Shuttle Discovery launch uncertain

With the space shuttle Discovery slated for launch on October 23, NASA is trying to decide whether three of the reinforced carbon panels protecting the leading edges of the spacecraft's wings need replacing. The outer coating on the panels has experienced "degradation" from an unknown cause. Some engineers are optimistic, noting that Discovery has flown twice with this problem and not experienced any further degradation or resulting difficulties. Others are still unnverved by the "unknown cause" part of the equation.