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Gemini 12
Part of Gemini

Gemini 12

Gemini 12
Aldrin exits the spacecraft
Credit: NASA

First completely successful space walk. Final Gemini flight. Docked and redocked with Agena, demonstrating various Apollo scenarios including manual rendezvous and docking. Successful EVA without overloading suit by use of suitable restraints.

Launched: 1966-11-11. Returned: 1966-11-15. Number crew: 2 . Duration: 3.94 days. Location: NASA Goddard Space Flight Center, Greenbelt, MD.

Two very serious astronauts get it all right to end the program. Docked and redocked with Agena, demonstrating various Apollo scenarios including manual rendezvous and docking without assistance from ground control. Aldrin finally demonstrates ability to accomplish EVA without overloading suit by use of suitable restraints and careful movement.

Major objectives of the mission were to rendezvous and dock and to evaluate extravehicular activities (EVA). Among the secondary objectives were tethered vehicle evaluation, experiments, third revolution rendezvous and docking, automatic reentry demonstration, docked maneuvering for a high-apogee excursion, docking practice, systems tests, and Gemini Agena target vehicle (GATV) parking. The high-apogee excursion was not attempted because an anomaly was noted in the GATV primary propulsion system during insertion, and parking was not attempted because the GATV's attitude control gas was depleted. All other objectives were achieved. Nine spacecraft maneuvers effected rendezvous with the GATV. The onboard radar malfunctioned before the terminal phase initiate maneuver, but the crew used onboard backup procedures to calculate the maneuvers. Rendezvous was achieved at 3 hours 46 minutes ground elapsed time, docking 28 minutes later. Two phasing maneuvers, using the GATV secondary propulsion system, were accomplished, but the primary propulsion system was not used. The first of two periods of standup EVA began at 19 hours 29 minutes into the flight and lasted for 2 hours 29 minutes. During a more than two-hour umbilical EVA which began at 42 hours 48 minutes, Aldrin attached a 100-foot tether from the GATV to the spacecraft docking bar. He spent part of the period at the spacecraft adapter, evaluating various restraint systems and performing various basic tasks. The second standup EVA lasted 55 minutes, ending at 67 hours 1 minute ground elapsed time. The tether evaluation began at 47 hours 23 minutes after liftoff, with the crew undocking from the GATV. The tether tended to remain slack, although the crew believed that the two vehicles did slowly attain gravity-gradient stabilization. The crew jettisoned the docking bar and released the tether at 51 hours 51 minutes. Several spacecraft systems suffered problems during the flight. Two fuel cell stacks failed and had to be shut down, while two others experienced significant loss of power. At 39 hours 30 minutes ground elapsed time, the crew reported that little or no thrust was available from two orbit attitude and maneuver thrusters. Retrofire occurred 94 hours after liftoff. Reentry was automatically controlled. The spacecraft landed less than 5 km from the planned landing point on November 15. The crew was picked up by helicopter and deposited 28 minutes later on the deck of the prime recovery ship, the aircraft carrier Wasp. The spacecraft was recovered 67 minutes after landing.

Official NASA Account of the Mission from On the Shoulders of Titans: A History of Project Gemini, by Barton C. Hacker and Charles C. Alexander, Published as NASA Special Publication-4203 in the NASA History Series, 1977.

The final curtain snagged twice before it opened on Gemini XII. Spare parts became a problem, as had long been feared. An autopilot and a rate gyroscope in the launch vehicle had to be replaced. Then, the replacements were themselves replaced. But, on Veterans' Day - 11 November - Flight Director Glynn Lunney signaled for the overture to begin.

At 2:08 p.m. the substitute Atlas lifted the refurbished Agena from pad 14 and lofted it into orbit. A few minutes earlier, over on pad 19, the pressure-suited crew had shuffled up a ramp, bearing signs on their backs - "THE" and "END." This bit of humor was more than symbolism, for when launch vehicle No. 12 broke its landlock 30 seconds after 3:46 p.m., the Gemini preparations team faded into space history. Francis Carey, Martin's chief test conductor, and Colonel John Albert, Chief of the Gemini Launch Vehicle Division, 6555th Aerospace Test Wing, took justifiable pride in the 12 for 12 record, but they mourned the fact that the job had ended and the team would soon break up. That it was over could hardly have been more vividly underlined - almost at once wreckers were hacking the launch stand into scrap iron. Apollo was the future. A harbinger of this new era, Lunar Orbiter II, had been launched only five days earlier 6 November in a trip to the Moon to photograph possible Apollo landing sites.

