Introducing Students To Ocean Engineering

Ocean Engineering is a complex multidisciplinary field involving sub-disciplines such as fluids, acoustics, and control systems, that undergraduates either never see or experience only in upper level classes. The problem, then, is how to introduce this subject to beginning students – freshmen who have enthusiasm, energy, and interest but not the necessary background to delve deeply into the subject. To solve this problem we have, for the past 4 years, been running a spring seminar class aimed exclusively at freshmen with the goal of introducing the broad sweep of ocean engineering disciplines in a way that is both engaging and tractable to the students. The core activity of this class is the construction and testing of a simple remotely-operated vehicle (ROV) made out of PVC pipe, toy motors, and other simple components. It is through the discussion and analysis of this vehicle and its various parts that the many facets of Ocean Engineering are introduced to the students. This paper outlines the course and our experiences in teaching it. The paper also describes some of the simple technologies have been developed to enable students to engineer underwater both easily and inexpensively. Introduction Ocean engineering is a difficult field because the ocean is such a harsh environment. Underwater systems (e.g. submarines, instrument packages) are surrounded by corrosive seawater, subjected to enormous pressure, and buffeted by currents. Radio communication is nearly impossible because electromagnetic radiation is absorbed over short distances. Control and communication must be handled through slow acoustic links with surface personnel or computers, or handled by onboard computers as is the case in complex autonomous systems. Space is at a premium in underwater systems because of the cost of underwater housings, especially those resistant to high pressure. This raises significant challenges in packaging of the components and assemblies and necessitates the efficient use of limited power. Some of these engineering constraints are relaxed when marine systems are confined to the surface but other challenges take their place. Chief among these is weather; surface systems such as boats and buoys must be able to survive hurricane conditions and long term temperature extremes. As a result of the myriad problems associated with marine engineering, ocean engineers often have multiple specialties. They have expertise in more traditional fields like electrical engineering or mechanical engineering plus expertise in the properties of the marine environment and the effects those properties have on marine systems. This multidisciplinary aspect not only makes ocean engineering technically challenging, but also challenging to teach. In particular, it is difficult to introduce the field to beginning engineering students – they seem to have to know so much in order to begin to “get wet”. For the past four years we have tackled the problem of P ge 751.1 “Proceedings of the 2002 American Society for Engineering Education Annual Conference & Exposition Copyright ” 2002, American Society for Engineering Education” engaging students in our exciting field through the use of a seminar class that introduces ocean engineering via a hands-on project experience. The course is entitled “Build a PVC ROV! ” (MIT course 13.S36). In it the students learn about ocean engineering by building a small battery powered remotely-operated vehicles (ROVs). The ROV is a vehicle in both the conventional sense of a submarine and, importantly, in the sense of a vehicle for learning in which concepts are introduced as the little machine is built. Course 13.S36 is in the tradition of hands-on type courses that have long been recognized as an important part of engineering education. Hands-on courses connect theory with practice and by doing so help to clarify the theory in the students’ minds. These courses also give the students solid practice in problem solving of the type they will probably encounter on the job. Finally, hands-on courses give the students technical skills (e.g. machining) that they would not have gotten in their core engineering courses. What follows are a detailed description of course 13.S36, some of the technical aspects of the course, and an evaluation of its effectiveness in giving the students a window into the world of ocean engineering. Build a PVC ROV! Course 13.S36 – “Build a PVC ROV! ” is a seminar course geared toward freshmen students. Seminar courses for freshmen at MIT are designed to offer students some diversity in what is otherwise a standardized set of science and math courses that all freshmen are required to take. Seminar courses often offer an introduction to some sort of advanced topic and whet the students’ appetites for future courses while at the same time helping to keep students interested and motivated while grinding through the fundamentals. The intent of course 13.S36 is well matched with