Credit: © Mark Wade
Status: Retired 1966. First Launch: 1964-04-08. Last Launch: 1966-11-11. Number: 12 . Payload: 3,600 kg (7,900 lb). Thrust: 2,090.00 kN (469,850 lbf). Gross mass: 150,530 kg (331,860 lb). Height: 32.80 m (107.60 ft). Diameter: 3.05 m (10.00 ft). Apogee: 300 km (180 mi).
Modifications to Titan II for use as the Gemini Launch Vehicle included:
LEO Payload: 3,600 kg (7,900 lb) in 1965 dollars. Flyaway Unit Cost 1985$: 3.158 million.
The first Gemini mission, Gemini-Titan I, was launched from Complex 19 at Cape Kennedy at 11:00 a.m., e.s.t. This was an unmanned flight, using the first production Gemini spacecraft and a modified Titan II Gemini launch vehicle (GLV). The mission's primary purpose was to verify the structural integrity of the GLV and spacecraft, as well as to demonstrate the GLV's ability to place the spacecraft into a prescribed earth orbit. Mission plans did not include separation of the spacecraft from the second stage of the vehicle, and both were inserted into orbit as a unit six minutes after launch. The planned mission encompassed only the first three orbits and ended about four hours and 50 minutes after liftoff. No recovery was planned for this mission, but Goddard continued to track the spacecraft until it reentered the atmosphere on the 64th orbital pass over the southern Atlantic Ocean (April 12) and disintegrated. The flight qualified the GLV and its systems and the structure of the spacecraft.
The second Titan II Gemini Launch Vehicle (GLV-2) carried the unmanned, instrumented Gemini spacecraft (GT-2) for a suborbital shot preliminary to the first U.S. two-man Gemini mission. During the countdown for Gemini-Titan (GT) 2, the fuel cell hydrogen inlet valve failed to open. Efforts to correct the problem continued until it was determined that freeing the valve would delay the countdown. Work on the fuel cell ceased, and it was not activated for the flight. The fuel cell installed in spacecraft No. 2 was not a current flight design. When fuel cell design was changed in January 1964, several cells of earlier design were available. Although these cells were known to have some defects, flight testing with the reactant supply system was felt to be extremely desirable. Accordingly, it was decided to fly the entire system on GT-2, but only on a "non-interference with flight" basis. When it became clear that correcting the problem that emerged during the GT-2 countdown would cause delay, fuel cell activation for the flight was called off.
First manned test flight of Gemini. Virgil I. Grissom and John W. Young entered an elliptical orbit about the earth. After three orbits, the pair manually landed their spacecraft in the Atlantic Ocean, thus performing the first controlled reentry. Unfortunately, they landed much farther from the landing zone than anticipated, about 97 km (60 miles) from the aircraft carrier U.S.S. Intrepid. But otherwise the mission was highly successful. Gemini III, America's first two-manned space mission, also was the first manned vehicle that was maneuverable. Grissom used the vehicle's maneuvering rockets to effect orbital and plane changes. Grissom wanted to name the spacecraft 'Molly Brown' (as in the Unsinkable, a Debbie Reynolds/Howard Keel screen musical). NASA was not amused and stopped allowing the astronauts to name their spacecraft (until forced to when having two spacecraft aloft at once during the Apollo missions). The flight by Young was the first of an astronaut outside of the original seven. Young, who created a media flap by taking a corned beef sandwich aboard as a prank, would go on to fly to the moon on Apollo and the Space Shuttle on its first flight sixteen years later.
