The rendezvous mission of Gemini VI and Gemini VII, along with the subsequent long-duration flight of Gemini VII, perfected techniques that made possible lunar exploration by astronauts.

Project Gemini was the intermediate step in America’s piloted spaceflight program, which had its genesis with Project Mercury and its greatest triumph with the lunar landings of the Apollo program. In 1961, President John F. Kennedy committed the United States to making a landing by astronauts on the Moon within the decade. Space program, U.S.;Project Gemini
Project Gemini
Orbital rendezvous
[kw]Gemini VI and VII Complete an Orbital Rendezvous (Dec. 15, 1965)
[kw]Orbital Rendezvous, Gemini VI and VII Complete an (Dec. 15, 1965)
Space program, U.S.;Project Gemini
Project Gemini
Orbital rendezvous
[g]North America;Dec. 15, 1965: Gemini VI and VII Complete an Orbital Rendezvous[08720]
[g]United States;Dec. 15, 1965: Gemini VI and VII Complete an Orbital Rendezvous[08720]
[c]Space and aviation;Dec. 15, 1965: Gemini VI and VII Complete an Orbital Rendezvous[08720]
[c]Science and technology;Dec. 15, 1965: Gemini VI and VII Complete an Orbital Rendezvous[08720]
Schirra, Walter M., Jr.
Stafford, Thomas P.
Borman, Frank
Lovell, James A.

At that time, there was considerable debate within the National Aeronautics and Space Administration National Aeronautics and Space Administration;Project Gemini (NASA) as to how this feat was going to be accomplished. Some scientists favored the development of a huge rocket that would fly directly to the Moon, make a landing, and then return to Earth. Others advocated an alternative method in which smaller spacecraft would rendezvous in Earth orbit before making the journey to the Moon. A variation of the latter method called for the launching of a multistage rocket that would send a spacecraft into lunar orbit. A piloted lander would then separate from the orbiting spacecraft and descend to the lunar surface. Upon completion of the mission, the lander would depart from the lunar surface and rendezvous and dock with the lunar orbiter. The orbiter would then ignite its engine and head back to Earth.

Either of the rendezvous methods promised an enormous savings in fuel and rocket weight and in development costs. Choosing a rendezvous technique also meant that the lunar mission could be attempted sooner. The only apparent drawback was that no one had ever attempted a rendezvous mission and scientists had no idea how difficult it might be. Perfecting the technique of rendezvous and docking became one of the primary objectives of the Gemini program.

Unlike the Mercury spacecraft, which had a single astronaut-pilot, the spacecraft designed for the Gemini program would carry two astronauts Astronauts and cosmonauts into space. The spacecraft was conical in shape and was about 5.6 meters long and 3 meters in diameter at its base. It was composed of reentry and adaptor modules, which had a combined weight of about 3,150 kilograms. The reentry module was designed to withstand the extreme heat of reentry into Earth’s atmosphere from orbit. The cabin, which was to be occupied by the astronauts as well as the reentry control system and the rendezvous and recovery sections, was contained within the reentry module. The adaptor module enabled the spacecraft to be mated to the launch vehicle.

The primary launch vehicle for the Gemini program was the Titan 2 Titan (rocket program)
Rockets rocket. First developed as an intercontinental ballistic missile Missiles;intercontinental ballistic (ICBM) for the U.S. Air Force, this two-stage vehicle stood 30.9 meters tall and weighed some 148,500 kilograms when fueled. The Titan 2 developed 430,000 pounds of take-off thrust from its two first-stage engines. The second stage developed 100,000 pounds of thrust.

The Titan 2 was selected for the Gemini program because it had more power than America’s other ICBM, the Atlas Atlas launch vehicle . The countdown for the Titan 2 was also hours shorter than that required for the Atlas, and astronauts needed to enter their spacecraft only ninety minutes before liftoff. The Titan 2 also had a unique safety feature: If anything went wrong in the seconds between ignition and liftoff, the engines would shut down automatically. This feature, along with the insertion of various backup systems, allowed the Titan 2 to become rated for human safety and join the Gemini program.

In addition to rendezvous and docking, there were other objectives for the program. It had to be demonstrated that astronauts and their life-support systems could be sustained over a two-week mission, spacecraft could be guided accurately through the reentry phase of the mission, extravehicular activities Extravehicular activity (EVA) were possible and safe, and scientific experimentation could be carried out in space.

Gemini IV, the second piloted mission in the new program, met three of these objectives. (Beginning with Gemini IV, NASA began to use Roman numerals for Gemini mission designations to coordinate with the Roman number II, symbolic of the Gemini program.) Various medical experiments were conducted as well as radiation detection and weather-related observations, a spacewalk (EVA) was accomplished, and the crew successfully conducted a guided reentry into Earth’s atmosphere. The seven-day mission of Gemini V accomplished a portion of the final endurance requirement, and Gemini VI was to be the first attempt at orbital rendezvous.

