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. The highlight of the mission was the first space walk by an American, during which White remained outside the spacecraft tied to a tether for 22 minutes.
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 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.
After several tries to get closer and with half their thruster fuel spent, McDivitt and White finally gave up, deciding with Houston that the EVA was more important than the rendezvous, something that could be performed on later missions. (During those missions success was achieved when the chasing spacecraft first dropped to a lower, faster orbit before rising again.)
Tied to a tether, White fired his oxygen powered "zip gun" and floated out of the capsule. He traveled five meters out, and began to experiment with maneuvering. He found it easy, especially the pitch and yaw, although he thought the roll would use too much fuel.
White maneuvered around the spacecraft while McDivitt took photographs. After 15 minutes 40 seconds White was instructed by Houston to reenter the spacecraft. He said, "It's the saddest moment of my life." The hatch proved difficult to relatch, but with both astronauts pulling on the hatch handle, they were able to close it.
They powered down the spacecraft intending to drift for the next two and a half days. They also intended to sleep alternate four hour periods but this turned out to be nearly impossible with the constant radio communications and the small cabin meaning each was almost in the other person's lap.
The mission's highlight turned out to be White's 22-minute space walk, with McDivitt's photographs being published worldwide.
Experiments 5-5 and 5-6 were both photography experiments where they used a 70-millimeter Hasselblad camera to photograph the weather and terrain below them. There were two medical experiments: M-3 and M-4. The first was a bungee cord that the crew used for exercise. They said, after the mission, that this got harder as the mission went on, though this may have been due to a lack of sleep. The second was the phonocardiogram experiment, which had sensors attached to their bodies that measured heartbeat rates, especially during liftoff, EVA, and reentry.
There were four engineering experiments. MSC-1 measured the electrostatic charge in the spacecraft, MSC-2 was a proton-electron spectrometer, MSC-3 was a tri-axis magnetometer and MSC-10 involved the crew photographing the red-blue Earth limb.
The computer failed on the 48th revolution. This was unfortunate for IBM which had just put an advertisement in the Wall Street Journal saying that its computers were so reliable that even NASA used them. The computer failure meant that the capsule would not be able to perform a lifting reentry as planned.
The Gemini 4 mission was supported by the following U.S. Department of Defense resources: 10,249 personnel, 134 aircraft and 26 ships.
The callsign for the mission became simply Gemini 4. There was no patch flown on the crew's suits, although one was created by NASA well after the fact. Since the crew was prohibited from naming their spacecraft, they decided to put the American flag on their suits, surprisingly the first crew to do so, although Soviet crews used the Cyrillic "СССР" on their spacesuit helmets. Previous astronauts had only had the NASA logo and a strip with their name on their suits.
The mission is also mentioned (though not by name) in the song Eve of Destruction, which was recorded in July, 1965. The lyrics include the lines, "Ah, you may leave here, for four days in space, but when you return, it's the same old place."