In the movie, First Man, Neil Armstrong and his colleague David Scott, as part of the Gemini 8 program, attempt to dock with the Agena but it turns out to be disastrous as they go into a continuous roll over.

What caused the continuous roll over and how did the RCS Brakes help in stabilization of the vessel?

  • $\begingroup$ Welcome to space stack exchange! You should separate these 2 questions. You should only have 1 question per post. The first one has been addressed many times on this site, the second one is an interesting question. $\endgroup$ Commented May 3, 2019 at 15:28
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    $\begingroup$ Could you please link the answer to the first question? I've edited my question to include only the second one. $\endgroup$
    – penguin99
    Commented May 3, 2019 at 15:28
  • $\begingroup$ Search the site for 'nova rocket apollo' This is probably the most relevant: space.stackexchange.com/questions/19450/… $\endgroup$ Commented May 3, 2019 at 15:29

1 Answer 1


A yaw thruster failed on in the Gemini's Orbital Attitude and Maneuvering System (OAMS) causing the attitude problems. Suspecting the Agena target to be at fault, they undocked, which made it worse because the spacecraft mass was now much less.

The fix was to turn off the OAMS and switch to the redundant Re-entry Control System (RCS). This disabled the failed-on thruster but terminated the mission early due to mission rules regarding the use of the RCS.


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    $\begingroup$ Why do you say redundant? $\endgroup$
    – penguin99
    Commented May 3, 2019 at 15:35
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    $\begingroup$ Redundant in spacecraft design is not a bad thing. It simply means that there is a backup system. If the primary system never fails, the 'redundant' system may never be used. $\endgroup$ Commented May 3, 2019 at 15:36
  • $\begingroup$ Why did the roll over continue for a really long time? Is it because the earth's gravity was causing it to revolve that way without any opposing friction? Like a never ending car drift on a smooth road? $\endgroup$
    – penguin99
    Commented May 3, 2019 at 15:39
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    $\begingroup$ It didn't have much to do with the earth's gravity (although that is what holds it in orbit). A spacecraft in orbit will accelerate (start to move or rotate) when a force pushes on it. It will continue to accelerate as long as the force acts on it. If the mass of the spacecraft suddenly gets smaller, the acceleration gets bigger. The famous equation F=ma describes this. In this case, the force was the jet firing. They couldn't stop the ship from accelerating because they couldn't shut the jet off. $\endgroup$ Commented May 3, 2019 at 15:44
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    $\begingroup$ @kikjezrous if the information in the linked source is not sufficient for you, please ask a separate question. $\endgroup$ Commented May 6, 2019 at 16:59

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