rocket propulsion introduction

Rocket propulsion

ByMorla RaghuramAsst. Professor

Rocket working principle

• Newton third law of motion• Law of conservation of momentum• The chemical energy stored in the fuel is

converted into kinetic energy by burning the fuel in the thrust chamber and subsequent expansion in the nozzle to produce thrust

• Rockets obtain thrust by reaction from the ejection of fast moving exhaust fluid from rocket engine.

Difference b/w jet and rocket engine

Jet engine• Air breathing engine• It cannot be operated in

vacuum• Thrust produced depends on

altitude and flight velocity.• Friction increases with

flight speed• Oxygen supply depends on

atmospheric conditions. It carries only fuel

Rocket engine• Non air breathing engine• Space travel possible• Trust production does not

depends on altitude.• It offers no surface drag. No

gravitational effect. Rate of climb increases with altitude.

• It carries oxidizer as well as fuel.

Construction and working• A rocket is a non air breathing engine and it

has a few moving parts.• It carries fuel and oxidizer on the board of the

craft.• The high pressure gases coming from the

combustion chamber act as rocket propellants.• These gases expand through the nozzle, and

produces thrust on the rocket.

ROCKETS

PROPELLANT

SOLID

LIQUID

HYBRID

NUMBER OF

STAGES

SINGLE STAGE ROCKET(WITH

ONE MOTOR

)

MULTI STAGE ROCKET(WITH MORE THAN ONE

MOTOR)

FUEL

CHEMICAL

NUCLEAR

SOLAR

ELECTRICAL

RANGE

SHORT

MEDIUM

LONG

APPLICATIONSWEATHER

FORECASTINGMILIT

ARYSPACE

EXPLORER

BOOSTER

ROCKETS

RETRO ROCKETS

Solid propellant rocket

Solid propellant rocket

• Solid propellant rocket burns a solid block made of fuel, oxidizer, and binder (plastic or rubber). The block is called grain. Ammonium per chlorate oxidizer and other chlorine compounds are toxic, corrosive, and damage the ozone layer. Ammonium nitrate oxidizer is hygroscopic, but is usually more desirable, because it is safe, cheap, and smokeless.

Solid propellant rocket• Solid propellant rocket is inexpensive, but has

a low specific impulse (2-3 km/s), has to carry heavy casing, and cannot be throttled or stopped; it burns until all the grain is exhausted. When used in outer space, they may produce space junk in the form of micrometer-size aluminum oxide particles and centimeter-size slag.

Applications• Assisted take off of missiles and

projectiles.• Small range rockets.

LIQUID PROPELLANT ROCKETS

• Fuel and oxidizer mixed in the mixing chamber and preheated to suitable temperature.

• Then it is injected in the combustion chamber. Where the mixture is ignited by an electric torch.

• The steam is produced by mixing a very high concentrated H2O2 with KMNO4.

• The pumps are driven by a steam turbine.

Constructional details1. Fuel tank2. Oxidizer tank3. Fuel pump4. Oxidizer pump5. Injector6. Steam turbine7. Combustion

chamber8. Control valves

LIQUID PROPELLANT ROCKET

Analysis of Rocket Propulsion• Thrust(F)=Momentum thrust+ Pressure thrust• Momentum thrust=M(jet velocity – propellant entry

velocity) i.e.,M(Vjet –Vi)• But, oxygen and fuel are stored within rocket itself,

thus entry of propellant relative to rocket is zero.• So, Momentum thrust=MVjet

• Pressure thrust =(pe-pa)Ae

• where Pe is exit pressure • Pa is air pressure

Analysis of Rocket Propulsion• Specific thrust=

Ratio of thrust developed to mass flow rate of propellant.

• Specific impulse =

• Total impulse= product of specific impulse and weight flow rate of propellant used.

• total impulse =F

Analysis of Rocket Propulsion

rocket propulsion introduction

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