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