NASA Administrator Charles Bolden speaks during a news conference in Berlin on Monday. Bolden said no single country was indispensable to the International Space Station's success. Michael Sohn/AP hide caption

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From left: U.S. astronaut Steve Swanson, and Russian cosmonauts Alexander Skvortsov and Oleg Artemyev prior to the launch of their Soyuz-FG rocket Wednesday at the Baikonur Cosmodrome in Kazakhstan. Dmitry Lovetsky/AP hide caption

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NASA astronaut Chris Cassidy performs a spacewalk in May to inspect and replace a pump controller box on the International Space Station. On Saturday, two astronauts will perform the first in a series of similar spacewalks to fix a broken cooling line on the ISS. AP hide caption

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Canadian Space Agency astronaut Chris Hadfield strums his guitar, a Larrivee Parlor, on the International Space Station in December. NASA hide caption

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The Falcon 9 SpaceX rocket lifted off from space launch complex 40 at the Cape Canaveral Air Force Station in Cape Canaveral, Fla., early Tuesday. John Raoux/AP hide caption

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