How does a rocket engine work?

The law of "actio equals reaction" - the physics behind it

This law of force and counterforce was already recognized and formulated by Newton: Bodies always exert forces on one another. These forces are equal, but directed in opposite directions. This law is also known as the principle of interaction. This law sounds abstract at first, of course, but it can be filled with life with numerous examples from everyday life:

• If you and your partner are on roller skates or ice skates and you bump your partner, you will inevitably be pushed in the opposite direction by the "reactio". The same can be seen when two people are on roller carts - an experiment from physics class.
• When you push a car, it only works if you simultaneously give the floor an equal amount of force in the opposite direction; You have to repel yourself. That this force exists (even if you don't see it explicitly) shows when the ground is icy and your legs slide backwards.
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• So anyone who has ever fired a shot with a crossbow or a rifle experiences a force that is directed backwards. This force has to be absorbed by the shoulder. The counterforce to the shot can also be observed well with cannons. However, the Baron von Münchhausen could not pull himself out of the swamp.

Movement by recoil - this is how the rocket engine works

The recoil principle, which is responsible for the rocket propulsion, is based on the law of force and counterforce discussed above.

• However, with the recoil principle, backward hurled or Ejected matter in the game, because a rocket cannot support itself in a vacuum for its movement, as it is possible when walking or driving on the ground.
• A good example of this recoil principle is a balloon that you inflate and then simply let go of - without closing its opening. The pressurized air flows out and propels the balloon forward. At the same time, the example shows that an effective ejection of material is required for effective propulsion.
• Even with rocket propulsion, mass is ejected backwards and, through recoil, ensures that the rocket moves forward. These are the highly accelerated, because very hot combustion gases from the rocket, which are ejected into the (almost vacuum) space.
• Indeed, these combustion gases are rearward from the engines at high speed ejected so that a forward force is exerted on the missile, causing the missile drives. The same happens with the jet engines of modern aircraft and of course with fireworks rockets.
• By the way, how the rocket drive works can be demonstrated with a handy rocket model: For this, the rocket fuselage of the model is filled with a little water and additionally under compressed air (pump) set. When starting - as with a balloon - the inlet at the back is opened. The pressure drives the water out as a fountain and the rocket is carried upwards.