A | B | C | D | E | F | G | H | CH | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
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| Program overview | |
|---|---|
| Country | United States |
| Organization | NASA |
| Purpose |
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| Status | Completed |
| Program history | |
| Cost |
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| Duration | 1961–1966 |
| First flight |
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| First crewed flight |
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| Last flight |
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| Successes | 10 |
| Partial failures | 2 (Gemini VIII and IX-A) |
| Launch site(s) | Cape Kennedy |
| Vehicle information | |
| Crewed vehicle(s) | Gemini capsule |
| Launch vehicle(s) | |
| Part of a series on the |
| United States space program |
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Project Gemini (IPA: /ˈdʒɛmɪni/) was the second United States human spaceflight program to fly. Conducted after the first American manned space program, Project Mercury, while the Apollo program was still in early development, Gemini was conceived in 1961 and concluded in 1966. The Gemini spacecraft carried a two-astronaut crew. Ten Gemini crews and 16 individual astronauts flew low Earth orbit (LEO) missions during 1965 and 1966.
Gemini's objective was the development of space travel techniques to support the Apollo mission to land astronauts on the Moon. In doing so, it allowed the United States to catch up and overcome the lead in human spaceflight capability the Soviet Union had obtained in the early years of the Space Race, by demonstrating mission endurance up to just under 14 days, longer than the eight days required for a round trip to the Moon; methods of performing extravehicular activity (EVA) without tiring; and the orbital maneuvers necessary to achieve rendezvous and docking with another spacecraft. This left Apollo free to pursue its prime mission without spending time developing these techniques.
All Gemini flights were launched from Launch Complex 19 (LC-19) at Cape Kennedy Air Force Station in Florida. Their launch vehicle was the Gemini–Titan II, a modified Intercontinental Ballistic Missile (ICBM).[note 1] Gemini was the first program to use the newly built Mission Control Center at the Houston Manned Spacecraft Center for flight control.[note 2]
The astronaut corps that supported Project Gemini included the "Mercury Seven", "The New Nine", and "The Fourteen". During the program, three astronauts died in air crashes during training, including both members of the prime crew for Gemini 9. The backup crew flew this mission.
Gemini was robust enough that the United States Air Force planned to use it for the Manned Orbital Laboratory (MOL) program, which was later canceled. Gemini's chief designer, Jim Chamberlin, also made detailed plans for cislunar and lunar landing missions in late 1961. He believed Gemini spacecraft could fly in lunar operations before Project Apollo, and cost less. NASA's administration did not approve those plans. In 1969, Lukas Bingham proposed a "Big Gemini" that could have been used to shuttle up to 12 astronauts to the planned space stations in the Apollo Applications Project (AAP). The only AAP project funded was Skylab (The first American space station) – which used existing spacecraft and hardware – thereby eliminating the need for Big Gemini.
