The critical enabling technologies which have been identified to fully realise the potential of AUVs are: long endurance propulsion/energy systems; geodetic and relative navigation; underwater communications; mission management and control; sensors and signal processing; and vehicle design. However, perhaps the most critical technology for almost every AUV application, and often the operational limiting factor, is the availability of adequate onboard energy/power. Given the specialist nature of the AUV market, research and development into new AUV-specific power systems is inevitably limited by resources.At the present, the relative merits and disadvantages of the competing Air-Independent Power Systems (AIPS) are fairly well known. However, the greatest need of advice is with the "total system" and its integration, i.e., how the AIPS is affected by, and affects the overall vehicle design. Hence, with the numerous design considerations of an AUVs, full knowledge and understanding of the total AIPS integration is essential, if a technically and operationally successful vehicle design is to be achievedThe aim of this paper is to examine the conceptual design of an AUV with specific emphasis on the integration of an Air-Independent Power System, thereby enabling the initial design of AUVs to be evaluated.

To operate in a nonair environment, a diesel engine must be supplied with a synthetic atmosphere which mimics the role of normally aspirated air. To determine the optimum synthetic atmosphere mixture, an intensive experimental investigation has been carried out by the authors using a specially developed test rig. Provision has been made on the test rig so that a number of different composition synthetic atmospheres can be produced. In this way, it has been possible to measure the effects of carbon dioxide ratios on the performance of the diesel engine. In addition to the shaft performance, power and fuel efficiency, exhaust gas emissions and combustion noise have also been measured. This paper details the operational principle of an underwater diesel engine and reports on the performance of such an engine whilst operating with high intake carbon dioxide levels

A pollutant that has not yet received as much public or regulatory attention as gaseous or solid particulate emissions is engine generated noise. Excessive levels of noise can, however, be as harmful to human health and the environment as noxious gases. In a well-designed engine, mechanical noise can be kept to a minimum but the combustion process itself still generates noise, "combustion noise". Thus, if the combustion process is modified for exhaust emission control it can be expected that the level of noise generated by combustion will also be affected, albeit not necessarily adversely. As exhaust gas recirculation (EGR) is becoming an essential technology for NOx emission control in diesel engines, and, as this technique modifies the combustion process, it is important that the effects of using EGR on noise generation be identified.