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I'm trying to understand how a rocket Gimble turns a rocket using unbalanced resultant forces . For simplicity lets say a compressed air rocket.

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If the rocket is straight ahead the escaping gas creates an unbalanced resultant force in the head of the rocket creating forward movement. (I always like the start of this video for a simple explanation of how gas escaping creates an unbalanced force inside the rocket. https://www.youtube.com/watch?v=Ixf9ZyZaE9Q&t=1130)

So if the Gimble is angled and the random gas is escaping out a hole in a new direction and it follows that the opposite unbalanced force is now to the opposite side in the rocket head (as indicated by the thrust lines) It is explained that as the line of thrust does not pass thru the centre of mass it creates a moment causing the rocket to rotate about its centre of mass.

However the thrust line could stay at the head of the rocket and the random escaping gas could still travel 'straight down' the rocket. As it exits the rocket the Gimble angle could be deflecting the gas causing an unbalanced force on the side of the Gimble As this is below the centre of mass it could also causing a moment in the same direction.

Which is the correct cause of the moment ?

Is the random gas still travelling 'straight down' the rocket & the gimble is deflecting it or has the gas escaping in a new direction caused the resultant force and thrust line to move away from the centre of mass?

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  • $\begingroup$ The escaping gss doesn't exert a force to a side of the gimbal. Pressure should be the same in both side, or better all around, the wall. The escape direction must be the gimbal direction. Anyway the final effect is that of a rudder. Do not over think. Already the thrust can be explained in alternatives ways. $\endgroup$ – Alchimista Feb 5 at 8:58

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