A large segment of a Chinese rocket is expected to make an uncontrolled re-entry into the Earth's atmosphere on the weekend, but Beijing has downplayed fears and said there is a very low risk of any damage. A Long March-5B rocket launched the first module of China's new space station into Earth's orbit on April 29. Its 18-tonne main segment is now in freefall and experts have said it is difficult to say precisely where and when it will re-enter the atmosphere. Re-entry is expected to be around 2300 GMT on Saturday, according to the Pentagon, with a window of nine hours either side. Chinese authorities have said most of the rocket components would likely be destroyed on re-entry.