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Gemini-4: America's first spacewalk

Anatoly Zak, Spaceflight Correspondent
Jul 25, 2015, 22:52 UTC

Sen—The successful completion of the Gemini-3 test flight in March 1965 gave NASA a new spacecraft capable of many previously impossible missions. The most exciting item on the agency's wish list was a spacewalk, known in astronaut's lingo as an ExtraVehicular Activity, or EVA for short. Ever since Konstantin Tsiolkovsky envisioned space travel in the 1880s, humans dressed in spacesuits and floating freely in weightlessness had been a fixture of science fiction novels. However, not until the Soviet Voskhod-2 and American Gemini spacecraft appeared on the scene eight decades later had it really become possible.

Initially, NASA cautiously planned to allow one of two Gemini-4 pilots to open the hatch above his seat and stand up, sticking his head and shoulders outside. However, after Alexei Leonov upped the ante with his historic spacewalk in March, NASA decided on a bolder plan. Not only, was the pilot allowed to float freely like in sci-fi novels, but he was provided with a kind of "jet pistol," officially dubbed Hand-Held Maneuvering Unit, which would theoretically enable controlled moves in weightlessness!

Overshadowed by the spacewalk spectacular, the primary goal of the Gemini-4 mission was actually to push NASA's experience in flight duration to a new height. Gemini-4 was scheduled to orbit the Earth for four days, or nearly three times longer than the longest U.S. space mission to date. (Gemini-4 would still fall short of Valery Bykovsky's five-day flight aboard Vostok-5 almost two years earlier, however Gemini-4 would carry two people versus a single pilot onboard Vostok.)

Last but not least, a new gleaming mission control center was declared operational in Houston, right on time for the Gemini-4 launch.

NASA rookie astronauts James McDivitt and Edward White were assigned to the Gemini-4 mission.


Gemini-4 lifts off. Image credit: NASA

The Titan-2 rocket carrying the 3,574-kilogram Gemini-4 spacecraft lifted off from Cape Canaveral on June 3, 1965, at 10:15:59.562 a.m. EST (15:15 UTC). Right after entering space, the crew turned their capsule around and maneuvered, attempting formation flying with the empty second stage of their rocket, which had just delivered them into orbit. The experiment was cut short to conserve fuel during maneuvers which proved more difficult than expected and instead to focus on the highlight of the mission—the EVA.

After around an hour and a half of hectic preparations, the astronauts depressurized their cabin and opened the hatch at 2:34 p.m. EST, as Gemini-4 was flying over Hawaii, more than four hours after liftoff.

The second man to walk in space, Ed White pushed himself out of the spacecraft and floated freely. Spectacular videos and photos of the spacewalk were to follow. White loved his hand-held maneuvering system, even though it run out of gas in less than four minutes, which was enough for Gemini-4 to reach the U.S. West Coast.

White then resorted to use of the eight-meter tether that secured him to the spacecraft and supplied oxygen from the ship's life-support system. He made a few shaky steps on the hull of his spacecraft, before it slipped away from him. The enterprising spacewalker even appeared in front of his commander's window leaving a trace of residue on the clear glass. "You smeared up my windshield you dirty dog!" McDivitt jokingly reprimanded his pilot.


Ed White during spacewalk. Image credit: NASA

Around 20 minutes into the spacewalk, both astronauts got an impatient call from the ground to wrap up the exercise. "It is the saddest moment of my life," responded White as he prepared to return into the capsule.

After some serious and a potentially fatal struggle with the locking mechanism, which required frantic efforts by both astronauts to resolve, the ship's hatch was finally closed 36 minutes after it had been opened. As it transpired later, a spring in the locking mechanism had not had enough lubricant and had baked in the vacuum of space. It took close to an hour to re-pressurize the capsule, so that both astronauts could open their helmets and breathe the cabin atmosphere again.

With the most spectacular and riskiest part of the mission behind them, McDivitt turned off all unessential systems onboard Gemini-4 and left the capsule in a free drift to conserve power, propellant and other resources for a large part of their four-day mission. According to the flight program, astronauts tried to take turns sleeping but with a mixed success. It proved difficult to fall asleep next to a working colleague, along with other disturbances like noise, smell and temperature fluctuations. The toilet also had some glitches and needed some cleaning up. When mission control congratulated the crew on beating Mercury's flight-duration record, White responded that they still had a time to fly. Fortunately, none of the issues in orbit were serious enough to impact the duration of the flight.

At the conclusion of the mission, the computer responsible for automated landing of the capsule failed to reboot and the crew was left with a ballistic descent mode under manual control. Gemini-4 made a successful water landing on June 7, 1965, logging 97 hours 56 minutes in space and 62 orbits.


Gemini-4 after landing. Image credit: NASA

The splashdown was harder than usual and 44 miles off target, but a rescue helicopter reached the capsule within half an hour. Medics at the Wasp navy ship found the astronauts tired, unshaven but in good health.

The Gemini-4 mission provided a huge moral boost for the U.S. space program. Among its many implications for the future of human spaceflight, the successful EVA proved that astronauts on lunar missions could relatively easily leave their spacecraft and even get from one module to another without a pressurized tunnel. A door to a one-week mission had also been opened.