Design of Unmanned Untethered Submersible for Quick Swimming

Abstract

Unmanned vehicles have great advantage for' survey of sea bed in the deep sea. Many models of tethered submersibles have been developed as devices for exploitation of subsea oil resources. In the deep sea, drag force acting on the umbilical cable prevents tethered submersible from swimming freely ; therefore, the development of untethered submersibles is highly expected, which are free from restriction of the umbilical cable. But few researches relating to unmanned untethered submersibles have been performed because of their disadvantages such as slow rate of communication between the surface support ship and the vehicle, and limit of energy supply. It is essential for unmanned untethered submersibles to swim autonomously and with a small amount of battery energy consumption.In this paper, a concept of gliding submersibles is proposed for inspection of the surface of sea bed along a long measurement line. The submersible glides, descents autonomously from the surface without consuming battery energy and comes to the target point. Then it swims above the surface keeping constant height. A pilot model named PTEROA 40 is designed and its characteristics of longitudinal behaviors are examined analytically and experimentally.It is shown that a model of 1. 5 m length swims over 7 knots when the weight is 5% larger than the buoyancy of the vehicle. Longitudinal stability and maneuverability are also acceptable as a vehicle which should climb when there is an obstacle along the line of measurement.