From the beginning, NASA knew astronauts would have to leave their spacecraft. They’d have to fix things outside, transfer between orbiting vehicles in an emergency, and—most ambitious of all—walk on the moon.
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All the techniques of extravehicular activity (EVA) had to be invented and perfected beforehand—how to “ingress” and “egress” through hatches, then airlocks; how to pre-breathe oxygen to avoid the bends (which also afflicts divers); how to anchor yourself in weightlessness; and how to maintain a comfortable temperature in your spacesuit.
Today, with more than 300 spacewalks logged since Alexei Leonov’s first, on Voskhod 2 in March 1965, orbiting construction workers clamber around a space station the size of a skyscraper with hardly a thought to their surroundings. What once seemed magical has become standard operating procedure. See the photo gallery at right for more on the history of spacewalks.
Tony Reichhardt is a senior editor at Air & Space/Smithsonian.