Gemini XI conducting a tether experiment using the Agena Target Vehicle
| |
| Mission type |
|
|---|---|
| Operator | NASA |
| COSPAR ID | 1966-081A  |
| SATCAT no. | 2415 |
| Mission duration | 2 days 23 hours 17 minutes 9 seconds |
| Orbits completed | 44 |
| Spacecraft properties | |
| Spacecraft | Gemini SC11 |
| Manufacturer | McDonnell |
| Launch mass | 3,798 kilograms (8,374 lb) |
| Landing mass | 1,920 kilograms (4,230 lb) |
| Crew | |
| Crew size | 2 |
| Members |
|
| EVAs | 2 |
| EVA duration | 2 hours 41 minutes |
| Start of mission | |
| Launch date | September 12, 1966, 14:42:26 (1966-09-12UTC14:42:26Z) UTC |
| Rocket | Titan II GLV |
| Launch site | Cape Kennedy LC-19 |
| End of mission | |
| Recovered by | USS Guam |
| Landing date | September 15, 1966, 13:59:35 (1966-09-15UTC13:59:36Z) UTC |
| Landing site | 24°15′N 70°0′W / 24.250°N 70.000°W / 24.250; -70.000 (Gemini 11 splashdown) |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime | Low Earth orbit |
| Perigee altitude | 298 kilometers (161 nmi) |
| Apogee altitude | 1,368 kilometers (739 nmi) |
| Inclination | 28.8 degrees |
| Period | 101.57 minutes |
| Epoch | September 14, 1966[1] |
| Docking with GATV-5006 | |
| Docking date | September 12, 1966, 16:16:00 UTC |
| Undocking date | September 14, 1966, 16:55:00 UTC |
| Time docked | 2 days 39 minutes |
 Gordon (left) and Conrad | |
Gemini 11 (officially Gemini XI)[2] was the ninth crewed spaceflight mission of NASA's Project Gemini, which flew from September 12 to 15, 1966. It was the 17th crewed American flight and the 25th spaceflight to that time (includes X-15 flights over 100 kilometers (54 nmi)). Astronauts Charles "Pete" Conrad Jr. and Richard F. Gordon Jr. performed the first direct-ascent (first orbit) rendezvous with an Agena Target Vehicle, docking with it 1 hour 34 minutes after launch; used the Agena rocket engine to achieve a record high-apogee Earth orbit; and created a small amount of artificial gravity by spinning the two spacecraft connected by a tether. Gordon also performed two extra-vehicular activities for a total of 2 hours 41 minutes.
| Position | Astronaut | |
|---|---|---|
| Command Pilot | Charles "Pete" Conrad Jr. Second spaceflight | |
| Pilot | Richard F. Gordon Jr. First spaceflight | |
| Position | Astronaut | |
|---|---|---|
| Command Pilot | Neil A. Armstrong | |
| Pilot | William A. Anders | |
Highest orbit (followed twice):
| Gemini 11 | Agena info |
|---|---|
| Agena | GATV-5006 |
| NSSDC ID: | 1966-080A |
| Mass | 7,000 pounds (3,200 kg) |
| Launch site | LC-14 |
| Launch date | September 12, 1966 |
| Launch time | 13:05:01 UTC |
| 1st perigee | 156.4 nautical miles (289.7 km) |
| 1st apogee | 165.8 nautical miles (307.1 km) |
| Period | 90.56 min |
| Inclination | 28.84 deg |
| Reentered | December 30, 1966 |
The direct-ascent rendezvous and docking with the Agena vehicle was achieved approximately 94 minutes after lift-off, depending on the on-board computer and radar equipment with only minimal assistance from ground support.[4]
Gemini 11 used the rocket on its Agena target vehicle to raise its apogee to 853 miles (1,373 km), the highest Earth orbit ever reached by a crewed spacecraft.[5] The perigee was 179 miles (288 km), and maximum velocity (at perigee) was 17,967 miles per hour (28,915 km/h).[4] The apogee record stands as of October 2022, even though men have achieved greater distances from Earth by flying to the Moon in the Apollo program.[6] The maximum operational altitude of the Space Shuttle was much lower, at 386 miles (621 km) for the STS-31 flight in 1990. The September 2021 SpaceX flight of Inspiration4, while having an apogee higher than most Space Shuttle flights, only reached 585 kilometres (364 mi).[7]
The crew docked and undocked four times and still had sufficient Gemini maneuvering fuel for an unplanned fifth rendezvous. They did not remain in the high orbit, but changed it back to a near-circular one at 184 miles (296 km).[4]
Gordon's first EVA, planned to last for two hours, involved fastening a 100-foot (30 m) tether, stored in the Agena's docking collar, to the Gemini's docking bar for the passive stabilization experiment. Gordon achieved this, but as with previous Gemini EVAs, trying to do work for an extended period proved more fatiguing than in ground simulation, and the EVA had to be terminated after only half an hour.
