The Goliath, a brand-new roller coaster at Six Flags New England, stands 200 feet high, reaches speeds of 65 miles per hour, and pulls 4 G's of force – half the max felt by fighter pilots. Riders dangle beneath its 1,204 feet of track as it plunges and twists in corkscrew cobra rolls. It is a marvel of coaster engineering.

As Goliath's first-ever white-knuckled riders whiz by on a sunny spring day, its creator stands back, arms folded, taking in the screams and looking pretty pleased with himself. "We could actually knock you out if we wanted to," says Larry Chickola. "The science is bringing you to that edge." As Six Flags' chief engineer, Chickola presides over the nation's largest fleet of coasters (120) and 680 other thrill rides in 19 amusement parks throughout North America. His expertise is in finding that sweet spot between terror and exhilaration.

"Some rides are about height, some speed," he says. "And on some, we're gonna mush you, fling you, really work you over. Goliath is that action ride – we're letting you know we're putting some forces on you."

A former mechanical engineer at Hughes Aircraft, where he designed hinges and gears for spacesatellites – "things that could fit in a bread basket and cost $1 million" – Chickola says he'd always wanted to make "something huge." The Detroit native got his chance in 1995, when Six Flags asked him to overhaul a 21-year-old coaster, Runaway Mine Train, at a park in New Jersey. He rejiggered everything, from its cars, brakes, and motor to its computer operating system. Six years later, he was one of the top coaster engineers in the country.

In his button-down, belted khakis, and worn-to-a-shine loafers, 48-year-old Chickola looks equal parts giddy kid and geeky genius. He sometimes sketches coaster ideas on napkins. Some of these concepts are more ambitious than practical, such as one to build a coaster with seats that spin, as if somersaulting. (When he tested it on a 3D computer program, now an industry staple, "the riders went upside down at the wrong time," he says. "It would not have been fun.")

Chickola usually spends 12 to 14 months taking a coaster from napkin to reality, working with a team of 10 engineers and an army of outside construction firms, electricians, carpenters, and ironworkers. "I love how we can mimic the sensation of flying," he says. "But we want you to be scared, not crippled."

Chickola earned cult celebrity last year after he redesigned Six Flags' beloved Texas Giant at its park in Arlington, Texas. After 20 years, the 143-foot-tall wooden coaster needed constant track and bolt replacements. But fans worried that improvements would ruin its rough-hewn look and the nail-biting appeal of its rickety climb to the peak.

Chickola decided on a new steel-rail fabricating technique that would not only make the ride smoother but also allow for steeper hills and more treacherous turns. At the same time, it would allow him to keep the ride's wood exterior. It was voted Best New Ride of 2011 by Amusement Today magazine.

"Larry has had an amazing impact on this industry," says David Lipnicky of American Coaster Enthusiasts, the nation's largest roller-coaster preservation group. "No one has ever turned an old wooden coaster into a hybrid coaster. It was a big risk."

Roller-coaster physics haven't changed much since the ride was invented in France more than 200 years ago. Basically, you ratchet a train up a track and let it go. But computers have advanced the design process considerably over the past 15 years. Chickola works with systems that brake cars at points along the ride – meaning they can go much faster in certain parts because you can slow them down in others; this helps him take rides ever closer to those maximum G-forces. For Chickola, figuring out how to push those limits while keeping rides fun – not sickening – is the next frontier of coaster design.

You'll rarely find Chickola hurtling through the sky for thrills, though. Based at Six Flags' New Jersey park, he spends his mornings kayaking and fishing on its 70-acre lake. When the park is closed, you may see him rappelling off the steel struts of coasters to perform maintenance and safety checks – a skill he picked up after he took the Six Flags job. "I've actually rappelled off the world's tallest coaster," he says. That would be the park's 456-foot Kingda Ka. "But I don't climb rocks. I only like to do coasters."