The second manned and first long-duration mission in the Gemini program. Major objectives of the four-day mission were demonstrating and evaluating the performance of spacecraft systems in a long-duration flight and evaluating effects on the crew of prolonged exposure to the space environment. Secondary objectives included demonstrating extravehicular activity (EVA) in space, conducting stationkeeping and rendezvous maneuvers with the second stage of the launch vehicle, performing significant in-plane and out-of-plane maneuvers, demonstrating the ability of the orbit attitude and maneuver system (OAMS) to back up the retrorockets, and executing 11 experiments. The stationkeeping exercise was terminated at the end of the first revolution because most of the OAMS propellant allocated for the exercise had been used; further efforts would jeopardize primary mission objectives and could mean the cancellation of several secondary objectives. No rendezvous was attempted. The only other major problem to mar the mission was the inadvertent alteration of the computer memory during the 48th revolution in an attempt to correct an apparent malfunction. This made the planned computer-controlled reentry impossible and required an open-loop ballistic reentry. All other mission objectives were met. The flight crew began preparing for EVA immediately after terminating the stationkeeping exercise. Although preparations went smoothly, McDivitt decided to delay EVA for one revolution, both because of the high level of activity required and because deletion of the rendezvous attempt reduced the tightness of the schedule. Ground control approved the decision. The spacecraft hatch was opened at 4 hours 18 minutes into the flight and White exited 12 minutes later, using a hand-held maneuvering gun. White reentered the spacecraft 20 minutes after leaving it. The hatch was closed at 4 hours 54 minutes ground elapsed time. Drifting flight was maintained for the next two and one-half days to conserve propellant. The spacecraft landed in the Atlantic Ocean about 725 km east of Cape Kennedy - some 65 km from its nominal landing point. The crew boarded a helicopter 34 minutes after landing and was transported to the prime recovery ship, the aircraft carrier Wasp. Spacecraft recovery was completed at 2:28 p.m., a little more than 100 hours after Gemini 4 had been launched. Gemini 4 was the first mission to be controlled from the mission control center in Houston.
The space walk was hurriedly included after the Russian first in Voskhod 2. White seemed to have a lot more fun than Leonov and McDivitt took the pictures that came to symbolize man in space. With this flight the US finally started to match Russian flight durations.
Major objectives of the eight-day mission were evaluating the performance of the rendezvous guidance and navigation system, using a rendezvous evaluation pod (REP), and evaluating the effects of prolonged exposure to the space environment on the flight crew. Secondary objectives included demonstrating controlled reentry guidance, evaluating fuel cell performance, demonstrating all phases of guidance and control system operation needed for a rendezvous mission, evaluating the capability of either pilot to maneuver the spacecraft in orbit to rendezvous, evaluating the performance of rendezvous radar, and executing 17 experiments. The mission proceeded without incident through the first two orbits and the ejection of the REP. About 36 minutes after beginning evaluation of the rendezvous guidance and navigation system, the crew noted that the pressure in the oxygen supply tank of the fuel cell system was falling. Pressure dropped from 850 pounds per square inch absolute (psia) at 26 minutes into the flight until it stabilized at 70 psia at 4 hours 22 minutes, and gradually increased through the remainder of the mission. The spacecraft was powered down and the REP exercise was abandoned. By the seventh revolution, experts on the ground had analyzed the problem and a powering-up procedure was started. During the remainder of the mission the flight plan was continuously scheduled in real time. Four rendezvous radar tests were conducted during the mission, the first in revolution 14 on the second day; the spacecraft rendezvous radar successfully tracked a transponder on the ground at Cape Kennedy. During the third day, a simulated Agena rendezvous was conducted at full electrical load. The simulation comprised four maneuvers - apogee adjust, phase adjust, plane change, and coelliptical maneuver - using the orbit attitude and maneuver system (OAMS). Main activities through the fourth day of the mission concerned operations and experiments. During the fifth day, OAMS operation became sluggish and thruster No. 7 inoperative. Thruster No. 8 went out the next day, and the rest of the system was gradually becoming more erratic. Limited experimental and operational activities continued through the remainder of the mission. Retrofire was initiated in the 121st revolution during the eighth day of the mission, one revolution early because of threatening weather in the planned recovery area. Reentry and landing were satisfactory, but the landing point was 145 km short, the result of incorrect navigation coordinates transmitted to the spacecraft computer from the ground network. Landing occurred August 29, 190 hours 55 minutes after the mission had begun. The astronauts arrived on board the prime recovery ship, the aircraft carrier Lake Champlain, at 9:25. The spacecraft was recovered at 11:51 a.m.
