HUNTSVILLE, Ala. (AP) — Charlie Duke is part of a tiny fraternity that’s getting even smaller: People who walked on the moon. Duke on Wednesday visited his Apollo 16 spaceship at a space museum in Huntsville, Alabama, to mark the 50th anniversary of his one and only trip to the moon. Only four of the 12 U.S. astronauts to who walked on the moon are still alive, and Duke stays busy with speaking engagements. Duke says he still has vivid memories from the journey, and he is looking forward to NASA’s upcoming return flight to the moon with its new Space Launch System rocket that’s at the core of the Artemis program.