(05/06/1969) -- Astronaut John W. Young suits up for the Apollo 10 Countdown Demonstration Test (CDDT) which ended successfully at 1:01 p.m. today, clearing the way for a May 18 launch. Young, command module pilot, will keep lonely vigil in lunar orbit while Thomas P. Stafford, commander, and Eugene A. Cernan, lunar module pilot, drop to within 10 miles of the Moon in the lunar module before returning to the parent spacecraft.