Seven astronauts died when the Space Shuttle Columbia disintegrated upon reentry on Feb. 1, 2003. NASA Deputy Administrator Pam Melroy looks back on the tragedy and how it shaped the agency.
Bob Ebeling was one of five booster rocket engineers at a NASA contractor who tried to stop the 1986 launch of the space shuttle Challenger, which exploded 73 seconds into its flight. He was 89.
After NPR reported Bob Ebeling's story on the anniversary of the Challenger explosion, hundreds of people responded. Ebeling, now 89, says those letters "helped bring my worrisome mind to ease."