Astronaut Bruce McCandless II is pictured here further away from the confines and safety of his ship (Challenger) than any previous astronaut has ever been, a move made possible by his Manned Manuevering Unit or MMU, a nitrogen jet propelled backpack. After a series of test maneuvers McCandless went "free-flying" to a distance of 320 feet away from the Orbiter. Image date: February 12, 1984.