Epaulard = An Unmanned, Untethered Vehicle For Deep Ocean Survey
Authors: Duranton Raoul , Michel Jean Louis , Grandvaux Bernard 
Published: October 2008

Developped in France by the CNEXO (Centre National pour I'EXploitation des OcBans), the EPAULARD is an acoustically remote controlled vehicle for deep ocean survey.

During the year 1979, different campaigns of trials have been conducted in the Mediterranean Sea and the Atlantic Ocean till depth of 4200 meters.

This paper describes briefly the system and reports some results obtained during the first sea-trials.

INTRODUCTION

In 1976, the CNEXO conducted a brief technico-economic study which has shown that for routine observation of large ocean deep-bottom areas, the concept of an unmanned, untethered vehicle would have a lower exploitation cost compared to manned submersibles or even to cable-towed fishes.

After preliminary experiments which have proven the feasibility of an acoustic remote control to monitor the navigation of a sea-bed vehicle, a decision was taken to develop the EPAULARD system.

French Societe ECA Company acted as prime contractor of the vehicle and ship-plant while «CIT-ALCATEL» achieved the acoustic link (positioning and remote control). The system was designed and built in 1977 and 1978. Experiments started in February 1979.

DESCRIPTION OF THE SYSTEM

General features

The ((EPAULARD)) system consists of an unmanned, autonomous submersible associated to a mother-ship installation including control, positioning and logistics equipments.

It has been designed to perform photographic and topographic tasks over the sea-beds, at 6000 meters depth (20 000 feet), on 12 nautical-miles ranges per dive.

The overall conception of the logistics allows two dives per 24 hours. As soon as the submersible enters the water, the communications with the ship are only acoustical: they allow the control of the dive from the surface, data transmission and positioning with respect to the ship.

Due to the reasonable sizes of the submersible and the on-board equipment, the system can be exploited on rather small vessels equipped with adequate handling facilities. Launching and recovery of the vehicle can be performed without divers.

Description of the submersible (See fig. 1)

The EPAULARD weighs less than 3 tons. Its overall dimensions are: length : 4 m (13 ft), width : 1,1 m (3,6 ft), height : 2 m (7 ft). Its external shape is that of a fish with a vertical rear rudder. This shape has been designed to provide the vehicle with drag resistances as low as possible, both in vertical and horizontal directions (descent and ascent phases, as well as horizontal motion over the seabed).

The submersible architecture consists of a central frame (made of sheet-aluminum) upon which are secured all the components, as well as the syntactic foam floats, molded to the external shape.

The principal functions of the fish are achieved as follows:Energy storage : with a lead-acid accumulator, 48 volts, capacity : 15 000 w. h, easily interchangeable.Horizontal propulsion : by means of a central electric thruster, which provides one reverse speed, one normal forward speed (2 knots) and one temporary forward overdrive. A vertical rudder associated with a magnetic compass provide an automatic heading control of the fish.