As 1966 was nearing an end, preparations for the first manned Apollo mission planned for February 1967 were moving swiftly ahead. Almost lost in the flurry of activity were the preparations for the final mission of the Gemini program. Conceived to help NASA gain the experience needed to fly Apollo to the Moon and return safely to Earth, the Gemini program had managed to meet almost all of its objectives over the course of nine crewed missions during the past two years racking up an impressive list of achievements in the process. The objectives of NASA’s Gemini 12 mission would be to address the final issues raised by the earlier flights so that Apollo could proceed.


Gemini Program Objectives

The purpose of NASA’s Gemini program was to develop the technologies and techniques needed to fulfill President Kennedy’s goal of landing a man on the Moon by 1970. The major objectives of the program were:

– Demonstrate that humans and their equipment can survive up to two weeks in space
– Demonstrate rendezvous and docking techniques in orbit
– Demonstrate the technology and techniques needed to perform EVAs (Extra-Vehicular Activities)

Meeting all of these objectives was necessary if the Apollo lunar program were to be successful.

Diagram showing the major systems of the Gemini spacecraft. Click on image to enlarge. (McDonnell)

Gemini was a two-man spacecraft that was roughly conical in shape with a base diameter of 3.3 meters which stood 5.8 meters tall.  Built by the McDonnell Aircraft Corporation (which merged with Douglas in 1967 to become McDonnell Douglas which subsequently merged with Boeing 30 years later), it consisted of two major sections. The first section was the reentry module which housed the crew, their equipment, food supplies and so on in orbit as well as the recovery systems needed to safely return them to Earth. The nose of this module also contained an L-band radar system for orbital rendezvous operations. Unlike today’s crewed spacecraft, the Gemini crew cabin was pressurized with pure oxygen at about one-third standard atmospheric pressure to save weight. The next section, the adapter section, connected the reentry module to the launch vehicle during ascent and housed equipment needed to support the crew while in orbit. It consisted of a retrograde section which held a set of four solid retrorockets used to start the descent to Earth from orbit and an equipment section which housed the in-orbit propulsion system called OAMS (Orbital Attitude and Maneuvering System), life support, power systems and all other equipment not needed for the return to Earth.

Diagram showing the major components of the Gemini-Titan II. Click on image to enlarge (NASA)

With a typical launch mass of up to about 3,700 kilograms or more, Gemini needed the largest operational rocket available at the time to get into orbit: a modified Titan II ICBM built by Martin Marietta (which is now part of Lockheed Martin). A number of modifications were made to simplify the operation of this rocket, smooth out its ride and improve its reliability to support crewed missions. With the Gemini spacecraft mounted on top, the Titan II GLV (Gemini Launch Vehicle) was 33 meters tall and had a fully fueled launch mass of about 154 metric tons.

Since its first manned mission in March 1965, the Gemini program had made steady progress in meeting its objectives in support of Apollo over the following 20 months. A series of three long duration missions culminating in the two-week flight of Gemini 7 in December 1965 demonstrated that a crew and its spacecraft could operate in space for periods of time longer than that needed for Apollo to land on the Moon and return (see “Rendezvous in Space: The Launch of Gemini 7”). With this major program objective met, the rest of the Gemini missions concentrated on perfecting rendezvous and docking techniques as well developing the skills needed to perform EVAs.

A view of Gemini 7 following the first successful rendezvous by Gemini 6. (NASA)

Gemini 6 successfully performed the first rendezvous using Gemini 7 as a target (see “Rendezvous in Space: Gemini 6 and 7”). Gemini 8 completed the first docking in orbit in March 1966 although its mission was cut short due to a thruster malfunction (see “Gemini 8: The First Docking in Space”). Gemini 9 attempted to repeat the feat of its predecessor in June with a faster and more aggressive rendezvous profile but was unable to dock with its target because its launch shroud had failed to jettison properly. Difficulties were also encountered during the mission’s EVA forcing it to be cut short due to astronaut fatigue (see “The Angry Alligator & The Snake: The Mission of Gemini 9”).  Building on the experience of the earlier missions, Gemini 10 not only rendezvoused and docked with its Agena target vehicle in July, but used the target’s highly capable propulsion system to boost the combined craft to a record setting altitude. Gemini 10 then successfully performed a rendezvous with a second target – the derelict Agena used earlier during the Gemini 8 mission. A pair of EVAs were also performed during this mission with mixed results (see “Gemini 10: Dual Rendezvous in Space”). In September, Gemini 11 went on to perform the most aggressive rendezvous profile and docked with its target vehicle before the end of the first orbit. The Agena’s propulsion system was then used to raise the apogee to a record 1,373 kilometers. Again, the pair of EVAs produced mixed results with astronaut fatigue resulting from insufficient restraints creating problems (see “Gemini 11: Preparing for Apollo”). The objectives of the Gemini 12 mission were to continue gaining experience in rendezvous and docking in support of the Apollo program. Most importantly, the Gemini 12 mission needed to address and resolve the ongoing EVA issues.

