Review of Autonomous Undersea Vehicle (AUV) Developments 
the operator within seconds of acquisition, and the advance speed of the vehicle was optimized 
during sonar imaging for the travel time of the sonar pings. 
An important AUSS goal was to produce a small, lightweight system that could be transported 
easily and placed upon a large cross section of ships of opportunity. As with any overall vehicle 
system, the size of AUSS depends heavily upon the weight and size of the undersea vehicle. If 
the vehicle is allowed to increase in size, the launch and recovery gear, the handling gear, and 
the maintenance areas grow in kind. There is also a vicious cycle of growth associated within 
the self-powered vehicle design. A larger vehicle requires more propulsion power, requiring 
more energy for the same speed and endurance. More energy leads to more weight and 
volume in the energy source, which leads to a larger vehicle. 
Deep service syntactic foam is a much less efficient form of buoyancy than properly designed 
pressure vessels. Syntactic foam was used extensively on the AUSS prototype vehicle, as has 
been the case for many undersea vehicles. Thus a commitment was made to avoid its use on 
the improved vehicle. To meet this objective, several measures were taken. 
Extremely efficient graphite-pressure hull technology was developed with the prototype and 
applied to the improved system. A 30-inch-diameter graphite cylinder was manufactured to 
provide all of the buoyancy required for the improved vehicle. Other measures taken were the 
use of SpectraTM (which has a specific gravity very close to that of sea water) for the free- 
flooded fairings, magnesium for the chassis inside the vehicle, titanium for the wet connectors, 
and titanium and aluminum for redesigns of various sensor housings. The only syntactic foam 
in the system was the deployable nose float used for recovery. 
The time required for signals to travel between the surface and vehicle is dependent on speed 
of sound in water and the distance to the surface. Range of operation therefore affects the 
response time of the vehicle to supervisory commands, and it also affects the delay time taken 
for sensor information to reach the supervisor. These delays will increase with operational 
range, amounting to a round-trip delay of ten seconds or more at 20,000-foot depth with 
moderate standoff. The only way to prevent degradation of performance with range in an 
acoustically supervised system is to develop strategies that utilize vehicle autonomy. 
An example of more autonomy yielding better range independence is with an approach 
developed during the AUSS interactive sea test/development process for viewing objects on the 
bottom of the ocean. Neither the prototype nor the improved vehicles had side thrusters, and 
hovering over an object in a current proved impossible. With the prototype, pictures of the 
object were taken while the vehicle glided above the object at some forward velocity. The 
operator had to guess when to command the vehicle to take a picture. The combined acoustic 
link/supervisor reaction time increased with range to the vehicle. This process was marginally 
possible for ranges of 2500 feet, and would have been nearly impossible at the maximum range 
of 20,000 feet. 
During the improved vehicle evolution, an autonomous “hover at a radius" algorithm was 
implemented. This simple algorithm is analogous to a boat standing off from a buoy; the vehicle 
points at a position and maintains a given standoff from that position. The vehicle 
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