About four to five hours after launching from Cape Kennedy, Gemini IV pilot Edward H. White II opened his hatch above the Pacific tracking station and stepped into the void. "Okay, I'm out," he radioed. For approximately twenty-three minutes, White floated at the end of a 25-foot umbilical, becoming the first American to perform extravehicular activity. He used a Hand-Held Maneuvering Unit—a "zip gun" firing pressurized oxygen—to move around the spacecraft, reporting to command pilot James McDivitt, "The gun works great, Jim. It's very easy to maneuver." The Soviet Union's Alexei Leonov had beaten White to the first spacewalk by ten weeks, but the Gemini IV EVA proved that Americans could operate outside their spacecraft with control and confidence. The four-day mission also carried eleven experiments, including navigation with a sextant for future Apollo cislunar operations. The crew attempted to rendezvous with the spent Titan II second stage but found the task far more difficult than anticipated without onboard radar, a lesson that shaped subsequent training. White's golden visor, reflected against the brilliant Earth below, became an enduring image of the space age—a man literally walking in space, tethered to his ship by nothing more than an oxygen line and nerve.