The passive stabilization experiment proved to be a bit troublesome. Conrad and Gordon separated the craft in a nose-down (i.e., Agena-down) position, but found that the tether would not be kept taut simply by the Earth's gravity gradient, as expected. However, they were able to generate a small amount of artificial gravity, about 0.00015 g, by firing their side thrusters to slowly rotate the combined craft like a slow-motion pair of bolas.[4]
Gordon successfully performed a second EVA standing up with his head and shoulders out of the hatch to photograph the Earth, clouds, and stars. This was not tiring and lasted more than two hours.[4]
The 12 scientific experiments were:[8]
The mission ended with the first totally automatic, computer-controlled reentry by the U.S., which brought Gemini 11 down 2.8 miles (4.5 km) from its recovery ship USS Guam, only 1.5 miles (2.4 km) from the planned position.[4]
Astronaut recovery was done by Navy Helicopter Squadron HS-3.
The Gemini 11 mission was supported by 9,054 United States Department of Defense personnel, 73 aircraft, and 13 ships.[10]
Since Conrad and Gordon were both members of the US Navy, the embroidered mission patch was designed in Navy colors: blue and gold. Stars are used to mark the major milestones of the mission. The first orbit Agena rendezvous is marked by a small gold star just above the Earth, to the left. The Agena docking is marked by a large star on the left. The star at the top marks the record high apogee reached by Gemini 11. Note that the scale is greatly exaggerated; their maximum altitude of 850 miles (1,370 km) is roughly the distance from St. LouistoCape Kennedy. Finally, the star on the right marks Dick Gordon's spacewalk. The docking, record apogee and spacewalk are also shown on the patch by the Agena, orbital apogee path and spacewalking astronaut.
Gemini 11's record altitude was ultimately the result of an internal race to the Moon. As early as 1961, NASA's Jim Chamberlin and McDonnell Aircraft had advocated using Gemini spacecraft to get to the Moon sooner than Apollo. Their proposals considered using Centaur rockets to boost the Gemini on a circumlunar trajectory (similar to the Soviet's Zond program), lunar orbit missions using Centaur rockets for translunar injection and Agena for lunar orbit insertion, and even lunar landing missions using Gemini in place of the Apollo Command Module and a small open-cockpit Langley Light LM in place of the Apollo Lunar Module. Multiple Titan or Saturn IB rockets, and even the abandoned Saturn C-3 were considered as the launch vehicles.
Pete Conrad liked these ideas and together with McDonnell corporations strongly advocated his Gemini 11 to be circumlunar. Discretely called 'Gemini - Large Earth Orbit', the plan would use a Titan IIIC-launched Transtage. The Gemini 11 crew would be launched with the Titan II GLV as they did in reality, and would dock with the Transtage, which would then boost them to translunar velocity. Conrad managed to stir Congressional interest, but NASA administrator James Webb informed them that any extra funds Congress cared to appropriate for such a project would be better spent accelerating the Apollo program. After further internal struggles, Conrad finally got NASA approval for the Agena on his Gemini 11 flight to boost him onto two record highly elliptical 1,370 km orbits. This high flight was the only remnant of lunar Gemini.[11]
The spacecraft is on display at the California Science CenterinLos Angeles, California.
This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.
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| Preceded by Gemini 10 crew |
Human altitude record 1966-1968 |
Succeeded by Apollo 8 crew |
