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Nereid HT hybrid ROV and AUV underwater robot during engineering sea trials off Panama for specialized high voltage power supplies. Nereid HT is powered by rechargeable lithium ion batteries in a custom WHOI casing. They can be trickle charged and spent battery packs swapped over quickly—each with a 12- hour endurance. Bowen admits that for now, this places some limitations on the endurance of the robot. But the pace of change in battery technology improvement is now very rapid, going hand-in-hand with developments in electric car design. So he is confident that this will be less of a factor going forward as greater amounts of power can be stored onboard the vehicle. “More onboard power could enable extension of the vehicle’s capabilities eventually allowing it to take over some of the tasks normally reserved for heavy work class ROVs,” said Bowen. The tether also contributes to making launch and retrieval operations simpler and

54 Marine Log // November 2016

faster, and needing less crew intervention. The final 100 meters is specially designed to have varying density vs. length, so that the tether naturally forms an “S” shape without the need to externally add weight or floats. This gives the vehicle enough freedom from the ship, decoupling the Nereid from the ship’s movements, allowing more streamlined operations and may make missions in a higher sea state possible. This new tether design was used to successfully support ROV-type operations at 2,500 meters for the first time in Panama. The Dalio Foundation supported the vehicle development, and as part of its Dalio Ocean Initiative also made the expeditionary vessel Alucia available. The Alucia, a 55 meter vessel, originally built in 1974, was extensively refitted between 2008 and 2012 for its current science and filming role. “What we are trying to do onboard Alucia

is to give the ship, and others like her, the capability to access depths that would be impossible for a ship of this type using conventional technology — we are aiming for 5,000 meters using this novel, lightweight reusable umbilical system. It’s a much smaller diameter tether than would typically be used for ROVs of this size and capability.” said Bowen. When operating as a tetherless ROV WHOI’s new optical modem technology, provides the operators with real-time control, including full motion video uplinks and direct downlink control of thrusters, manipulators, etc. The optical modem introduces high-speed broadband capabilities to the deep ocean. The revolutionary WHOIdesigned system allows total control over the vehicle off tether. Norman Farr, Optical Engineer, WHOI, and designer of the system, says, “We can wirelessly control the untethered vehicle in autonomous mode while transmitting live video back to the pilot. Its very exciting to have a link that is just rock solid, one that you don’t really have to worry about, I feel that all of our work has paid off.” It took the team over five years to reduce the form factor of the modem to a workable size. The current modem operates using LEDs. The wavelength of light used is determined by the operating depth and levels of ambient light. Most of the time in the biologically productive coastal waters of Panama 50 meters was achieved. Earlier tests confirm that in clearer water conditions a range of up to 100 meters is to be expected. In Panama, bi-directional communications worked effectively at over 10 MB/s, technically speeds of 20 MB/s is possible permitting full HD video transmission live from the vehicle to the ship with no latency. Its highly portable control systems have also been designed so that a dedicated ROV control van is no longer needed. This usually

© Luis Lamar, Woods Hole Oceanographic Institute (WHOI)


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November 2016 Marine Log  

November 2016 Marine Log  

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