The phenomenon of rocket propulsion is a marvel of modern science.

If combustion requires oxygen, how do rockets fly in space, where there is no oxygen?

The answer lies in understanding how rockets generate impulse and how propulsion works in the vacuum of space!

How Rockets Work on Earth

On Earth, most forms of propulsion, including car engines, airplanes, and even fireworks, rely on combustion. Combustion is a chemical reaction between a fuel and oxygen, which releases energy in the form of heat and gas.

This energy creates pressure that pushes against the surrounding air or materials, creating movement. But this process depends on having an oxidizer—oxygen or another substance that can provide the necessary chemical reaction.

Rocket Propulsion in Space: The Key Difference

In space, however, the situation is different. Outer space is a vacuum, meaning it contains almost no air and, therefore, no oxygen. Yet, rockets still manage to propel themselves forward. The key to understanding how this is possible lies in Newton’s Third Law of Motion, which states, "For every action, there is an equal and opposite reaction."

Rockets are designed to use chemical propulsion, where fuel and oxidizer are combined in the rocket’s engine. The combustion happens inside the rocket's engine, not relying on external oxygen. The fuel and oxidizer are stored in separate tanks and mixed when needed. This internal process produces hot gases that are rapidly expelled out of the rocket’s nozzle.

The Role of Fuel and Oxidizer in Rocket Engines

Since there is no oxygen in space, rockets must carry both fuel and oxidizer onboard to produce combustion. The oxidizer is a chemical compound that supplies the necessary oxygen for combustion. In modern rocket design, common oxidizers include liquid oxygen (LOX) or other compounds like nitrogen tetroxide (N2O4).

The fuel can vary, from liquid hydrogen (LH2) to kerosene-based compounds like RP-1. These fuel-oxidizer mixtures are combined in the rocket engine, creating the necessary chemical reaction to generate the impulse needed for lift-off and space travel.

The Rocket Engine: A Self-Sustaining System

Unlike a car or airplane, where the engine draws in oxygen from the surrounding atmosphere, a rocket engine is a self-contained system. This means that the combustion process doesn't require any external air. The rocket carries both the oxidizer and fuel in separate tanks, which are carefully mixed and combusted inside the engine to produce gases at extremely high pressures.

These gases are then expelled through a nozzle, creating impulse that propels the rocket into space. The efficiency and power of the rocket engine depend on the precise balance of fuel and oxidizer, along with the engineering of the rocket’s nozzle, which directs the exhaust gases in such a way that maximizes the impulse.

Why This Matters for Space Exploration

The ability for rockets to operate without relying on external oxygen is fundamental to space exploration. This self-contained combustion system allows rockets to escape Earth’s atmosphere and travel through the vacuum of space, where oxygen is nonexistent.

This is also why liquid oxygen and other highly reactive compounds are crucial for modern rockets. Without the right mixture of fuel and oxidizer, rockets would be unable to generate enough impulse to break free from Earth’s gravitational pull.

Rocket propulsion in space works because rockets don’t rely on external oxygen like other forms of combustion. Instead, they carry both fuel and oxidizer within the rocket, allowing combustion to occur internally. This innovative engineering principle makes space travel possible, and it continues to push the boundaries of our exploration of the cosmos!