I'm fairly new to physics, so please forgive me if I lack basic understanding.
I'm wondering how rocket engines actually work. I know the answer of "actio est reactio", but I feel like this is a very abstract and unclear explanation because it doesnt touch whats actually going on. Here is my issue:
As I understand, the engine generates an explosion which throws out gas particles into one direction (say down) and thus creates an inverted force that pushes the rocket into the other direction (say up). What I dont get is: How do the leaving particles interact with the rocket? They dont necessarily touch the rocket, at least not in a way that would make it go up, so how can they possibly have an effect? As far as I know, a force can either act through
- a field
Now I guess the gas particles dont create some sort of force field, so at some point there has to be a 'meaningful' contact.
I get that mathematically the force of gas particles that are coming out equals the force with which the rocket is accelerated, but I have a hard time understanding how particles that are already on their way out of the rocket are the cause of the acceleration.
My explanation would be that the rocket is flying for the same reason anything is 'flying' near an explosion: The explosives hit other objects and drag them with them (conservation of momentum). The same force applies in a rocket on all walls of the engine, and since the particles can escape "down", the only momentum the rocket gets is "up" (left and right cancel each other out). But I run into issues with that explanation as well, because lets say we make the exit of the engine reaaally long, say a few hundred meters (thought experiment), and then close it up. now that means that at first the effect would be the same, rocket goes up, but once the explosion hits the other end of the engine, the rocket will be 'dragged' back again. seems strange to me.
please help me solve this issue. thanks!