The systematic optimization of the propulsion efficiency of in-service autonomous underwater vehicles

Understanding the ocean environment is dependent upon adequate sampling of many parameters. For reasons of affordability and practicality many of the measurements within the ocean will need to be undertaken by AUVs. Current propeller driven AUVs have limited range and endurance. Whilst new designs of vehicle may readily incorporate new technologies to address the issue, considerable investment has gone into current generation. These are often successful designs with many years of useful life remaining. This paper describes a means of assessing the propulsion performance of in-service vehicles with a view to their further optimization. A system-engineering approach to the problem is proposed. The characteristics of the system are examined and the in-service performance compared with that anticipated at the design stage. Shortfalls in performance are identified. This results in a need to take account of the effects of a greater level of subsystem detail than is usual at the design stage. The need to address complexity leads to difficulties in design of effective measurement systems. The design of a programme of scale model experiments and full-scale trials with the aim of improving understanding of the propulsion system, with particular attention to drag and its causes, are described. The baseline vehicle used is the AUTOSUB AUV, developed by the Southampton Oceanography Centre.