Pronunciation
The constellation for which the project was named is commonly pronounced /ˈdʒɛmɪnaɪ/, the last syllable rhyming with eye. However, staff of the Manned Spacecraft Center, including the astronauts, tended to pronounce the name /ˈdʒɛmɪni/, rhyming with knee. NASA's public affairs office then issued a statement in 1965 declaring "Jeh-mih-nee" the "official" pronunciation.[2] Gus Grissom, acting as Houston capsule communicator when Ed White performed his spacewalk on Gemini 4, is heard on flight recordings pronouncing the spacecraft's call sign "Jeh-mih-nee 4", and the NASA pronunciation is used in the 2018 film First Man.[2]
Program origins and objectives
The Apollo program was conceived in early 1960 as a three-man spacecraft to follow Project Mercury. Jim Chamberlin, the head of engineering at the Space Task Group (STG), was assigned in February 1961 to start working on a bridge program between Mercury and Apollo.[3] He presented two initial versions of a two-man spacecraft, then designated Mercury Mark II, at a NASA retreat at Wallops Island in March 1961.[3] Scale models were shown in July 1961 at the McDonnell Aircraft Corporation's offices in St. Louis.[3]
After Apollo was chartered to land men on the Moon by President John F. Kennedy on May 25, 1961, it became evident to NASA officials that a follow-on to the Mercury program was required to develop certain spaceflight capabilities in support of Apollo. NASA approved the two-man / two-vehicle program rechristened Project Gemini (Latin for "twins"), in reference to the third constellation of the Zodiac with its twin stars Castor and Pollux, on December 7, 1961.[3] McDonnell Aircraft was contracted to build it on December 22, 1961.[4] The program was publicly announced on January 3, 1962, with these major objectives:[5]
- To demonstrate endurance of humans and equipment in spaceflight for extended periods, at least eight days required for a Moon landing, to a maximum of two weeks
- To effect rendezvous and docking with another vehicle, and to maneuver the combined spacecraft using the propulsion system of the target vehicle
- To demonstrate Extra-Vehicular Activity (EVA), or space-"walks" outside the protection of the spacecraft, and to evaluate the astronauts' ability to perform tasks there
- To perfect techniques of atmospheric reentry and touchdown at a pre-selected location on land[note 3]
Team
Chamberlin designed the Gemini capsule, which carried a crew of two. He was previously the chief aerodynamicist on Avro Canada's CF-105 Arrow fighter interceptor program.[6] Chamberlin joined NASA along with 25 senior Avro engineers after cancellation of the Canadian Arrow program, and became head of the U.S. Space Task Group's engineering division in charge of Gemini.[6][7] The prime contractor was McDonnell Aircraft Corporation, which was also the prime contractor for the Project Mercury capsule.[8]
Astronaut Gus Grissom was heavily involved in the development and design of the Gemini spacecraft. What other Mercury astronauts dubbed "Gusmobile" was so designed around Grissom's 5'6" body that, when NASA discovered in 1963 that 14 of 16 astronauts would not fit in the spacecraft, the interior had to be redesigned.[9] Grissom wrote in his posthumous 1968 book Gemini! that the realization of Project Mercury's end and the unlikelihood of his having another flight in that program prompted him to focus all his efforts on the upcoming Gemini program.
The Gemini program was managed by the Manned Spacecraft Center, located in Houston, Texas, under direction of the Office of Manned Space Flight, NASA Headquarters, Washington, D.C. Dr. George E. Mueller, Associate Administrator of NASA for Manned Space Flight, served as acting director of the Gemini program. William C. Schneider, Deputy Director of Manned Space Flight for Mission Operations served as mission director on all Gemini flights beginning with Gemini 6A.
Guenter Wendt was a McDonnell engineer who supervised launch preparations for both the Mercury and Gemini programs and would go on to do the same when the Apollo program launched crews. His team was responsible for completion of the complex pad close-out procedures just prior to spacecraft launch, and he was the last person the astronauts would see prior to closing the hatch. The astronauts appreciated his taking absolute authority over, and responsibility for, the condition of the spacecraft and developed a good-humored rapport with him.[10]
Spacecraft
NASA selected McDonnell Aircraft, which had been the prime contractor for the Project Mercury capsule, in 1961 to build the Gemini capsule, the first of which was delivered in 1963. The spacecraft was 18 feet 5 inches (5.61 m) long and 10 feet (3.0 m) wide, with a launch weight varying from 7,100 to 8,350 pounds (3,220 to 3,790 kg).[11]
The Gemini crew capsule (referred to as the Reentry Module) was essentially an enlarged version of the Mercury capsule. Unlike Mercury, the retrorockets, electrical power, propulsion systems, oxygen, and water were located in a detachable Adapter Module behind the Reentry Module which would burn up on reentry. A major design improvement in Gemini was to locate all internal spacecraft systems in modular components, which could be independently tested and replaced when necessary, without removing or disturbing other already tested components.
