On May 21, 1965, NASA released the Gemini 4 press kit. It opened with the standard mission description, in this case for a four-day orbital flight that would send commander Jim McDivitt and pilot Ed White around the Earth 62 times to evaluate "the effects of extended spaceflight on crew performance and physical condition."

Then there was an intriguing page that hinted at something bigger: "No decision has been made whether in the Gemini 4 mission the crew will engage in extravehicular activity... A decision to undertake the extravehicular test can be made as late as the day before the launch." The possibility of an EVA on Gemini 4 came as a surprise not only the American people that day, but to many within NASA as well.

EVAs, colloquially known as spacewalks, were one of the three main program goals for NASA's Gemini program designed to support the Apollo program. If NASA was going to send men all the way to the moon, there was no point in having them sit inside and look out the window. They were going outside....