Meanwhile, Lovell and Aldrin began to wonder if everybody had gone away too soon. For 25 minutes, with one brief exception, they heard nothing from the ground. The Ascension Island tracking station had the wrong acquisition time, so its communicators had not talked with the pilots. Lovell was relieved when he heard Conrad hailing him through the remote line at Tananarive with some needed data for a maneuver that was scheduled to take place within a few minutes.

Things now went smoothly and a little more than an hour after launch, Aldrin reported, "Be advised we have a solid lockon . . . 235.52 (nautical) miles (436.18 kilometers)." From Houston, Conrad replied, "It looks like the radar meets the specs." When the spacecraft moved into a circular orbit below and behind its target, the radar showed the Agena to be 120 kilometers away. But this was the last figure the crew could trust; reception got so poor that the onboard computer refused to accept the radar's intermittent readings.

The radar failure meant that Gemini XII would have to rely on the backup charts it carried to complete the rendezvous. Aldrin, a member of the team that had planned and worked out chart procedures, now had a chance to see if his doctoral studies at MIT and the simulator training in St. Louis with McDonnell and MSC engineers really were practical in space. The pilot, who was sometimes called "Dr. Rendezvous," had already pulled out and used the T-2 manual navigation sighting sextant to take a look at the target. When the radar went on the blink, this piece of experimental gear became operationally important.

In the automatic rendezvous mode, the radar would have fed range and range rates to the computer. Lovell would then have flown the spacecraft by the resulting numbers. This time the computer would be left in the catchup mode, and either Aldrin or Mission Control - or both - had to figure range and range rates to see if the computer was correct. For this backup method, Aldrin used the sextant to measure the angle between the local horizontal of the spacecraft and that of the Agena, ahead of and above them. He checked this information with his rendezvous chart and cranked the necessary corrections into the computer. Lovell flew the spacecraft with these numbers to rendezvous with the target, arriving there after 3 hours and 45 minutes of flight. They had used only 127 kilograms of fuel. Lovell called the Coastal Sentry Quebec at 4:13 hours elapsed time, saying, "We are docked." But Gemini XII was the fourth flight to make that announcement, and the shipboard flight controller merely replied, "Roger."

For the second time, a Gemini crew was able to practice docking and undocking. They unlatched the vehicles and Lovell tried the task during the night. But the spacecraft was misaligned; the target's docking cone did not unlatch. Instead, it locked bumpers, catching on one of the three latches. Much like an automobile driver mired in the mud, Lovell fired the aft and forward thrusters, trying to rock the spacecraft free. Both vehicles were shaken, but he broke loose without damage to either. A few minutes later, Aldrin docked without difficulty.

The next item on the agenda was the firing of the Agena to go to a higher altitude, but that part of the flight plan had to be changed. Eight minutes after the Agena was launched, its main engine suffered a momentary six percent decay in thrust chamber pressure and a corresponding drop in turbine speed. So, while Lovell and Aldrin chased and caught the Agena, then practiced docking, Mission Director Schneider and Flight Director Lunney had to decide whether the main engine should be fired. They soon decided that prudence was the better course - it should not.

Although the pilots missed the ride to high altitude, Lunney soon found something for them to do with their spare time. The flight plan had originally called for them to photograph a solar eclipse, if it did not conflict with the rest of the mission. This task fell by the wayside when the two-day launch delay - from 9 to 11 November - meant that the eclipse would occur during their high-altitude excursion. Canceling the main engine burn inspired two of the mission planners to thoughts of reinstating the eclipse photography. Schneider and Lunney conferred with James R. Bates, Experiments Advisory Officer for Gemini XII, on the effect this might have on the rest of the experiments. Since the flight plan had to be changed anyway, Bates said, why not include the eclipse?

