What really pushes a rocket up?

Question

To launch a rocket, fuel is burnt and is released in opposite direction relative to rocket and it pushes the rocket upwards because of third law of motion but the fuel molecules are not actually pushing the rocket upwards as it released in the opposite direction. So what is exactly pushing the rocket upwards or where does the force coming from?

Answer 1

Fuel molecules push the rocket upwards.

If the chamber was closed, there was a pressure to all directions. As there is a hole in the bottom, the pressure upwards is not compensated by the same pressure downwards.

Answer 2

Molecules are bouncing inside the reaction chamber and hitting the sides. The molecules hitting the left side are balanced out by the molecules hitting the right side, so the rocket doesn't go left or right. The molecules hitting the back of the reaction chamber, opposite the exhaust, push the rocket forward. And nothing balances those molecules out.

So the answer is: the molecules hitting the back of the reaction chamber, opposite the exhaust, push the rocket forward.

Answer 3

I think you are referring to the region of burning, in which molecules are moving rapidly in all directions, and colliding with each other in a random manner. At the bottom of this region, molecules are released in the exhaust at high velocity. These molecules no longer push the rocket up, but they did attain their high velocity due to collisions with other molecules, which were kicked back upwards. At the top of this region, other high velocity molecules are not released, but instead bounce of the rocket. That generates the force which pushes the rocket up. Between the top and the bottom, all is chaos.