Reentry module
Many components in the capsule itself were reachable through their own small access doors. Unlike Mercury, Gemini used completely solid-state electronics, and its modular design made it easy to repair.[12]
Gemini's emergency launch escape system did not use an escape tower powered by a solid-fuel rocket, but instead used aircraft-style ejection seats. The tower was heavy and complicated, and NASA engineers reasoned that they could do away with it as the Titan II's hypergolic propellants would burn immediately on contact. A Titan II booster explosion had a smaller blast effect and flame than on the cryogenically fueled Atlas and Saturn. Ejection seats were sufficient to separate the astronauts from a malfunctioning launch vehicle. At higher altitudes, where the ejection seats could not be used, the astronauts would return to Earth inside the spacecraft, which would separate from the launch vehicle.[13]
The main proponent of using ejection seats was Chamberlin, who had never liked the Mercury escape tower and wished to use a simpler alternative that would also reduce weight. He reviewed several films of Atlas and Titan II ICBM failures, which he used to estimate the approximate size of a fireball produced by an exploding launch vehicle and from this he gauged that the Titan II would produce a much smaller explosion, thus the spacecraft could get away with ejection seats.
Maxime Faget, the designer of the Mercury LES, was on the other hand less-than-enthusiastic about this setup. Aside from the possibility of the ejection seats seriously injuring the astronauts, they would also only be usable for about 40 seconds after liftoff, by which point the booster would be attaining Mach 1 speed and ejection would no longer be possible. He was also concerned about the astronauts being launched through the Titan's exhaust plume if they ejected in-flight and later added, "The best thing about Gemini was that they never had to make an escape."[14]
The Gemini ejection system was never tested with the Gemini cabin pressurized with pure oxygen, as it was prior to launch. In January 1967, the fatal Apollo 1 fire demonstrated that pressurizing a spacecraft with pure oxygen created an extremely dangerous fire hazard.[15] In a 1997 oral history, astronaut Thomas P. Stafford commented on the Gemini 6 launch abort in December 1965, when he and command pilot Wally Schirra nearly ejected from the spacecraft:
So it turns out what we would have seen, had we had to do that, would have been two Roman candles going out, because we were 15 or 16 psi, pure oxygen, soaking in that for an hour and a half. You remember the tragic fire we had at the Cape. (...) Jesus, with that fire going off and that, it would have burned the suits. Everything was soaked in oxygen. So thank God. That was another thing: NASA never tested it under the conditions that they would have had if they would have had to eject. They did have some tests at China Lake where they had a simulated mock-up of Gemini capsule, but what they did is fill it full of nitrogen. They didn't have it filled full of oxygen in the sled test they had.[16]
Gemini was the first astronaut-carrying spacecraft to include an onboard computer, the Gemini Guidance Computer, to facilitate management and control of mission maneuvers. This computer, sometimes called the Gemini Spacecraft On-Board Computer (OBC), was very similar to the Saturn Launch Vehicle Digital Computer. The Gemini Guidance Computer weighed 58.98 pounds (26.75 kg). Its core memory had 4096 addresses, each containing a 39-bit word composed of three 13-bit "syllables". All numeric data was 26-bit two's-complement integers (sometimes used as fixed-point numbers), either stored in the first two syllables of a word or in the accumulator. Instructions (always with a 4-bit opcode and 9 bits of operand) could go in any syllable.[17][18][19][20]
Unlike Mercury, Gemini used in-flight radar and an artificial horizon, similar to those used in the aviation industry.[17] Like Mercury, Gemini used a joystick to give the astronauts manual control of yaw, pitch, and roll. Gemini added control of the spacecraft's translation (forward, backward, up, down, and sideways) with a pair of T-shaped handles (one for each crew member). Translation control enabled rendezvous and docking, and crew control of the flight path. The same controller types were also used in the Apollo spacecraft.[9]
The original intention for Gemini was to land on solid ground instead of at sea, using a Rogallo wing rather than a parachute, with the crew seated upright controlling the forward motion of the craft. To facilitate this, the airfoil did not attach just to the nose of the craft, but to an additional attachment point for balance near the heat shield. This cord was covered by a strip of metal which ran between the twin hatches.[21] This design was ultimately dropped, and parachutes were used to make a sea landing as in Mercury. The capsule was suspended at an angle closer to horizontal, so that a side of the heat shield contacted the water first. This eliminated the need for the landing bag cushion used in the Mercury capsule.
