Spacewalking was a late addition to the Gemini 4 mission. Not that NASA hadn’t been thinking about it—a “stand-up EVA” had originally been scheduled, whereby the astronauts would open the overhead hatch of their tiny, two-man capsule so that one could poke his head out into the vacuum. But after Soviet cosmonaut Alexei Leonov ventured outside his Voskhod 2 spacecraft in March 1965, NASA added a full spacewalk to Gemini 4.
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Engineers rushed to get all the equipment—including a handheld “zip gun” for maneuvering in orbit—ready in time. (A press kit released two weeks before launch said only that a spacewalk was “possible.”) With just days to go, the plan was approved, and on June 3, 1965, 34-year-old Ed White did what no American had so far done: emerge from his spacecraft to float free. The spacewalk lasted just 20 minutes, long enough to demonstrate the feasibility of working outside, and to check off another major milestone in NASA’s race for the moon.
The Zip Gun
White’s handheld maneuvering unit fired a burst of compressed gas to push the astronaut in the desired direction. The “zip gun” was a last-minute add-on, and was touted as more advanced technology than the Soviets had used on Leonov’s spacewalk. During and after the flight, White had nothing but praise for the gun. Keeping it close to his body so the thrust went through his center of mass, he could control his position and stop and start his momentum easily. His only regret was that the gun ran out of gas just four minutes into a 20-minute spacewalk, leaving him unable to move around except by pulling on his tether. White liked the gun so much that he told NASA debriefers he would trust it for short excursions outside the spacecraft, even without a tether. “I might not tell somebody else to do that,” he said, “but I’d be willing.”