Tough Mudder vet Nicholas Horbaczew­ski created the Drone Racing League in early 2015 to appeal to video game and Formula One fanatics. The business, in New York City, has raised more than $8 million--despite a rocky debut that taught Horbaczewski the danger of overpromising and underdelivering.

-- As told to Leigh Buchanan

Early on, we confidently invited a group of angels and VCs to attend our first race, which we billed as the Grand Prix of Drone Racing. At Drone Racing League, we mount cameras on our drones and release video after each race on our YouTube channel,  Facebook, and  Twitch, so that viewers feel like they are actually inside the tiny vehicles. For this debut event, we assumed our big challenge would be things like judging and scoring. Building the drones, we thought, would be easy. Dozens of vendors and experts recommended circuit boards, flight controllers, and other parts, promising they would be silver bullets. We conducted flight tests for months. It turned out, there was no end to the ways those drones could fail.

Two months before the event, we realized we had to build the drones from scratch. Clearly, we would not be able to pull off the dazzling race I'd envisioned. I felt chagrin about underestimating what it would take and setting expectations too high. I had to go back and reset those expectations. While my team dug into design and arranged manufacturing, I personally visited each of our potential investors and told them all that I wasn't going to deliver what I thought I could deliver. Instead of the Grand Prix, they would see some racing and a technical demonstration: essentially, proof of concept. It was a humbling experience. I could only hope they still saw the promise as I did.

The event was set for an abandoned power plant in Yonkers, New York--aptly nicknamed the Gates of Hell. We had hoped to bring 120 completed drones. (Drones crash repeatedly, so pilots constantly need a new supply.) We had 12, some with parts missing. Nine pilots came from as far off as Australia. We had only enough drones for six to participate.

Most of the potential investors came--but they were skeptical. We'd explained that we realized just how hard this was going to be to pull off. Compared with what we'd promised, the event was a disappointment. But for the investors, who had never seen anything like this outside of a science fiction movie or a video game and had no idea what to expect, it was enormously educational. And there were enough moments of greatness--such as six drones flying at top speed practically on top of one another through the arch of a massive room--that they could see the vision. Afterward, almost all the attendees invested. Our first round was oversubscribed. We've since produced a race in Miami, which has been viewed more than 43 million times. A race in Los Angeles will soon be released. But that early experience taught us that you have to sell potential partners on your vision while being brutally realistic about what it will take to achieve it.