Assembling gingerbread houses with spicy cookie sheets and thick gobs of white frosting is a minor trick of engineering; if the cookies don't fit together perfectly, a little more frosting usually does the trick. Unfortunately, shipbuilders assembling complicated naval vessels from 25-ton, 50-foot metal sheets don't have the same kind of luxury. Currently, up to 25 percent of the cost of welding ships is the result of correcting weld defects. By combining low-cost infrared sensors with predictive modeling techniques, ONR-sponsored researchers have developed a new welding technique that promises to save the Navy $10 million per year at Ingalls shipyard alone. Welders mount the sensor adjacent to the welding arc to assess changes in surface temperature distribution of the sections about to be welded. Information gathered by the sensor is fed into a computer model that modifies in real time the welding machine's arc voltage and current in real time to create the best seam possible the first time around.