The official patch for Gemini 12 mission. (NASA)


The Gemini 12 Mission Plan

On June 17, 1966, NASA officially announced the crew of its final Gemini mission. The primary crew consisted of USN Captain James A. Lovell, Jr. as the command pilot and USAF Major Edwin E. “Buzz” Aldrin, Jr. as the pilot. Originally Lovell and Aldrin had served as the backup crew for Tom Stafford and Gene Cernan in the Gemini 9 mission which had just been completed on June 6 (see “The Angry Alligator & The Snake: The Mission of Gemini 9”). Since the objectives of the new Gemini 12 mission were broadly similar to those of Gemini 9, Lovell and Aldrin were already well prepared for the flight and could quickly incorporate the lessons learned from the Gemini 9 through 11 flights into the new mission.

The primary crew for the Gemini 12 mission: James Lovell, command pilot (right) and Edwin “Buzz” Aldrin, pilot (left). (NASA)

The 38 year old Lovell was an Annapolis graduate who had an impressive military career as a pilot and instructor before being selected with the second group of NASA astronauts in September 1962. He had previously flown as the pilot with Frank Borman on the Gemini 7 mission which spent a record-setting two weeks in orbit (see “Rendezvous in Space: The Launch of Gemini 7”). Buzz Aldrin, 36, was a graduate of West Point who flew 66 combat mission in Korea. Afterwards, Aldrin earned his doctorate in science from MIT for his work with manned orbital rendezvous. He had been assigned to the Gemini Target Office of the Air Force Space Systems Division before being transferred to the USAF Field office at NASA’s Manned Space Center in Houston, Texas (today’s Johnson Space Center). Aldrin was selected in October 1963 as part of NASA’s third astronaut group and Gemini 12 would be his first space mission. The backup crew for the Gemini 12 mission were veteran astronauts Gordon Cooper, who had last served as command pilot on the five-day Gemini 5 mission, and Gene Cernan, who was the pilot on Gemini 9.

Like the previous four missions, the first set of objectives for the Gemini 12 mission centered on orbital rendezvous and docking. The docking target chosen for the Gemini program was a modified Agena D upper stage known as the Gemini Agena Target Vehicle (GATV) launched into orbit using the SLV-3 (Standard Launch Vehicle-3) version of the Atlas booster built by General Dynamics. Built by the Lockheed Missile and Space Company (which is now part of the aerospace giant, Lockheed Martin), the Agena D not only served as an upper stage for use with Thor, Atlas and Titan IIIB rockets, but had also been integrated into range of Department of Defense payloads such as the Corona reconnaissance satellites to provide in-orbit support functions during these missions. The standardized Agena D, with its adaptable modular design, could be easily modified to serve as a docking target for Gemini.

The modified Agena D in its role as the Gemini Agena Target Vehicle (GATV). Click on image to enlarge. (NASA)

In addition to modifications to its primary and secondary propulsion systems (PPS and SPS) to support its role as a docking target, the forward end of the Agena D was fitted with an auxiliary rack holding special rendezvous and telemetry equipment. Also added were strobe lights and an L-band radar transponder to aid in rendezvous operations as well as command equipment to allow the GATV to be controlled from the ground or by the Gemini crew. A cone shaped target docking adapter (TDA), which was under a shroud during launch, was added to the forward end of the stage to allow the nose of the Gemini reentry module to dock with the Agena and mechanically lock the two spacecraft together. Once in orbit, the GATV was 9.7 meters long with a mass of about 3,200 kilograms.

