After Project Mercury came Project Gemini. Gemini continued to push the bounds of human space flight as we knew it, and was influential in paving the way toward a successful Apollo program. While Mercury only flew one astronaut at a time, Gemini flew two.

Gemini Capsule carrying two astronauts for the first time in American history
Gemini Capsule (from NASA)

Goals

During Project Gemini, NASA needed to achieve a variety of different test objectives in order to prove the Apollo missions would be possible. The most basic of these objectives was achieving long duration flights. The longest flight on Project Mercury was only about a day and a half. However, it takes about 3 days to travel to the Moon. Assuming no time is spent orbiting the Moon or landing on it, a Moon mission has a minimum duration of about 6 days. Gemini needed to prove this was possible, with a substantial margin for lunar exploration. Therefore, the Gemini missions were planned to prove humans could live in space for up to 2 weeks. This was achieved in December of 1965 on Gemini VII.

The Gemini VII Capsule
Gemini VII Capsule (from National Air and Space Museum)

While Gemini VII was planned to be the longest mission, it also unexpectedly became part of the first rendezvous in space, another huge goal for the Gemini missions. Originally, Gemini VI was planned to rendezvous with an unmanned Agena Target Vehicle. However, the Agena vehicle exploded during launch. To avoid huge delays in schedule (which would have delayed Apollo as well), they decided to revise the original plan and have Gemini VI-A (renamed by then) rendezvous with Gemini VII. Coming within 110 meters of each other in orbit, these two missions successfully achieved the first rendezvous in space, also in December of 1965.

First rendezvous in space between Gemini VI-A and Gemini VII
First rendezvous in space between Gemini VI-A and Gemini VII (from Smithsonian)

After the rendezvous, Gemini VII remained in space for two more days to complete the two-week mission while Gemini VI-A returned to Earth. Gemini VI-A’s landing became the first computer-controlled precision landing, checking off a third major goal – perfecting re-entry and landing.

Gemini VI-A: Walter Schirra and Thomas Stafford (from NASA)

Finally, after proving that a rendezvous between two spacecraft was possible, the last of the major goals was docking two spacecraft in orbit. The Apollo missions were founded on the possibility to rendezvous and dock a portion of the Lunar Modules with the Apollo capsules in orbit around the Moon, and this needed to first be proven in Earth’s orbit for Apollo to even be possible. This was achieved in March of 1966 on Gemini VIII to another Agena vehicle.

Docking of Gemini VIII with an Agena Target Vehicle (from NASA)

Mission Highlights

Gemini III – March 1965

While Gemini I and II were uncrewed tests of the spacecraft and launch vehicles, Gemini III became the first crewed mission. Flown by Gus Grissom and John Young, this was the first time two Americans had been in space at once. It was also the first time any spacecraft had performed an orbital maneuver.

Grissom and Young in Gemini III
Crew of Gemini III – Grissom and Young (from NASA)

Gemini IV – June 1965

Gemini IV was flown by Edward White and James McDivitt. White performed the first American Extravehicular Activity (EVA) that lasted 23 minutes. 11 experiments were also flown onboard Gemini IV including measuring radiation and electrostatic charge, using a bungee cord for exercise, and using a sextant to measure the spacecraft’s position by measuring the angular distance between two stars.

Ed White floating in space during the first American EVA on Gemini IV
Ed White during the first American EVA (from NASA)

Gemini V – August 1965

Gemini V set a record by being the longest mission in space with a total time of 9 days. Previously, the Soviet Union held the record from the 1963 Vostok 5 mission. The Soviet Union had been beating the United States on many fronts – first man and woman in space, first time more than one human had been in space at once, and first spacewalk – so this was a turning point in the United States’ side of the Space Race. It was piloted by Gordon Cooper and Pete Conrad.

Cooper and Conrad onboard Gemini V
Gemini V Crew – Cooper and Conrad (from NASA)

Gemini VI-A & Gemini VII – December 1965

Gemini VI was renamed to Gemini VI-A after a mission change following the explosion of an Agena vehicle in October of 1965. Gemini VI-A launched on December 15, 11 days after Gemini VII, with Walter Schirra and Thomas Stafford onboard. Geminis VI-A and VII performed the first rendezvous in space, coming within 110 meters of each other before pulling away. Gemini VI-A also performed the first computer-controlled reentry of a spacecraft. Two days after Gemini VI-A returned to Earth, the crew of Gemini VII, Frank Borman and Jim Lovell, completed their 14-day mission, the longest of all Gemini missions.

Gemini VII as seen in space from Gemini V
Gemini VII as seen from Gemini V (from NASA)

Gemini VIII – March 1966

Gemini VIII, flown by Neil Armstrong and David Scott, was the first mission to dock two spacecraft together in space. After docking to an Agena, the two spacecraft began to spin violently out of control. Thankfully, Armstrong was able to regain control of the vehicle, though this ended the mission early.

