Project Gemini

• 1. Introduction

  ›

  Project Gemini launched its first crewed mission on the 23rd of March 1965, but the real story begins four years earlier, in a problem no one had solved: how do you teach people to work in space before you send them to the Moon? Between Mercury and Apollo sat a gap, a gap in knowledge, in skill, in confidence, and Gemini was built to close it. Could two astronauts survive two weeks sealed inside a capsule barely larger than a car's front seat? Could a spacecraft find and lock onto another object orbiting hundreds of miles above Earth, at speeds of thousands of miles per hour? Could a human being step outside a vehicle in the void of space and actually do anything useful, without exhausting themselves to the point of danger? These were not rhetorical questions. They were the questions that stood between the United States and the Moon.

• 2. A Program Born from a Gap

  ›

  Jim Chamberlin, an engineer who had led aerodynamics on the Avro Canada CF-105 Arrow fighter interceptor, arrived at NASA along with 25 senior Avro colleagues after Canada canceled the Arrow program. By February 1961 he was assigned to design a bridge between Mercury and Apollo. He presented two versions of a two-man spacecraft at a NASA retreat at Wallops Island in March 1961, and scale models were shown at the McDonnell Aircraft Corporation offices in St. Louis that July.

  President John F. Kennedy's declaration on the 25th of May 1961, committing the United States to a lunar landing, made the bridge program urgent. NASA formally approved the two-man program on the 7th of December 1961, naming it Project Gemini after the Latin word for twins, a reference to the third constellation of the Zodiac and its twin stars Castor and Pollux. McDonnell Aircraft was contracted to build it just two weeks later, on the 22nd of December 1961, and the program was publicly announced on the 3rd of January 1962.

  The objectives were specific and demanding: prove humans and hardware could endure at least eight days in space; figure out how to rendezvous and dock with another vehicle; demonstrate that astronauts could work outside the capsule; and land at a pre-selected location on reentry. Each goal was a direct rehearsal for what Apollo would need to do on the way to the Moon.

• 3. The Spacecraft Itself

  ›

  The first Gemini capsule was delivered in 1963. It measured 18 feet 5 inches long and 10 feet wide, and its launch weight ranged from 7,100 to 8,350 pounds. Gus Grissom, one of the original Mercury Seven astronauts, had such deep involvement in its design that other Mercury astronauts nicknamed it the "Gusmobile." The craft was so shaped around Grissom's 5 foot 6 inch frame that when NASA discovered in 1963 that 14 of the 16 astronauts could not fit inside it, engineers had to rebuild the interior.

  Gemini used completely solid-state electronics, a major step forward from Mercury. It was also the first crewed American spacecraft to carry an onboard computer, the Gemini Guidance Computer, which weighed 58.98 pounds and held 4,096 memory addresses, each containing a 39-bit word. Unlike Mercury, Gemini gave astronauts manual control over the spacecraft's translation in all directions, using a pair of T-shaped handles, one for each crew member. That translation control was what made orbital rendezvous physically possible.

  The original plan for Gemini called for landing on solid ground using a Rogallo wing, with the crew seated upright guiding the craft's forward motion. That design was dropped, and parachutes were used instead. The capsule splashed down at an angle so that a side of the heat shield hit the water first, removing the need for the inflatable landing bag that Mercury had required.

• 4. The Ejection Seat Gamble

  ›

  Gemini replaced the escape tower that Mercury used with aircraft-style ejection seats, a decision that created one of the most serious hidden risks of the entire program. Chamberlin, who had never liked the Mercury escape tower, reviewed films of Atlas and Titan II ICBM failures to estimate explosion sizes. He concluded that the Titan II's hypergolic propellants would produce a smaller fireball than cryogenically fueled rockets, and that ejection seats were sufficient.

  Maxime Faget, who had designed the Mercury escape system, was less convinced. He pointed out that the seats would only be usable for roughly 40 seconds after liftoff, after which the booster would be approaching Mach 1 and ejection would no longer be safe. He also worried about astronauts being launched through the Titan's exhaust plume during an in-flight ejection.

  What neither Faget nor Chamberlin fully anticipated was a subtler danger. The ejection system was never tested with the cabin pressurized with pure oxygen, as it was before every launch. In December 1965, Thomas P. Stafford and command pilot Wally Schirra came within a breath of ejecting during the Gemini 6 launch abort. In a 1997 oral history, Stafford described what would have happened: the suits and cabin had been soaking in pure oxygen for an hour and a half, and ejecting into the ambient atmosphere would likely have ignited everything. He quoted himself reflecting later, "So thank God." The fatal Apollo 1 fire in January 1967, caused by a pure oxygen atmosphere, made visible what Gemini had quietly lived with throughout its program.

