Gemini 4 - Flight - Extra-vehicular Activity (EVA)

Extra-vehicular Activity (EVA)

Originally planned for the second revolution, the astronauts postponed the EVA until the third after McDivitt decided that White, following the stress of the launch and the failed rendezvous, looked tired and hot. After a rest, the pair finished performing the checklist for the EVA. Flying over Carnarvon, Australia, they began to depressurize the cabin. Over Hawaii, White pulled the handle to open his hatch, but the latches failed to move.

Fortunately, McDivitt knew what the problem was, because the hatch had failed to close in a vacuum chamber test on the ground, after which McDivitt worked with a technician to see what the cause was. A spring, which forced gears to engage in the mechanism, had failed to compress, and McDivitt got to see how the mechanism worked. In flight, he was able to help White get it open, and thought he could get it to latch again.

There were communication problems during the spacewalk. Gemini spacecraft were the first to use a voice-operated switch (known as VOX) on the astronaut's microphones, but McDivitt soon realized his VOX circuit wasn't working properly; he could only hear the Capsule Communicator (CAPCOM) in the push-to-talk setting, but not on VOX (though both astronauts could be heard by each other and the ground.) Plus, while outside the spacecraft, White was unable to receive transmissions from the ground and had to have all messages relayed through McDivitt. McDivitt must have switched to the VOX setting somewhere around the time White was exiting the spacecraft, because at that point, for most of the EVA, neither he nor White responded either to the Hawaii CAPCOM, or to the Houston CAPCOM, Gus Grissom. Grissom tried to talk to Gemini 4 a total of 40 times in 13 minutes before he got a response.

Tied to a tether, White floated out of the spacecraft, using a Hand-Held Maneuvering Unit (informally called a "zip gun") which expelled pressurized oxygen to provide thrust for controlling his travel. He went fifteen feet (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 gas. He maneuvered around the spacecraft while McDivitt took photographs. White enjoyed the experience, but exhausted the HHMU gas sooner than he would have liked.

White was running up against two factors which constrained the time for his EVA: loss of signal from the Bermuda tracking station, and crossing the solar terminator. The flight controllers were becoming increasingly frustrated with their inability to remind White of the time constraint, because they didn't want the first EVA to be performed in darkness, or out of communication with Earth. Finally McDivitt decided to take his microphone off of VOX:

McDivitt, to White: I'm going out to PUSH-TO-TALK and see what the Flight Director has got to say.

Flight Director Chris Kraft, to Grissom: The flight director says, get back in! (Kraft was not on the air-to-ground loop with the astronauts.)

McDivitt: Gus, this is Jim. Got any message for us?

Grissom: Gemini 4, get back in!

McDivitt: Okay. ... (to White): ... They want you to come back in now.

White tried to use taking more pictures as an excuse to stay out longer, and McDivitt had to coax him in. He finally came back in after a total of approximately 20 minutes. He said, "It's the saddest moment of my life." By the time he got in, the spacecraft had entered darkness.

The hatch proved to be as stubborn to relatch as it was to open. This would have been disastrous, resulting in both men's deaths on reentry. But McDivitt was able to fix the mechanism once again, so White could close it. The mission plan called for opening the hatch again to throw out White's now-unnecessary EVA equipment, but McDivitt elected not to do this, instead keeping the unnecessary equipment on board for the rest of the flight.

They powered down the spacecraft's maneuvering system, intending to drift for the next two-and-a-half days to conserve the remaining fuel. They also intended to sleep alternate four-hour periods, but this turned out to be extremely difficult with the constant radio communications and the small cabin, about the size of the front seats of a compact car.

White's 20-minute space walk was the mission's highlight, with McDivitt's photographs being published worldwide.