BEIJING (AP) — Three Chinese astronauts emerged from their capsule Sunday after a milestone mission to carry out the country’s first spacewalk, showing off China’s technological know-how and cementing its status as a space power and future competitor to the United States. A senior space official said the mission — China’s most ambitious yet — took the country one step closer in its plan to build a space station and then to land a man on the moon. Wang Zhaoyao, deputy director of manned space flight, said the program is looking to launch a new orbiting vehicle and set up a simple space lab by 2011.