Liberdade class underwater glider

Liberdade class blended wing bodies are autonomous underwater gliders developed by the US Navy Office of Naval Research which use a blended wing body hullform to achieve hydrodynamic efficiency. It is an experimental class whose models were originally intended to track quiet diesel electric submarines in littoral waters, move at 1–3 knots and remain on station for up to six months.[2] The "Liberdade" (Portuguese for "Liberty") was the name of a ship cobbled together by Joshua Slocum prior to the one he single-handedly piloted around the world.

Liberdade XRay underwater glider.jpg
Liberdade XRay1 glider
Class overview
Name: Liberdade wing gliders
Builders: LBI (Connecticut)
Operators: United States United States Navy
Active: ZRay (2010)
Retired: StingRay (2004), XRay1 (2006), XRay2 (2007)
General characteristics
Type: Autonomous blended wing body underwater glider
Beam: 6.1 meters
Speed: 1–3 knots
Range: 1200–1500 km (planned)[1]
Test depth: 300 m
Complement: Unmanned
Sensors and
processing systems:
Hydrophone arrays, vector sensor and electric field sensors
Notes: Acoustic and satellite communications capabilities

Members of the Liberdade class are the world's largest known underwater gliders and were developed as part of the US Navy's Persistent Littoral Undersea Surveillance Network (PlusNet) system of unmanned surveillance vehicles. The gliders can be deployed covertly with the capability of monitoring over 1000 km of ocean. The glider is designed to be difficult to detect using passive acoustic sensing.[2]

The Marine Physical Lab at Scripps Institution of Oceanography, and the Applied Physics Lab at the University of Washington are the primary developers of the Liberdade class.[1] The hull of the latest model was constructed by Legnos Boat, and consists of an ABS outer shell over a titanium frame.[3] First major field tests of the Liberdade XRay took place in 2006 in Monterey Bay, California. Also participating in the development of the Liberdade class wings were:[1]

In 2007, XRay 2 was completed and demonstrated a 20 to 1 lift-to-drag ratio. In 2008, 55 field tests were conducted. In 2010, the latest generation "ZRay" model was completed and includes a 27 channel hydrophone array. Its goal is to track and automatically identify marine mammals.[3] ZRay has a 35 to 1 lift-to-drag ratio,[4] and has water jets for fine attitude control, as well as propulsion on the surface.[3]


  1. ^ a b c Wood, Stephen L. (November 7, 2008), "Autonomous Underwater Gliders", Underwater vehicles (pdf), Florida Institute of Technology, p. 517, retrieved May 26, 2012
  2. ^ a b Liberdade XRay Advanced Underwater Glider, Office of Naval Research, April 19, 2006, retrieved May 25, 2012
  3. ^ a b c Hildebrand, John A.; D'Spain, Gerald L.; Roch, Marie A. (November 10, 2010), Glider-based Passive Acoustic Monitoring Techniques in the Southern California Region (PDF), Office of Naval Research, retrieved May 25, 2012
  4. ^ D'Spain, Gerald L., XRay/ZRay Gliders, Scripps Institution of Oceanography, retrieved May 25, 2012[permanent dead link]