14 Juli 2011

Underwater Gliders for the US Navy

14 Juli 2011

Slocum Glider UUV (all photos : Defense Industry Daily/Hydro Interntional/AUVAC)

Teledyne Brown Engineering, Inc., in Huntsville, AL recently received approval from the U.S. Navy to move into the Full Rate Production (FRP) Phase on the underwater Littoral Battlespace Sensing-Glider (LBS-G) Program. The first Full Rate Production option calls for the manufacture of 35 gliders, with additional options for 100 more, and a total contract value of $53.1 million if all options are exercised. US Space and Naval Warfare Systems Command manages the contract.

The Teledyne Team has already delivered 15 Low Rate Initial Production LBS-Gs to the US Navy’s Program Executive Office for C4I, under a December 2010 contract. That team includes Teledyne Brown (System Integration), Teledyne Webb Research in East Falmouth, MA (Slocum Glider development and production), and the University of Washington – Applied Physics Lab (Glider Operations Center software). Their 2m long design features a very innovative propulsion concept…

Teledyne’s glider uses changes in buoyancy to propel itself through the ocean. Instead of using mechanical means to change that buoyancy, however, it mostly relies on the ocean’s own temperature and pressure changes.

To sink, a valve allows oil from a flexible bladder on the outside to flow in, lowering volume but keeping mass constant. The glider sinks. Liquid wax inside internal tubes shrinks and solidifies as it descends into colder waters, letting oil in. The glider will continue descending to about 5,000 feet, then another internal storage tank filled with oil and nitrogen at 3,000 psi pressure is used to force oil back into the external bladder. As the now-buoyant glider heads toward the surface, its wings provide lift and forward motion, while sensors in the nose gather oceanographic data.

The glider will eventually surface about 5 km/ 2.75 miles away, where surface water temperatures of about 80F/ 27C liquefy the wax again. Liquids can’t really be compressed, so the liquid wax forces the oil and nitrogen back into the storage tank, resetting the gas “spring” for use in the next cycle. At the surface, the glider reports its position, transmits data via satellite, and receives any sent commands.

That propulsion system means the glider can be at sea for weeks at a time, allowing subsurface sampling on a regional scale. In 2009, a Slocum Glider managed to cross the Atlantic in 223 days.
The US Navy plans to use its fleet of deep and shallow water LBS gliders to acquire critical oceanographic data, which will improve positioning of fleets during naval maneuvers. It also has obvious uses for submarine hunting, and hiding, given the effect of temperature layers on sonar propagation.

(Defense Industry Daily)

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