Gemini 4 (officially Gemini IV) was a June 1965 manned space flight in NASA's Gemini program. It was the 2nd manned Gemini flight, the 10th manned American flight and the 18th spaceflight of all time (includes X-15 flights over 100 km). It was crewed by James McDivitt and Edward White.
Gemini 4 would be the first multi-day space flight by the United States, designed to show that it was possible for humans to remain in space for the length of time required to fly the moon and back.
A second objective for the four-day, 62-orbit mission was for Gemini 4 to rendezvous and fly in formation with the spent second stage of its Titan II booster rocket.
And although not originally scheduled for this mission, Gemini 4 would also see the first ever American Extra-vehicular activity (EVA, known popularly as a space walk). NASA moved up the original schedule after Aleksei Leonov on Voskhod 2 the previous March performed the first EVA ever, lest the US appear to be falling behind the Soviets in the space race.
Gemini 4 would set a record for flight duration, and ease fears about the medical consequences of longer missions. It also would also be the first use of the new Mission Control center outside Houston, which because of the flight's long duration, had to conduct three-shift operations.