Drones–aerial robots that carry visual sensors, navigation systems, and weapons–are saving the lives of American military personnel by enabling them to spy on and kill enemies from thousands of miles away. They’re giving law enforcement a leg up on catching criminals, and could eventually assist search and rescue missions through extreme surveillance methods.

But they’re mired in controversy. Drones–also known as remotely piloted aircraft and unmanned aerial vehicles (UAVs)–have accidentally killed innocent civilians and opened the door for increased invasion of privacy. A possible future of completely autonomous spying, surveying, and killing machines feeds into our darkest sci-fi nightmares.

In Rise of the Drones, NOVA addresses many of those ethical and political challenges through an explanation of the technology. Filmmakers of the hourlong documentary–which airs Jan. 23 on PBS–gained unprecedented access to drone scientists, engineers, and pilots to explain how the drones work, how they’re piloted, their history, and future.

“There were two main challenges in making this film,” producer/director Peter Yost told us. “The first was getting access–with cameras. A few years ago, it might not have been as challenging. But in recent months, it’s gotten harder. I think we had highly unusual access, if not unprecedented, to the training and inside working of these systems.

“The second, more difficult challenge was figuring out how to craft a story around a subject that is so sprawling,” he adds. “This technology affects everything from our most local privacy issues to the most far-off international ethical questions. We ultimately solved it by basing the film around the technology, showing people what these things are and how they work, which very few news reports have done up until now. We often hear debates about how can and should they be used, without necessarily fully understanding what they are.”

The film is punctuated with assessments from several drone experts–Abraham Karem, the aeronautics pioneer known as the “father of the Predator”; retired Air Force Lieutenant General David Deptula, who played a major role in the military’s transition to remotely piloted aircraft; University of Pennsylvania scientist Vijay Kumar, who develops environmentally sensing drones; and Dr. Peter W. Singer, senior fellow and director of the 21st Century Defense Initiative at the Brookings Institute, and author of Wired for War. Along with Yost, they elaborated upon some of the film’s topics at a PBS press conference last week.