No alliances, just teams. No bikinis, just coveralls. No rats, just--well, if there are rats under those junk piles, at least we never see them. Over the last year, this engineering showdown (which airs new episodes starting Sept. 12) quietly became the class of the reality-TV field, turning groups of tinkerers loose on a scrap heap to build cannons, gliders, rockets and the like out of detritus, then pit their improvised creations against each other. With humor and an adorable host (Cathy Rogers, the thinking viewer's Julie Chen)--and without the robo-macho aggressiveness of Comedy Central's BattleBots--Junkyard shows that, sometimes, making smart, escapist TV is rocket science.