Adapter module
The adapter module in turn was separated into a Retro module and an Equipment module.
Retro module
The Retro module contained four solid-fuel TE-M-385 Star-13E retrorockets, each spherical in shape except for its rocket nozzle, which were structurally attached to two beams that reached across the diameter of the retro module, crossing at right angles in the center.[22] Re-entry began with the retrorockets firing one at a time. Abort procedures at certain periods during lift-off would cause them to fire at the same time, thrusting the Descent module away from the Titan rocket.
Equipment module
Gemini was equipped with an Orbit Attitude and Maneuvering System (OAMS), containing sixteen thrusters for translation control in all three perpendicular axes (forward/backward, left/right, up/down), in addition to attitude control (pitch, yaw, and roll angle orientation) as in Mercury. Translation control allowed changing orbital inclination and altitude, necessary to perform space rendezvous with other craft, and docking with the Agena Target Vehicle (ATV), with its own rocket engine which could be used to perform greater orbit changes.
Early short-duration missions had their electrical power supplied by batteries; later endurance missions used the first fuel cells in crewed spacecraft.
Gemini was in some regards more advanced than Apollo because the latter program began almost a year earlier. It became known as a "pilot's spacecraft" due to its assortment of jet fighter-like features, in no small part due to Gus Grissom's influence over the design, and it was at this point where the US crewed space program clearly began showing its superiority over that of the Soviet Union with long duration flight, rendezvous, and extravehicular capability.[note 4] The Soviet Union during this period was developing the Soyuz spacecraft intended to take cosmonauts to the Moon, but political and technical problems began to get in the way, leading to the ultimate end of their crewed lunar program.
Launch vehicle
The Titan II debuted in 1962 as the Air Force's second-generation ICBM to replace the Atlas. By using hypergolic fuels, it could be stored longer and be easily readied for launch in addition to being a simpler design with fewer components. The only caveat was the propellant mix (nitrogen tetroxide and hydrazine) were extremely toxic compared to the Atlas' liquid oxygen/RP-1. However, the Titan had considerable difficulty being man-rated due to early problems with pogo oscillation. The launch vehicle used a radio guidance system that was unique to launches from Cape Kennedy.
Astronauts
Deke Slayton, as director of flight crew operations, had primary responsibility for assigning crews for the Gemini program. Each flight had a primary crew and backup crew, and the backup crew would rotate to primary crew status three flights later. Slayton intended for first choice of mission commands to be given to the four remaining active astronauts of the Mercury Seven: Alan Shepard, Grissom, Cooper, and Schirra. (John Glenn had retired from NASA in January 1964 and Scott Carpenter, who was blamed by some in NASA management for the problematic reentry of Aurora 7, was on leave to participate in the Navy's SEALAB project and was grounded from flight in July 1964 due to an arm injury sustained in a motorbike accident. Slayton himself continued to be grounded due to a heart problem.) As for Shepard, during training on the Gemini Project, his inner ear deficiency due to Menière's Disease would effectively ground him as well and keep him removed from the flight roster until he underwent corrective surgery and would not fly on Gemini at all, but return to flight with Apollo 14 as Commander.
