Gemini Space Program

One of the most significant and necessary programs run by the United States in the space race with the Soviet Union. Experience and information gained from the Gemini program made possible a manned lunar landing.

Origins and History

An outgrowth of the Mercury program of the National Aeronautics and Space Administration (NASA), Gemini was a transitional program that was designed to allow scientists to test the systems and maneuvers that would be needed in future space programs. Initially, the program was identified as Mercury Mark 2.

The two-man Gemini spacecraft were designed so that astronauts could fly precise orbital maneuvers. The spacecraft were constructed in a modular fashion that minimized weight, made efficient use of space, and reduced the time needed to install and repair crucial systems during prelaunch preparations. The vessels could maintain life support for up to two weeks, permitted astronauts to exit their cabin, and could physically join with unmanned target vehicles. NASA selected the U.S. Air Force’s Titan 2 intercontinental ballistic missile as Gemini’s launch vehicle.

The First Flights

The first two Gemini flights were unmanned. Gemini 1, launched April 8, 1964, tested the Titan’s ability to deliver the spacecraft into orbit and determined the compatibility of booster and spacecraft systems. No attempt was made to separate spacecraft and booster, so the combined vehicle suffered an eventual orbital decay. Gemini 2, launched January 19, 1965, on a suborbital trajectory, was designed to generate maximum heat upon reentry to test the heat shield.

Having qualified Gemini’s spacecraft and booster, NASA prepared to launch its first manned Gemini flight. Gemini 3 was launched on March 23, 1965, bearing Virgil I. “Gus” Grissom and John W. Young. Although the spacecraft made only three orbits, this mission featured the first manually controlled maneuvers performed by astronauts or cosmonauts. On three occasions, Gemini 3’s thrusters altered the spacecraft’s orbital parameters.

Spacewalks

Gemini 4 was launched on June 3, 1965, with James A. McDivitt and Edward H. White on board. After the spacecraft was in orbit, McDivitt attempted to approach the second stage of the Titan 2, which was in a nearly identical orbit. However, because the spacecraft was consuming too much fuel, McDivitt discontinued the rendezvous attempt. On the third orbit, White opened the spacecraft hatch, and secured by a short umbilical tether and holding a gas-thruster maneuvering gun in his hand, he attempted NASA’s first extravehicular activity (EVA), or spacewalk. White’s gun quickly ran out of gas, so he was forced to maneuver by tugging on his tether. White closed the hatch after spending twenty-three minutes outside. The remainder of Gemini 4’s flight provided scientists with physiological data concerning prolonged exposure to weightlessness. Gemini 4 splashed down after four days, doubling NASA’s cumulative man-in-space experience.

Gemini 5 had three major objectives: to demonstrate a new electrical power generation system called fuel cells, to complete an eight-day flight, and to evaluate rendezvous techniques. Fuel cells combine liquid hydrogen and oxygen, providing electrical power and drinkable water as reaction by-products and saving precious weight over storage batteries used on longer flights. Eight days was the minimum required for Apollo’s lunar landing mission. Gemini 5 data would medically clear astronauts to attempt Apollo’s challenge. Gemini 5 was launched August 21, 1965, with L. Gordon Cooper and Charles “Pete” Conrad on board. Fuel cell pressurization problems forced Cooper and Conrad to power down their spacecraft and drift in orbit, spending much of the mission in that condition. Rendezvous evaluations were canceled. Cooper and Conrad endured their ordeal inside bulky pressure suits, yet they returned to Earth in good shape.

Docking and Rendezvousing

Gemini 6 was to attempt the first docking to an unmanned Agena vehicle launched by an Atlas booster. Unfortunately, Agena 6 failed to achieve orbit on October 25, 1965, and the flight of Gemini 6 was canceled. Instead, scientists proposed a joint flight involving two manned Gemini spacecraft. Gemini 7 would serve as a target with which Gemini 6 could rendezvous.

Gemini 7 was launched December 4, 1965, with Frank Borman and James A. Lovell on board. The fourteen-day mission was designed to be sufficiently long for technicians to prepare Gemini 6A for launch from the very same pad from which Gemini 7 had departed and for NASA to gather valuable medical data.

Gemini 6A’s first launch attempt ended with a suspenseful engine shutdown on the pad. Astronauts Walter M. Schirra and Thomas P. Stafford remained calm, not ejecting from the spacecraft. On December 18, 1965, Gemini 6A was launched and began its orbital chase to locate Gemini 7, ultimately closing within a foot of that spacecraft. Gemini 6A and 7 flew in formation for several hours before completing their separate missions. Gemini 6A splashed down after 17 orbits; Gemini 7 after 206.

After a dual Atlas-Agena and Gemini-Titan launch sequence on March 16, 1966, Neil A. Armstrong and David R. Scott flew a series of rendezvous maneuvers and docked Gemini 8 to their Agena. Shortly thereafter, a spacecraft thruster fired uncontrollably, dangerously spinning the mated vehicles. The astronauts separated Gemini 8 from the Agena, located the faulty thruster, and regained attitude control, but because they had activated the reentry system to stabilize the craft, they were committed to an early return. The Gemini 8 splashed down in the Pacific Ocean, near a contingency landing zone. Scott had expected to attempt a spacewalk lasting one full orbit, but the early return made that maneuver impossible.

