In the spring of 2015, André Borschberg and Bertrand Piccard set out to do something that no one had ever done before–fly an airplane, known as the Solar Impulse 2, around the globe without any fuel. Entirely solar-powered, the plane took 15 months to fly more than 22,000 death-defying miles. But Borschberg and Piccard succeeded–and perhaps showed the world just how powerful solar energy can be.

This week, PBS will debut The Impossible Flight, a Nova documentary film about the Solar Impulse project. Fast Company recently spoke with the film’s producers, Quinn Kanaly and Noel Dockstader, about spending more than a year alongside the Solar Impulse pilots and engineers.

Fast Company: Tell me about the Nova project.

Noel Dockstader:
In a nutshell, it’s about two men trying to fly to the moon to help save the planet. Throughout, you begin to realize just how close they are to the edge of what’s possible in terms of solar flight. They’re doing something that nobody’s done before, that’s a major technical challenge. But it also brings up a lot of psychological elements, and personality differences between people like engineers who are trained to engineer for safety and security, and non-risk, whereas the nature of adventure is to do something that’s never been done before, that’s simply not possible.

FC: What was Solar Impulse’s goal?

Quinn Kanaly: To fly around the world without a drop of fuel. They started in Abu Dhabi in March, 2015. They thought it would only take 3-5 months, and ultimately, it took about 17 months.

It was a roller coaster of emotions, of setbacks, of technical and…