Titles used for the left-hand (command) and right-hand (pilot) seat crew positions were taken from the U.S. Air Force pilot ratings, Command Pilot and Pilot. Sixteen astronauts flew on 10 crewed Gemini missions:
| Group | Astronaut | Service | Mission, prime crew position | Mission, backup crew position |
|---|---|---|---|---|
| Astronaut Group 1 | Gordon Cooper | USAF | Gemini 5 Command Pilot | Gemini 12 Command Pilot |
| Virgil "Gus" Grissom | Gemini 3 Command Pilot | Gemini 6A Command Pilot | ||
| Walter M. Schirra | USN | Gemini 6A Command Pilot | Gemini 3 Command Pilot | |
| Astronaut Group 2 | Neil Armstrong | Civilian[note 5] | Gemini 8 Command Pilot | Gemini 5 Command Pilot |
| Gemini 11 Command Pilot | ||||
| Frank Borman | USAF | Gemini 7 Command Pilot | Gemini 4 Command Pilot | |
| Charles "Pete" Conrad | USN | Gemini 5 Pilot | Gemini 8 Command Pilot | |
| Gemini 11 Command Pilot | ||||
| Jim Lovell | USN | Gemini 7 Pilot | Gemini 4 Pilot | |
| Gemini 12 Command Pilot | Gemini 9A Command Pilot | |||
| James McDivitt | USAF | Gemini 4 Command Pilot | — | |
| Thomas P. Stafford | Gemini 6A Pilot | Gemini 3 Pilot[note 6] | ||
| Gemini 9A Command Pilot | ||||
| Ed White | Gemini 4 Pilot | Gemini 7 Command Pilot | ||
| John Young | USN | Gemini 3 Pilot | Gemini 6A Pilot | |
| Gemini 10 Command Pilot | ||||
| Astronaut Group 3 | Edwin "Buzz" Aldrin | USAF | Gemini 12 Pilot | Gemini 9A Pilot |
| Eugene Cernan | USN | Gemini 9A Pilot | Gemini 12 Pilot | |
| Michael Collins | USAF | Gemini 10 Pilot | Gemini 7 Pilot | |
| Richard F. Gordon | USN | Gemini 11 Pilot | Gemini 8 Pilot | |
| David Scott | USAF | Gemini 8 Pilot | — | |
| Astronauts selected but did not fly | ||||
| Astronaut Group 1 | Alan Shepard | USN | Gemini 3 Command Pilot[note 7] | — |
| Astronaut Group 2 | Elliot See | Civilian[note 8] | Gemini 9 Command Pilot[note 9] | Gemini 5 Pilot |
| Astronaut Group 3 | William Anders | USAF | — | Gemini 11 Pilot |
| Charles Bassett | Gemini 9 Pilot[note 9] | — | ||
| Alan Bean | USN | — | Gemini 10 Command Pilot | |
| Clifton Williams | USMC | — | Gemini 10 Pilot | |
Crew selection
In late 1963, Slayton selected Shepard and Stafford for Gemini 3, McDivitt and White for Gemini 4, and Schirra and Young for Gemini 5 (which was to be the first Agena rendezvous mission). The backup crew for Gemini 3 was Grissom and Borman, who were also slated for Gemini 6, to be the first long-duration mission. Finally Conrad and Lovell were assigned as the backup crew for Gemini 4.
Delays in the production of the Agena Target Vehicle caused the first rearrangement of the crew rotation. The Schirra and Young mission was bumped to Gemini 6 and they became the backup crew for Shepard and Stafford. Grissom and Borman then had their long-duration mission assigned to Gemini 5.
The second rearrangement occurred when Shepard developed Ménière's disease, an inner ear problem. Grissom was then moved to command Gemini 3. Slayton felt that Young was a better personality match with Grissom and switched Stafford and Young. Finally, Slayton tapped Cooper to command the long-duration Gemini 5. Again for reasons of compatibility, he moved Conrad from backup commander of Gemini 4 to pilot of Gemini 5, and Borman to backup command of Gemini 4. Finally he assigned Armstrong and Elliot See to be the backup crew for Gemini 5. The third rearrangement of crew assignment occurred when Slayton felt that See wasn't up to the physical demands of EVA on Gemini 8. He reassigned See to be the prime commander of Gemini 9 and put Scott as pilot of Gemini 8 and Charles Bassett as the pilot of Gemini 9.
The fourth and final rearrangement of the Gemini crew assignment occurred after the deaths of See and Bassett when their trainer jet crashed, coincidentally into a McDonnell building which held their Gemini 9 capsule in St. Louis. The backup crew of Stafford and Cernan was then moved up to the new prime crew of Gemini 9A. Lovell and Aldrin were moved from being the backup crew of Gemini 10 to be the backup crew of Gemini 9. This cleared the way through the crew rotation for Lovell and Aldrin to become the prime crew of Gemini 12.
