This paper discusses the ultimate limits to the range of conventionally powered deep ocean Autonomous Underwater Vehicles (AUVs). It is intended as an introduction to the unique problems of vehicles designed for speeds between 0.2 and 2 knots. We first present the relationship between range, size, no propulsion energy requirements and flotation efficiency for vehicles using various common battery technologies. We then demonstrate that, at these speeds, the non-propulsion energy requirements severely limit the ultimate range. We next discuss strategies for implementing navigation and control systems at power levels of 0.1 to 1 Watt. We present systems which are based on existing technologies in use in various areas of oceanographic research but not generally utilized in the AUV community. We conclude that ocean crossing AUV's of modest size are possible. To support this thesis, we present a design example of a vehicle suitable for economical monitoring of a hypothetical deep ocean dumpsite. This 3.5 m vehicle will have a range in excess of 6000 km at a speed of 0.5 mI sec.
Why are we doing this? Long range, slow moving Autonomous Underwater Vehicles (AUV's) appear to be an attractive solution to problems of environmental monitoring, geophysical exploration and military surveillance. Many authors have written enthusiastically and extensively about the potential applications of AUV's and we will not repeat their arguments here. Instead, we assume the reader is impatient to discuss the limitations to the range obtainable by AUV's based on current technology. We will demonstrate that, if the AUV can accomplish its mission while moving slowly, the range-limiting factor is the parasitic non-propulsion power requirements or "hotel" load. We will show that, if this overhead power is minimized, ranges sufficient to cross ocean basins are realizable.
