The spectacular performance of the Patriot missile, which is shown in a file photo, promises big returns for its maker, Raytheon Co. While overwhelming superiority may not be proved yet, the perception has translated into requests from foreign customers for the missiles, which, including the radar and ground control system, cost more than $1 million each. Analysts predict there will be more demand. In a few days of fighting, the anti-missile missiles have destroyed a dozen or more Iraqi-fired Scud missiles. Raytheon says it has tightened security around its 6,000-employee plant near Boston.