With this flight, the US finally took the manned spaceflight endurance record from Russia, while demonstrating that the crew could survive in zero gravity for the length of time required for a lunar mission. However the mission was incredibly boring, the spacecraft just drifting to conserve fuel most of the time, and was 'just about the hardest thing I've ever done' according to a hyperactive Pete Conrad. An accident with freeze dried shrimp resulted in the cabin being filled with little pink subsatellites.
An Air Force Titan II Gemini Launch Vehicle lifted Gemini 7 (GT-7) into orbit from Cape Canaveral. Astronauts Frank Borman and James Lovell completed the 14-day mission, the longest U.S. space flight to date (330 hours, 35 minutes) and 206 revolutions, and were recovered on 18 December, 700 miles southwest of Bermuda. During their record flight, Borman and Lovell piloted GT-7 as the target vehicle for the first space rendezvous between manned spacecraft. Astronauts Walter Schirra and Thomas Stafford aboard Gemini 6 were launched on 15 December and completed the first space rendezvous with Gemini 7 the same day. Primary objectives of the mission were demonstrating manned orbital flight for approximately 14 days and evaluating the physiological effects of a long-duration flight on the crew. Among the secondary objectives were providing a rendezvous target for the Gemini VI-A spacecraft, stationkeeping with the second stage of the launch vehicle and with spacecraft No. 6, conducting 20 experiments, using lightweight pressure suits, and evaluating the spacecraft reentry guidance capability. All objectives were successfully achieved with the exception of two experiments lost because of equipment failure. Shortly after separation from the launch vehicle, the crew maneuvered the spacecraft to within 60 feet of the second stage and stationkept for about 15 minutes. The exercise was terminated by a separation maneuver, and the spacecraft was powered down in preparation for the 14-day mission. The crew performed five maneuvers during the course of the mission to increase orbital lifetime and place the spacecraft in proper orbit for rendezvous with spacecraft No. 6. Rendezvous was successfully accomplished during the 11th day in orbit, with spacecraft No. 7 serving as a passive target for spacecraft No. 6. About 45 hours into the mission, Lovell removed his pressure suit. He again donned his suit at 148 hours, while Borman removed his. Some 20 hours later Lovell again removed his suit, and both crewmen flew the remainder of the mission without suits, except for the rendezvous and reentry phases. With three exceptions, the spacecraft and its systems performed nominally throughout the entire mission. The delayed-time telemetry playback tape recorder malfunctioned about 201hours after liftoff, resulting in the loss of all delayed-time telemetry data for the remainder of the mission. Two fuel cell stacks showed excessive degradation late in the flight and were taken off the line; the remaining four stacks furnished adequate electrical power until reentry. Two attitude thrusters performed poorly after 283 hours in the mission. Retrofire occurred exactly on time, and reentry and landing were nominal. The spacecraft missed the planned landing point by only 10.3 km miles, touching down on December 18. The crew arrived at the prime recovery ship, the aircraft carrier Wasp, half an hour later. The spacecraft was recovered half an hour after the crew.
Far surpassing the Gemini 5 flight, Gemini 7 set a manned spaceflight endurance record that would endure for years. The incredibly boring mission, was made more uncomfortable by the extensive biosensors. This was somewhat offset by the soft spacesuits (used only once) and permission to spend most of the time in long johns. The monotony was broken just near the end by the rendezvous with Gemini 6.
