In the 1970s, the United States began developing a new generation of reusable orbital spacecraft known as the Space Shuttle, and launched a range of unmanned probes. The USSR continued to develop space station technology with the Salyut program and Mir ('Peace' or 'World', depending on the context) space station, supported by Soyuz spacecraft. They developed their own large space shuttle under the Buran program. However, the USSR dissolved in 1991 and the remains of its space program were distributed to various Eastern European countries. The United States and Russia would work together in space with the ShuttleMir Program, and again with the International Space Station.

Answer this question, if possible (if impossible, reply "unanswerable"): What year did the USSR disband?
1991