Gatekeeper: An untethered, persistent, station-keeping gateway buoy

Tethered buoys have long served as a common gateway for communications between underwater, terrestrial, and air assets. Although common, tethered buoys lack the versatility envisioned with an anchorless buoy that can closely maintain a station or waypoint as long as needed and be remotely commanded to move to another waypoint. Indeed, an untethered gateway buoy would have multiple uses in the defense, commercial and scientific sectors. The predominant challenge to develop an untethered buoy is generating enough energy for the buoy to maintain a station for months in open ocean currents. Falmouth Scientific, Inc. and its partners have developed an untethered, station-keeping, gateway buoy, named Gatekeeper, under an SBIR contract with the U.S. Navy. A spar-shape buoy, Gatekeeper inherently offers superior stability to meet the requirement for a persistent radio and satellite link A bail winch system for dropping and raising an acoustic transducer provides a robust underwater acoustic link. The primary energy and power source for the Gatekeeper is a 35 kilowatt-hour patent-pending Salt Water Activated Power System (SWAPS?), which provides at least 200 Watts of power. The Gatekeeper's SWAPS? uses 55 pounds of an environmentally friendly metal alloy that reacts with saltwater to produce hydrogen for a fuel cell generator. SWAPS? is an order of magnitude better than any battery technology in terms of mass, volume and cost for the same amount of energy. A solar panel array serves as a renewable energy source for the Gatekeeper system in order to preserve the SWAPS? fuel, which is not renewable during deployment. A 2 kilowatt-hour battery is also used to store energy from the SWAPS? and solar panels when the Gatekeeper is idling. Gatekeeper demonstrated excellent navigational and station-keeping capability at speeds up to 2 knots during a SBIR Phase ? sea trial in the Fall of 2008 and operated solely from the SWAPS? and a solar array at speeds up to about 1.5 knots. Gatekeeper is projected to endure deployments that last several weeks with its configuration from the fall of 2008, which is a significant milestone. Improvements to Gatekeeper's endurance will be made in preparation for an at-sea endurance test that is planned for the early spring of 2010.