The Air Force is readying the first airborne laser weapon, which could be used to intercept Scud missiles. Mark Farmer takes you inside the project. In a starkly sanitized clean room, a stocky Lockheed Martin engineer wearing a shower cap and laboratory smock scuttles in and about black plastic curtains, talking with near-manic intensity and flashing his bright eyes and wry smile. "Want to see something really cool?" asks Paul Shattuck as he yanks back the curtains, revealing a maze of psychedelically colored optics and black anodized metal hardware. "This," he says, "is what they call the Wall of...