If he´s lucky, when he turns the throttle, his 90 percent hydrogen peroxide will expand to 5,000 times its size and convert to steam that will reach 1,300�F. If he´s lucky, he will then be thrust 30 feet into the air, where he will fly for as long as 30 seconds, all while tethered to a 20-foot safety pole. If he´s lucky, self-taught Mexican rocket scientist Juan Manuel Lozano will someday become one of just a handful of people in history to make an untethered flight with a rocket belt.

Amateur rocketeers from all over North America are converging in Lethbridge, Canada, this weekend for the 24th annual Large Dangerous Rocket Ship convention. Some come to launch small kits, others to fire up giant home-brewed rocket motors, but everyone enjoys the thrill of a good explosion. Check out our preview of this year's event, from July's Popular Science.

The visitor who pulls up to this upstate New York hayfield on a sunny July Saturday afternoon might well wonder whether he’s stumbled upon a 4-H Club event or a third-world arms bazaar. There’s a