Diagram showing the details of the forward end of the GATV with its target docking adapter (TDA). Click on image to enlarge. (NASA)

Like so many other components from the Gemini program, the supply of Agena targets had already been exhausted as plans were being made for Gemini 12. Instead of procuring a new target vehicle, the decision was made to refurbish the first Agena D target vehicle, GATV-5001. Originally, GATV-5001 arrived at Cape Kennedy on May 29, 1965 where it was used for a variety of ground tests in preparation for the first GATV launch in October 1965 in support of the original Gemini 6 mission (see “The Unflown Mission of Gemini 6“). Anticipating the need for one more Gemini docking target, GATV-5001 was returned to Lockheed on November 23 for a complete disassembly, inspection and refurbishing after which it would be designated GATV-5001R. Likewise, a new Atlas SLV-3 booster to launch the GATV had to be procured as the original allotment had already been used. Fortunately, the launch of Lunar Orbiter 1 was delayed in May 1966 freeing up what would become Atlas TLV-5307 (Target Launch Vehicle 5307) after modifications were made to support the Gemini 12 mission (see “Lunar Orbiter 1: America’s First Lunar Satellite”).

Agena GATV-5001 shown mated with Atlas TLV-5301 for a countdown rehearsal at LC-14 in August 1965. This target vehicle was later returned to Lockheed for refurbishing to become GATV-5001R in order to serve as the last Gemini docking target. (NASA)

A number of different rendezvous modes with the GATV had been identified during theoretical studies of the technique. For the Gemini rendezvous missions, the “coelliptical” method was chosen where the active spacecraft would first be placed into a circular orbit below and some distance behind the passive target spacecraft. The active spacecraft would then catch up to its target over the course of several orbits then maneuver to match the target’s orbit in order to perform the actual docking. While this approach took longer than other possible profiles, it was much more flexible and allowed more time to plan and execute maneuvers – a desirable characteristic for the first attempts of the untried procedure of orbital rendezvous. Ultimately it was decided that the Apollo Lunar Module (LM) would follow a similar rendezvous profile as it returned to orbit following launch from the lunar surface.

A schematic showing the “M=4” co-elliptical rendezvous profile originally used on Gemini 6 and subsequent Gemini 8 and 10 flights. Units on this diagram are in nautical miles (1 nm = 1.852 km). Click on image to enlarge. (NASA)

In the case of the Gemini 6, 8 and 10 flights, the crew followed what was called a “M=4” rendezvous profile where the initial rendezvous with the target took place during the mission’s fourth revolution. The Gemini 9 mission followed a faster M=3 rendezvous which better approximated the desired rendezvous procedure for the LM. This was accomplished by the crew performing an IVAR (Insertion Velocity Adjust Routine) maneuver of up to 9 meters per second right after separating from their spent Titan II launch vehicle to reduce the inevitable orbit insertion errors using data provided by the spacecraft’s guidance system. After this, the Gemini 9 crew combined what had been several individual orbit adjustments performed over the course of a couple of revolutions during an M=4 rendezvous into a single maneuver to reduce the time to rendezvous. The Gemini 11 mission successfully executed the most aggressive M=1 rendezvous profile similar to the one that would be employed by the LM after leaving the lunar surface. For the Gemini 12 mission, an M=3 rendezvous was chosen like the one Lovell and Aldrin had already trained for as part of the Gemini 9 backup crew which would simulate many key aspects of an Apollo rendezvous.


Perfecting the EVA

The other major mission objectives for Gemini 12 centered on resolving some of the most pressing issues remaining with EVA. While the first 20-minute EVA performed by astronaut Ed White during the Gemini 4 mission in June 1965 was successful (see “The Forgotten Mission of Gemini 4”), subsequent EVAs starting with the Gemini 9 mission had encountered a number of issues relating to planning, equipment and training which resulted in dangerous levels of astronaut fatigue forcing EVAs to be cut short. While there had been incremental improvements in meeting EVA objectives during the Gemini 10 and 11 missions, the issues which still remained gave cause for concern with Apollo mission planners.