This conference with Bates marked a significant change in mission control operations. Formerly working out of an adjacent staff support room, the experimenters' representative was now allowed by the engineers in charge to operate as a part of the flight control team in the main control room. Although there had been an experiments console in the control room by Gemini X, it had been only occasionally manned. Bates, on Gemini XII, was the first full-time experiments officer. This experience worked out so well that the custom was continued in Apollo.

Even after the eclipse became a flight-plan casualty, planners continued to plot its path. Now there was a chance to work this experiment back into the mission. The Agena's secondary propulsion system had enough power to get the spacecraft into position for an eight-second photographic pass at the proper time. Schneider and Lunney agreed that this piece of realtime planning would give an added fillip to the mission.

"The eclipse got to us after all," Lovell remarked. "Yes, it looks like it," Conrad answered. Although the crew had wanted to do the experiment when it was first planned, these sudden preparations came at an inconvenient time. They were still working with the Agena and were scheduled to begin such activities as eating, sleeping, and working on other experiments.

Nevertheless, at 7:05 hours after launch, Jim Lovell fired the Agena's smaller engines to slow his speed 13 meters per second. Agena still had its doubters - Conrad had told them, "If It gets away from . . . take it over with the (spacecraft)." But the target vehicle performed splendidly, and the crew then bedded down for the night.

The Canary Island controller greeted the crew in the morning with the news that there would be a second maneuver - 5 meters forward - to line the vehicles up properly. The prospects panned out richly, and the crew reported seeing the eclipse "right on the money at 16:01:44 g.e.t." The path of the eclipse cut a swath across South America from north of Lima, Peru, nearly to the southernmost tip of Brazil. Although they thought for a moment, they were slightly off track, their aim had been accurate.

The sudden change in the flight plan had disturbed the crew, because of its possible interference with the first planned extravehicular exercise. After all, this objective had become the heart of their mission. Despite interruptions (especially that caused by the second maneuver), the hatch was opened on time, about 20 minutes before sunset in space. Aldrin exclaimed, in near speechless awe, "Man! Look at that!" Aldrin was amazed and impressed at seeing so much of Earth and the universe spread before his eyes.

Aldrin went about his chores slowly and deliberately, working for a short period and then resting. First, he just stood in the hatch, becoming acclimated. Then he cast loose a garbage bag. Moments later, he murmured, "Stars in the daylight? I don't think so." He soon realized that he was watching the pouch as it drifted away. He was in darkness for eight minutes before his eyes became adjusted and he could see real stars and planets. Aldrin studied his every movement - every action and reaction - so he could compare his standup experience to the umbilical period later.

He set up an ultraviolet astronomical camera. During two night passes, he photographed star fields, although Lovell had trouble turning the spacecraft in specific directions because the Agena had nearly a full load of fuel. During daylight, the pilot installed a movie camera; fixed a handrail leading to the target docking adapter cone; pulled off the ultraviolet camera, reloaded it, and put it back; retrieved a micrometeorite collection package; and took pictures. At 21:58, the crew buttoned themselves back into the spacecraft after recording their first, highly successful, 2-hour-and-20-minute exercise.

The next day Lovell and Aldrin got ready for the main event of the mission - see if a man could perform useful tasks in space at the end of an umbilical. Near the 43-hour point in the flight, Aldrin stood up in his seat and reinstalled the movie camera just as easily as before - then removed it, stepped into space, and replaced it, using only a handrail to maintain position. The astronaut then moved, hand over hand, along the rail to the nose of the Agena docking-adapter. Using his waist tether for restraint, he tied the two vehicles together for the gravity-gradient experiment without any of the problems Gordon had encountered.

The pilot floated to the hatch area and exchanged cameras with Lovell. Moving along the handrail, Aldrin went aft to the spacecraft adapter. He placed his feet in the golden slippers (overshoe-type restraints). Then he moved his body back and forth and from side to side, to see if the slippers really helped as much in holding him down as the program office had hoped. They allowed him to relax completely and to lean as much as 45 degrees to either side and 90 degrees backward.

