Autonomous underwater vehicle (AUV)

 The AUV is part of the group of unmanned underwater vehicles that includes the better-known remotely operated underwater vehicles (ROVs).  The difference is that the AUV lacks the umbilical cord found trailing behind the ROV.  Rather, the AUV is programmed to engage in certain specified behavior while propelling itself below the surface of the water.  Like unmanned satellites launched into space, the AUV can be much smaller and constructed less expensively than a manned submersible.  It can also operate in more extreme conditions.  Because work on AUVs is relatively recent, the technology is as yet nowhere near its potential.  Regardless, deployment of AUVs is increasing.  Originally developed as a pure research tool, the AUV is now being used for military purposes (such as determining the presence of mines or monitoring a protected area for intruders) and commercial purposes (such as making detailed maps of the seafloor prior to construction of subsea infrastructure).  All AUVs are equipped with a propulsion system, sometimes multiple systems, and a steering mechanism.  Most utilize batteries for power, although a few make use of fuel cells.  They are equipped with navigation systems of varying sophistication: some use acoustic systems, but most rely on GPS and/or inertial navigation.  The major aspect of variation among AUVs is with regard to sensors.  Depending upon the purpose for which the AUV is being used, sensors may include depth monitors, sonars, magnetometers, thermistors, or conductivity probes, among others.  AUVs are growing in size.  Early ones were about two feet in length and several inches in diameter, used mostly in lakes and bays.  Current ones are over ten feet in length and two feet in diameter.  Underwater gliders are being developed capable of crossing oceans, surfacing occasionally to report position and observations.  The next step will be AUVs capable of performing actual work while submerged, in addition to conducting surveys.  AUVs will soon be the maritime equivalent of the Mars Rovers.