SOLID PROPELLANT ROCKET ENGINE

SOLID PROPELLANT ROCKET ENGINE

A solid propellant rocker engine Solid propellant is the combination of solid fuel (plastic or resin material) and oxidizer (nitrates, perchlorates, etc.) Solid fuel and oxidizer are homogeneously mixed and packed inside the shell. A liner is provided between the shell and the propellant. The purpose of liner is to protect the shell because high temperature will be generated during combustion process. 

Working 

In solid propellant rocker engine the igniter located at the top and ignites the spark. So combustion takes place. When the combustion takes place in the combustion chamber, very high pressure and very high temperature gases are produced The highly heated products of combustion gases are then allowed to expand in the nozzle section. In the nozzle pressure energy of the gas is converted into kinetic energy. So the gases coming out from the unit with very high velocity. Due to high velocity of gases coming out from the unit, a force (or) thrust is produced in opposite direction. This thrust propels the rocket. 


Advantages of solid propellant rocker engine

1. Simple in design and construction.
2. They do not require feed system. So they are free from the problems of moving parts such as pumps, valves, etc. 
3. Less vibration due to absence of moving parts.
4. Less maintenance. Suitable for short range applications. 
5. Problems arising from the sudden emptying of propellant tanks are absent. 

Disadvantages of solid propellant rocker engine

1. In case of emergency it is difficult to stop the engine in the mid way. 
2. Decrease of speed is not possible.
3. Low specific impulse. 
4. At the end of an operation the burnt up debries cannot be reused. So it is uneconomical. 
5. Nozzle cooling is not possible. 
6. Nozzle erosion is unavoidable due to the presence of solid particles in the high temperature and high speed gases.
7. Transportation and handling of these rockets before firing require greater care due to the presence of propellants throughout.

Solid Propellant 

Solid propellants are classified into the following two groups. 

(a) Heterogeneous (or) composite propellants. 
(b) Homogeneous propellants 

(a) Heterogeneous (or) composite propellants.
In heterogeneous solid propellants, plastics, polymers and polyvinyl chlorides are used as fuels. Nitrates and perchlorates are used as oxidizers. 

(b) Homogeneous propellants
In homogeneous solid propellants, nitroglycerine and nitrocellulose are used. It combines the properties of fuels and oxidizers. 

Properties of Solid Propellants

1. It should release large amount of heat during combustion. 
2. Physical and chemical properties should not change during processing. 
3. It should have high density. 
4. It should not be poisonous and hazardous. 
5. It should be cheap and easily available. 
6. It should be non-corrosive and non-reactive with components of the engine. 
7. Storage and handling should be easy.

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