Over a half-century ago, NASA only spent three years landing astronauts on the moon before the nation lost interest in continuing the program. SEE ALSO: Artemis II just reached a point of no return. Next stop: The moon. That meant the U.S. space agency didn't get to launch at least three more planned Apollo missions that would have explored new regions of the lunar surface.  But NASA never forgot — demonstrated by a little artifact the agency tucked inside the Orion spacecraft : An American flag that would have flown on Apollo 18 in the early 1970s. "The flag serves as a powerful emblem of America's renewed commitment to human exploration of the moon," NASA said, "while honoring the legacy of the Apollo pioneers who first blazed the trail." SEE ALSO: You can track Artemis II in real time as Orion flies to the moon NASA's Artemis II mission, which blasted off April 1 , is a crowded flight, carrying four astronauts in a spacecraft the size of two minivans.…