Agena Target Vehicle docking with Gemini VIII
Gemini VIII docking to Agena (from NASA)

Gemini IX-A – June 1966

Gemini IX was renamed to Gemini IX-A for two reasons – the original crew (Elliot See and Charles Bassett) unexpectedly died in a T-38 jet crash on their way to St. Louis, Missouri to inspect their Gemini spacecraft; and the original launch date of May 17th was cancelled due to an Agena launch failure. When they finally launched in June, the original mission called for docking to an Agena, but the Agena they were able to launch failed to reach orbit. Fortunately, they had a backup target called the Augmented Target Docking Adapter (ATDA). But, yet another setback, when they reached the ATDA, they discovered the nose cone shroud covering the docking hatch hadn’t separated properly. They affectionately named it the Angry Alligator and quickly replanned the mission. Despite all of these obstacles, Tom Stafford and Gene Cernan completed a successful mission that included two rendezvous maneuvers simulating what would eventually happen on the Apollo missions.

Nose cone shroud of the Agena vehicle did not release properly and was called an "Angry Alligator"
The Angry Alligator seen by Gemini IX-A (from NASA)

Gemini X – July 1966

Flying Gemini X, John Young and Michael Collins successfully docked with their Agena target vehicle (Gemini Agena Target Vehicle-10 or GATV-10) toward the beginning of their mission. Because they burned over double the amount of fuel they were expecting to burn during the rendezvous and docking, they used the GATV-10’s propulsion system to put them into a higher orbit. Using another spacecraft’s propulsion system had never been accomplished before. Eventually, they were able to put Gemini X into the same orbit that Gemini VIII was in. In that orbit was the old GATV-8, whose batteries had died months earlier. After disconnecting from GATV-10, Young and Collins performed a rendezvous to bring their spacecraft within 15 meters of GATV-8. Collins left the Gemini X spacecraft and travelled those 15 meters to collect a micrometeoroid detection unit from GATV-8, another feat that had never been attempted before.

Gemini X docking with GATV-10
Gemini X docking with GATV-10 (from Space.com)

Gemini XI – September 1966

Gemini XI performed the first-ever direct-ascent rendezvous, meaning it completed its rendezvous with GATV-11 on the first orbit after launch. This would become crucial during the Apollo missions so the Lunar Module could quickly dock with the Command Module orbiting the Moon. Two other substantial feats were achieved during this mission – the highest altitude ever achieved (a record that would remain until Apollo 8 ventured to the Moon), and creating artificial gravity in space for the first time by spinning the capsule which was attached by a tether to the GATV-11. Gemini XI was flown by Pete Conrad and Richard Gordon.

Gemini XI tethering (from NASA)

Gemini XII – November 1966

Concluding the Gemini program and finally bridging the gap between Mercury and Apollo, Gemini XII proved that astronauts could work effectively outside of a spacecraft. The crew consisted of James Lovell and Buzz Aldrin. Aldrin performed three EVAs over the course of the mission and performed a variety of different tasks to achieve the final goal of the Project Gemini.

Crew of Gemini XII completing the Gemini missions
Crew of Gemini XII after landing and completing the Gemini missions (from NASA)

Cool Facts

Gemini is Latin for “twins” since the capsule was designed to carry two astronauts.

Project Gemini was the first program to use NASA’s new Mission Control Center.

NASA's Mission Control in the 1960s
NASA’s Mission Control in the 1960s (from NASA)

The Launch Abort System that was used was not a rocket-powered escape “tower,” but rather ejection seats like in an aircraft. Thankfully no aborts were ever necessary though!

The ejection seats on Gemini
Gemini’s ejection seats (from Smithsonian)

Gemini was the first spacecraft to carry an on-board computer, which was necessary in order to control and perfect re-entry and landing.

The first on-board computer used during the Gemini era
Gemini’s on-board computer (from Smithsonian)

Fuel cells were first seen on spacecraft during Project Gemini. Fuel cells are like batteries, except that they produce energy as long as fuel and oxidizer is supplied. Therefore, they don’t need recharging and they don’t deplete resources. This makes them an extremely valuable source of energy for long-duration space flights.

Cutaway of the Gemini fuel cell
Cutaway of the Gemini fuel cell (from Smithsonian)

The first musical instruments played in space were a harmonica and some small bells. Schirra and Stafford on Gemini VI gave Mission Control a “Christmas Surprise” as they played Jingle Bells on these instruments and claimed to see Santa’s Sleigh traveling from the North Pole.

Gemini X time lapse (from Space.com)