Question

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

Answer 1

:Hint:Rockets that employ chemical propellants come in different forms, but all share analogous basic components. Chemical rocket propulsion systems are classified into two general types according to whether they burn propellants stored as solid or as liquid.

Complete answer:
Chemical 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 solid oxidizers such as ammonium perchlorate, nitrate or chlorate.
(b) Double base propellants: These are solid propellants which mainly use nitro-glycerine and nitrocellulose. The nitrocellulose gels in nitro-glycerine 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).

Note:
All rocket engines produce thrust by accelerating a working fluid. Chemical rocket engines use the combustion of propellants to produce exhaust gases as the working fluid. The high pressures and temperatures of combustion are used to accelerate the exhaust gases through a rocket nozzle to produce thrust.