Buzz Aldrin shown during zero-g training for his EVA on board an aircraft travelling parabolic arcs. (NASA)

The first issue, planning, was addressed by simplifying and limiting the astronaut’s workload during the EVA with many scheduled rest periods. Many practical improvements in equipment were incrementally made as well especially with astronaut restraints. Experience had shown that inadequate mobility aids and restraints at work stations was a major cause of exhaustion as the EVA astronaut struggled to keep himself in position while performing even the simplest of tasks. With each mission, more restraints were carried with the number increasing from nine employed on the Gemini 9 mission to a total of 44 on Gemini 12. Training issues were addressed by the addition of practicing entire EVAs from beginning to end underwater where buoyancy helped to simulate weightless conditions in orbit. Earlier training in aircraft repeatedly travelling parabolic arcs would produce zero-g conditions for only about a half minute at a time. It was found that this training was inadequate in identifying restraint issues and the constant interruptions made it difficult to gauge the true time required to complete EVA tasks.

In order to determine if the latest improvements in planning, equipment and training resolved the issues, a total of three EVAs were planned for the Gemini 12 mission instead of the two performed on the three previous missions – a pair of standup EVAs, where Aldrin would perform his tasks standing in the open hatch of the Gemini reentry module, and an umbilical EVA where he would perform a series of tasks at various stations on the Gemini and the Agena target. As a result of the additional EVA, the Gemini 12 mission was lengthened from three to four days.

Aldrin was the first astronaut to use underwater neutral buoyancy training to rehearse EVAs. (NASA)

The Gemini 12 mission was scheduled to start on November 9, 1966. Like the earlier rendezvous missions, the Agena target vehicle would be sent on its way into its 298-kilometer orbit first with liftoff from Launch Complex 14 (LC-14) planned for 2:16 PM EST. As the Agena was about to finish its first orbit, Gemini 12 would be launched from LC-19 during a 33-second window starting at about 3:54:31 PM EST with the precise time dictated by the actual orbit attained by GATV-5001R.

Once in orbit, Gemini 12 would then follow an M=3 rendezvous profile with docking scheduled to occur three hours and 55 minutes after launch. Both members of the Gemini crew would then practice undocking and docking with the GATV as had been done in earlier missions. Before the beginning of the crew’s first sleep period, they would fire the main engine on Agena’s primary propulsion system (PPS) eight hours and five minutes into the mission to raise the apogee of the joined spacecraft to 740 kilometers. Unlike during the Gemini 10 and 11 missions which also flew high-apogee orbits with the assistance of the PPS, the apogee of this new orbit was planned to occur over the northern hemisphere to allow synoptic photography over the US.

Jim Lovell shown preparing to enter the Gemini Mission Simulator in September 1966. (NASA)

The first significant activity of Lovell and Aldrin’s first full day in orbit was the standup EVA scheduled to take place 20 hours and 14 minutes after launch. This EVA was scheduled to last two hours and 20  minutes while Gemini 12 and its docked Agena target continued in their high-apogee orbit. Aldrin would perform photography as well as install a handrail and practice some procedures for his upcoming umbilical EVA. Later in the day at a mission elapsed time of 30 hours and 15 minutes, the Agena PPS would be fired again this time to lower the apogee and place the spacecraft into a circular 298-kilometer orbit.

Aldrin shown during neutral buoyancy training using a handrail he was to deploy during his first EVA. (NASA)

The next day Aldrin would perform his two-hour umbilical EVA. Exiting the spacecraft 42 hours and 37 minutes after launch, Aldrin would execute a series of tasks on the Agena and the Gemini. During the second part of this EVA while he was at the base of Gemini’s adapter section, Aldrin would evaluate some tools and a new set of overshoe-like foot restraints nicknamed “golden slippers” which would help him maintain his position while freeing his hands. About two and a half hours after the EVA was over, Gemini would undock from the Agena GATV and unfurl a 30-meter long tether that Aldrin was scheduled to attach to the two spacecraft during his EVA. Lovell and Aldrin would then conduct a station keeping exercise to place the combined Agena-Gemini into a stable configuration where the local gravity gradient would maintain the orientation of the combined spacecraft. A similar maneuver was unsuccessfully attempted during the Gemini 11 mission and the lessons learned were to be applied to Gemini 12. After five hours, the Agena would be cut loose and Gemini would perform a separation maneuver to continue its mission solo.