The primary objective of the mission, crewed by command pilot Astronaut Walter M. Schirra, Jr., and pilot Astronaut Thomas P. Stafford, was to rendezvous with spacecraft No. 7. Among the secondary objectives were stationkeeping with spacecraft No. 7, evaluating spacecraft reentry guidance capability, testing the visibility of spacecraft No. 7 as a rendezvous target, and conducting three experiments. After the launch vehicle inserted the spacecraft into an 87 by 140 nautical mile orbit, the crew prepared for the maneuvers necessary to achieve rendezvous. Four maneuvers preceded the first radar contact between the two spacecraft. The first maneuver, a height adjustment, came an hour and a half after insertion, at first perigee; a phase adjustment at second apogee, a plane change, and another height adjustment at second perigee followed. The onboard radar was turned on 3 hours into the mission. The first radar lock-on indicated 246 miles between the two spacecraft. The coelliptic maneuver was performed at third apogee, 3 hours 47 minutes after launch. The terminal phase initiation maneuver was performed an hour and a half later. Two midcourse corrections preceded final braking maneuvers at 5 hours 50 minutes into the flight. Rendezvous was technically accomplished and stationkeeping began some 6 minutes later when the two spacecraft were about 120 feet apart and their relative motion had stopped. Stationkeeping maneuvers continued for three and a half orbits at distances from 1 to 300 feet. Spacecraft No. 6 then initiated a separation maneuver and withdrew to a range of about 30 miles. The only major malfunction in spacecraft No. 6 during the mission was the failure of the delayed-time telemetry tape recorder at 20 hours 55 minutes ground elapsed time, which resulted in the loss of all delayed-time telemetry data for the remainder of the mission, some 4 hours and 20 minutes. The flight ended with a nominal reentry and landing in the West Atlantic, just 10 km from the planned landing point, on December 16. The crew remained in the spacecraft, which was recovered an hour later by the prime recovery ship, the aircraft carrier Wasp.
Gemini 6 was to have been the first flight involving docking with an Agena target/propulsion stage. However the Agena blew up on the way to orbit, and the spacecraft was replaced by Gemini 7 in the launch order.
For lack of a target, NASA decided to have Gemini 6 rendezvous with Gemini 7. This would require a quick one week turnaround of the pad after launch, no problem with Russian equipment but a big accomplishment for the Americans. The first launch attempt was aborted; the Titan II ignited for a moment, then shut down and settled back down on its launch attachments. Schirra waited it out, did not pull the abort handles that would send the man catapulting out of the capsule on their notoriously unreliable ejection seats. The booster was safed; Schirra had saved the mission and the launch three days later went perfectly. The flight went on to achieve the first manned space rendezvous controlled entirely by the self-contained, on-board guidance, control, and navigation system. This system provided the crew of Gemini 6 with attitude, thrusting, and time information needed for them to control the spacecraft during the rendezvous. Under Schirra's typically precise command, the operation was so successful that the rendezvous was complete with fuel consumption only 5% above the planned value to reach 16 m separation from Gemini 7.
The Atlas-Agena target vehicle for the Gemini VIII mission was successfully launched from KSC Launch Complex 14 at 10 a.m. EST March 16. The Gemini VIII spacecraft followed from Launch Complex 19 at 11:41 a.m., with command pilot Neil A. Armstrong and pilot David R. Scott aboard. The spacecraft and its target vehicle rendezvoused and docked, with docking confirmed 6 hours 33 minutes after the spacecraft was launched. This first successful docking with an Agena target vehicle was followed by a major space emergency. About 27 minutes later the spacecraft-Agena combination encountered unexpected roll and yaw motion. A stuck thruster on Gemini put the docked assembly into a wild high speed gyration. Near structural limits and blackout, Armstrong undocked, figuring the problem was in the Agena, which only made it worse. The problem arose again and when the yaw and roll rates became too high the crew shut the main Gemini reaction control system down and activated and used both rings of the reentry control system to reduce the spacecraft rates to zero. This used 75% of that system's fuel. Although the crew wanted to press on with the mission and Scott's planned space walk, ground control ordered an emergency splashdown in the western Pacific during the seventh revolution. The spacecraft landed at 10:23 p.m. EST March 16 and Armstrong and Scott were picked up by the destroyer U.S.S. Mason at 1:37 a.m. EST March 17. Although the flight was cut short by the incident, one of the primary objectives - rendezvous and docking (the first rendezvous of two spacecraft in orbital flight) - was accomplished.
