Research Article: Marine Engineering: The Story of Surveying the Edge of the Sea

Research Article:
Marine Engineering:
The Story of Surveying the Edge of the Sea

Exploring the "Hump": Why Is Advanced Underwater Technology Important?

Dr. Ballard and other scientists are busily investigating an area of the ocean off the coast of southern Florida, about 29 km (about 18 mi) south of the Florida Keys. This area is famous for its relic reefs, some of which date back to before the Ice Age! Relic reefs are "drowned" reefs that no longer bear living corals. Those off southern Florida are quite deep in the sea: 73-183m (about 80-200yd) below the surface. Dr. Ballard and his colleagues want to know more about the seafloor in this area, including the reefs that dot the seafloor. They are especially interested in a reef called the "Hump," which has never before been explored!

Because the Hump area is an inhospitable location, researchers such as Dr. Ballard use advanced technology wherever they can - not only to make detailed observations and measurements, but also to protect them from harsh conditions.

What Are Engineers And Why Are They Important to the JASON Project?

Who thinks of these tools? How are they created? Designing, building, and using special research tools requires special skills-the skills of engineers. Engineers use scientific principles to design, build, and operate things that people need. For example, engineers talk with researchers like Dr. Ballard to find out what they are trying to accomplish, then they design and build tools that can help the researchers accomplish their goals. To be useful, engineers must build tools that work well, do the things the researchers want them to do, and are economical.

No matter what tools researchers use in their scientific investigations, their research will be successful only if they use the tools properly. Many researchers, including Dr. Ballard, rely on a team of marine engineers to help them:

identify what tools are best suited for the task at hand.
devise a plan for using these tools to get the job done.
operate and maintain the tools during the research project.

Dr. Ballard's team of engineers is headed by Dr. Dana Yoerger, of the Woods Hole Oceanographic Institute. A robotics specialist, Dr. Yoerger will help Dr. Ballard and his colleagues use a manipulator arm to collect samples from the seafloor.

Dr. Jon Howland, a specialist in imaging and data processing, will help the researchers put together images of the study site-a task that is critical to the mapping process.

The third member of Dr. Ballard's engineering team, Commander David Olivier, is an electrical engineer and the Officer in Charge of the U. S. Navy submarine NR-1. Commander Olivier will help the researchers navigate so that they get to the correct research area and know precisely where they are at any given time. He will also help the researchers use the NR-1's acoustic and visual imaging equipment in mapping experiments.

What Tools Do Marine Engineers and Researchers Use?

The NR-1

U. S. Navy submarine NR-1 is an 11-person research submarine designed to run deep in the ocean. It can sink, rise, and move forward. Examine the diagram of the NR-1 below. Notice that the hull (body) was built with circular cross sections, to help the submarine withstand the very high pressures found deep in the ocean. The cross sections also reduce friction or "drag," making it easier for the submarine to move through the water.

Another engineering feature of most submarines, including the NR-1, are ballast tanks that can hold water or air. Find the ballast tanks on the diagram. By adding or withdrawing water or air, submarine operators can change the weight of the ballast tanks-and thus of the submarine as a whole. Adding water to the ballast tanks, for example, makes the submarine heavier, causing it to sink. Taking out the water and replacing it with air makes the submarine lighter, causing it to rise.

The NR-1 relies on nuclear power for all its systems, from propulsion to generating breathable oxygen for the crew. The small reactor on board uses nuclear fission to convert atomic energy to electrical and mechanical energy to run the ship's systems.

The NR-1's special tools allow it to move close to a seabed to collect samples and other data about the ocean's chemical, thermal, optical, biologic, and acoustic characteristics. Some NR-1 tools used for these missions include a side-looking sonar system, a bottom profiling sonar system, a depth profiling sonar system, a manipulator arm and work module, electronic still cameras, stereo imaging equipment, and viewing ports.

Sonar Systems

Sonar stands for SOund NAvigation Ranging. A sonar system uses sound waves to detect objects, create images of objects and structures, and measure distances. The NR-1's sonar system has a device called a transducer that emits bursts of sound waves. Each burst of sound waves that the transducer sends out travels through the water around the submarine, bounces off objects in the area, and then returns to the submarine, where it is detected by the transducer.

The sonar system's processing unit measures how long it takes for sound waves emitted by the transducer to return to the submarine. Based on that length of time, the sonar system computes the distance traveled by the sound waves-the distance between the submarine and the object. By analyzing many different returned sound waves (called echoes) that have bounced off different objects or different parts of the same object, the sonar system creates an image of objects in the submarine's path. The distance measurements also help the submarine operators navigate-so that they know where they are.

The NR-1 is equipped with three types of sonar:

Depth-profiling sonar, in which the submarine directs broad sweeps of sound waves down to the bottom of the ocean from the surface. By measuring the distances traveled by different sound waves, the submarine's sonar system can determine the depths of various parts of (and objects on) the seafloor.
Bottom-profiling sonar, in which the submarine stops and sends a series of sound waves down to the bottom of the ocean to "see" the shape and depth of specific objects (e.g., specific coral reefs) on the seafloor.
Side-looking sonar, in which the submarine sends out sound waves while it is underwater so that the sonar system "sees" the sides of underwater objects.

During JASON Project research, Dr. Yoerger will demonstrate these techniques to the other researchers as well as to students.

Stereo Images

Stereo imaging is the process of creating a three-dimensional image of an area or object. How is this done? A scientist uses a camera to take many different pictures, each one from a slightly different angle. When the scientist views all these pictures through two eyepieces, a three- dimensional image appears. This gives the scientist a better sense of the depth and shape of the object being viewed, as well as the amount of space it occupies. This is very helpful in underwater studies, where the water often distorts visual images. Imagine what it would be like if everything you saw was flat (as in regular photographs) and you had no sense of depth!

Manipulator Arm and Work Module

The NR-1's manipulator arm is a robotic device that can pick up objects (samples) and deposit them in a basket called a work module. The work module is then carried to the surface so that researchers can handle and examine the samples. Find the manipulator arm and work module on the diagram of the NR-1. Why do you think these instruments would be useful for deep dives near the "Hump"?

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Gene Carl Feldman (gene@seawifs.gsfc.nasa.gov) (301) 286-9428
Todd Carlo Viola, JASON Foundation for Education (todd@jason.org)
Revised: 30 Oct 1995