Aldrin shown training for his EVA activities at the base of Gemini’s adapter section. (NASA)

The last full day in orbit would see Aldrin start his third EVA 63 hours and 20 minutes after launch. After Aldrin had jettisoned unneeded equipment and trash overboard at the start of his standup EVA, he would attempt to photograph a solar eclipse that would be visible across South America on November 12, 1966. A phasing maneuver made the previous day after separating from the Agena would allow the eclipse to be observed as Gemini 12 passed over the Galapagos Islands 28 minutes after the scheduled start of the standup EVA. The eclipse-related activities were considered a low priority in this mission and would only take place if they did not interfere with other parts of the flight plan. Aldrin’s final EVA was scheduled to last 40 minutes.

This map shows the path of the total solar eclipse over the southern hemisphere on November 12, 1966. Gemini 12 would attempt to pass through the Moon’s shadow and photograph the Sun. Click on image to enlarge. (NASA/GSFC)

After completing their final rest period in orbit, Lovell and Aldrin would complete their experiments and pack up for the return home. The retrorockets were scheduled to be fired 94 hours and 41 seconds after launch as Gemini 12 passed near Hawaii. The Gemini 12 reentry module would then fly a computer-controlled reentry to a precision landing in the West Atlantic recovery area. Splashdown would occur 94 hours and 37 minutes after launch ending NASA’s final Gemini mission.


The Start of the Last Mission

The first major piece of flight hardware to arrive at Cape Kennedy (which reverted to its original name of Cape Canaveral in 1973) for the final Gemini mission was the TDA section of the refurbished Agena GATV-5001R on August 14, 1966. This was followed by the first stage of the Titan II GLV-12 on August 30 and its second stage three days later. With the arrival of the Agena from Lockheed on September 4 and Gemini spacecraft number 12 from McDonnell on September 6, all of the major spacecraft components for the Gemini 12 mission had been delivered save for Atlas TLV-5307 which arrived on September 19 after modifications had been completed.

A view of Cape Kennedy’s launch complexes with the Gemini program’s last Atlas-Agena on the pad at LC-14 in the distance near the center. (NASA)

On the same day the Atlas arrived, Titan II GLV-12 was erected on the pad at LC-19 just a week after the successful liftoff of Gemini 11. By October 23 the assembled and tested GATV-5001R had been mated with its Atlas booster at LC-14. Two days later, spacecraft number 12 was mated to its Titan II launch vehicle for the beginning of a week of prelaunch testing.

Gemini-Titan 12 shown being prepared for launch from LC-19 at Cape Kennedy, Florida. (NASA/KSC)

The day before the scheduled November 9 launch, a problem was detected in the Titan’s secondary autopilot and rate gyro forcing a one-day postponement. The following day the launch was postponed yet again when the replacement components were themselves found to be faulty and required replacement. Finally all was ready for the first launch attempt on November 11. Because of the relatively late launch time, Jim Lovell and Buzz Aldrin were not woken up until 10:30 AM EST. After their medical exams, they then had a traditional launch day breakfast with ten fellow astronauts. By 12:30 PM, the crew were at LC-16 where they donned their modified G4C spacesuits which they would wear for their four-day mission.

Lovell and Aldrin shown leaving the trailer at LC-16 where they donned their G4C spacesuits. (NASA)

While Aldrin experienced some problems during suiting, they were resolved and the astronauts arrived at LC-19 wearing placards which said “THE” and “END”. Lovell and Aldrin were inside their spacecraft when Atlas TLV-5307 lifted off from LC-14 carrying the last Agena GATV at 2:07:58.7 PM EST. Agena GATV-5001R entered a 294.5 by 303.5 kilometer orbit with the only anomaly noted during the ascent being a brief 6% drop in chamber pressure during the firing of the 71-kilonewton Bell 8096 engine of Agena’s PPS and a simultaneous drop in turbopump turbine speed. But with the GATV safely in orbit, all was set for Gemini 12 whose guidance computer and precise launch time were updated following Agena orbit insertion.

