Hybrid rockets use a liquid oxidizer and solid fuel. They are mechanically simpler than other rocket types and can provide denser fuels. A hybrid rocket consists of a pressure vessel containing liquid oxygen and a combustion chamber housing solid fuel. When thrust is desired, the liquid oxidizer flows into the combustion chamber where it reacts with the solid fuel surface in a boundary layer flame. Hybrid rockets offer higher safety during fabrication and operation compared to solid rockets, and allow for throttling capability not available with other rocket types. While hybrid rockets currently have some performance disadvantages, their safety features make them promising for future propulsion applications.

1. Introduction to Hybrid
Rockets
Prepared for a regular seminar classes

2. ROCKET
Rocket is a missile , space craft , aircraft or other
vehicles that obtain thrust from the rocket engines
Rocket engines are divided into three types based on
their propellants
They are
1. Solid Propellants
2. Liquid Propellants
3. Hybrid Propellants

3. HYBRID ROCKET
One component propellant is stored in liquid phase
and other in solid phase are called Hybrid rockets.
These rockets mostly employs a liquid oxidizer and
solid fuel.
Liquid oxidizers are used because solid oxidizers are
problematic and lower performing than liquid.
Solid fuels are used because of their higher density
than liquid fuels.
The main advantage of this rockets are mechanically
simpler and denser fuels.

4. BASIC CONCEPTS
Hybrid rockets consists of pressure vessel contains
liquid oxygen.
The combustion chamber contains solid fuel and
valve isolate the two.
When thrust is desired a suitable ignition is
introduced into combustion chamber.
The liquid propellant flows into combustion chamber
where it is vaporized.
It reacts with the solid propellant occours in a
boundary layer diffusion flame adjacent to the surface
of the solid fuel.

5. HYBRID ROCKET OXIDIZERS
Oxidizers are used to throttle the rockets and to
restart the motor
Pressurizing the liquid oxidizer is not an important
element of hybrid technology.
Liquid oxidizer either can be cryogenic or non
cryogenic liquid depending upon the requirement.
The most common liquid oxidizer is nitrous oxide.

6. HYBRID ROCKET FUEL
The solid fuel is used as a fuel.
Solid fuels allows for the incorporation of the metal
additives to fuel grain increasing specific impulse .
The mass flow rate increases with increase in pressure
Burning rate increases with in pressure
If some amount of additional impurities , mass flow
rate decreases with increase in pressure but the
burning rate increases

7. Working
Liquid oxidizer which is stored in separate tank is
injected into the combustion chamber
When liquid oxidizer mixes with solid fuel in the
combustion chamber combustion takes place
When this happens very high temperature and
pressure gases are produced which comes out
through the nozzle section
Due to the high velocity gases comes out from the
nozzle thrust is produced

8. ADVANTAGES COMPARED WITH
SOLID ROCKETS
Higher theoretical ISP is obtained.
More controllable.
Less explosion hazard.
Safety during fabrication, storing and operation.
The ability to smoothly change motor thrust over a
wide range on demand.
Environmental safety

9. Disadvantages
Mixture ratio and hence specific impulse will vary
somewhat during steady state operation and
throttling
Lower density – Specific impulse than solid
propellants system
Some fuel sliver may be retained in the combustion
chamber at the end of burning which slightly reduces
the motor mass fraction
Unproven propulsion system in large scale
Oxidizer to fuel ratio shift

10. HYBRID ROCKET PROPULSION

11. LIQUID OXYGEN
Liquid oxygen is highly paramagnetic.
It has the density of 1.141kg/cm3.
It is highly cryogenic with the freezing point of 50.5k.
It has the boiling point of about 90.19k.
Liquid oxygen has expansion ratio 1:861 at 293k.
Liquid oxygen is highly useful because it creates a
very high specific impulse.

12. Paraffin wax
Paraffin wax has a typical melting point between
about 46 and 68 °C (115 and 154 °F), and having a
density of around 0.9 g/cm3.
Pure paraffin wax is an excellent electrical insulator,
with an electrical resistivity of between 1013 and 1017
ohm metre
Paraffin wax is an excellent material to store heat,
having a specific heat capacity of 2.14–2.9 J g−1 K−1
(joule per gram Kelvin) and a heat of fusion of 200–
220 J g−1.

13. Hybrid Safety
Pressure vessel failures - Chamber insulation
failure may allow hot combustion gases near the
chamber walls leading to a "burn-through" in which
the vessel ruptures.
Blow back - For oxidizers that decompose
exothermically.
Hard starts - An excess of oxidizer in the
combustion chamber prior to ignition.

14. Future aspects
This type of rockets are cheap and economic and can
be used in large scales
New type of solid fuels with high graininess can be
found and used in this rockets
Fuel and oxidizer ratio may be changed to increase
the performance
They can be used as short span power boosters in
space props

15. Conclusion
We have seen a small explanation about hybrid
rocket and its working.
 This type of rocket has many advantages over the
other type of rockets though it has some
disadvantages also.
 The rocket can be modified to overcome these
disadvantages.
Thus we conclude that hybrid rockets will play a
major role in propulsion in future.