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| Gemini VIII command pilot Neil Armstrong (L) and pilot Dave Scott (R). Credit: NASA. |
The crew of Gemini VIII were command pilot Neil Armstrong and pilot Dave Scott. During their mission in 1966, they were the first crew to dock two spacecraft while in Earth orbit.
This was a crucial milestone in human spaceflight; it had to succeed to develop skills for later lunar landing missions.
After a successful linkup with an uncrewed Agena docking vehicle, things went sideways. A thruster started firing on its own, and neither astronaut could control it. They assumed the Agena was malfunctioning, so they undocked.
Then things got really bad.
"We have serious problems here," Scott said. "We're tumbling end over end. We're disengaged from the Agena."
"We're rolling up and we can't turn anything off," Armstrong said.
ARMSTRONG
We never, however, were able to reduce the rates in any axis completely. It was obvious at this time that the only satisfactory way for diagnosing the control system was undocking the vehicle so that we could disengage possible Agena problems from possible spacecraft problems.
After a successful linkup with an uncrewed Agena docking vehicle, things went sideways. A thruster started firing on its own, and neither astronaut could control it. They assumed the Agena was malfunctioning, so they undocked.
Then things got really bad.
"We have serious problems here," Scott said. "We're tumbling end over end. We're disengaged from the Agena."
"We're rolling up and we can't turn anything off," Armstrong said.
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| Agena docking vehicle. Credit: Dave Scott, NASA |
They eventually got everything under control, and it took cool heads and quick thinking to save the day.
After a successful emergency splashdown in the Pacific Ocean 500 miles east of Okinawa, the crew shared these these alarming comments.
We never, however, were able to reduce the rates in any axis completely. It was obvious at this time that the only satisfactory way for diagnosing the control system was undocking the vehicle so that we could disengage possible Agena problems from possible spacecraft problems.
To do so, we had to get the rates of the combination down to a value that was suitable for undocking with some assurance that we would not have a recontact problem.
We, of course, had to have the OAMS [orbital attitude and maneuvering system - the small gas thrusters that moved the spacecraft around] on to reduce these rates and it took us quite a bit of time to get the rates down to a value that we both agreed would be satisfactory to try a release.
Upon mutual agreement, Dave undocked with the use of the Undocking Switch and I used the forward-firing thrusters to back away from the Agena as quickly as possible, using about a 5 second burst...
SCOTT
...we backed straight off a good 4 or 5 feet before we started tumbling there and lost sight of the Agena...
ARMSTRONG
Shortly after backing off, we noticed that we were essentially losing control of the spacecraft in roll and yaw and we suspected that we were over the lifetime of these attitude thrusters.
The spacecraft was continuing, however, to accelerate, and we were obtaining rates in roll at least that approached 200 to 300 degrees per second, or perhaps more.
SCOTT
Yes, I would agree with that. It looked like even more to me, and it was by far more in roll than in yaw. The roll was the most predominate.
ARMSTRONG
We realized that physiological limits were being approached, and that we were going to have to do something immediately, in order to salvage the situation...
SCOTT
I might add in there that the rates were high enough that both of us had trouble seeing the overhead panel due to the vertigo problems and the centrifugal force as we went around.
Sources:
[1] "Gemini VIII Technical Debriefing"; March 21, 1966; https://www.hq.nasa.gov/alsj/57115999-Gemini-VIII-Technical-Debriefing.pdf
[2] "Gemini's First Docking Turns to Wild Ride in Orbit"; Bob Granath; August 7, 2017; https://www.nasa.gov/feature/geminis-first-docking-turns-to-wild-ride-in-orbit
We, of course, had to have the OAMS [orbital attitude and maneuvering system - the small gas thrusters that moved the spacecraft around] on to reduce these rates and it took us quite a bit of time to get the rates down to a value that we both agreed would be satisfactory to try a release.
Upon mutual agreement, Dave undocked with the use of the Undocking Switch and I used the forward-firing thrusters to back away from the Agena as quickly as possible, using about a 5 second burst...
SCOTT
...we backed straight off a good 4 or 5 feet before we started tumbling there and lost sight of the Agena...
ARMSTRONG
Shortly after backing off, we noticed that we were essentially losing control of the spacecraft in roll and yaw and we suspected that we were over the lifetime of these attitude thrusters.
The spacecraft was continuing, however, to accelerate, and we were obtaining rates in roll at least that approached 200 to 300 degrees per second, or perhaps more.
SCOTT
Yes, I would agree with that. It looked like even more to me, and it was by far more in roll than in yaw. The roll was the most predominate.
ARMSTRONG
We realized that physiological limits were being approached, and that we were going to have to do something immediately, in order to salvage the situation...
SCOTT
I might add in there that the rates were high enough that both of us had trouble seeing the overhead panel due to the vertigo problems and the centrifugal force as we went around.
Sources:
[1] "Gemini VIII Technical Debriefing"; March 21, 1966; https://www.hq.nasa.gov/alsj/57115999-Gemini-VIII-Technical-Debriefing.pdf
[2] "Gemini's First Docking Turns to Wild Ride in Orbit"; Bob Granath; August 7, 2017; https://www.nasa.gov/feature/geminis-first-docking-turns-to-wild-ride-in-orbit
