GEMINI VIII (March 16-17, 1966)

David Scott and Neal Armstrong - Gemini 8

DAVID SCOTT AND NEIL ARMSTRONG



Gemini VIII had two major objectives, of which it achieved one. The two objectives were:

1. to accomplish an in-orbit rendezvous and docking, and

2. to accomplish an extended extra-vehicular Activity.

The first major objective was accomplished by the spacecraft commander, Neil Armstrong, who piloted Gemini VIII to within 0.9 meters of the prelaunched Agena Target Vehicle, then slowly docked.

This was the world's first orbital docking. The second objective was to have been accomplished by Pilot David Scott, who was to spend up to two hours outside of the spacecraft, but subsequent events cancelled the planned space-walk.




GEMINI 8 ABOUT TO DOCK WITH THE AGENA.


What followed the successful docking by Armstrong were some of the most hair-raising few minutes in space-program history. The Gemini VIII capsule, still docked to the Agena, began rolling continuously. Never having faced this in simulation, the crew undocked from the Agena. The problem was a stuck thruster on the spacecraft, which now tumbled even faster at the dizzying rate of one revolution per second. The only way to stop the motion was to use the capsule's reentry control thrusters, which meant that Armstrong and Scott had to cut short their mission and make an emergency return to Earth 10 hours after launch. They were still nauseated after splashdown, as well as disappointed: Scott had missed out on the planned space-walk.


The Mission.


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 it when they were 140 km away and at 102 km they turned the computer onto automatic.

After several small burns they were 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.

Armstrong started 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 acting up and might not have the correct program stored in it. Just before they went off contact with the ground, the crew of Gemini 8 were informed that if anything strange were to happen, they were to turn off the Agena.

After Scott had instructed the Agena to turn them 90° to the right, he noticed that they were in a roll. Armstrong used the Gemini's Orbit Attitude and Maneuvering System (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, and approached one revolution per second. The astronauts were now in danger of blacking out due to the violent motion. At this point Armstrong shut down the OAMS and used the Re-entry Control System RCS to stop the spin. After steadying the spacecraft they tested each OAMS thruster in turn and found that Number 8 had stuck on. Mission rules dictated that the flight be terminated once the RCS had been fired for any reason, so Gemini VIII prepared for an emergency landing.

Landing



Armstrong and Scott await the USS Leonard F. Mason.


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 later on.

So USS Leonard F. 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 the pilot of one (Captain Les Schneider, USAF), managed to see the spacecraft as it descended. Three pararescuers jumped from the plane and attached the flotation collar to the capsule. Three hours after splashdown, the Mason had the spacecraft on board.

Had Gemini 8 landed in the western Atlantic Ocean (the scheduled recovery area) as planned, the U.S. Navy Atlantic Recovery Fleet's prime recovery ship was the carrier, USS Boxer. During this time the Wasp (the usual Atlantic Fleet Gemini recovery carrier) was in dry dock for repairs.

The Gemini 8 mission was supported by the following U.S. Department of Defense resources; 9,655 personnel, 96 aircraft and 16 ships.

Cause and outcomes

Several things changed because of this mission. The Deputy Administrator of NASA, Robert Seamans, was at a dinner when the problem arose. Afterwards, 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 to Houston. It was decided from then on that they would have people in both the Cape and Houston.

No conclusive reason for the thruster sticking on was found. It was probably caused by an electrical short, most likely due to a static electricity discharge. Even if the switch to the thruster was off, power could still flow to it. To prevent recurrence of this problem, the system was changed, so that the thruster could be isolated.

Armstrong's cool-headedness and his ability to recover from an extremely dangerous space emergency was a pivotal factor in his selection as Apollo 11 commander.

Likewise, Scott's performance contributed to his flight on Apollo 9 and (as commander) on Apollo 15.

The flight of Gemini VIII concluded with the successful (manual) emergency recovery of the tumbling orbiting spacecraft piloted by Neil Armstrong and David Scott. The first major objective was accomplished by the spacecraft commander, Neil Armstrong, who piloted Gemini VIII to within 0.9 meters of the prelaunched Agena Target Vehicle, then slowly docked.

This was the world's first orbital docking.

The second objective was to have been accomplished by Pilot David Scott, who was to spend up to two hours outside of the spacecraft, but subsequent events cancelled the planned space-walk.