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

The iconic "Earthrise" photo taken by astronaut Bill Anders through a window on the Apollo 8 command module on Dec. 24, 1968. Bill Anders/NASA hide caption

itoggle caption Bill Anders/NASA

Apollo 11 climbs toward orbit after liftoff on July 16, 1969. In 2 1/2 minutes of powered flight, the S-IC booster lifts the vehicle to an altitude of about 39 miles, some 55 miles downrange. NASA hide caption

itoggle caption NASA