China launched a three-man crew into space Thursday, including one who will make the country's first spacewalk - its most challenging mission since its first orbital flight in 2003. The Shenzhou 7 spacecraft, China's third manned mission, blasted off atop a Long March 2F rocket into a clear night sky in northwestern China. The spacewalk could occur either Friday or Saturday, depending on how well the astronauts adapt to weightlessness and other physical demands of their environment, according to the China Manned Space Engineering Office. The astronauts would return to Earth soon afterward, the office said.

Underscoring the mission's weighty political overtones, President Hu Jintao was shown live on state television before blastoff praising the crew at the launch site near the northwestern town of Jiuquan.

"You will definitely accomplish this glorious and sacred mission. The motherland and the people are looking forward to your triumphant return," Hu told the three, who were dressed in their flight suits and stood behind glass to avoid germs.

Following the announcement of a successful launch, Hu congratulated the crew and ground controllers, calling it the "first victory of the Shenzhou 7 mission."

The launch was carried live on state television in a display of China's growing confidence in the 16-year manned space program. Shortly before the transmission ended, one of the crew reported in that all were in good condition and had extended the three-module spacecraft's solar panels.

The mission, expected to last three to four days, is devoted almost entirely to the spacewalk. The event is expected to help China master the technology for docking two orbiters to create China's first space station in the next few years.

The two astronauts who don spacesuits for the Shenzhou 7 spacewalk will be supported by Russian experts throughout the mission. Only one will actually leave the orbiter to retrieve scientific experiments placed outside. One of the astronauts will wear China's homemade Feitian suit, while the other will wear a Russian-made suit.

Zhai Zhigang, an unsuccessful candidate for two earlier missions, has been touted by the official Xinhua News Agency as the leading astronaut to carry out the spacewalk, expected to last about 40 minutes. He is joined in the craft by Jing Haipeng and Liu Boming. All are 42-year-old fighter pilots with more than 1,000 hours of flying time.

China's last manned mission was in 2005, two years after the country first put a man into orbit. Dean Cheng, an expert on the Chinese space program, said the additional year China took in launching Shenzhou 7 may reflect a desire for caution in the face of the complexity of walking in space.

"This is part of a sustained, methodical effort," said Cheng, of the Center for Naval Analyses Corp. in Alexandria (web|news), Va.