China said it successfully launched an unmanned spacecraft on Tuesday to carry out a key docking mission, taking its next step toward the goal of building its first space station by 2020. The Shenzhou VIII blasted off from the Gobi desert in China's northwest at 05:58 (21:58 GMT) before separating from its carrier rocket about 200km above the Earth, the state Xinhua news agency said. It is due to join with the Tiangong-1 or "Heavenly Palace" experimental module in two days, in what would be the country's first space docking - a key step in China's ambitious space programme. The ability to dock successfully is crucial to the success of China's ambitions to build a space station where astronauts can live for several months, as they do on the International Space Station.