Primary objectives of the scheduled three-day mission were to rendezvous and dock with the Gemini Agena target vehicle (GATV) and to conduct extravehicular activities. Secondary objectives included rendezvous and docking during the fourth revolution, performing docked maneuvers using the GATV primary propulsion system, executing 10 experiments, conducting docking practice, performing a rerendezvous, evaluating the auxiliary tape memory unit, demonstrating controlled reentry, and parking the GATV in a 220-nautical mile circular orbit. The GATV was inserted into a nominal 161-nautical mile circular orbit, the spacecraft into a nominal 86 by 147-nautical mile elliptical orbit. During the six hours following insertion, the spacecraft completed nine maneuvers to rendezvous with the GATV. Rendezvous phase ended at 5 hours 58 minutes ground elapsed time, with the spacecraft 150 feet from the GATV and no relative motion between the two vehicles. Stationkeeping maneuvers preceded docking, which was accomplished at 6 hours 33 minutes ground elapsed time. A major problem developed 27 minutes after docking, when a spacecraft orbit attitude and maneuver system (OAMS) thruster malfunctioned. The crew undocked from the GATV and managed to bring the spacecraft under control by deactivating the OAMS and using the reentry control system (RCS) to reduce the spacecraft's rapid rotation. Premature use of the RCS, however, required the mission to be terminated early. The retrofire sequence was initiated in the seventh revolution, followed by nominal reentry and landing in a secondary recovery area in the western Pacific Ocean. The spacecraft touched down less than 10 km from the planned landing point. The recovery ship, the destroyer Leonard Mason, picked up both crew and spacecraft some three hours later. Early termination of the mission precluded achieving all mission objectives, but one primary objective - rendezvous and docking - was accomplished. Several secondary objectives were also achieved: rendezvous and docking during the fourth revolution, evaluating the auxiliary tape memory unit, demonstrating controlled reentry, and parking the GATV. Two experiments were partially performed.
At the first launch attempt, while the crew waited buttoned up in the spacecraft on the pad, their Agena docking target field blew up on the way to orbit. NASA decided to use an Atlas to launch an Agena docking collar only. This was called the Augmented Target Docking Adapter. Ths was successfully launched and the Gemini succeeded in rendezvousing with it. However, the ATDA shroud had not completely separated, thus making docking impossible. However three different types of rendezvous were tested with the ATDA. Cernan began his EVA, which was to include flight with a USAF MMU rocket pack but the Gemini suit could not handle heat load of the astronaut's exertions. Cernan's faceplate fogs up, forcing him to blindly grope back into the Gemini hatch after only two hours.
Seventh manned and third rendezvous mission of the Gemini program. Major objectives of the mission were to rendezvous and dock with the augmented target docking adapter (ATDA) and to conduct extravehicular activities (EVA). These objectives were only partially met. After successfully achieving rendezvous during the third revolution - a secondary objective - the crew discovered that the ATDA shroud had failed to separate, precluding docking - a primary objective - as well as docking practice - another secondary objective. The crew was able, however, to achieve other secondary objectives: an equi-period rendezvous, using onboard optical techniques and completed at 6 hours 36 minutes ground elapsed time; and a rendezvous from above, simulating the rendezvous of an Apollo command module with a lunar module in a lower orbit (completed at 21 hours 42 minutes ground elapsed time). Final separation maneuver was performed at 22 hours 59 minutes after liftoff. EVA was postponed because of crew fatigue, and the second day was given over to experiments. The hatch was opened for EVA at 49 hours 23 minutes ground elapsed time. EVA was successful, but one secondary objective - evaluation of the astronaut maneuvering unit (AMU) - was not achieved because Cernan's visor began fogging. The extravehicular life support system apparently became overloaded with moisture when Cernan had to work harder than anticipated to prepare the AMU for donning. Cernan reentered the spacecraft, and the hatch was closed at 51 hours 28 minutes into the flight. The rest of the third day was spent on experiments.
An Air Force Titan Gemini Launch Vehicle placed the Gemini 10 (GT-10) spacecraft into orbit for the three-day mission of Astronauts John Young and Michael Collins. Rendezvous and docking were accomplished with the Gemini Agena Target Vehicle (GATV) that had been launched from Cape Kennedy aboard an Atlas Booster just ahead of GT-10. Using the GATV-10 Primary Propulsion System (PPS), the docked vehicles achieved a manned-flight altitude record of 476 miles. Reentry was accomplished on 21 July and recovery was made 544 miles east of Cape Canaveral. Exciting mission with successful docking with Agena, flight up to parking orbit where Gemini 8 Agena is stored. Collins space walks from Gemini to Agena to retrieve micrometeorite package left in space all those months. Loses grip first time, and tumbles head over heels at end of umbilical around Gemini. Package retrieved on second try.
