Fail:
Thurst is reactive yes, as in for every action there is an equal and opposite reaction. The only difference in a rocket engine efficiency in an atmosphere and one in a vacuum is the size and shape of the bell. It does not have to push against anything.
Yeah that's right . Back in the day we were shown that as air pressure dropped then the big stage one Saturn V rocket was jettisoned and the narrower longer stage two nozzles were more efficient - and so on to the stage three , smaller still .
We were also shown that to work in a vacuum the nozzle would have to be very small and infinitely long .
Your last sentence defies logic since you already admit that thrust is a reactive force - the exhaust flow needs pressure to produce thrust .
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Have you ever shot a gun? Did you feel recoil? What were you feeling? The same goes for a high-pressure water hose. What are you feeling when the nozzle is pushed back in your hand? Not air resistance, you are feeling the opposite reaction of the water leaving the nozzle.
This is really simple science.
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From this response it's clear that your knowledge of the physical sciences is limited . Ballistics and rocketry are different fields , bullets aren't rockets .
When a jet of water encounters the resistance of the atmosphere or some surface , thrust - that reactive force - is produced causing the reaction that you feel .
This is basic science although I do believe everything taught nowadays is "dumbed down " which probably accounts for the basic lack of knowledge about scientific principles shown in posts like yours .