The plan for conducting orbital rendezvous was to send first a target vehicle into orbit. This target vehicle would be unpiloted. After a stable orbit had been achieved, the piloted spacecraft then would be sent into orbit. By using the thrusters on the Gemini spacecraft, astronauts would be able to alter the position and orientation of the spacecraft until it caught up with the target vehicle. The Agena-B Agena-B[Agena B] was used as the target vehicle in the Gemini program. This second stage of the Atlas-Agena configuration was 7.5 meters in length, had a diameter of 1.5 meters, and weighed 765 kilograms.

Gemini VI, as photographed by Gemini VII during their space rendezvous.

(NASA-JSC)

The launch of the target vehicle for Gemini VI took place at 10:00 a.m., eastern standard time, on October 25, 1965. At the time of the launch, astronauts Walter M. Schirra, Jr., and Thomas P. Stafford were already in their Gemini spacecraft, which was set on top of a Titan 2. The countdowns for Gemini VI and the target vehicle proceeded simultaneously. The Atlas performed well, but the Agena failed to orbit because of an instability that caused the vehicle to break up. The Gemini VI launch was promptly called off.

After much discussion, NASA officials decided to use the Gemini VII spacecraft as the target vehicle for Gemini VI rather than wait for another Atlas-Agena. Gemini VII, which had been planned as a fourteen-day mission, was launched into orbit by a Titan 2 rocket at 2:30 p.m. on December 4. The primary objectives of the flight were to evaluate the effects of a prolonged mission upon the crew, conduct a rendezvous with Gemini VI, and carry out some twenty in-flight experiments.

For the first several days of the flight, astronauts Frank Borman and James A. Lovell conducted various experiments such as the use of a laser for voice communications, made stellar observations, and worked on navigation problems. Meanwhile, at the Kennedy Space Center, technicians were preparing the hardware and the pad for the launch of Gemini VI.

The launching of Gemini VI was not without its share of drama. Two seconds after ignition on December 12, both of the Titan’s engines shut down. Telemetric data indicated that there had been a liftoff, although the astronauts had felt no physical sense of motion. As commander of the spacecraft, Schirra had to make an instantaneous decision. He could eject the astronauts from the spacecraft, quite possibly injuring both of them and, at best, forcing a long mission delay. His other option was to do nothing and assume that the data were incorrect and there had been no liftoff. If the data were correct and there had been a slight liftoff, the Titan might well fall back on the pad and explode. Schirra chose the latter option, which as it turned out was the correct one. The mission was saved but would be postponed for a few days.

Gemini VI was launched at 8:37 a.m. on December 15, eleven days after the launch of Gemini VII. The mission’s primary objective was to achieve an orbital rendezvous with Gemini VII. At the time of launch, Gemini VII was about 2,200 kilometers ahead of Gemini VI. Within about five hours, Gemini VI was about 1,200 kilometers from Gemini VII.

During Gemini VI’s second orbit of Earth, the astronauts made several course correction maneuvers that enabled them to close to within 320 kilometers of Gemini VII. After switching to a computerized rendezvous mode, Gemini VI continued to close the distance between the two spacecraft. At 2:33 p.m. on December 15, the spacecraft were only 36 meters apart and were in full view of each other. For nearly four complete orbits of Earth, the distance between the two spacecraft varied from 87 meters to as little as one-third of a meter. The astronauts could see each other easily, and the Gemini VI astronauts noted the eleven-day growth of beard on Borman and Lovell.

The flight of Gemini VI was planned as a two-day mission; its objective completed, it reentered Earth’s atmosphere to splash down in the Atlantic Ocean at 10:20 a.m. on December 16. Although there were some minor problems with fuel cells aboard Gemini VII, it was able to complete its fourteen-day mission and return to Earth at 9:05 a.m. on December 18.

To accomplish exploration Lunar exploration of the Moon by astronauts, NASA had decided upon a technique that became known as the lunar orbital rendezvous mode. This approach was different from other proposed methods in that the command and service modules of the Apollo spacecraft would remain in lunar orbit, while the lunar excursion vehicle (LEM) would undock and descend to the lunar surface. At the conclusion of the mission, the LEM would then depart the surface at the exact calculated moment and catch up with the orbiting Apollo spacecraft. The LEM, then, would dock with the command and service module combination, and the astronauts would leave the LEM and enter the command module. After the LEM was jettisoned, the Apollo spacecraft would begin its flight back to Earth.

The techniques used in the lunar orbital rendezvous mode first had to be tested and perfected. This was the primary mission of the Gemini program. It had to be shown that two spacecraft could rendezvous and dock, and that life-support systems could sustain human life aboard a spacecraft for a mission of long duration.