Next he unpacked some small penlights and set to work in the busy box, torquing bolts and cutting metal. On one occasion, a bolt and washer slipped free. Aldrin maneuvered the weightless fittings into a comer, capturing one in each hand. Lovell asked him over the intercom if he was playing orbital mechanics in the adapter and the pilot replied "Yes. I had to do a little rendezvous there." At sunrise, he returned to the open hatch. After resting for a few minutes, Aldrin again went forward to the Agena - this time to a busy box attached to the target. Lovell watched him as he pulled electrical connectors apart and put them together again. Aldrin also tried a torque wrench that had been designed for the Apollo program. For this task, he first used both waist tethers, then one, then none. On the way back to the hatch to end his second two hours of extravehicular time, Aldrin stopped to wipe the command pilot's window with a cloth. As he did, Lovell asked, "Hey, would you change the oil, too?" The "air in the tires" was "A-OK," so Aldrin climbed aboard, stood in the hatch, and watched while Lovell fired some of the thrusters. He then sat down in the spacecraft seat. The door closed easily, and Aldrin released the oxygen in his life support system to help repressurise the cabin.

The third hatch opening (and the second stand-up-in-the-seat period) came on the fourth day and lasted an hour. The pilot tossed out a lot of equipment he had used during the umbilical, as well as some empty food containers. The astronauts were not really litter bugs. Discarded items from the flights, like other things in orbit around Earth, eventually reenter and burn up in the atmosphere. Aldrin then snapped several ultraviolet photographs of constellations. That finished, he went back inside and closed the hatch; the last extravehicular performance of the Gemini program was ended. But NASA engineers, mission planners, and astronauts now believed they knew much more about the fundamentals of EVA.

Between the second and third hatch openings, Lovell and Aldrin went into their tethered vehicles act. Lovell backed Gemini XII carefully away from the Agena, forming a pole vertical to Earth. The tether deployed smoothly (with only a brief hangup) but remained slack. Lovell was exasperated at his inability to tighten it, using the spacecraft thrusters. "About this time we had a little . . . problem," he said, ". . . every time I wanted to pitch up or yaw, I would roll." Despite the control problem the crew did obtain the gravity gradient they sought. Both vehicles got upset on occasion, the spacecraft at one time wigwagging about 300 degrees. What caused these disturbances, the program office stated in its formal mission report, "is not completely understood, nor is the system behavior during and immediately following these excursions." The tether exercise lasted four hours, proving that both the controllers and the crew were confident enough to continue this form of stationkeeping through the nighttime passes.

Earlier in the mission (about the time of the docking and undocking practice), the fuel cell had hinted that it might cause trouble and not last the full four days. But 30 hours passed before a power loss was actually registered. Eventually, the experts decided that there may be too much water in the tanks. Whenever the crew drank water or used it to prepare their food, the fuel cell warning light went off.

The ground controllers were not sure what had happened to the water storage system's two tanks that held the crew's drinking water and (separated by a bladder) the fuel cell product water. But, in some way or another, the astronauts had lost a place in which to store from 15 to 18 kilograms of water produced by the fuel cell. So the crew had to drink more water to make more room in the tanks and to purge the system more frequently to remove gases that accumulated in the fuel cell, if they were going to complete the mission. Drinking lots of water and watching the red warning light, they nursed the fuel cell along for more than 80 hours. The flight neared its end before the batteries had to take over the electrical load.

So, even in the face of problems with the radar, the Agena main engines, and the fuel cells, Gemini XII had gone very well. Most of the mission objectives were accomplished, and some data were obtained from 12 of the 15 experiments assigned to the flight. At times, considerable ingenuity had been required to get around the hardware difficulties.

Compared to other flights, Gemini XII's accomplishments tended to obscure its hardware problems, of which this final mission had more than its fair share. Some troubles that forced slight changes in the flight plan actually turned into triumphs. The failure of the radar during the terminal phase of rendezvous, for example, had underscored the fact that backup techniques, using onboard charts and computations, really worked. Radar malfunction barely caused a ripple in the routine. Other troubles nagged and frustrated the crew, and some had adverse effects on operations; but here, again, they were not able to mar the impression of success. What was remembered was Aldrin's flawless performance during the well planned extravehicular periods.

