Inside Unmanned Systems

OCT-NOV 2017

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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37 unmanned systems inside October/November 2017 ENGINEERING. PRACTICE. POLICY. One area of focus for Cahill and her col- leagues is the pollution choking Fairbanks, Alaska's second-largest city. Fairbanks expe- riences what are known as temperature inver- sions, where a layer of warmer air overlies a layer of cool air at the surface. (Under normal conditions, air usually gets colder with height.) Fairbanks' low-level inversions can trap air pollution close to the ground, "giving it some of the worst air in the country," Cahill said. "We've had trouble monitoring and model- ing the inversions in the past, so one thing we hope to do in the winter is to use unmanned aircraft, most likely the Ptarmigan, to take vertical profiles of the atmosphere at low al- titudes during the worst periods, when people are burning wood and a lot of smoke is getting trapped," Cahill said. The hope is to predict "when an inversion sets in and how it sets up so you can maybe tell people to stop burning to protect people's health," she said. The advantage of using unmanned aircraft over manned aircraft or balloons to monitor the air are many. "A helicopter totally mixes up the atmosphere, disrupting what we want to sample," Cahill said. "Balloons can sample the atmosphere going up and down, but they're limited moving horizontally. Unmanned air- craft are a good option — we can vertically and horizontally map pollutants without disturb- ing the atmosphere too much. And unmanned aircraft are great in terms of safety aspects — you don't need to stick a pilot over the heart of a forest fire." One concern when it comes to using UAS to search for air pollution is that the aircraft may disturb the very air they seek to analyze. "We don't want the wash from the rotors to mix the atmosphere too much, so how do we get the air inlet that takes in the air away from the rotor wash?" Cahill said. "We don't place it to the top or the bottom, but to the side. We see a lot of the same difficulties we encoun- tered for years through air monitoring with manned aircraft." " UNMANNED AERIAL VEHICLES CAN BE USED TO TAKE AIR QUALITY SAMPLES IN PLACES WHERE IT WOULD BE HAZARDOUS TO COLLECT YOURSELF, SUCH AS WITH REALLY TOXIC CHEMICALS." Markus Hilpert, associate professor, Columbia University In addition, working in Alaska can pose a number of special challenges. "In the cold, plastic can get brittle, so you can shatter ro- tors—we go to carbon fiber instead," Cahill said. "Icing is also a huge challenge for us, and we actually work with folks to put drones in an icing wind tunnel, doing experiments with de-icing coatings and active de-icing systems that get rid of ice in f light." And there are other problems that most researchers don't face. "In the Arctic we have to guard against polar bears so we don't get eaten," Cahill said. In addition, "the runways we use are often gravel, and we have to be care- ful about what happens when the larger un- manned aircraft land and kick up gravel into instruments." Redundancy is key to successful missions with the drones. "Our largest unmanned air- craft have three different command and con- trol links," Cahill said. "If the 2.4 gigahertz ra- dio channel goes out, we can f ly using Iridium satellite communications and can still get the aircraft back." Right now, testing air pollution in cities re- mains a challenge because of FAA regulations concerning long-distance f lights past line of sight, f lights over people, and f lights where unmanned aircraft might collide with manned aircraft. Still, Cahill noted that through work at their test site and others, the FAA is devel- oping ways that may one day allow unmanned aircraft "to f ly over cities safely, so that they can be used to their fullest potential," she said. "That way we can get the information about the air that we need to protect people."

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