• 5. The Astronauts Who Flew It

  ›

  Deke Slayton, as director of flight crew operations, orchestrated the crew assignments for all ten crewed Gemini missions, and the process involved four separate rearrangements, each driven by circumstances no one could fully predict. Slayton's original intention was to give first choice of mission commands to the four remaining active Mercury Seven astronauts: Alan Shepard, Grissom, Gordon Cooper, and Schirra. John Glenn had retired from NASA in January 1964. Scott Carpenter was on leave and was grounded from flight in July 1964 after an arm injury sustained in a motorbike accident. Slayton himself remained grounded due to a heart condition.

  Shepar's inner ear deficiency from Meniere's Disease grounded him from Gemini entirely. The third rearrangement came when Slayton concluded that Elliot See was not physically ready for EVA duties, moving him to prime commander of Gemini 9 instead of Gemini 8.

  The fourth and final rearrangement was made necessary by tragedy. See and Charles Bassett, the prime crew for Gemini 9, died when their training jet crashed, and it crashed coincidentally into a McDonnell building in St. Louis that held their Gemini 9 capsule. The backup crew of Tom Stafford and Gene Cernan moved into the prime slot for what was redesignated Gemini 9A. Jim Lovell and Buzz Aldrin were shifted to become the prime crew of Gemini 12. That chain of reassignments, combined with the deaths of Grissom, Ed White, and Roger Chaffee in the Apollo 1 fire, directly shaped which astronauts would be in position to attempt the first Moon landing.

• 6. Ten Missions, Ten Lessons

  ›

  Gemini 3, crewed by Grissom and John Young in March 1965, was the first American spacecraft to actively change its own orbit using thrusters. Gemini 4 carried Ed White on the first American spacewalk, a 22-minute EVA on the 3rd of June 1965. Gemini 5, flown by Cooper and Pete Conrad from the 21st to the 29th of August 1965, completed the first week-long flight and introduced fuel cells to generate electrical power, proving that the basic biological demands of an Apollo mission were manageable.

  Gemini 6A and Gemini 7 together accomplished the first space rendezvous in December 1965, with the two craft holding station-keeping at distances from 1 to 300 feet for more than five hours. Gemini 7 set a 14-day endurance record on that flight. During the quiet hours, Schirra and Stafford aboard Gemini 6A played "Jingle Bells" on a harmonica and a ring of small bells, the first musical instruments played in space.

  Gemini 8 achieved the first docking with another spacecraft, locking onto an uncrewed Agena target vehicle, before a thruster malfunction sent the docked assembly into a near-fatal spin. Neil Armstrong separated from the Agena and used the reentry control system to stop the tumbling, bringing the craft back under control and effecting the first emergency landing of a crewed American space mission. Gemini 11, in September 1966, used the Agena's engine after a first-orbit rendezvous to reach an altitude record of 739.2 nautical miles. On Gemini 12, Buzz Aldrin set an EVA record of 5 hours and 30 minutes, demonstrating that carefully placed footholds, handholds, and rest periods could allow a person to work effectively in open space.

• 7. What It Cost and What Remained

  ›

  From 1962 to 1967, Project Gemini cost $1.3 billion in 1967 dollars. A NASA report to Congress in January 1969 broke that down as $797.4 million for spacecraft, $409.8 million for launch vehicles, and $76.2 million for support.

  The hardware scattered across the country after the program ended. Gemini III sits at the Grissom Memorial in Spring Mill State Park in Mitchell, Indiana. Gemini IV and Gemini VII are at the National Air and Space Museum in Washington, D.C. Gemini VIII found its way to the Armstrong Air and Space Museum in Wapakoneta, Ohio. Gemini XII, the last capsule to fly, is at the Adler Planetarium in Chicago.

  The program also left behind proposals that were never built. Jim Chamberlin drew up detailed plans in late 1961 for cislunar and lunar landing missions using Gemini spacecraft, arguing they could reach the Moon before Apollo and at lower cost. NASA's administration declined. In 1969, a proposal called Big Gemini envisioned a craft capable of carrying up to 12 astronauts to planned space stations under the Apollo Applications Project. The only Apollo Applications Project mission that was funded was Skylab, which used existing hardware, and Big Gemini was never needed. The Manned Orbital Laboratory, the Air Force's own Gemini-derived program, was canceled in 1969 when Secretary of Defense Melvin Laird determined that uncrewed spy satellites could do the same job more cheaply.