Question

Write notes on chemical propellants used in propulsion system of rockets.

Answer 1

Chemical propellants $\to$ The propellants are chemical substances which on ignition provide thrust for the rocket to move forward.

Propulsion systems for rockets use chemical propellants. These propellants can be solid, liquid or hybrid.

• Solid propellants : The solid propellants are mixtures of solid fuel and a solid oxidiser. These are further divided into two classes,

(a) Composite propellants:- These are solid propellants which use polymeric binders such as polyurethane or polybutadiene as a fuel and a solid oxidiser such as ammonium perchlorate, nitrate or chlorate.

(b) Double base propellants:- These are solid propellants which mainly use nitroglycerine and nitrocellulose. The nitrocellulose gels in nitroglycerine set in as a solid mass.

• Liquid propellants: These consist of an oxidizer such as liquid oxygen or nitric acid and a fuel such as kerosene, alcohol, hydrazine or liquid hydrogen.

Monopropellants: The propellants in which a single chemical compound acts as fuel, as well as an oxidizer, are called monopropellants, e.g., hydrazine, nitromethane, etc.

Bipropellants: These are propellants in which the fuel and oxidiser are stored separately but are allowed to combine at the time of combustion. For example, kerosene and liquid oxygen.

• Hybrid propellants: These are the propellants which consist of solid fuel and a liquid oxidiser, e.g., acrylic rubber (solid fuel).