Gemini 9’s Agena vehicle also failed to achieve orbit. However, an alternate, less-capable target called the augmented target docking adapter (ATDA) was available. The ATDA achieved orbit, but astronauts Stafford and Eugene A. Cernan could not lift off on the first attempt. Gemini 9A was launched on June 3, 1966, and successfully rendezvoused with the ATDA. Unfortunately, the ATDA’s payload shroud failed to separate during ascent, leaving its docking cone covered. The ATDA resembled an angry alligator with partially opened jaws. Gemini 9A rendezvoused several times with the ATDA but could not dock. Cernan attempted a spacewalk with a special thruster backpack that was housed in the adapter section, at the outside rear of Gemini 9A. Unfortunately, the visor on his pressure suit fogged up, and he was forced to return prematurely to the spacecraft.

Perfecting Their Craft

Gemini 10 was launched on July 18, 1966, after its Agena vehicle achieved stable orbit. This mission, flown by astronauts Young and Michael Collins, included a dual rendezvous with Agena 10, to which Gemini 10 docked, and the older Agena 8. Collins performed both a stand-up EVA to make ultraviolet stellar observations and a tethered spacewalk to retrieve a scientific package from Agena 8. Young and Collins returned to Earth after three days.

Gemini 11 was launched on September 10, 1966. Conrad and Richard F. Gordon accomplished rendezvous and docking with their Agena after just one orbit. Agena 11’s engine boosted their spacecraft to a record 850-mile-high altitude. Gordon attempted a work-intensive EVA but overloaded his life-support system and had to come back inside the cabin after attaching a tether to the two vehicles. That tether was used for an artificial-gravity exercise involving joined rotating spacecraft, an attitude-control test that did not require thruster firings.

Gemini 12 was launched on November 11, 1966, with Lovell and Edwin E. “Buzz” Aldrin on board. After the spacecraft docked with its Agena, Aldrin performed two stand-up EVAs and one lengthy tethered spacewalk, finally demonstrating a successful way to work in space using body restraints, periodic rest breaks, and short tethers. Previous spacewalkers had expended far too much energy simply maintaining body position while weightless. After four days, Lovell and Aldrin concluded the Gemini program with a splashdown close to recovery forces.

Impact

NASA’s Mercury program ended after Cooper’s daylong flight, and NASA seemed likely to assume leadership in the space race with its ambitious Gemini missions. However, the Soviet Union, having demonstrated a propensity for dangerous space spectaculars for Cold War propaganda purposes, scored two big victories that stole Gemini’s initial thunder: The Soviets flew the first multiperson mission and accomplished the first spacewalk. In October, 1964, Voskhod 1, a modified Vostok spacecraft, carried three cosmonauts into orbit for a daylong mission. Then, less than a week before the Gemini 3 mission, Alexei Leonov exited his Voskhod 2 spacecraft for a brief jaunt in open space attached to his inflatable airlock by a short tether. Specters of another surprise space achievement by the Soviets would loom in the background throughout the remaining Gemini missions, but not a single Soviet flew in space as Gemini astronauts forged a clearly leading position in space.

The Gemini program provided a technological and operational bridge from the fledgling voyages of Mercury astronauts to the lunar missions of the Apollo program. All the program goals long-duration flight, maneuvers during orbit, rendezvous and docking exercises, and spacewalks were thoroughly investigated, providing the data and experience necessary for lunar landing missions. Gemini astronauts, in just twenty months, flew ten missions of varying complexity and success, providing the framework whereby Apollo had a reasonable chance of accomplishing the ambitious goal, set by President John F. Kennedy, of landing a man on the Moon during the 1960’s.

Subsequent Events

Two months after the Gemini program concluded, a fire on the Apollo 1 spacecraft claimed the lives of three astronauts, postponing the push toward landing a man on the Moon until the Apollo spacecraft could be thoroughly redesigned. NASA marshaled its forces and, after four evolutionary missions, was ready to attempt landing Apollo 11 in the Sea of Tranquility in July, 1969.

Many Gemini astronauts played prominent roles in the Apollo program. Six of them landed and walked on the Moon’s surface, and some flew to the Moon twice.

Additional Information

Liftoff (1988), by Michael Collins, provides descriptions of the astronaut’s experience on Gemini 10 as well as of his historic Apollo 11 flight. On the Shoulders of Titans: A History of Project Gemini (1977), by Barton C. Hacker and James M. Grimwood, is a NASA History Series text that provides detailed information about program management, development, and flight operations. Schirra’s Space (1988), by Walter M. Schirra with Richard N. Billings, describes the astronaut’s experience on the joint Gemini 6A and 7 rendezvous mission as well as the rest of Schirra’s career with NASA. USA in Space (1996), edited by Russell R. Tobias, includes essays written by a variety of authors about each of the manned Gemini missions. We Reach the Moon (1969), by John Noble Wilford, provides a look at the space program from NASA’s inception to the Apollo 11 lunar landing and discusses contributions made by the Gemini program.