During the 59th revolution, Gemini XII began its controlled automatic reentry. Everything worked neatly, until the spacecraft reached its peak g loads. At that point, a pouch containing books, filters, and small pieces of equipment broke free from the Velcro on the sidewall of the cabin and landed on Lovell's lap. The pilots had unstowed the D-rings that activated the ejection seats and were holding them down between their legs. Lovell resisted the impulse to catch the pouch for fear he might "just grab a hold of the D-ring and keep pulling it." If he had, the commander, along with his pilot, would have exploded into the atmosphere, riding the ejection seats. This thought was bad news to Lovell, "because I didn't want to see myself punching out right at this high heating area." Instead, he squeezed his knees together and hoped that the pouch would not go any farther. It did not. The rest of the reentry was smooth until the moment of landing, when the spacecraft plopped down hard on the ocean.

It landed only 4.8 kilometers from the point at which it had aimed and only 5.5 kilometers from the carrier Wasp. A helicopter deposited the triumphant astronauts on the deck of the prime recovery vessel 28 minutes after touchdown. There, on 15 November 1966, at 2:21 p.m. est., the curtain closed on the Gemini manned space flight program.

So the Gemini flag and the Gemini pennant that had flown over the Manned Spacecraft Center during each of the missions, beginning with Gemini IV were lowered for the last time. The manned flights had started in 1965. Gemini had succeeded in putting manned space flight on something like a routine basis, as envisioned in the Project Development Plan of 1961. This accomplishment did not go unnoticed. President Lyndon B. Johnson said:

"Ten times in this program of the last 20 months we have placed two men in orbit about the earth in the world's most advanced spacecraft. Ten times we have brought them home.

"Today's flight was the culmination of a great team effort, stretching back to 1961, and directly involving more than 25,000 people in the National Aeronautics and Space Administration, the Department of Defense, and other Government agencies; in the universities and other research centers; and in American industry.

Early in 1962, John Glenn made his historic orbital flight and America was in space. Now, nearly 5 years later, we have completed Gemini and we know that America is in space to stay."

More at: Gemini 12.

Family: Manned spaceflight. People: Aldrin, Lovell. Country: USA. Spacecraft: Gemini. Launch Sites: Cape Canaveral. Agency: NASA Houston.
Photo Gallery

Gemini 12Gemini 12
Last Gemini-Titan ascends
Credit: NASA

Gemini 12Gemini 12
Agena in orbit
Credit: NASA

Gemini 12Gemini 12
Spaceman Aldrin
Credit: NASA

Gemini 12Gemini 12
Aldrin aboard Gemini 12
Credit: NASA

1964 January - . LV Family: Titan. Launch Vehicle: Titan II.
1964 April 13 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1964 April 30 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1964 September 24 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1964 November 10 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1964 November 30 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1965 January 20 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1965 February 1 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1965 March 9 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1965 March 18 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1965 March 23-24 - . Launch Vehicle: Atlas SLV-3 Agena D.
1965 May 6 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1965 May 10 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1965 May 27 - . Launch Vehicle: Atlas SLV-3 Agena D.
1965 October 28 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1965 November 19 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1965 December 14 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1966 January 20 - . LV Family: Titan. Launch Vehicle: Titan II.
1966 April 22 - .
1966 May 8 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1966 June 17 - .
1966 July 21 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1966 July 29 - . LV Family: Titan. Launch Vehicle: Titan II.
1966 August 16 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1966 September 2 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1966 September 6 - .
1966 September 12 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1966 September 16 - .
1966 September 19 - . LV Family: Titan. Launch Vehicle: Titan II.
1966 September 21 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1966 September 23 - .
1966 September 23 - .
1966 September 26 - .
1966 October 5 - . LV Family: Titan. Launch Vehicle: Titan II.
1966 October 11 - . LV Family: Titan. Launch Vehicle: Titan II.
1966 October 23 - . LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1966 November 8 - .
1966 November 11 - . 19:07 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC14. LV Family: Atlas. Launch Vehicle: Atlas SLV-3 Agena D.
1966 November 11 - . 20:46 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC19. LV Family: Titan. Launch Vehicle: Titan II GLV.
1966 November 12 - . 16:15 GMT - .
1966 November 13 - . 15:34 GMT - .
1966 November 14 - .
1966 November 14 - . 14:52 GMT - .
1966 November 15 - .

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