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

itoggle caption Kim Shiflett/NASA

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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Japan Aerospace Exploration Agency astronaut Aki Hoshide makes a space walk outside the International Space Station in 2012. NASA/Getty Images hide caption

itoggle caption NASA/Getty Images