Thirteen years ago, Johnny Jetpack made his first flight, and over 100 launches later Arnold refuses to stop tinkering on what will forever be a work in progress. You have to protect the technology, of course, so the decision over who gets the parachute — Johnny or the jetpack — is easy. But the jetpack is fragile, and even with a gentle landing, each launch requires roughly 40 hours of preparation. When that kind of time is involved, it’s easy to write it off as a back-to-the-drawing-board situation every launch.

What’s coming next? Water, compressed air, and soda bottles have served Johnny Jetpack well for a while now, but there comes a time when the laws of physics draw a line. Striding over that line, Arnold picks up a canister of liquid nitrogen. “It’s a possibility I’ve been looking at,” he says.

The MythBusters television guys tried to find a way to launch something more mortal than Johnny with 2-liter bottles, but without a good background, they failed despite mounting 15 bottles to a pack. Arnold thinks they just weren’t trying hard enough.

“Improper line of force,” he says, “They concluded that there was no way to launch a person with soda bottles. I don’t agree with that.”

—Dan Gonsiorowski

>>Nathan Arnold’s website: johnnyjetpack.com