To start with, the ignition and afterwards, a sustained supply of fuel and oxidant.
A combustion chamber is where combustion occurs in a controlled fashion. Because the basic idea of a rocket is burning fuels and directing them in the opposite direction to that of travel, a controlled burning - as happens in the combustion chamber - is exactly what a rocket needs to work.
combustion
combustion
Chemical rocket
Chemical rocket
The rocket pushes back on the gas.
The rocket pushes back on the gas.
The forward motion of a rocket is caused by the expulsion of high-speed exhaust gases from the combustion of rocket fuel. Newton's third law of motion states that for every action, there is an equal and opposite reaction, so the force of the expelled gases propels the rocket forward.
thrust
The combustion chamber of a rocket is the part of the engine where fuel and oxidizer are mixed and burned to produce hot, high-pressure gas that is expelled through the nozzle to create thrust. It is a critical component that helps propel the rocket into space.
Rockets exert force at the upper part of the combustion chamber. This pushes the rocket forward.
Rockets are propelled forward by thrust generated by the combustion of rocket fuel and controlling the direction of the exhaust.