The launch of Atlas TLV-5307 from LC-14 carrying the last Gemini target vehicle, GATV-5001R. (NASA)

At 3:46:33.4 PM EST as GATV-5001R was completing its first orbit, Gemini 12 successfully lifted off from LC-19 for a perfect 12-for-12 Gemini program launch record. Six minutes after liftoff, the 3,763-kilogram Gemini 12 had separated from its spent launch vehicle and 20 seconds later performed its IVAR maneuver – the first of many to come over the following hours. Gemini 12 was now in its initial 161 by 270 kilometer orbit some 925 kilometers behind and below its target.

Gemini 12 lifts off from LC-19 on November 11, 1966 for NASA’s last Gemini mission. (NASA)

Lovell and Aldrin then proceeded with a sequence of maneuvers like those employed by the earlier Gemini 9 mission. Just over an hour after launch, Gemini got a radar lock on GATV-5001R at a range of 436 kilometers. But after they had closed the gap to 120 kilometers, the reception from Agena’s radar transponder became so poor that the Gemini guidance computer refused to accept the data. Lovell was then forced to make maneuvers based on sextant sightings and calculations made using charts Aldrin himself had helped to prepare based on his thesis work which had earned him the nickname “Dr. Rendezvous”.

Buzz Aldrin shown inside the Gemini 12 cabin. (NASA)

At three hours and 45 minutes after launch, Gemini 12 had completed its rendezvous with GATV-5001R despite the radar issue after consuming only 127 kilograms of Gemini’s 416-kilogram OAMS propellant load. Some 28 minutes later, Lovell reported “We are docked”. The astronauts then took turns undocking and redocking the spacecraft. Jim Lovell encounter a problem during the initial undocking when a misalignment between the two spacecraft caught one of the docking latches preventing separation. After rocking the spacecraft using the OAMS thrusters, Lovell was able to disconnect the two craft without damage. Aldrin was subsequently able to redock with the Agena without any issue.

Agena GATV-5001R shown in orbit before docking with Gemini 12. (NASA)

After completing their first meal in orbit, the next order of business in the Gemini 12 flight plan was to be a firing of the Agena’s PPS to raise the apogee. Unfortunately, after engineers had a chance to examine the telemetry from the Agena, it was felt that there may be a problem with the Bell 8096 engine and that the PPS firing should not be attempted. While disappointing, the change in plan did open up the possibility of reinstituting the eclipse photography experiment which had been cancelled as a result of the two-day launch delay. A firing of Agena’s smaller SPS (Secondary Propulsion System) just over seven hours after launch with a delta-v of 13 meters per second and a subsequent maneuver would allow Gemini to pass through the Moon’s shadow during the mission’s first full day in orbit as the eclipse raced across South America. Once again, the eclipse photography would be performed so long as it did not interfere with higher priority tasks in the flight plan.


Getting the Job Done

After sleeping fitfully for a couple of hours during their first night in orbit, Jim Lovell and Buzz Aldrin were ready to start their first full day of activity in orbit. They performed a five-meter per second maneuver using the Agena SPS which tweaked Gemini’s path to allow it to spend seven seconds in the Moon’s shadow – enough time to get a couple of photographs. At 16 hours, one minute and 44 seconds after launch, Gemini hit its target allowing a brief glimpse of the solar eclipse.

A photograph of the November 12, 1966 solar eclipse as seen from Gemini 12 as it passed over South America. (NASA)

As Lovell and Aldrin began preparing for the first of three EVAs, they had to take time to deal with issues with two of the three power-producing fuel cells in Gemini’s adapter section. The problem was resolved for the moment when the astronauts drew off some drinking water which shrank its storage bladder freeing up some space for more waste water in the tank it shared. Buzz Aldrin opened up his hatch 19 hours and 29 minutes into the mission for his first EVA. With a half hour to go before orbital sunset, Aldrin exclaimed in awe as he peered outside, “Man! Look at that!”.

Aldrin performing his tasks during the mission’s first standup EVA. (NASA)

Held in place using adjustable waist tethers, Aldrin then proceeded to perform his tasks of jettisoning trash, recovering samples and deploying a handrail for his next EVA resting frequently between tasks. During the nighttime portions of his EVA, Aldrin used a camera he mounted to the spacecraft to take UV photographs of selected star fields. Although Lovell had some difficulties pointing the spacecraft because of the GATV’s unexpectedly heavy propellant load, the crew was able to complete their tasks. Aldrin finally closed his hatch ten minutes after orbital dawn ending a successful standup EVA with a record long duration of two hours and 20 minutes. The crew spent the balance of the day resting from the EVA as well as performing system checks and conducting experiments. They finally started their second sleep period as midnight approached at Cape Kennedy about 32 hours into the mission.

