance of just one-half meter.

The apparatus was configured to be carried on ALVIN, the three-man submersible owned and operated by the Woods Hole Oceanographic Institute, Woods Hole, MA. Carrying a pilot and two observers, ALVIN is designed to operate at depths down to 14,764 ft., and remain submerged for approximately 10 hours under normal conditions. Much of ALVIN's systems run off 12 and 26 VDC, and an inverter additionally produces one kilowatt of 115V, 60 Hz for scientific experiments. The ALVIN manual specifically states that "electrical and thru-hull wiring must be ungrounded to limit the chance for corrosion of structural parts in the event of inadvertent grounding of any conductor."

The package

To meet all of the requirements, the sensor was divided into two units. The sensor is a wand carried in one of ALVIN's manipulators, and is constructed by potting one or more 0.1mm diameter gold wires in a length of PEEK tubing with marine-grade epoxy. When the epoxy cures, the sensor end is cut and polished, and one end of the wire is plated with mercury. The reaction of certain elements with mercury-plated gold wire produces a small electrical current that provides the marker. Wands have been made carrying five detectors in a 1 1/4-in. diameter tube, down to a 1/4-in. diameter unit that can probe into the holes of underwater worms to detect elements that would give a window into what they consume.

The wand is attached by a cable to a pod externally mounted to the bottom of ALVIN. The pod, made of a 2-in. thick tube that is 8 in. in diameter and 3 ft. long, contains a Pentium-based computer and an Analytical Instrument Systems analyzer that was modified to fit the tube.. An RS232 cable runs to a hull connector on ALVIN, where it is then routed to an on-board computer. The pod is sealed with O-rings on 2-in. thick end caps bolted into place. Nuzzio selected aluminum over titanium for the pod, as it was less expensive.

Results

The sensor has succeeded in detecting compounds such as H₂S and FeS, which together form pyrite and the hydrogen gas that is helping the local microbes grow. It is also capable of simultaneously sensing thiosulfate, polysulfide and other compounds, which suggests that the analyzer can be used in other applications, such as in pollution control systems.

Luther hopes the "snooper" eventually will aid scientists in sniffing out ancient bacteria and yield important information about other vent life. "Learning more about the chemistry of the vents should help us better understand the biology of the vents, and why deep-sea organisms live where they live," he says. "Some of these vent dwellers may possess enzymes useful in processing foods, drugs and other important applications."

For more information-

Circle 450 - University of Delaware College of Marine Studies, or connect directly with their website via the Online Reader Service Program at http://www.1rs.com/005df-450

Circle 451 - Analytical Instrument Systems, Inc. http://www.1rs.com/005df-451

How to draw a boat

Changes in CAD products over the last three years have been tremendous, primarily in the areas of collaborative design and object-based rendering. Concurrently, work in the shipyards has been shifting from being directly competitive with one another to "co-op-itition" -- that is, competing over Navy projects while cooperating on others. This parallels the aerospace industry, where designers at companies like Lockheed and Boeing are friends on some projects and enemies on others. This, in turn, has drawn attention to the IT departments in these operations, and the need for more universal software.

Shipyards often use more than one CAD system, frequently because of all the different shipyard departments, divisions and groups required to design a product so huge, to say nothing of the array of sub-contractors. One CAD system may be dedicated to detailed steelwork design, another to designing systems and equipment for outfitting, and still another for stress analysis. Specialized systems such as these weren't intended, originally, to support a fully collaborative operation. Newer parametric and object-based softwares, such as CATIA and others, help this process immensely, as each design component is imbued not only with built-in classification and attribute data (its identity), but grouping and connectivity information that, should an adjoining system be affected, will inform the designers that it is being affected as well. For example, if a bulkhead in a stateroom design is being moved, the staff handling the HVAC system might receive an alert that ducting running through that bulkhead is being affected. These types of models also simplify the generation of specific application views, such as general arrangement drawings and bills-of-material, because all applications share and are based on identical information. With object design technology, functional designs can be defined in the absence of part designs, an advantage when projects move to a fast track status.

Much of the preceding information was contributed by Edward S. Popko, IBM Market Manager for Aerospace, Defense and Shipbuilding. For more information on CATIA - Circle 455 or connect directly with their website via the Online Reader Service Program at http://www.1rs.com/005df-455