Damndest stuff, part 2: Project Pluto
THIS is such a whacked-out idea, I'm suprised BushCo hasn't dug it back out and tryed to update it.
Project Pluto, as conceived, would have been a locomotive-sized nuclear missle, but instead of a single warhead or even a MIRV it would have had a number of bombs it would drop, making it more of an unmanned bomber. Traveling at Mach 3 at "just treetop level" to avoid detection on radar, it would leave behind it a trail of radioactive fallout spewed out of its engine nozzle. When it finally ran out of bombs, it could just fly around, spewing radioactive material, until it finally crashed (and would then be a kind of "dirty bomb", contaminating the crash site).
Research went as far as testing the engine, though flight tests were never done (one idea had the missle flying in a big circle, attached to a tether, like a wire-controlled model plane), and it was ultimately abandoned due to developments in ICBM technology... and the realization of just HOW whacked-out the idea was.
The SF writer Charles Stross has done a "novelette" incorporating the Project Pluto idea; it's on-line here..