Astronaut Tom Stafford (foreground) sits with Wally Schirra in the Gemini 6 spacecraft prior to launch. NASA
Sixty years ago, a fleet of sleek little spaceships paved the way for America to land a man on the Moon. Project Gemini was a series of two-man, Earth-orbital missions that pioneered rendezvous, docking, and maneuvering in-space, as well as spacewalking — all of which had to be perfected before there was any chance of traveling to the Moon.
Creating Gemini
Project Mercury, America’s first human space program, had systems that were largely automated. Gemini was different, for the first time putting pilots in control.
Less reliant on fault-prone electronics, Gemini was simpler to fly — truly a pilot’s spaceship. It was also tiny, affording its occupants a meager 80 cubic feet (2.27 cubic meters) of pressurized space for multi-day missions. Astronaut John Young likened it to sitting sideways in a phone booth. That compactness earned it the moniker Gusmobile, after Gemini 3 commander Virgil “Gus” Grissom, whose diminutive 5-foot 7-inch (1.7 m) stature made him the only astronaut who could fit in the cockpit and shut the hatch without hitting his head. This proved problematic for the 6-foot-tall (1.8 m) Tom Stafford, who piloted Gemini 6. Stafford eventually persuaded engineers to remove insulation inside the hatch, producing a slight bump that could accommodate taller astronauts.
Stafford also lobbied for dual hand controllers for commanders and pilots to perform maneuvers. The astronauts’ influence in controlling these minutiae of Gemini’s operational design went “far beyond … the normal test pilot in determining what was to be done and when,” write Barton Hacker and James Grimwood in NASA’s official Project Gemini history, On the Shoulders of Titans.
Preparing to fly gemini also meant an intense training schedule. “The days just seemed to have 48 hours, the weeks 14 days and still there was never enough time,” Grissom told an interviewer. “We saw our families just enough to reassure our youngsters they still had fathers.”
Of the 16 men who flew the 12 Gemini missions between March 1965 and November 1966, all but five later visited the Moon and six walked on its surface. Most were test pilots, a third held master’s degrees, and Gemini 12’s Buzz Aldrin had a doctorate.
Their eclectic skillsets drew them like moths to the entrancing flame of Gemini’s unique mission demands. Ed White, Dave Scott, and Gene Cernan drew spacewalk assignments. Frank Borman commanded the long-duration Gemini 7 flight. And Wally Schirra, along with Stafford, won seats on Gemini 6, the first space rendezvous.
Meeting in orbit
A rendezvous is an intricate ballet of celestial mechanics to bring two spacecraft in differing orbital planes together. It was essential for Project Apollo, when the Lunar Module, (LM) ascending from the Moon’s surface, would dock to the orbiting Command/Service Module (CSM). If emergencies arose, rendezvous had to happen quickly. And Gemini would master its art for the first time.
But early Gemini crews’ efforts to station-keep with the discarded upper stages of their Titan II rockets in orbit yielded mixed results. Astronauts struggled to judge distances by eyesight alone. Tracking lights were hard to see against Earth’s glare. In June 1965, as Gemini 4 commander Jim McDivitt maneuvered toward his target, he was perplexed when the slowly tumbling booster seemed to move away from him.
It was an important lesson: Adding velocity raises altitude, which moved Gemini into a higher orbit than the target. But paradoxically, it also caused them to fall behind the target as their orbital period (a direct function of their distance from Earth’s center of gravity) also increased. To clinch a rendezvous, astronauts had to drop to a lower orbit, move ahead of the target, and then rise back up to meet it.
For pilots accustomed to flying in tight formations with jet aircraft, it went against the grain of their professional experience. “It’s a hard thing to learn,” wrote astronaut Deke Slayton in his memoir, Deke, “since it’s kind of backward from anything you know as a pilot.”
Plans for Gemini 5 to rendezvous with a small deployable pod in August 1965 were thwarted by a fuel cell failure. But Gordon Cooper and Charles “Pete” Conrad simulated this meeting with a “phantom” rendezvous instead, successfully maneuvering their ship into the same orbital plane as their imaginary target.
The first true rendezvous was then to be performed by Gemini 6 in October 1965 — but it almost didn’t happen. The mission’s Agena-D target spacecraft, intended for launch ahead of the astronauts’ capsule, exploded shortly after launch. NASA instead decided to fly Gemini 6 in tandem with Gemini 7, using the latter as the target spacecraft. In December 1965, Schirra and Stafford triumphantly maneuvered Gemini 6 within 12 inches (30 centimeters) of Gemini 7 and held that position for five hours. The craft were so close that the two crews could wave to each other.
Schirra reported Gemini handled crisply and precisely, allowing him to make velocity inputs of just 1.2 inches per second (3 cm/s) — good enough for a controlled rendezvous and physical docking. But it was highly unforgiving of errors in terms of time and propellant wastage.
The Mark One Cranium Computer
Although Gemini astronauts used a combination of radar, inertial guidance platforms, and computers to assist them, the men remained part of the equation. During Gemini 6’s rendezvous, Stafford employed a circular slide-rule and plotting chart to cross-check radar data.
In March 1966, Gemini 8’s Neil Armstrong and Dave Scott rendezvoused and docked with an Agena-D for the first time without incident. But soon a thruster short-circuit threw the combined spacecraft into an uncontrollable roll that peaked at 60 revolutions per minute. Only the astronauts’ quick actions activating Gemini’s retrorockets halted the roll and saved their lives — but their planned three-day mission was aborted after only 10 hours.
“With our vision beginning to blur, locating the right switch was not simple,” wrote Scott in his memoir, Two Sides of the Moon. “Neil knew exactly where that switch was without having to see it. Reaching above his head … while at the same time grappling with the hand controller … was an extraordinary feat.”
In July 1966, John Young and Mike Collins used an expanded computer memory and portable sextant to calculate maneuvers independently of NASA’s mission control during Gemini 10. When a computer glitch almost caused them to miss their Agena-D target, Young took manual control and made a successful rendezvous and docking. “They really had to eyeball their way in,” wrote an admiring Slayton.
Soon after that, Gemini 11 in September 1966 achieved an Agena-D docking on its first orbit, 85 minutes after launch, simulating an emergency rendezvous between an Apollo LM and CSM. The astronauts also boosted their orbit to 850 miles (1,370 km) above Earth — the highest altitude of any non-lunar manned mission until Polaris Dawn in September 2024.
Finally, on Gemini 12 in November 1966, a radar failure forced Jim Lovell and Buzz Aldrin to also rendezvous manually with their Agena-D. As Lovell flew the ship, Aldrin broke out charts and scrutinized closely spaced lines of data, bringing Gemini to a close by proving yet again the worth of the human brain — the “Mark One Cranium Computer” — to complex spaceflight operations.
Touching down
Despite the hiccups while testing rendezvous and docking, Gemini’s astronauts always made it back to Earth. The spacecraft computer could predict the end-of-mission splashdown point, allowing the commander to steer toward the target in the ocean. Although incorrect wind tunnel data caused two missions to land short of their intended point, later flights splashed down impressively close to target. Notably, Gemini 9 in June 1966 landed just 2,300 feet (700 m) from its intended spot — so close that the astronauts offered thumbs-up signals to the recovery ship’s crew.
The pace of Project Gemini was matched only by the nation’s fervor to achieve boots on the Moon by 1970. “We had been running on adrenaline,” wrote Dave Scott about his Gemini 8 experience — an apt phrase that could be well applied to the entire program: an endeavor that not only brought America closer to a lunar landing but also demonstrated the centrality of the astronaut in achieving mission success.
