Currently, 28 astronauts have been honored with the award, 17 of which were awarded posthumously for those who died in American spaceflight. Three died in the Apollo 1 fire, seven died in the Space Shuttle "Challenger" disaster, and seven in the Space Shuttle "Columbia" disaster. An asterisk indicates a posthumous award. Four of the twelve moonwalkers received the medal (Armstrong, Conrad, Shepard, and Young), but only Neil Armstrong for his lunar mission. The New Nine class of U.S. astronauts (the second group of astronauts selected by NASA) has the most recipients of the medal, with seven. Second is NASA Astronaut Group 8 which received five awards, four for astronauts killed in the "Challenger" Disaster ( is the only group 8 astronaut to receive the award who was not killed in the "Challenger" Disaster).