Defense Technology International - April 2008 - (Page 12) TECH WATCH JORIS JANSSEN LOK STEALTHY AS SHRIMP Autonomous underwater vehicles have a way to go before reaching maturity, but eventually will be vital components of maritime forces due to their versatility and ability to mimic marine life. At the recent annual program review conference of the Assn. for Unmanned Vehicle Systems International in Washington, the U.S. Office of Naval Research (ONR) discussed how it is developing AUV technologies in conjunction with marine biologists. Autonomous sensing is the theme in underwater systems development, says Thomas Swean, team leader for ocean engineering and marine systems and science at ONR. This includes work in oceanography, MARINE PHYSICAL LABORATORY hydrodynamic mechanism and neuron control. ONR is working to characterize the hydrodynamics and neuromuscular function of the pectoral fins of fish to develop high-lift maneuvering devices, says Swean. The kinematics and material properties of fish fins are analyzed and incorporated into advanced modeling and simulation programs to aid in component design. ONR is also developing next-generation muscle-like actuators from conductive polymers. The ultimate step is to fabricate a fully functioning, low-aspect-ratio pectoral fin out of such polymers for use in a maneuvering propulsion system. XRay prototype underwater glider is a self-adapting, high-lift/lowdrag vehicle that can be fitted with a large-aperture sensor array. mine countermeasures, naval special warfare, anti-submarine warfare and intelligence, surveillance and reconnaissance. “We’re looking at developing mobile, scalable, persistent networks that are easy to deploy so we can maximize options, and that are affordable so we can afford to lose a unit,” Swean says. Under the Defense Dept.’s multidisciplinary university research initiative, ONR is involved in a five-year program to enhance the maneuverability and stealth of AUVs for the Navy. Swean says the systems-oriented science and engineering research involves the development of an integrated artificial muscle in addition to a high-lift, bioThis will result in a self-propelled line array, or Spline, which Swean describes as an innovative solution for distributed network systems. The Spline will be an autonomous array of fin-maneuvered hydrophone elements, which are controlled by nonlinear algorithms based on neuroscience, and will feature high-lift hydrodynamics inspired by the movements of fish and birds. A key element of a Spline system will be what ONR calls a “biomimetic AUV,” two of which should be able to maneuver on command a linear sensor array into an orientation and maintain it on station for weeks, says Swean. The biorobotic Spline could “swim around” in the ocean for months, says Swean, acting as an early-warning system to detect hostile submarines. Its fins could be used to orient the array in any plane. “We’re planning to test the Spline concept in a couple of years to see if we can do this in the ocean,” Swean says. The bio-inspired approach will yield what he calls “shark-like lowpower consumption, shrimp-like low noise and fish-like low-speed maneuverability.” Several institutions are partners with ONR on the Spline development, including the Massachusetts Institute of Technology and New York University Medical Center. The Scripps Institute of Oceanography and the University of Washington’s Applied Physics Lab are working with ONR on another effort to adapt flying-wing-design technology for underwater gliders. The objective is to create self-controlled and selfadapting, high-lift/low-drag vehicles with a large-aperture sensor array capable of persistent area missions. More than 70 “flights” were made in 2007 with XRay, the first prototype of the Liberdade series of underwater gliders, says Swean. Features of the glider include active pitch, roll and heading control; spiral flight allowing for good station-keeping and synthetic-aperture sensing; creeping flight to minimize noise generation and energy consumption; and the ability to perform knife-edge maneuvers to create a vertical sensor aperture. Another underwater vehicle, the Slocum thermal glider, has been developed by the Woods Hole Oceanographic Institution and Webb Research Corp. Slocum is a long-range, high-endurance AUV that relies on environmental temperature variations for propulsion energy. Slocum can operate at depths of 1,200 meters (4,000 ft.) for as long as 3-5 years, and should be able to negotiate 70% of the oceans, says Swean. In a trial last December, the Slocum prototype traveled uninterrupted across the 4,000-meter-deep Virgin Islands Basin between St. Thomas and St. Croix. “As of Feb. 9, the vehicle had covered 1,450 km. (783 naut. mi.), and was still in the water as of the end of February,” Swean says. I AviationWeek.com/dti 12 DEFENSE TECHNOLOGY INTERNATIONAL APRIL 2008 http://AviationWeek.com/dti
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