This embroidered emblem is worn on the right shoulder of U.S. spacesuits used in Extravehicular Activity (EVA) or spacewalks. The original patch displayed three stars, one for each U.S. space program that included spacewalks (Gemini, Apollo, Skylab). Two more stars were added for the Space Shuttle and International Space Station programs. Hamilton Sundstrand, a manufacturer of EVA suits, designed this patch because company logos are not allowed on NASA equipment. The design, by NASA engineer Fred Keune, is based on Leonardo da Vinci's "Vitruvian Man" depiction of the ideal proportions of the human body.