As Hurricane Maria roared northward, Joseph Cione, a research meteorologist with the NOAA Hurricane Research Division, was staring at a computer screen and bouncing in his seat aboard a NOAA P-3 Orion, well inside the storm. Also aboard were seven Coyotes, small disposable remotely operated vehicles built by Raytheon and designed for military reconnaissance. Cione wanted to see if the drones could collect data from the lowest levels of a hurricane where it’s hard for scientists to reach.
The Coyotes, wrapped inside a protective sleeve, weigh only 13 pounds and have a wingspan of five feet—not much larger than some flyable model airplanes. The P-3 deploys them from its dropsonde-dropper with a small parachute. But, unlike the dropsonde, when the Coyote is free of its protective sleeve, its wings and rudders swing into flying position. Each Coyote can fly for about one hour, piloted remotely by a Raytheon representative aboard the P-3, before its battery fails and the tiny drones fall into the ocean.
The Coyotes were deployed, one by one, to determine the radius, top speed, and exact location of Maria’s maximum winds. That data is critical to forecasting potential wind damage, storm surge and could have a major impact on storm evacuations. Maria had already passed over Puerto Rico, devastating the island, and forecasters were eager to know how badly it would impact the mainland; although in this case the Coyote-drop was an experiment, it returned useful data.
Because the Coyotes go places that are too turbulent and dangerous for crewed aircraft, where winds exceed 100 mph and waves reach up to 60 feet, recovery is impossible.
“We did a few of these with [Hurricane] Edouard back in 2014 but we had some engineering hurdles,” says Cione. “That was the first time an air deployed UAS [unmanned aerial system] went into a hurricane.” But the Coyote could only venture a couple of miles from the P-3, and not much useful data came back. “So we spent some time, basically three years, to get the range higher and to get a better sensor package. We did more testing, and then we had to get the right storm. And that right storm was just two weeks ago.”
The extended time off proved worthwhile. During Hurricane Maria the Coyotes proved able to operate up to 35 miles away from their P-3 mothership. Four of the aircraft “worked remarkably well” and provided “extraordinary data,” says Cione. Three of those aircraft flew within the hurricane’s eyewall at low altitude, a feat that crewed hurricane hunters cannot risk. While the small aircraft were tempest-tossed, essentially hitchhiking on the swirling winds, they only made it part way around the eye wall before they were lost.
“That first flight we flew about 42 minutes, and we had controlled flight down to about 400 feet,” says Cione. (For safety, NOAA flies their P-3s at 8,000 feet, and prefers 10,000.) “That was actually the best we did. The other two eyewall missions got down to 1,100 feet” before the aircraft were lost. It’s also where the strongest winds were found. “We measured 143 mph, which to my knowledge is a record for UAS wind speed recorded anywhere,” says Cione. “This is a pretty violent environment.”
Cione still has one of the seven Coyotes left. He wants that aircraft to make a complete orbit within the eyewall, because he’s convinced that will reveal where to find the highest winds. He has until mid-November, when hurricane season ends, to make that happen. It’s been a busy season so far, so he might not have long to wait.