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June 1, 2002 Hi! My name is Mark Saldaa, and I am a student in Ms. Shield’s 7th Grade Science class. After our school’s trip to Woods Hole, I became greatly interested in the technology and mechanics behind the Alvin, ABE, and the instruments they use. Combined with my interest of engineering and technology, I was itching to find out a little more. More specifically, how and who developed the technology used by you and your fellow scientists? I am under the impression that many (if not all) of the technology was designed by and specifically for the Woods Hole team, but how many people did this take, and how long? Were you inspired by other similar inventions? How has this technology evolved since it was first invented? Thank you very much for devoting the time to read this email, and I hope the team has a great expedition!! Sincerely, Hello Mark: Hi Mark, My background is in Navy Nuclear Power, and big black submarines. I have been with the little white submarine and Alvin Group for 9 years, and also have gotten familiar with Jason, Johnson Sea Link, ABE, and other underwater oceanography assets. I have found that the things I learned in my high school physics, chemistry and math classes serve me well every day. The mechanical and electrical engineering principals I learned in the Navy directly apply to the equipment I work on now. A good education is important, but you don’t have to get it in a classroom. Due to the depths we work at, vehicles like ABE and Alvin use a few tricks to overcome the effects of the tremendous water pressure we deal with. Consider the fact that the Space Shuttle goes from 14.7 psi at the earth’s surface to zero psi in space. Alvin goes from that same 14.7 psi on the surface to 6,600 psi at 4500 meters. A much harder change to deal with! The Space Shuttle and Alvin both have a lot of other issues to address, but taken from a change in pressure viewpoint, the astronauts have it easy. One of the most important tricks used in deep submergence is “compensation.” We take something like a plastic box, which isn’t strong enough to maintain its shape under the crushing force of the water, and fill it up with oil. Oil is a mostly incompressible fluid, so the box is now essentially a solid. The force the water exerts to crush the box, focused inward, is compensated by the force the oil exerts on the box, focused outward. The forces cancel out and the box goes down to the seafloor and comes back up the same shape. Arthur C Clarke said something like: “Technology, raised to a sufficient level, is indistinguishable from magic.” If I let you step on my plastic box and crush it, and then I sent it to the bottom of the ocean and it came back the same shape, you’d call me a magician. I recommend you go to the library and get some books on William Beebe. He was among the first modern ocean explorers who went below the surface. I have asked my friend Dr. Al Bradley, who has been involved in deep submergence a lot longer than I, to discuss the historical view. Al is one of the guys who built ABE. Regards, Hi Mark, First, our technology is based on what our industrial civilization can supply. We’re always on a tight budget and have more things that we want to do than we can afford. We therefore use commercially available equipment whenever we can because it’s much more economical. But sometimes there just isn’t anything available to do what we want and we have to make it ourselves. Sometimes industry makes this easy. Pressure cases are a good example. Every instrument we build needs some kind of pressure case. We calculate how thick the walls have to be, do a drawing specifying all the seals and attachments, and just send it to our shops. They buy the raw stock and machine the case to our plan. Sometimes it gets harder. We needed very efficient thrusters for ABE. One very energetic company wanted to move into the autonomous underwater vehicle market and offered to do a special design for us at a very low cost. When they delivered their prototype, it was awful! They were used to big thrusters that were at the 2 kilowatt level. ABE’s thrusters had to operate at the 150 Watt level. To drive it forward we use 3 thrusters, each using 50 Watts. ABE has 7 thrusters in all, 3 forward, 2 vertical and 2 horizontal, but most of the power is used by the forward thrusters. Their prototype needed 7 Watts even when it was just sitting there and not turning. Seven of these would take 49 Watts, one third of our power budget wasted! They were used to kilowatt levels of power and they (no matter how many times we told them) didn’t think that 7 Watts would be a problem. So we had to build our own. It took six months, but they have been working beautifully. When waiting for a command from ABE’s control computer, they use 0.1 Watt instead of 7 Watts. Sometimes modifying commercial equipment is the easiest way to get what we need. On this cruise, we just found out that the scanning sonar on ABE makes a lot of noise right in the middle of our navigation frequency band. We’ll have to take it apart and modify it. Maybe replacing the metal gears with nylon will work. If you’re interested in this kind of thing and think you’d like to be an engineer or scientist, I have several suggestions. First, build things. Examples are model airplanes, boats and cars. (I always like working with balsa airplanes.) Go with what you like best, but try to stay from the “any dummy can assemble this kit” stuff. Leggo Mindstorms is ok, but too much is done for you. Stay away from video games, they only teach you to be a couch potato! In school, whenever you have a choice, take the hardest science and math you can get. (It’s a lot more fun!) Best of Luck!
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