Chinese astronauts step out of spacecraft

Before Sunday, Chinese astronauts had conducted only one other spacewalk－by Liu and Zhai Zhigang during the three-day Shenzhou VII mission in September 2008. Another crew member in that mission－Jing Haipeng－remained in their spacecraft to control and monitor equipment.

During the operation, Zhai stayed out of the spacecraft for about 15 minutes while Liu moved the upper half of his body out of the craft for several minutes to assist him.

Their short adventure made China the third nation, after the former Soviet Union and the United States, able to independently conduct a spacewalk.

According to Ji Qiming, assistant director of the China Manned Space Agency, the Shenzhou XII crew will make two lengthy spacewalks to use the robotic arm to install equipment and check the Tianhe module's external condition.

Aside from the spacewalk, the robotic arm the astronauts used on Sunday was another highlight because it is the largest, strongest and most advanced apparatus of its kind ever built by China, according to Liang Changchun, a chief designer of the machine at the China Academy of Space Technology.

Fully extended, the robotic arm is 10.2 meters long, and it can handle payloads weighing up to 25 metric tons. It has seven motorized joints that allow it to act, to the greatest extent possible, like a human arm.

It is self-relocatable and can reach many parts of the module through an inchworm-like motion, Liang said.

The first person to ever go on a spacewalk was Alexei Leonov, of the Soviet Union, who stayed more than 12 minutes outside the Voskhod 2 spacecraft on March 18, 1965.

By now, 232 astronauts, mostly American and Russian, have made spacewalks.