The Office of Naval Research has successfully tested a new guidance system for cannon shells able to achieve accuracies of under 20m CEP (and probably a lot less). The system includes GPS, six micro-sensors, and pop-out control fins. The system, screwed into the front of the shell, costs about $2,000, but if it reduces the number of $750 shells which must be fired at a given target, it may be worth it. The Navy says it can now destroy with three shells what used to take 30.--Stephen V Cole