Gemini 4 White was selected to be the pilot of Gemini 4, with McDivitt as his command pilot. The Chief of the Astronaut Office, Mercury Seven astronaut Deke Slayton, paired them because they knew each other well, having attended the University of Michigan and test pilot school together. The mission objectives were ill-defined at first, but consideration was given to performing extravehicular activity (EVA), space rendezvous and orbital station-keeping. Knowing that EVA (sometimes called a "spacewalk") was a possibility, McDivitt pressed for it to be included in the mission. As a result, NASA management agreed to ensure that the Gemini space suit for the mission was capable of being used for EVA. Kenneth S. Kleinknecht told the July 1964 press conference that announced the mission that one of the crew might open the hatch and stick his head outside, but this attracted little attention. On March 18, 1965, cosmonaut Alexei Leonov became the first man to perform an EVA, on the Voskhod 2 mission, but not until May 25 was EVA approved for Gemini 4 by NASA administrator James E. Webb. White was a devout Methodist. On the Gemini 4 mission he carried three pieces of religious jewelry to take with him on his EVA: a gold cross, a St. Christopher Medal and a Star of David. White commented: "I felt while I couldn't take one for every religion in the country, I could take the items most familiar to me." On June 3, 1965, the Gemini 4 crew was launched into space to begin its four-day mission. After separation from the Titan II upper stage, McDivitt attempted to rendezvous with the booster. However, this was unsuccessful since the astronauts were not adequately trained to rendezvous in orbit. The objective had to be abandoned since the allocated propellant had been used up, and the maneuvers had pushed the spacecraft's orbit too far away from Earth. The mission also included 11 different scientific experiments, including the use of a sextant for celestial navigation. After the failed rendezvous attempt, White appeared tired and hot, so the EVA was postponed from the second revolution to the third revolution. At 19:46 UTC, White became the first American to make an EVA. During his spacewalk, White used an oxygen-propelled gun called the Hand-Held Maneuvering Unit to propel himself. White found the experience so exhilarating that he was reluctant to terminate the EVA at the allotted