the goals of these freshmen-oriented seminar classes. Having decided to introduce students to Ocean Engineering at the freshmen level by way of a seminar course, the next topic addressed was the content of the course. For the reasons outlined above we decided to create a hands-on, laboratory course. At that point in the course development we obtained a copy of a remarkable book entitled, “Build Your Own Underwater Robot,” by Harry Bohm and Vickie Jensen. This book describes a number of simple marine building projects designed for high school (and younger) students. Among the projects is a simple and elegant little remotely-operated vehicle made from PVC pipe and toy motors named the Sea Perch. We decided to use the Sea Perch as the core building project of course 13.S36 for three major reasons. The Sea Perch is very easy to build and thus is accessible to students with no prior experience in building things or tool use. Despite its simplicity, the vehicle does display all the properties of a marine vehicle and so can serve to introduce many of the core topics of the field. Finally, the Sea Perch is easy to customize; underwater cameras, motorized grippers and other devices can be developed and added by the students as their skills grow. The class has a maximum of 8 students to permit close student-teacher interaction and there is an upper class undergraduate who served as a course assistant. There are no tests, the only assignments are readings, and the course is graded pass/fail based on the student’s performance in the lab as judged by the instructor. A simple format is followed for the course; it meets once per week in the laboratory for a two-hour session. Each session opens with a summary of the state of the class – what the class has done, what will be done today, what is planned for the future. That is followed by a brief discussion of the ocean engineering web site of the week. P ge 751.2 “Proceedings of the 2002 American Society for Engineering Education Annual Conference & Exposition Copyright ” 2002, American Society for Engineering Education” The web site of the week highlights a site that is either technically relevant to the topic of the day, or it is a site which covers a major aspect of ocean engineering (Appendix 1). Often both goals could be combined with the same site. For example, the NOAA El Niño site was chosen as a prelude to a lecture on sensors because of its extensive discussion of the TAO array of dataacquisition buoys. This site is also a window into the many of ocean engineering-related activities carried out by NOAA. After the web site presentation there is a short, 15 minutes or so, lecture on the engineering topic at hand. For example, a brief discussion of Bernoulli’s principle and its relation to propeller function is presented when it is time to add propellers to the vehicles. The remainder of the class is dedicated to constructing and testing the Sea Perch vehicles. Table 1 presents the entire syllabus for the course as given in the spring of 2001, including the web sites, the lecture topics, and activities. As can be seen in this table there are straightforward connections between the various parts of the Sea Perch and the technical subjects that encompass much of ocean engineering. The Sea Perch ROVs (Fig. 1) are simple to understand, construct, and operate. Two horizontal and one vertical propellers (Dumas model DUMB 1860 model boat propellers, Tower Hobbies, Champaign, IL) move the vehicle. Inexpensive DC brush-type “toy”motors power the propellers and they are waterproofed by placing them in plastic 35mm film cans filled urethane rubber potting compound (Flexane 80 Liquid, model 15800, Devcon, Danvers, MA). The motors and two floats are mounted on a boxy frame made from 1⁄2” PVC pipe. The bottom of the frame is covered with plastic netting and acts as a payload bay. The control tether is a 12 meter-long eight-conductor cable that brings power to the motors. Finding a cable with enough conductors that is flexible was something of a challenge. We have successfully used very cheap surplus computer cables as well as more expensive, yet very thin and supple, multi-conductor Mogami cable (model W2789-00-656, Marshall Electronics, Culver City, CA). The tether terminates in a small plastic box that contains an array of switches that permit the user to control the motors. Two DPDT, center-off, switches control the horizontal thrusters and two SPDT, momentary-on, pushbutton switches control the vertical thruster. The vehicle is powered by a 12 V battery; we use sealed lead acid batteries (at least 7 AH). For a detailed description of the Sea Perch see Bohm and Jensen. Some students had difficulties grasping the Sea Perch chain of control from a pressed switch on the control box to the resultant vehicle motion in the water. We addressed this with a careful explanation that started with the control box and followed the chain of control from the switch closures, to the voltage polarities of the motors,