Along with the deaths of Grissom, White, and Roger Chaffee in the fire of Apollo 1, this final arrangement helped determine the makeup of the first seven Apollo crews, and who would be in position for a chance to be the first to walk on the Moon.
Missions
In April 1964 and January 1965, two Gemini missions were flown without crews to test systems and the heat shield. These were followed by 10 flights with crews in 1965 and 1966. All were launched by Titan II launch vehicles. Some highlights from the Gemini program:
- Gemini 3 (Grissom and Young) was the first crewed Gemini mission, first multi-crewed US mission, and the first crewed spacecraft to use thrusters to change its orbit.
- On Gemini 4, Ed White became the first American to make an extravehicular activity (EVA, or "spacewalk") on June 3, 1965.
- Gemini 5 (August 21–29, 1965) demonstrated the 8-day endurance necessary for an Apollo lunar mission with the first use of fuel cells to generate its electrical power.
- Gemini 6A accomplished the first space rendezvous with its sister craft Gemini 7 in December 1965, with Gemini 7 setting a 14-day endurance record for its flight.
- Gemini 8 achieved the first space docking with an uncrewed Agena target vehicle.
- Gemini 10 established that radiation at high altitude was not a problem, further demonstrated the ability to rendezvous with a passive object, and was the first Gemini mission to fire the Agena's own rocket. Michael Collins would be the first person to meet another spacecraft in orbit, during his second successful EVA.
- Gemini 11 first direct-ascent (first orbit) rendezvous with an Agena Target Vehicle, docking with it 1 hour 34 minutes after launch. Set a crewed Earth orbital altitude record of 739.2 nautical miles (1,369.0 km) in September 1966, using the Agena target vehicle's propulsion system. This record still stands as of 2022.[23]
- On Gemini 12, Edwin "Buzz" Aldrin became the first space traveler to prove that useful work (EVA) could be done outside a spacecraft without life-threatening exhaustion, due to newly implemented footholds, handholds, and scheduled rest periods.
Rendezvous in orbit is not a straightforward maneuver. Should a spacecraft increase its speed to catch up with another, the result is that it goes into a higher and slower orbit and the distance thereby increases. The right procedure is to go to a lower orbit first and which increases relative speed, and then approach the target spacecraft from below and decrease orbital speed to meet it.[24] To practice these maneuvers, special rendezvous and docking simulators were built for the astronauts.[25]
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Edward White during spacewalk, Gemini 4, June 1965 -
Rendezvous of Gemini 6A and 7, December 1965 -
First docking; Agena target is seen from Gemini 8, March 1966
| Mission | LV serial No | Spacecraft Nº | Command Pilot | Pilot | Mission dates | Launch time | Duration |
|---|---|---|---|---|---|---|---|
| Gemini 1 | GLV-1 12556 | SC1 | Uncrewed | Uncrewed | 8–12 April 1964 | 16:00 UTC | 03d 23h1 |
| First test flight of Gemini; spacecraft was intentionally destroyed during re-entry 1: The mission duration was 4h 50m, sufficient to achieve all of the mission aims in three orbits; the spacecraft remained in orbit for 3d 23h. | |||||||
| Gemini 2 | GLV-2 12557 | SC2 | Uncrewed | Uncrewed | 19 January 1965 | 14:04 UTC | 00d 00h 18m 16s |
| Suborbital flight to test heat shield | |||||||
Gemini 3
|
GLV-3 12558 | SC3 | Grissom | Young | 23 March 1965 | 14:24 UTC | 00d 04h 52m 31s |
| First crewed Gemini flight, three orbits. | |||||||
Gemini IV 
|
GLV-4 12559 | SC4 | McDivitt | White | 3–7 June 1965 | 15:16 UTC | 04d 01h 56m 12s |
| Included first extravehicular activity (EVA) by an American; White's "space walk" was a 22-minute EVA exercise. | |||||||
Gemini V
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