Smithsonian.com has a super interesting piece on the building of the world’s tallest water slide in Kansa City.

From the moment that Jeff Henry, owner of Schlitterbahn Waterparks in Kansas City, Kansas, looked at his partner John Schooley and told him that he wanted to build the world’s tallest water slide, the two men knew that they were venturing into uncharted territory.

“Water slides, like boats, are an evolutionary technology, in which you do one thing and then you learn something, and then you take another step and learn another thing. In this particular ride we jumped a few steps,” Schooley explains. The ride, dubbed Verrückt (which translates to “insane” in German) measures 168-feet tall, approximately 17 stories high—taller than Niagara Falls—and was officially verifed by Guinness World Records as the tallest water slide in the world.

“We pretty much built the ride in house, from start to finish, with some outside consulting from safety experts and engineers,” Schooley says of the Kansas City, Kansas attraction. “A project like this is really a group effort.”

So how does one go about building the world’s tallest water slide—and more importantly, ensuring it’s safe? Amazingly, it’s little more than trial and error…

“The Verrückt water slide was to be a crossover fusion design between water slides and roller coasters. In some ways it was evolutionary in that we already had experience with steep speed slide geometry, rafts and uphill water coaster technology. In others it was revolutionary in that we had to invent and develop several new systems to operate this very large jump from existing technology,” Schooley explains. To begin, they started by calculating the height, dictated by the requirement that the slide snatch the title of “World’s Tallest Water slide” away from the 134-foot tall Insano Water slide in Brazil. Then they plotted the steepness—at what angle would riders plummet down the slide’s first drop? Schooley and Henry settled on 60 degrees, a fairly steep angle that would send riders zipping down the first drop at nearly 65 miles per hour (the typical water slide has a more gentle slope closer to 45 degrees). For the Verrückt, 60 degrees was deemed steep enough to achieve a sense of weightlessness in the rider, but gradual enough that a raft could still maintain good contact with the slide…

Friction and gravity are the two principle forces that dictate how thrilling a ride down a water slide can be (but they’re not the only forces—a rider’s weight, air resistance and the material of the slide, among other things, all come into play). Riders at the top of a water slide begin the ride at rest; once they begin to plummet down the water slide, gravity pulls them downward, increasing their speed. The rider, or in the case of Verrückt, the rider atop a raft, encounters friction with the slide, slowing them down. The key is to balance a rider’s momentum and friction so that they are able to race down the slide at an exhilirating speed without risking their lives.

Schooley’s models could predict some of the friction and G-forces that would act on a rider plummeting down the Verrückt, but drawing precise conclusions from these calculations is tricky because of the as-of-yet unmentioned major component: water.

“What’s really difficult on these slides is that we can know something about friction with the size of the raft and how much weight will be in it, but when you start adding water into the equation, there’s actually no way to really know what’s going to happen in terms of hydraulic friction forces on it other than testing it,” he explains.

Head over to Smithsonian.com to read the full article.