Question

Which of the following could act as a propellant for rockets? (a) liquid hydrogen + liquid oxygen (b) liquid oxygen + liquid argon (c) liquid hydrogen + liquid nitrogen (d) liquid nitrogen + liquid oxygen

Short answer

The correct propellant combination is (a) liquid hydrogen + liquid oxygen.

Step-by-step solution

Understanding Propellants

Rocket propellants are substances that consist of a fuel and an oxidizer. Together, they undergo a chemical reaction to produce high-speed gases for propulsion. Commonly used rocket fuels include hydrogen or hydrocarbons, and common oxidizers are oxygen or fluorine.

Evaluate Each Option

We'll evaluate the components of each option to determine if they fulfill the roles of fuel and oxidizer. (a) Liquid hydrogen + liquid oxygen: Liquid hydrogen is a fuel, and liquid oxygen is an oxidizer. They react explosively to produce water vapor and energy. (b) Liquid oxygen + liquid argon: Both components are not a set of a fuel and an oxidizer. Liquid argon is an inert gas and does not support combustion. (c) Liquid hydrogen + liquid nitrogen: Hydrogen is a fuel, but nitrogen is not an oxidizer. It is inert and does not react with hydrogen. (d) Liquid nitrogen + liquid oxygen: Nitrogen is not a fuel; it's an inert gas. This combination cannot act as rocket propellants.

Identify the Correct Propellant

From the evaluated options, only (a) liquid hydrogen + liquid oxygen meets the criteria of having a reactive fuel and oxidizer. This combination is widely used in spacecraft propulsion systems due to its high efficiency and thrust.

Key concepts

Rocket Propellants

Rocket propellants are crucial for rocket propulsion, serving as the primary source of energy that moves rockets through space. At their core, rocket propellants are combinations of a fuel and an oxidizer. These two components are necessary to produce the controlled explosions required for propulsion. The fuel acts as the substance that burns, while the oxidizer provides the oxygen needed to support the combustion of the fuel. Together, they react to release high-speed gases that are ejected out of the rocket's engine, creating a thrust in the opposite direction - a fundamental principle based on Newton's Third Law of Motion. Choosing the right combination of fuel and oxidizer is essential for achieving efficient propulsion, making them vital for the success of any rocket mission.

Fuel and Oxidizer

The pairing of a fuel and an oxidizer is what makes a rocket propellant effective. In these pairs: - **Fuel**: It is the component that actively combusts. In rocket science, fuels can be either liquid, such as liquid hydrogen, or solid, like powdered metals. - **Oxidizer**: This is the chemical that provides oxygen for the fuel to burn, as there's no atmospheric oxygen in space to do that. Common oxidizers include liquid oxygen and fluorine. The interaction between fuel and oxidizer in a rocket engine occurs in a tightly controlled environment. This ensures the rapid release of energy necessary to propel a rocket. By carefully selecting and combining these chemicals, engineers can maximize thrust while balancing considerations like weight and stability.

Liquid Hydrogen

Liquid hydrogen is a popular rocket fuel due to its remarkable properties. It is the lightest and the most energy-rich of all traditional fuel types, making it an excellent choice for rockets. Liquid hydrogen is a cryogenic, which means it stays in a liquid state at extremely low temperatures, specifically below -253°C (-423°F). In the presence of an oxidizer, liquid hydrogen burns exceptionally hot, producing water vapor as a byproduct. It holds a high specific impulse, which measures how efficiently a rocket uses its propellant, indicating that less fuel is needed to generate the same amount of thrust compared to other fuel types. Moreover, liquid hydrogen is abundant and relatively cost-effective, further adding to its appeal in the aerospace industry.

Liquid Oxygen

Liquid oxygen, commonly abbreviated as LOX, is a staple oxidizer in many rocket propellant systems. Like liquid hydrogen, liquid oxygen is also cryogenic and must be stored at extremely low temperatures, around -183°C (-297°F), to stay in a liquid form. LOX is highly reactive with many elements, particularly hydrogen, due to its strong ability to accept electrons. In the vacuum of space, atmospheric oxygen is absent, so liquid oxygen is essential for combustion in rocket engines. It allows the enormous energy potential of fuels like liquid hydrogen to be tapped into effectively. By pairing LOX with liquid hydrogen, engineers harness the explosive reaction between the two to produce water vapor and thrust, propelling rockets with high efficiency and power.