Rocket engines use Newton's third law of motion to propel rockets. They work by ejecting exhaust gases at high velocity in one direction, which pushes the rocket in the opposite direction. Rockets can use liquid or solid propellants stored in separate tanks, and some use a combination of liquid and solid propellants. Rocket engines are classified based on their fuel, propellants, number of stages, size, and application. Liquid propellant rockets allow for more control but are more complex, while solid propellant rockets are simpler but cannot easily control thrust. Rocket engines must efficiently inject, mix, vaporize, and combust propellants to produce high exhaust velocities and thrust.

2. Unit Five

3. BASICS OF ROCKET
Rocket moves in accordance with Newton's third law of motion.

4. ROCKET PROPULSION
• It is the propulsion of an aircraft
by the reaction of gases coming
out with high velocity.
• Since the altitude of the rocket
engine is very high, enough air is
not available at the surrounding
atmosphere for combustion
purposes.
• Hence a separate tank is filled
with oxygen and another tank is
filled with fuel.

5. Sl.
no
JET PROPULSION ROCKET PROPULSION
1 Oxygen is obtained from
surrounding atmosphere
for combustion purposes
It consists of its own
oxygen supply for
combustion purposes.
2 Jet consists of air plus
the combustion products
Jet consists of exhaust
gas only
3 Altitude limitation No altitude limitation
4 Thrust decreases with
altitude
Thrust improves slightly
5 Rate if climb decreases
with altitude
Rate of climb increases
with altitude
6 Mechanical devices are
uses
Mechanical devices are
not used

6. Classification of Rocket
Engine
Classification based on fuel used:-
Chemical rockets: Heat energy developed
during combustion is used to propel the
rocket.
Nuclear rockets: Heat energy generated by
fission and fusion processes are used to
propel the rocket.
Solar rockets: Heat energy derived from
sun is used to propel the rocket
Electrical rockets: Rockets powered by
electrical motors with the help of battery
or solar cells.

7. Classification of Rocket
Engine
Classification based on propellants used:-
Liquid propellant rockets
Solid propellant rockets
Hybrid rockets
Classification based on number of stages:-
Single stage rockets
Multistage rockets
Classification based on size and ranges:-
Short range rockets
Long range rockets

8. Classification of Rocket
Engine
Classification based on its application:-
Weather forecasting rockets
Military rockets (spying rockets and missiles)
Space exploration rockets
Booster rockets(Multistage rockets – Generally
used to elevate the main rocket to a greater
height
Retainer or sustainer rockets – They are small
rockets which impart low thrust for long duration
for additional energy supply to space vehicles,
Retro rockets – fired in opposite direction to
decrease the speed of a main rocket like braking

9. Solid
Propellant
Rockets

10. Solid Propellant Rockets
Uses solid fuel and oxidizers (propellant)
Solid fuel( plastic or resin material)
Oxidizer(Per chlorates, nitrates)
Both are mixed in single propellant and
packed inside the shell.
When ignitor ignites, combustion starts.
A liner is provided between the shell and
propellant to protect from high temp.
After combustion, the exhaust gas comes
out with high velocity.

11. Advantages:-
♣Simple in design and construction
♣Free from moving system such as pumps,
turbines, hence pay load capacity is high.
♣Density of fuel is high, therefore large
quantity of fuel is packed into small space.
Disadvantages:-
♠Decrease in speed is not possible because
combustion cannot be stopped in midway.
♠Nozzle erosion decreases nozzle life
♠Nozzle cooling is not possible
Solid Propellant Rockets

12. Liquid
Propellant
Rockets

14. Liquid Propellant Rockets
Uses liquid fuel and oxidizers (propellant)
Liquid fuels( liquid hydrogen,UDMH,
hydrazine, alcohol, etc)
Oxidizer(liquid oxygen, liquid fluorine, red
fuming nitric acid (RFNA).
Fuel and oxidizers are stored separately.
The mixture is at low temperature(-150⁰C –
100⁰C) is preheated and injected in the
combustion chamber.
Combustion temperature is very high and
thrust propels in the opposite direction.