The Gemini X mission began with the launch of the Gemini Atlas-Agena target vehicle from complex 14. The Gemini Agena target vehicle (GATV) attained a near-circular, 162- by 157-nautical-mile orbit. Spacecraft No. 10 was inserted into a 145- by 86-nautical-mile elliptical orbit. Slant range between the two vehicles was very close to the nominal 1000 miles. Major objective of the mission was achieved during the fourth revolution when the spacecraft rendezvoused with the GATV at 5 hours 23 minutes ground elapsed time and docked with it about 30 minutes later. More spacecraft propellant was used to achieve rendezvous than had been predicted, imposing constraints on the remainder of the mission and requiring the development of an alternate flight plan. As a result, several experiments were not completed, and another secondary objective - docking practice - was not attempted. To conserve fuel and permit remaining objectives to be met, the spacecraft remained docked with the GATV for about 39 hours. During this period, a bending mode test was conducted to determine the dynamics of the docked vehicles, standup extravehicular activties (EVA) were conducted, and several experiments were performed. The GATV primary and secondary propulsion systems were used for six maneuvers to put the docked spacecraft into position for rendezvous with the Gemini VIII GATV as a passive target. The spacecraft undocked at 44 hours 40 minutes ground elapsed time, separated from the GATV, and used its own thrusters to complete the second rendezvous some three hours later. At 48 hours and 42 minutes into the flight, a 39-minute period of umbilical EVA began, which included the retrieval of a micrometorite collection package from the Gemini VIII Agena. The hatch was opened a third time about an hour later to jettison extraneous equipment before reentry. After about three hours of stationkeeping, the spacecraft separated from the GATV. At 51 hours 39 minutes ground elapsed time, the crew performed a true anomaly-adjust maneuver to minimize reentry dispersions resulting from the retrofire maneuver.
More highjinks with Conrad. First orbit docking with Agena, followed by boost up to record 800 km orbit, providing first manned views of earth as sphere. Tether attached by Gordon to Agena in spacewalk and after a lot of effort tethered spacecraft put into slow rotation, creating first artificial microgravity.
The primary objective of the Gemini XI mission was to rendezvous with the Gemini Agena target vehicle (GATV) during the first revolution and dock. Five maneuvers completed the spacecraft/GATV rendezvous at 1 hour 25 minutes ground elapsed time, and the two vehicles docked nine minutes later. Secondary objectives included docking practice, extravehicular activity (EVA), 11 experiments, docked maneuvers, a tethered vehicle test, demonstrating automatic reentry, and parking the GATV. All objectives were achieved except one experiment - evaluation of the minimum reaction power tool - which was not performed because umbilical EVA was terminated prematurely. Umbilical EVA began at 24 hours 2 minutes ground elapsed time and ended 33 minutes later. Gordon became fatigued while attaching the tether from the GATV to the spacecraft docking bar. An hour later the hatch was opened to jettison equipment no longer required. At 40 hours 30 minutes after liftoff, the GATV primary propulsion system (PPS) was fired to raise the apogee of the docked vehicles to 741 nautical miles for two revolutions. The PPS was fired again, 3 hours 23 minutes later, to reduce apogee to 164 nautical miles. The crew then prepared for standup EVA, which began at 47 hours 7 minutes into the flight and lasted 2 hours 8 minutes. The spacecraft was then undocked to begin the tether evaluation. At 50 hours 13 minutes ground elapsed time, the crew initiated rotation. Initial oscillations damped out and the combination became very stable after about 20 minutes; the rotational rate was then increased. Again, initial oscillations gradually damped out and the combination stabilized. At about 53 hours into the mission, the crew released the tether, separated from the GATV, and maneuvered the spacecraft to an identical orbit with the target vehicle. A fuel cell stack failed at 54 hours 31 minutes, but the remaining five stacks shared the load and operated satisfactorily. A rerendezvous was accomplished at 66 hours 40 minutes ground elapsed time, and the crew then prepared for reentry.
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.