Researchers in Nebraska tested a new tool on Friday that could eventually help in fighting grass fires — drones.

A team from the University of Nebraska-Lincoln flew an unmanned aircraft over the prairie at the Homestead National Monument of America on Friday, dropping ping pong-like balls filled with a chemical mixture to ignite brush-clearing grass fires.

Local and federal officials are interested in the technology because it could help clear overgrown vegetation in rugged, hard-to-reach terrain, said Michael Johnson, a spokesman for the National Park Service.

The balls are filled with a chemical powder, potassium permanganate, before they're loaded into the drone. During flight, the aircraft pierces the ball with a needle and injects it with another chemical, glycol, before releasing it. The mixture ignites one to two minutes later. The technology is already used by helicopters to start controlled burns, but researchers note that the drone is cheaper and more portable.

"You could afford one of these on the back of your fire truck, whereas you probably can't afford to have a full-sized helicopter parked at your fire station," said Carrick Detweiler, a member of the Nebraska research team.

The drone, which is about two feet wide with six rotors — is programmed to drop the balls in a preset pattern to control how the fire spreads. On Friday, the unmanned aircraft rose out of the grass and hummed toward the horizon through a smoky haze. Minutes later, it released the balls one at a time, sparking a series of small fires that quickly grew and merged into one.

Researchers hope the technology eventually could be used to set controlled fires in hard-to-reach places that would clear out brush and small trees and make it more difficult for wildfires to sweep through an area.

The drone is the fourth prototype created by the university's Nebraska Intelligent Mobile Unmanned Systems Laboratory. It carries up to 13 balls and drops them from roughly 65 feet in the air, and carries a little more than one pound of cargo. Depending on the software used, the drones developed so far have cost between $6,000 and $8,000 apiece, said Jim Higgins, an engineering graduate student who has helped with the project. Universities in Colorado, Pennsylvania and Switzerland are exploring similar technology.

Higgins said researchers have had to work out some kinks. In earlier tests, the balls exploded. Another time, one caught fire before it was released from the drone. Another limiting factor is the wind. The lightweight drone could not be used in high winds, which sometimes stoke wildfires.

Sebastian Elbaum, a computer science and engineering professor, said firefighters also could eventually use drones to find hotspots and gather other key information about wildfires.

"It's very, very exciting stuff," Elbaum said. "Today, firefighters have maybe a shovel, maybe their gloves and their helmets. Imagine them having this in their backpack, pulling it out and telling it, 'Hey, go scout out there. Check whether it's hot. Check whether it's safe."

The project began two years ago as a new way to prevent wildfires in Nebraska and other Plains and western states. During a severe drought in 2012, Nebraska saw 1,570 wildfires that burned a total of 786 square miles — an expanse nearly seven times the size of Omaha. The combined costs of ground-level firefighting, aerial suppression and assistance from other states cost Nebraska more than $11 million that year.

Researchers will use Friday's test to examine how fire crews might use drones in the future, said Brittany Duncan, an assistant computer science professor and member of the Nebraska team.

"We want to know how we could display information to firefighters better," she said.