Inside Unmanned Systems provides actionable business intelligence to decision-makers and influencers operating within the global UAS community. Features include analysis of key technologies, policy/regulatory developments and new product design.
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38 unmanned systems inside December 2016/January 2017 MARINE RESEARCH ed a number of challenges, Jakuba said. For example, there are limits on the types of mate- rials that can be used. "We're not allowed to use any iron-contain- ing alloys and try to avoid hydrocarbons—oils and so forth"—because iron and hydrocarbons can both be significant contaminants, Jakuba told Inside Unmanned Systems. "Iron is a major limiting nutrient in the ocean—so not fertilizing the sample before you take it is a big deal. Hydrocarbon, similarly, can be broken down by microbes—again bio- logically reactive. We don't want to feed them," Jakuba quipped. Finding a way for Clio to move up and down the water column, and to do so with business- smart efficiency, took effort as well. "There are lots of ways to move vertically," Jakuba said, "One is to change your buoyan- cy. That's hard to do especially when you get very deep—buoyancy pumps become pretty challenging, ballast pumps become pretty challenging beyond, say, a couple thousand meters." The team didn't want to use weights, which contain iron. Moreover, he said, "you have to carry them with you, which doesn't support easy logistics." The team settled on having the AUV drive up and down with two built-in thrusters. To save energy that would otherwise have to be expanded while lingering at each sampling depth, they also chose to construct Clio so its compressibility would be as close as possible to that of water. "Buoyancy depends on the density of the background f luid," Jakuba said. "Water be- comes more dense as you go deeper because it is, itself, compressible. The same volume at the surface, at depth its buoyancy will increase. So the vehicle becomes lighter, essentially, as it goes deeper—if it's incompressible. If it's compressible that affect is reduced. Ideally it would be just as compressible as water so its buoyancy wouldn't change." The design team is using a variety of materi- als, some more compressible than others, so the overall compressibility of the vehicle is close to that goal. They are also taking very careful ac- count of the vehicle's buoyancy throughout the whole design process. "Our mechanical design feeds directly into a simulation that estimates the amount of en- ergy required to perform a dive," Jakuba said. The parts for Clio are currently on order and will be assembled over the winter with plans for an ocean test this summer. "The July test will put the machine through its paces," Saito said, to see if it can collect the samples they hope to collect. Photos by Alexander Dorsk (deck), Dawn Moran (orange algae), Purple coral is unattributed Clio uses thrusters to descend and ascend (above, left) and could require only one person on deck, unlike other systems (right). Clio could help scientists understand microbials like algae, seen in purple (above, top) and up close (below).