Gemini 4
Gemini 4 was the second crewed spaceflight in NASA's Project Gemini, occurring in June 1965. It was the tenth crewed American spaceflight. Astronauts James McDivitt and Ed White orbited the Earth 66 times in four days, making it the first US flight to approach the five-day flight of the Soviet Vostok 5. The highlight of the mission was the first space walk by an American, during which White floated free outside the spacecraft, tethered to it, for approximately 23 minutes.
The flight also included the first attempt to make a space rendezvous as McDivitt attempted to maneuver his craft close to the Titan II upper stage which launched it into orbit, but this was not successful.
The flight was the first American flight to perform many scientific experiments in space, including use of a sextant to investigate the use of celestial navigation for lunar flight in the Apollo program.
Mission Personnel
Primary and Backup Crews
NASA named primary and backup crews for Gemini IV on July 28, 1964.Support team
- Mission Director and Flight Director - Red Team: Christopher C. Kraft, Jr.
- Flight Director - Blue Team: John D. Hodge
- Flight Director - White Team: Eugene F. Kranz
- CAPCOMs: Gus Grissom, Roger B. Chaffee, and Eugene Cernan
- Worldwide support and recovery team: 10,249 U.S. Department of Defense personnel, 134 aircraft, and 26 ships.
Mission parameters
- Mass:
- Perigee :
- Apogee :
- Period: 88.94 min
- Inclination: 32.53°
- Perigee :
- '''Apogee :'''
Spacewalk
- Ed White - EVA - June 3, 1965
- Hatch opened: 19:34 UTC
- Start EVA: 19:39 UTC
- End EVA: 20:02 UTC
- Duration: 23 minutes
- Hatch closed: 20:22 UTC
Objectives
A second objective was the first American extra-vehicular activity, known popularly as a "space walk". The first space walk had already been performed by Soviet Alexei Leonov on Voskhod 2 in March 1965. NASA moved up the spacewalk from the original schedule, to demonstrate that the US was gaining on the early lead taken by the Soviets in what was known as the Space Race. As late as 11 days before the scheduled June 3 launch, newspapers were reporting NASA saying that it "had not yet determined whether White would be the first American astronaut to expose himself to the elements of space" and that "A decision might not be made until a day or two before launching."
A third objective was for Gemini 4 to attempt the first space rendezvous, flying in formation with the spent second stage of its Titan II launch vehicle.
Preparations
The Gemini 4 spacecraft completed major manufacturing activity, module tests, and equipment installation at McDonnell at the end of January 1965. The spacecraft was mated to the Titan II launch vehicle at Cape Canaveral Launch Complex 19 on April 23, 1965. Final system tests were performed over several additional weeks.NASA leadership approved the Gemini 4 EVA plan on May 25, 1965; the public was informed on the same day
Flight
Launch
Launched from LC-19 at Cape Kennedy Air Force Station, Florida, Gemini 4 was the first flight to be controlled by the new Mission Control Center at the Manned Spacecraft Center in Houston, Texas, which had to conduct three-shift operations due to the flight's long duration.The broadcast of the launch was itself historic. For the first time an international audience, from 12 European nations, could watch the lift-off on live television via the Early Bird satellite. Press interest, due to the satellite broadcast and the new center in Houston, proved to be so high that NASA had to lease buildings to accommodate the 1,100 print and broadcast journalists who requested accreditation. Flight control shifted from Cape Kennedy to Houston as soon as the vehicle cleared the launch tower.
At liftoff, two roll transients caused by misalignment of the Titan first-stage engines occurred; these were quickly corrected by the autopilot. The fuel top-off umbilical failed to detach and was pulled loose when the booster had climbed about. A small oscillation in the pitch and yaw planes resulted from this. Performance of all launch vehicle systems was nearly nominal. Some modifications had been made to the guidance program on Gemini 4's booster to produce a less lofted flight trajectory and a lower altitude at booster engine cut-off than on Gemini 3; these were generally successful despite a still somewhat lofted flight path. BECO occurred at T+152 seconds; second-stage engine cut-off occurred at T+333 seconds. The spacecraft entered into an orbit.
Rendezvous attempt
On the first orbit, McDivitt attempted to rendezvous with the spent Titan second stage. This was unsuccessful for a number of reasons:- NASA engineers had not yet worked out the idiosyncrasies of orbital mechanics involved in rendezvous, which are counter-intuitive. Simply thrusting the spacecraft toward the target changed its orbital altitude and velocity relative to the target. When McDivitt tried this, he found himself moving away and downward, as the retrograde thrust lowered his orbit, increasing his speed.
- The stage was dumping its residual propellant, causing it to move around in various directions relative to the Gemini.
- There were only two running lights on the stage, which made it hard at times for McDivitt to determine its orientation. McDivitt concluded that a rendezvous target should have at least three lights.
- There was no radar on board Gemini 4 to give a precise range to the target, so the astronauts had to rely on their visual depth perception to estimate the range, and this differed for the two men. Initially McDivitt estimated the distance at, while White believed that it was closer. At the worst point, McDivitt estimated it was about a half mile away, while White's estimate was three-quarters of a mile. McDivitt estimated that he was able to get as close as, but now White's estimate was between.
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 that 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 on the astronaut's microphones, but McDivitt soon realized that his VOX circuit was not working properly; he could only hear the Capsule Communicator in the push-to-talk setting, but not on VOX. 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 which expelled pressurized oxygen to provide thrust for controlling his travel. He went 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 VOX:
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 23 minutes, almost 10 minutes later than was planned. 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. McDivitt was able to fix the mechanism once again, so White could close it, about 20 minutes after he got in. 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. These also showed White wearing an Omega Speedmaster chronograph watch on his spacesuit sleeve, one of two makes which had been approved by NASA for space use following extensive tests. Omega were unaware of these tests or the fact that its product was going to be used in space, until the photos. The model worn during the spacewalk is now known as the "Ed White" by watch collectors.