As a propulsion expert with a background in aerospace engineering, I have spent considerable time studying the various types of rocket fuels and their applications. Rocket fuels are a critical component of space missions, and the choice of fuel can significantly impact the performance and efficiency of a rocket.

Rocket propulsion relies on the principle of action and reaction, where the rocket expels mass to generate thrust. The choice of propellant is based on several factors, including the specific impulse (a measure of how effectively a rocket uses propellant), density, toxicity, storability, and cost.

Liquid Propellants are widely used in rockets due to their high performance and controllability. They are typically divided into two categories: liquid oxidizers and liquid fuels. The oxidizer provides the oxygen needed for combustion, while the fuel is what burns. The performance advantage of liquid propellants, as you mentioned, is often attributed to the oxidizer.

Liquid Oxygen (LOX) is a common oxidizer used in rocketry. It is highly effective because it is a powerful oxidizer that can support the combustion of a wide range of fuels. However, it has the drawback of being extremely cold, requiring careful handling and storage.

Nitrogen Tetroxide (N2O4), also known as Aerozine-50 when mixed with certain fuels, is another popular oxidizer. It is hypergolic, meaning it ignites spontaneously upon contact with a fuel, which simplifies the ignition process in rocket engines.

Hydrogen Peroxide (H2O2) can also serve as an oxidizer, especially in concentrations of 70% to 90%. It is less powerful than liquid oxygen but has the advantage of being easier to store and handle.

When it comes to liquid fuels, Kerosene is often used due to its relatively high energy content and ease of storage. It is commonly used in combination with liquid oxygen as the oxidizer, as seen in the Space Shuttle's main engines.

Methane is another fuel that has been gaining attention, especially for missions to Mars, due to its potential to be produced on the Martian surface and its high performance when used with liquid oxygen.

Hydrogen is used in some high-performance rockets because it has a very high specific impulse. However, it is also very challenging to store and handle due to its extremely low boiling point.

Solid Propellants are another class of rocket fuels, which are typically made from a mixture of a fuel and an oxidizer combined into a solid matrix. The advantage of solid propellants is their simplicity and reliability. However, they generally have a lower specific impulse compared to liquid propellants.
Ammonium Perchlorate (AP) is a common oxidizer used in solid propellants.

Hybrid Propellants combine elements of both solid and liquid propellants. They typically have a solid fuel and a liquid oxidizer, or vice versa. Hybrid rockets offer the simplicity of solid rockets with some of the performance benefits of liquid rockets.

In conclusion, the choice of rocket fuel is a complex decision that depends on the mission requirements, the specific impulse of the propellant, and practical considerations such as cost, safety, and ease of handling. Liquid propellants, with their high performance and versatility, are often preferred for their ability to provide a high specific impulse when paired with a suitable oxidizer.

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The primary performance advantage of liquid propellants is due to the oxidizer. Several practical liquid oxidizers (liquid oxygen, nitrogen tetroxide, and hydrogen peroxide) are available which have better specific impulse than the ammonium perchlorate used in most solid rockets, when paired with comparable fuels.read more >>