15. Advantages:-
♥Engines can be reused after recovery.
♥Speed regulation, i.e., increase or decrease
in speed is possible by control of fuel valve.
♥High specific impulse (Thrust/Wgt flow rate)
Disadvantages:-
♦Construction is more complicated
♦Low pay load capacity.
♦Liquid propellant are poisonous and
corrosive, hence careful handling needed.
♦Density is low, hence more volume space is needed
Liquid Propellant Rockets

16. Solid & Liquid Propellant
Rockets

17. Hybrid
Propellant
Rockets
FUEL OXIDIZER
Beryllium
Hydride
Fluorine
Lithium Hydride Chlorine
trifluoride
Lithium Hydride Nitrogen
tetroxide
Hydrocarbon Nitrogen
tetroxide

18. Hybrid Propellant Rockets
Combination of liquid and solid propellants.
Fuels: Beryllium hydride, Lithium hydride, polythene
Oxidizer: Chlorotrifluorine, nitrogen tetra oxide
Liquid oxidizer is stored in a separate tank
is pumped through a valve and injected into
combustion chamber (solid fuel present).
When fuel and oxidizer mixes together,
combustion takes place automatically.
After combustion, the high temperature
exhaust gases are expanded through the
nozzle and propels the rocket

19. Advantages:-
 Pay load capacity is more
 Reduction in speed is possible
 Solid fuel is compact and more mass of fuel
can be stored.
 Light wgt compared to liquid propellant
 In case of accident or crash the explosion
is less compared to liquid propellant rocket
Disadvantages:-
 Nozzle erosion cannot be avoided.
Hybrid Propellant Rockets

20. Monopropellants: A liquid propellant which
contains both the fuel and oxidizer in a
single chemical.
e.g., Hydrazine, nitroglycerine, nitromethane,
hydrogen peroxide, etc.,
Bipropellants :
A liquid propellant which contains the fuel
and oxidizer in separate units.
Liquid Propellant

21. Liquid Fuel and Oxidizer used

22. Fuels:
 Hydrazine
 Liquid Hydrogen
 Ethyl alcohol or Ethanol
 UDMH (Unsymmetrical dimethyl-hydrazine)
Oxidizer
 Liquid Oxygen
 Hydrogen Peroxide
 Nitrogen Tetroxide (Hypergolic , i.e.,
combustion takes place without oxygen.
 Nitric Acid (RFNA & WFNA)
Fuels and Oxidizer

23.  It should release large amount of heat
during combustion.
 Physical and chemical properties should not
change during processing
 It should have high density.
 It should not be poisonous and hazardous.
 It should be cheap and easily available.
 It should be non-corrosive and non reactive
with components of the engine
 Storage and handling should be easy.
Properties of Solid propellants

24. Must have higher thermal conductivity.
It should have higher calorific value
Density of propellant must be high, hence
they require smaller tank
It should not chemically react with motor
system including tanks, piping, valves, etc.,
Combustion must have lower molecular
weight to produce high jet velocity and
thrust.
Must be able to produce high chamber
temperature.
Properties of liquid
propellants

25. RATO or JATO
When the aircraft power is not
sufficient for take off, rockets
(integral part of aircraft) are fired
to augment the power of the rocket
engine. This method of take off is
known as RATO or JATO
RATO – Rocket Assisted Take Off
JATO – Jet Assisted Take Off

26. Used in aircrafts as propulsion .
Used in missile in military
Used as a space vehicle or
satellites.
Used as a space flights
Used for scientific investigations
Used for weather prediction
Used for communication networks.
Application of rocket engines

27. There are two types of liquid feed system
Gas Pressure feed system
Pump feed system
COMBUSTION :
Combustion of a liquid propellant(Fuel and
oxidizer mixture) in the combustion
chamber requires the following basic
processes
1. Injection 2. Atomization 3. Mixing 4.
Vapourization 5. Ignition 6. Chemical reaction
between fuel and oxidizer
liquid propellant feed System

28. Gas Pressure feed System

29. An inert gas(Helium or Nitrogen) is stored in a
tank at high pressure and it is passed into
pressure-regulator valves. This high pressure
inert gas from the regulator is used to force
the propellants(fuel and oxidizer)
The propellants under high pressure are forced
to flow into the combustion chamber through
control valves.
Several regulating and check valves are used
for filling, draining and checking the flow of
propellants.
Moving parts such as pumps and turbines are
not used.
The pressurization of the propellant tank is
heavier, hence this system is not suitable for
large rocket engines and long range missions.
GAS PRESSURE FEED SYSTEM

30. TURBO PUMP FEED SYSTEM

31. In this system, liquid fuel and the liquid oxidizer
are stored in a separate tank at low pressure.
Liquid fuel and liquid oxidizer are forced into the
combustion chamber at high pressure by the fuel
and oxidizer pumps.
Gas turbine is used to operate the fuel and oxidizer
pumps.
Liquid hydrogen peroxide (H2O2) from the tank is
decomposed by a catalyst such as calcium or sodium
permanganate. Due to this, steam and oxygen are
generated. This steam is used to drive the turbine.
Because of the third liquid, the gas turbine, the
pumps and additional lines are necessary. So the
pump pressurization system is considerably more
complex than gas pressurization system.
Design of pump is a greatest problem that will
handle the liquids safely and without leaks.
TURBO PUMP FEED SYSTEM

32. LOSSES IN ROCKET ENGINE