Jim Lovell shown inside the cabin during the Gemini 12 mission with Buzz Aldrin by his side. (NASA)

Overnight, problems were detected in one of the fuel cell stacks as power output dropped. The crew were woken up an hour early and took the problem fuel cell offline. As they were preparing for the mission’s umbilical EVA, problems were also detected in a yaw and pitch OAMS thrusters. Aldrin would take a moment to examine them during his EVA. At 42 hours, 48 minute ground elapsed time, Aldrin open his hatch for the all-important umbilical EVA. He set up a camera to record his EVA activities and then set about his tasks. Moving to the Agena via the handrail he had deployed during his first EVA, Aldrin attached a pair of waist tethers then rested. He then proceeded with each assigned task then rested for two minutes each time. After attaching the tether between the Agena and Gemini’s docking bar for the upcoming station keeping exercise, Aldrin then set about performing some simple tasks at a pair of work stations nicknamed “busy boxes”. Especially stressing tasks were timed to take place during orbital nighttime so that Aldrin’s chest-mounted Extravehicular Life Support System (ELSS) pack could better deal with the extra heat load from his activity.

Buzz Aldrin shown in the first “selfie” taken during an EVA. (NASA

After completing his first set of assigned tasks on the Agena, Buzz Aldrin moved back to the Gemini and to the base of the adapter section. He found that his shorter tether made it much easier to move and maintain position. Buzz began his activities there testing the new “golden slipper” foot restraints and performing tasks at yet another “busy box”. At each busy box, Aldrin used various combinations of restraints to see how each affected his metabolic rate as he performed his assigned tasks. The only issue of note at this point was Aldrin’s inability to get the EVA camera to fit its mount to monitor his activities at the base of the adapter section. Aldrin then moved back to the Agena to perform tasks at another busy box using various combinations of waist tethers to find the optimum arrangement.

Aldrin shown working at the Agena during his umbilical EVA. (NASA)

As Aldrin left the Agena for the last time, he briefly stopped to wipe residue off of Lovell’s window for analysis back on Earth. Standing in his open hatch near the end of the EVA, Aldrin observed the OAMS thrusters as Lovell briefly fired them one at a time. A problem with at least the pitch thruster was confirmed as streams of vapor were seen exiting when it was commanded to fire. After two hours and six minutes, Aldrin closed his hatch completing his umbilical EVA. To the relief of all involved, the new EVA planning and training worked to make this the most successful umbilical EVA of the entire Gemini program with Aldrin’s metabolic rate staying well within an acceptable range.

Agena GATV-5001R shown attached to Gemini 12 by a tether for a station keeping exercise. (NASA)

With the successful umbilical EVA finished, attention now turned to the station keeping exercise. Two and a half hours after completing the EVA, Jim Lovell undocked from the Agena with its tail pointing towards the Earth and slowly backed Gemini away. While Lovell had some problems getting the tether taut, eventually he was able to steady the pair of spacecraft using gravity gradient stabilization. Four hours and 27 minutes after separating from the Agena GATV, the Gemini 12 docking bar which was connected to the tether was jettisoned. After 23 more minutes, the thrusters on Gemini 12 were briefly fired and the two spacecraft parted company.

Buzz Aldrin’s view during his final EVA of the Gemini 12 mission. (NASA)

The main activity for the final full day in orbit was Aldrin’s second standup EVA. Originally meant to be used to photograph the solar eclipse (a plan scuttled by the two-day launch delay), the purpose of this last EVA was now to toss overboard trash and any equipment that was no longer needed and perform more UV photography of astronomical targets. At a mission elapsed time of 66 hours and six minutes, Aldrin opened his hatch for one last time. He completed his work by orbital sunrise and ended his last EVA after 55 minutes. The earlier issues with EVA had been largely addressed and Buzz Aldrin was now a record holder with five and a half hours of EVA time.


