ITS name means “heavenly palace”. But Tiangong-1, an eight-tonne Chinese space station launched in 2011, will not remain in the heavens much longer. After visits from crews in 2012 and 2013, Tiangong-1’s mission officially ended in March 2016. A few months later China’s space agency appeared to confirm what amateur skywatchers had already suspected, that it had lost control of the station. It said it expected Tiangong-1 to fall from the sky sometime late in 2017.
In fact, the station is still up there, orbiting at an average height of 250km. But the inaccuracy of the agency’s prediction is understandable. At low altitudes (anything under about 2,000km), orbital mechanics is a surprisingly imprecise science. Earth’s thin outer atmosphere exerts a measurable drag on anything in such an orbit, and this drag means that, without regular boosts, that object will fall out of orbit eventually. The drag itself, however, is not constant. So exactly when this fiery fall will...Continue reading
Source: Science and technology http://ift.tt/2peTadh
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