After watching a rocket launch, you may wonder what the rocket fuel is made of? There are actually two kinds of fuel used in rockets. The fuel can be divided into liquid fuel and solid fuel.
With solid fuel, there must be both fuel and an oxidizer to make a solid fuel rocket go. An oxidizer is a chemical that is needed to make fuel burn. Since space has no atmosphere, rockets have to carry both their own fuel and their own oxidizers. The most common fuel in solid fuel rockets is aluminum. In order to make the aluminum burn, these solid fuel rockets use ammonium perchlorate as the oxidizer, or to make the aluminum burn. In order to work together, the aluminum and the ammonium perchlorate are held together by another compound called a binder. When mixed all together, the fuel has a slightly rubbery consistency. This rubbery substance is then packaged into a casing. As the fuel burns, the heat and energy cause the inside of the rocket to heat up. Water vapors and gasses then shoot out of the rocket, causing the rocket to be thrust, or pushed, upwards into the sky. You will find that many boosters, not the main engines, on rockets use solid fuel. This is because this fuel is short-lived and burns very quickly.
The main engines are more likely to be propelled by liquid fuel. Liquid fuel engines are composed of liquid oxygen and liquid hydrogen. The liquid hydrogen is the fuel and the liquid oxygen is the oxidizer. Remember, the oxidizer helps the fuel burn. The hydrogen needs to be in liquid form, not gas form, in order to have a smaller tank on the rocket. Gasses are lightweight, so it would take a larger tank to hold hydrogen gas than it would be to hold liquid hydrogen. The liquid hydrogen and oxygen are released into an engine where they begin to combine to make water. Just like the solid fuel, the water vapor creates energy and steam. The steam is released to make the rocket go upwards.
To get a rocket from the ground into space, rockets need both solid fuel and liquid fuel. You would think that rockets could just carry liquid fuel because liquid fuel is more efficient and gives more push when burned. However, having only liquid fuel would require a huge tank of fuel. Instead, rockets are boosted off the ground by solid fuel. The boosters are dropped off the rocket to make it lighter, and then the liquid fuel is burned to allow the rocket to keep moving upward in space.
Therefore, rocket fuel can be categorized into solid or liquid fuels. Rocket engines and boosters carry both fuel and an oxidizer. For solid fuel, the components are aluminum and ammonium perchlorate. For liquid fuel, the components are liquid hydrogen and liquid oxygen. When combined, the fuels release water, which allows the rocket to leave the ground.