Air Force Col. Steven Nagel joined NASA in 1978 and flew four space shuttle missions, logging more than 700 hours in space. He retired from the space agency in 2011. Nagel died of cancer on Thursday. NASA hide caption itoggle caption NASA The Two-Way Veteran Space Shuttle Astronaut Steven Nagel Dies At 67 August 23, 2014 The Air Force colonel was among the first group selected by NASA to train for the space shuttle program. He went on to fly four missions, two as commander.