Gemini 4

Gemini 4

COSPAR ID	1965-043A
SATCAT no.	01390
Crew
Members	2
End of mission

Gemini 4 (officially Gemini IV) was a June 1965 manned space flight in NASA's Gemini program. It was the 2nd manned Gemini flight, the 10th manned American flight and the 18th spaceflight of all time (includes X-15 flights over 100 km). It was crewed by James McDivitt and Edward White. The highlight of the mission was the first space walk by an American, during which White remained tethered outside the spacecraft for 22 minutes.

Crew

Position	Astronaut
Command Pilot	James A. McDivitt First spaceflight
Pilot	Edward H. White II First spaceflight

Backup Crew

Position	Astronaut
Command Pilot	Frank Borman
Pilot	James A. Lovell, Jr.

Objectives

Gemini 4 would be the first multi-day space flight by the United States, designed to show that it was possible for humans to remain in space for the length of time required to fly to the moon and back.

A second objective for the four-day, 62-orbit mission was for Gemini 4 to rendezvous and fly in formation with the spent second stage of its Titan II booster rocket.

Gemini 4 would also see the first ever American Extra-vehicular activity (EVA, known popularly as a space walk). NASA moved up the original schedule after Aleksei Leonov on Voskhod 2 the previous March performed the first EVA ever, lest the US appear to be falling behind the Soviets in the space race.

Gemini 4 would set a record for flight duration, and ease fears about the medical consequences of longer missions. It would also be the first use of the new Mission Control center outside Houston, which because of the flight's long duration, had to conduct three-shift operations.

Flight

Launch

The broadcast of the launch was itself historic. For the first time an international audience, from twelve 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 that requested accreditation.

Except for a few moments of pogo (axial vibrations in the rocket), the launch itself came off perfectly, the spacecraft entering into a 163 by 282 kilometers orbit.

The rendezvous

The attempt on the first orbit at an orbital rendezvous with its spent second stage taught space flight engineers about the idiosyncrasies of orbital mechanics. The astronauts found it difficult to target the stage due to the lack of depth perception. When they fired their thrusters in the direction of the stage, they found themselves moving away and downward, as a vent opened on the stage to dump propellant caused it to move around.

After several tries to get closer and with half their thruster fuel spent, McDivitt and White finally gave up, deciding with Houston that the EVA was more important than the rendezvous, something that could be performed on later missions. (During those missions success was achieved when the chasing spacecraft first dropped to a lower, faster orbit before rising again.)

Extra-vehicular activity (EVA)

Originally planned for the second orbit, 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. Attempting to open the hatch, a spring failed to compress in the mechanism. The astronauts, after some pushing and shoving, finally forced it open.

Tied to a tether, White fired his oxygen powered "zip gun" and floated out of the capsule. He traveled fifteen feet (five meters) 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 fuel.

White maneuvered around the spacecraft while McDivitt took photographs. After 15 minutes 40 seconds White was instructed by Houston to reenter the spacecraft. He said, "It's the saddest moment of my life." The hatch proved difficult to relatch, but with both astronauts pulling on the hatch handle, they were able to close it. Due to the difficulty with the hatch, a second opening and closing was canceled.

Ed White performing the first American EVA

They powered down the spacecraft intending to drift for the next two and a half days. They also intended to sleep alternate four hour periods but this turned out to be nearly impossible with the constant radio communications and the small cabin meaning each was almost in the other person's lap.

The mission's highlight turned out to be White's 22-minute space walk, with McDivitt's photographs being published worldwide.

Experiments

Eleven experiments were carried on the spacecraft. Experiment D-8 was five dosimeters that measured the radiation in the spacecraft environment. Of particular interest was the South Atlantic Anomaly. Experiment D-9 was an experiment in simple spacecraft navigation where the crew used a sextant to measure their position using the stars.

Experiments 5-5 and 5-6 were both photography experiments where they used a 70-millimeter Hasselblad camera to photograph the weather and terrain below them. There were two medical experiments: M-3 and M-4. The first was a bungee cord that the crew used for exercise. They said, after the mission, that this got harder as the mission went on, though this may have been due to a lack of sleep. The second was the phonocardiogram experiment, which had sensors attached to their bodies that measured heartbeat rates, especially during liftoff, EVA, and reentry.

There were four engineering experiments. MSC-1 measured the electrostatic charge in the spacecraft, MSC-2 was a proton-electron spectrometer, MSC-3 was a tri-axis magnetometer and MSC-10 involved the crew photographing the red-blue Earth limb.

The computer failed on the 48th revolution. This was unfortunate for IBM which had just put an advertisement in the Wall Street Journal saying that its computers were so reliable that even NASA used them. The computer failure meant that the capsule would not be able to perform a lifting reentry as planned.

Reentry

Reentry came on the 62nd revolution. A rolling reentry (as used in Mercury) was chosen due to the computer failure. The astronauts began rolling the spacecraft at 120,000 meters altitude to increase its stability. They started slowing this rolling at 27,000 meters and stopped it by 12,000 meters. The drogue parachute deployed shortly after this, and the main deployed at 3,230 meters. A malfunctioning thruster caused the roll to be much faster than planned, and the landing was rough. Neither of the crew encountered any problems, however, contrary to NASA doctors' concerns about their landing upright — as opposed to on their backs, as in Mercury — after four days in space. Even though they landed 80 kilometers short of the intended landing target, some ships had already started steaming to the touchdown point and a helicopter was able to see them land.

The Gemini 4 mission was supported by the following U.S. Department of Defense resources: 10,249 personnel, 134 aircraft and 26 ships.

Insignia

Gemini 4's crew originally intended to call their spacecraft American Eagle, but this was scuttled after NASA management issued a memo saying that they did not want a repeat performance of the previous mission, on which Gus Grissom had named his spacecraft Molly Brown.

The callsign for the mission became simply Gemini 4. There was no patch flown on the crew's suits, although the one shown here, created after the fact, is on display in McDivitt's museum. Since the crew was prohibited from naming their spacecraft, they decided to put the American flag on their suits, surprisingly the first astronauts to do so, although Soviet crews used the Cyrillic "СССР" on their spacesuit helmets. Previous astronauts had only had the NASA logo and a strip with their name on their suits.

Spacecraft location

The spacecraft is on display at the National Air and Space Museum, Washington, D.C..

Mission parameters

• Mass: 3,574 kg
• Perigee: 162.3 km
• Apogee: 282.1 km
• Inclination: 32.53°
• Period: 88.94 min

Spacewalk

• White - EVA - June 3, 1965
• Open hatch: 19:34 UTC
• Start EVA: 19:46 UTC
• End EVA: 20:06 UTC
• Close hatch: 20:10 UTC
• Duration: 20 minutes

See also

• Extra-vehicular activity
• List of spacewalks
• Splashdown

External links

• On The Shoulders of Titans: A History of Project Gemini: http://www.hq.nasa.gov/office/pao/History/SP-4203/cover.htm
• Spaceflight Mission Patches: http://www.genedorr.com/patches/Intro.html
• NASA NSSDC Spacecraft details: http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1965-043A
• NASA Gemini 4 press kit - May 21, 1965