To accomplish rendezvous in the Gemini VI and VII mission, Gemini VI was launched into an orbit essentially coplanar with the target vehicle, Gemini VII. During the first few orbits, the astronauts of Gemini VI performed several ground-supplied midcourse maneuvers that led to a rendezvous with Gemini VII. Although the Soviets previously claimed that two of their Vostok spacecraft had conducted a rendezvous on August 12, 1962, the Gemini astronauts conducted the first rendezvous of two piloted, maneuverable vehicles. The two Soviet spacecraft were in two completely different orbital planes, and their spacecraft could not be maneuvered to close the distance between them.

The successful rendezvous of Gemini VI and VII led to the first docking between two spacecraft in the Gemini VIII mission. These flights proved that rendezvous and docking could be perfected and that the lunar orbital rendezvous technique would be feasible.

During the fourteen-day mission of Gemini VII, the astronauts conducted several experiments related to the effect of zero gravity on human physiology. An in-flight exerciser was used to help prevent deterioration of the heart muscle. In addition, the astronauts experimented with the use of pneumatic pressure cuffs. These cuffs were secured around the astronauts’ legs and inflated. The resulting stress on the venous system in the astronauts’ legs simulated a low-gravity environment.

Other experiments conducted by the Gemini VII crew measured the effects of spaceflight on the chemistry of body fluids, the breakdown of bone and muscle tissue, and human equilibrium.

The long-duration flight of Gemini VII proved that humans could survive in space over long periods of time. In fact, astronauts Borman and Lovell found that they could conduct many of their mission requirements without wearing pressure suits. Their comfort and mobility were greatly enhanced without the suits, and no detriment to crew health was noted. Space program, U.S.;Project Gemini
Project Gemini
Orbital rendezvous

• Borman, Frank, with Robert Serling. Countdown. New York: William Morrow, 1988. A very readable autobiography. Several chapters are devoted to astronaut Borman’s experiences while a part of the Gemini and Apollo programs.
• Fehse, Wigbert. Automated Rendezvous and Docking of Spacecraft. New York: Cambridge University Press, 2003. Discusses the docking of space vehicles in orbit. Part of the Cambridge Aerospace series.
• Glasstone, Samuel. The Sourcebook on the Space Sciences. Princeton, N.J.: D. Van Nostrand, 1965. Covers a wide range of topics from historical background of space exploration, orbits, trajectories, and propulsion units to a general description of the Sun, the planets, and the universe. The technical level varies with the subject area covered, but for the most part, the reader should have an elementary knowledge of physics, chemistry, and mathematics.
• Godwin, Robert, ed. Gemini 6: The NASA Mission Reports. Burlington, Ont.: Apogee Books, 1999. Compiled through research in NASA archives. Contains reprints of the Gemini VI press kit, as well as pre- and postmission reports. Includes a CD-ROM with film footage of Gemini VI and more than 180 still photographs from the flight.
• _______. Gemini 7: The NASA Mission Reports. Burlington, Ont.: Apogee Books, 2002. Compiled through research in NASA archives. Like Godwin’s book on Gemini VI, this collection contains reprints of the Gemini VII press kit, pre- and postmission reports, a CD-ROM with film footage of Gemini VII, still photographs from the flight, and an interview with Lovell.
• Hacker, Barton C., and James M. Grimwood. On the Shoulders of Titans. Washington, D.C.: Government Printing Office, 1977. A well-illustrated, well-documented volume covering the Gemini program from its beginnings. Suitable for general readers.
• Harland, David. How NASA Learned to Fly in Space: An Exciting Account of the Gemini Missions. Burlington, Ont.: Apogee Books, 2004. A mission-by-mission account of the Gemini flights, with good descriptions of engineering and science topics as well as information on crew members.
• Malik, P. W., and G. A. Souris. Project Gemini: A Technical Summary. Springfield, Va.: Federal Scientific and Technical Information, 1968. A highly technical volume describing the various systems incorporated within the Gemini spacecraft. A brief summary of each mission is included.
• Shelton, William. American Space Exploration: The First Decade. Boston: Little, Brown, 1967. A nontechnical volume that presents a history of rocketry and spaceflight from the early experiments of Robert Goddard through the Gemini program.

Congress Creates the National Aeronautics and Space Administration

Pioneer Space Program Is Launched

NASA Launches Project Gemini

First Human Orbits the Earth

Glenn Becomes the First American to Orbit Earth

Soviet Cosmonaut Conducts First Space Walk

Surveyor Program Prepares NASA for Piloted Moon Landings

Soyuz 4 and 5 Spacecraft Dock in Orbit

First Humans Land on the Moon

Apollo 13 Crew Survives Onboard Explosion