A New Exploration System for Deep Sea Soil Sampling

1. ABSTRACT A conceptually new, modularly designed exploration system for the deep sea (6000 m) that yields prospective exploration methods, has been constructed and tested. This system comprises an underwater base unit in which different soil sampling tools can be integrated. For the time being this is a sediment sampler of the Kasten corer type, on orange peel grab and a hard rock drill corer, able to recover cores of Ø 48 mm (OD) with a length of 500 mm. Towed along via a coaxial cable from a research vessel, the system is TV-guided and can be actively positioned by means of 2 thrusters in order to be lowered precisely on the seafloor. Perfect horizontally levelled positions of the system on any terrain are achievable by adjustable legs. The total system is operated by the help of an on board computer and may be controlled by sensor displays and operation messages. Microprocessors control the underwater unit which is partially automated. Possibilities for potential further developments are presented. 2. INTRODUCTION Present geological research programs in the deep sea require tools that are suitable for selective sampling, i.e. precise visual site selection in the 1 m range prior to sampling. This is true for any examinations of partially restricted phenomena but in particular for the recent exploration of ocean minerals (massive sulfides, crusts etc.). Up to now, those demands could only be accomplished by manned systems that are scarcely available, costly and need extensive infrastructural support. Thus, the current trend in new developments of exploration systems aims at making devices more efficient by remote control, in order to be able to replace submarines for some of these specific tasks. This is why the German Ministry of Research (BMFT) initiated the development of a new system that combined the specification of visually working soil and inspection devices with those of sampling tools, extended by the capability of precise horizontal positioning. It is obvious that such a system should not be restricted to the application to a single type of ocean floor, yielding the decision to design the system modularly, i.e. to realise quick and easy exchangeability of all sampling tools. Within a three year's program, starting from September 1987, this Actively Positioned Exploration system (APEX) was conceptually developed, constructed and finally successfully tested at various test sites. 3. DESIGN APEX consists of an underwater base unit that is linked to a control post on board a research vessel via a standard coaxial (mono conductor) cable and that is thus towed along like conventional tethered vehicles. 3.1 MECHANICAL CONCEPTS The base unit incorporates all facilities for control, bidirectional data transfer and power supply as well as "plug-in" facilities for different soil sampling tools, so-called modules. Its structural element made of seawater-resistant aluminium is some 3 m high and encloses three adjustable legs for levelling, two reversable, continuously adjustable thrusters and an internal tool rack with module suspension that may be vertically transversed for 950 mm.