From three orbits to four days in space
Gemini 4 was the second crewed flight in the U.S. Gemini programme, with James McDivitt as command pilot and Edward White as pilot. Gemini 3 had previously completed only three orbits. This mission would investigate whether the spacecraft and its two occupants could operate continuously for about four days, testing rest, eating, stowage and real-time scheduling.
The flight also included an EVA, a station-keeping trial with the rocket's final stage, and scientific and medical experiments. Endurance and EVA shared limited electricity, oxygen and propellant. Because fuel-cell development had not met the original schedule, spacecraft 4 used batteries, and the planned duration was reduced from an earlier seven-day concept to four days.
How the spacewalk entered the plan
McDonnell built the spacecraft in St. Louis, while Martin was responsible for the Titan II launch vehicle. NASA Manned Spacecraft Center personnel, astronauts and contractors jointly prepared EVA equipment. The David Clark Company supplied the special spacesuit, and the Manned Spacecraft Center developed the handheld maneuvering unit. Astronauts practiced hatch opening, exit, entry and repressurization in vacuum chambers, simulators and weightless flights.
Soviet cosmonaut Alexei Leonov completed a spacewalk first, in March 1965, but U.S. EVA research and related Gemini 4 discussions had begun earlier. Execution still depended on equipment qualification and training. NASA Administrator James Webb approved inclusion of the EVA on 25 May. White would perform the first American spacewalk, not the first in human history.
References: [2]
An unsuccessful pursuit after launch
Gemini 4 lifted off from Cape Kennedy's Pad 19 in Florida on 3 June 1965. The original report recorded launch at 15:15:59.562 Universal Time, approximately 10:16 U.S. Eastern Standard Time. Before launch, a wiring fault in the tower had held the countdown for more than an hour; after correction, the spacecraft entered Earth orbit.
McDivitt then tried to approach the separated second stage, with White assisting observation. The spacecraft had no rendezvous radar, and visual distance estimates were inconsistent. Accelerating directly toward the target also changed the orbit, rather than simply closing the distance like a car chase on the ground. Once propellant use reached its allocation, the team abandoned further rendezvous attempts and retained resources for the EVA and four-day flight.
Twenty-two minutes outside the spacecraft
During the third orbit, after cabin depressurization, White opened the hatch and left the spacecraft using a handheld unit that expelled compressed oxygen. An umbilical and tether maintained his connection to the spacecraft. The original mission report recorded his actual time outside as about 22 minutes. Using the spacecraft as an orientation reference, he tested turning and position control, then continued moving with the tether after the maneuvering unit's gas ran out.
Inside, McDivitt controlled the spacecraft's attitude and took photographs, avoiding thruster firings when White was near them. After White returned, the two had difficulty latching the hatch and applied force together using a method practiced in training to close it. They consequently canceled plans to reopen it to discard equipment, requiring the retained items to be restowed.
Observations during four days
Houston's new Mission Control Center directed a crewed flight for the first time. Christopher Kraft, Eugene Kranz and John Hodge led three shifts, attending respectively to execution, system resources and subsequent planning. Communications noise and activity in the cramped cabin disrupted sleep, so the ground team adjusted work according to remaining propellant and crew condition rather than mechanically following the prelaunch schedule.
The mission scheduled eleven scientific, medical and engineering experiments. Cabin radiation measurements used two active dose-rate instruments and five passive dosimeters. During passages through the South Atlantic Anomaly, White moved a portable probe near his body and around the cabin to compare shielding conditions. The instruments operated normally; the report presented measurements of cosmic radiation outside the anomaly and treated the anomaly separately.
Terrain and weather photography produced usable imagery. A separate navigation experiment photographed Earth's limb through red and blue filters, obtaining 24 usable photographs, six of which received preliminary processing. The original report explicitly classified these analyses as preliminary, with detailed brightness calculations unfinished. Obtaining photographs and demonstrating final navigation performance were not the same step.
Rolling reentry and recovery at sea
Late in the flight, an anomaly occurred during computer power-down, preventing the planned computer-controlled reentry. The crew instead used a rolling reentry on the 62nd orbit. At about 12:12 U.S. Eastern Standard Time on 7 June, the spacecraft splashed down in the Atlantic after 97 hours, 56 minutes and 12 seconds, about 80 kilometers from the intended point.
Rescuers fitted a flotation collar and retrieved the astronauts by helicopter. About 57 minutes later they boarded USS Wasp; the spacecraft itself was hoisted aboard afterward. Four-day endurance and the first American EVA supplied practical experience, while rendezvous difficulties and the computer fault prompted improvements in training and equipment for later missions. The mission's success did not conceal those uncompleted objectives.