Wrapping Up the Gemini Program

With the last EVA completed, Jim Lovell and Buzz Aldrin continued to perform experiments. One of these was an attempt to observe a cloud of sodium vapor from 60 to 156 kilometers altitude released from a French sounding rocket launched at nighttime from a facility in Hammaguir, Algeria. Unfortunately the astronauts could not see the cloud even when using special goggles meant to improve its visibility. During the course of the day, Lovell and Aldrin struggled with more thruster and fuel cell issues, the latter of which was resolved by drinking more water to allow more space for the waste water produced by the fuel cells.

Goggles carried on the Gemini 12 mission to aid in enhancing the visibility of a sodium cloud released by a French rocket as part of a joint experiment with NASA. (NASA)

Lovell and Aldrin woke up from their last sleep period in orbit just before a mission elapsed time of 80 hours. Because of the increased drinking water usage, soon it became apparent that the adapter section’s water supply had been exhausted. A test of the OAMS thrusters nine hours into the crew’s last day showed that three yaw and one of the pitch thrusters were now inoperable. Continued issues with the fuel cells forced the crew to switch early to their four main reentry module batteries to meet power demands during the closing hours of the mission. With Gemini 12 limping along and the need to return early return averted by the actions of the crew and ground controllers, the retrorockets were fired at 93 hours, 59 minutes and 58 seconds after launch to begin the long half hour descent home.

A Navy pararescueman exits his helicopter to attend to the Gemini 12 reentry module following its splashdown in the Atlantic. (NASA)

Guided by its onboard computer, the Gemini 12 reentry module came down just 4.8 kilometers off its target for a recovery by the aircraft carrier, the USS Wasp, with a splashdown at 2:21 EST on November 15, 1966 for a total mission length of 94 hours, 34 minutes and 31 seconds. With this second mission in orbit under his belt, Jim Lovell now had a record 425 hours in space – an endurance record he would extend during the later Apollo 8 and 13 missions and which would not be exceeded until the first Skylab mission in 1973. Within eight minutes of splashdown, Navy pararescuemen had attached a floatation collar around the spacecraft as it bobbed in the Atlantic. Just a half an hour after landing, Jim Lovell and Buzz Aldrin were on the deck of the recovery ship after being picked up by helicopter bringing a successful end to the operational phase of NASA’s Gemini program.

Jim Lovell and Buzz Aldrin shown during the official welcoming ceremony on the USS Wasp following the end of the four-day Gemini 12 mission. (NASA)

Later that day during the 63rd revolution of Agena GATV-5001R, ground controllers attempted to restart the balky main engine of its PPS. As had been feared, the Bell 8096 engine had experienced some sort of failure in its turbopump which prevented it from restarting confirming the wisdom of the decision of not attempting to raise the apogee after docking. Agena GATV-5001R ran out of attitude control gas shortly afterwards and its orbit decayed until it reentered the Earth’s atmosphere on December 23. Coincidentally, the orbits of GATV-5005 and 5006 used in the Gemini 10 and 11 missions decayed six and seven days later, respectively. The last piece of Gemini program hardware, GATV-5003 used as a docking target for the Gemini 8 mission and revisited by Gemini 10, fell from orbit on September 15, 1967.

Lovell and Aldrin shake hands in front of NASA’s Gemini progress report sign at the Cape Kennedy skid strip. (NASA)

With the successful conclusion of the Gemini 12 mission, all of the program’s major objectives had been met in a stunningly successful series of ten crewed flights flown over the course of just 20 months. As engineers and scientists finished wrapping up and documenting the results of the mission, NASA now felt confident that it had the skills required to send people to the Moon and return them safely home. It was now time to transition to the Apollo program whose first manned mission was expected to be launched in three months.


Follow Drew Ex Machina on Facebook.


Related Video

Here is an excellent NASA documentary on the Gemini 12 mission:




Related Reading

A collection of essays describing each of the Gemini missions and many other aspects of the Gemini program can be found on this web site’s Gemini Program page.


General References

David Baker, The History of Manned Space Flight, Crown Publishers, 1981

Barton C. Hacker and James M. Grimwood, On the Shoulders of Titans: A History of Project Gemini, SP-4203, NASA History Division, 1977

David J. Shayler, Gemini: Steps to the Moon, Springer-Praxis, 2001

“Project: Gemini 12”, NASA Press Release 66-272, November 3, 1966