Perpetual motion over the oceans in perfect silence with no helmsman seems like a stretch of the imagination at first sight, shades of the Marie Celeste, but the autonomous maritime drone has become a reality with Liquid Robotic’s Wave Glider which has been successfully operated by the National Ocean and Atmospheric Administration, Woods Hole and others to obtain oceanographic research data.
Recently the California-based company, with a marine operations arm in Hawaii, announced it had gained a $22 million support investment from lead financier VantagePoint Capital Partners to work on the development of drones that may herald their deployment in diverse roles – naval warfare, customs and immigration surveillance, anti-terrorism, and anti-piracy.
Wave Glider – Photo: Liquid Robotics
Wave Glider Essentials
Current flagship Wave Glider is just 2.08 meters in length with a mass of 90 kg, while below a much smaller ‘glider’ (40 cm x 191 cm) with 107 cm wide wings is tethered underwater on a 7 meter cable. The surface craft sits low in the water and can endure briefly a 2 meter ducking below the surface in rough weather.
Propulsion is achieved by the mechanical conversion of wave energy (generated by the motion of the float and submerged glider together) giving a maximum speed speed of 2.0 knots. On deck solar panels provide up to 80 Watts to charge 665 Watt-hours Lithium-ion batteries which are used to power-up onboard electronics systems.
Wave Glider 'Full Speed Ahead' – Photo: Liquid Robotics
Wave Glider Navigation and Safety
Shore control is exercised via satellite using chart-based GUI (Graphical User Interface) with waypoint and course generation; feedback to ‘mission control’ is transmitted from the drone’s onboard GPS receiver and heading sensor by short-burst data modem. Altogether, quite an electronic punch is delivered by the craft’s standard modules that include: acoustic modem, AIS, meteorological sensors and passive acoustic recorder. The layout also allows third-party payloads to be fitted as required for other operations.
Visual warning of the drone’s presence comes from a shore-activated marker light, with the option of a RF beacon (presumably RACON or RAMARK) for radar identification by other vessels. Environmentally sensitive to marine life, if by chance, some denizen of the deep becomes entangled with the underwater tether then a pressure-activated release separates the float from the underwater glider.
The Solar Sailor Concept Unmanned Ocean Vessel
Sources indicate a growing interest in the market for this type of unmanned craft technology. In his 6, July 2011 address to a RINA technical meeting in Sydney, Australia, John Lord, Project Manager of Solar Sailor Holdings talked about his company’s patented concept ‘Unmanned Ocean Vessel’ (SS-UOV). Essentially this is a sailing vessel with a unique fold-down SolarSail™ that provides 99% of propulsion requirements, with electrical storage in lithium-ion batteries to power sail and steering controls, communications and other ‘smart’ systems; military, surveillance or oceanographic research roles are similarly envisaged for this Solar Sailor drone on the drawing board.