Gemini 8 (officially Gemini VIII) was a 1966 manned spaceflight in NASA's Gemini program. It was the 6th manned Gemini flight, the 12th manned American flight and the 22nd spaceflight of all time (includes X-15 flights over 100 km).
Mission Insignia
Mission Statistics
Mission:Gemini VIII
Number of Crew Members: 2
Launch:March 16, 1966
16:41:02.389 UTC
Cape Canaveral LC19
Landing:March 17, 1966
3:22:28 UTC
25 13.8' N, 136 0' E
Duration:10 hours
41 minutes, 26 seconds
Orbits: 7


The crew for the flight were both rookies
Neil Armstrong (Commander) and David Scott (Pilot).


The main objective of Gemini 8 was to rendezvous and dock with the Agena Target Vehicle, the first ever docking in space. The other main objective was to investigate Extra-Vehicular Activity to a greater extent than on Gemini 4, when Edward White had only spent 20 minutes outside of the spacecraft. On this mission it was planned that Dave Scott would spend up to two hours outside the spacecraft.



It was five months since NASA had tried to launch an Agena and Gemini. This time everything worked perfectly. The Agena put itself into a 298-kilometer circular orbit and orientated itself to the correct attitude for the docking. The Gemini spacecraft itself was put into a 160 by 272 kilometres by its modified Titan II ICBM.

Rendezvous and Docking

Their first burn was at 1 hour and 34 minutes into the mission, when they lowered their apogee with a 5 second burn. The second burn was at apogee of the second orbit. This time they raised their perigee by adding 15 metres per second to their speed. Their third burn made sure that they were in the same orbital plane. This time they were turned 90 from their direction of travel and made a burn of 8 metres per second while they were over the Pacific. They then had to make a 0.8 metres per second burn after the ground controller realised that they were slightly off due to problems with the thrusters not shutting off properly.

They found that at 332 kilometres from the Agena that the radar had acquired the target. At 3 hours, 48 minutes and 10 seconds into the mission they performed another burn that put them in a circular orbit 28 kilometres below the Agena. They first sighted the it when they were 140 km away and at 102 km they turned the computer onto automatic.

Agena as seen from Gemini 8
After several small burns they were sitting 46 metres away and with no relative velocity. After 30 minutes of visually inspecting the Agena to make sure that it had not been damaged by the launch, they were given the go for docking. He started to slowly (8 centimetres per second) to move towards the Agena and then informed the ground that he had docked.

The Spin

There was some suspicion on the ground that the Agena attitude system was playing up and it may not have the correct program stored in it. Just before they went off contact with the ground, the crew of Gemini 7 were informed that it anything strange happened they were to turn off the Agena.

After Scott had instructed the Agena to turn them 90 to the right, he noticed that for some strange reason they were in a roll. Armstrong used the Gemini's OAMS to stop the roll, but the moment he stopped using the thrusters, it started again. They immediately turned off the Agena and this seemed to stop the problem for a few minutes. Then suddenly it started again.

Scott noticed that the Gemini attitude fuel had dropped to 30% indicating that it was a problem on their own spacecraft. They would have to undock. After transferring control of the Agena back to the ground they undocked and with a long burst of translation thrusters moved away from the Agena.

It was at that point that the Gemini spacecraft began to roll even faster. It reached 1 revolution per second. The only thing to do was turn of the OAMS and change to the reentry control system. This would mean they would have to reenter as soon as possible but was the only thing to do if they didn't want to blackout. After steadying the spacecraft they tested each OAMS thruster in turn and found that Number 8 had stuck on.


It was decided to let the spacecraft reenter one orbit later so that it could land in a place that it could be reached by the secondary recovery forces. It had planned for Gemini 8 to land in the Atlantic, but that was supposed to be three days from now. So the USS Leonard Mason started to steam towards the new landing site 800 kilometres east of Okinawa and 1,000 kilometres south of Yokosuka, Japan.

Planes were also dispatched and in fact one managed to see the spacecraft as it descended. Three pararescuers jumped from the plane and attached the floation collar to the capsule. Three hours after landing the Mason had the spacecraft on board.

Cause and Outcome

Several things changed because of the mission. The Deputy Administrator of NASA Robert Seamans was at a dinner during the mission. After the problems of the flight he decided that he shouldn't be at public engagements during critical points in flights.

McDonnell, the main contractor on the spacecraft also changed its procedures. Usually its top engineers would be at Cape Kennedy for the launch, then fly to Mission Control in Houston, Texas for the rest of the mission. The problem occurred while they were still flying over the USA. It was decided from then on that they would have people in both the Cape and Houston.

No absolutely conclusion reason for the thruster sticking on was found. It was most probably an electrical short, most likely due to a static electricity discarge. The problem was that even if the switch to the thurster was off, power could still flow to it. To stop this occurring again they changed the system, so that power couldn't flow to the thruster.


The patch was shows the whole specturm of objectives that were hoped to have been accomplished on Gemini 8. The Roman numerals at the bottom are IIVIII, with the first two II being the zodiacal symbol for Gemini and VIII being eight, the mission number. The two stars are Castor and Pollux, which are in the constellation of Gemini.

Capsule Location

The capsule is on display at the Neil Armstrong Air and Space Museum, Wapanoneta, Ohio.

External links

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Gemini 6A
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Gemini 9A