A low cost free drifting position transmitter for the measurement of the thermocline properties

Abstract

This thesis describes the work undertaken in the conception o f a vehicle able to observe the thermocline, the temperature and the salinity from the sea surface to 200m deep. This work includes the mechanical design of the device, termed a “ballast system” or “subsurface profiler” and the control of its velocity. This profiler is able to accommodate sensors capable of collecting such data (temperature and salinity). These sensors are provided by Sea-Sense Ltd, Galway. The profiler is designed to be disposable, auto-controlled and located by satellites in order to eliminate the recovery cost. It is designed to achieve at least two hundred cycles from the sea surface to 200m deep. Furthermore, the profiler velocity must be controlled accurately and as close as possible to O.OSm-s"1. Once the mechanical design and the selection of the appropriate sensors mounting components are achieved, the mechanical strength of the profiler, using appropriate materials, is evaluated at 200m deep where the pressure is relatively high (about 20 bars). The profiler velocity is simulated via a motor, which pumps (discharges) water in order to become heavier (lighter). Tools such as mechanical design automation software, finite element analysis and dynamical simulation systems software were employed to provide a solution to each problem through this project.