The Orion capsule is poised to make its first test flight Thursday. If all goes as planned, the unmanned vehicle will orbit Earth twice before splashing into the Pacific Ocean. Kim Shiflett/NASA hide caption

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International Space Station Commander Barry "Butch" Wilmore holds up the first object made in space with 3-D printing on Nov. 25. NASA hide caption

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A member of the Indian security force keeps watch over a launch vehicle carrying the Mars Orbiter probe at the Indian Space Research Organization facility, in Sriharikota, in 2013. AFP/Getty Images hide caption

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In an image provided by NASA, astronaut Randy Bresnik prepares to enter Boeing's CST-100 spacecraft for an evaluation at the company's Houston Product Support Center. NASA awarded Boeing with a $4.2 billion contract Tuesday. AP hide caption

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During the Apollo 12 mission, astronaut Alan Bean holds a container of lunar soil. The astronaut Charles "Pete" Conrad, who took the photograph, is reflected in Bean's faceshield. Bean says he used to think that in his lifetime, we'd build a base on the moon and start preparing to travel to Mars. Hulton Archive/Getty Images hide caption

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An artist's concept shows the New Horizons spacecraft as it approaches Pluto and its largest moon, Charon, in July 2015. Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute hide caption

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Early days: NASA's International Sun-Earth Explorer C (also known as ISEE-3 and ICE) was undergoing testing and evaluation inside the Goddard Space Flight Center's dynamic test chamber when this photo was snapped in 1976. NASA hide caption

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