Discovery on Thursday(April 20, 2012) became the first spaceship of the retired US shuttle fleet to enter its permanent home as a museum artifact, marking a solemn end to the 30-year manned spaceflight program. The oldest surviving US shuttle, Discovery flew 39 missions to space beginning in 1984 and its transition from space-flying giant to tourist attraction drew mixed emotions from NASA veterans and space fans alike. Discovery ended its last mission to space in March 2011, and the return to Earth of Atlantis in July 2011 marked the end of the US shuttle program, leaving Russia as the only nation capable of sending astronauts to space. “The space shuttle…