BEIJING (AP) — China's defunct and reportedly out-of-control Tiangong 1 space station is expected to re-enter Earth's atmosphere sometime this weekend. It poses only a slight risk to people and property on the ground, since most of the bus-size, 8.5-ton vehicle is expected to burn up on re-entry, although space agencies don't know exactly when or where that will happen.

Below are some questions and answers about the station, its re-entry and the past and future of China's ambitious space program.

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WHAT WILL HAPPEN AND HOW GREAT IS THE DANGER?

The European Space Agency predicts the station w...