it consists of advantages and disadvantages of propellants

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2. THE ADVANTAGES OF DIFFERENT TYPES
OF PROPELLANTS

3. CONTENTS
1. INTRODUCTION
• ROCKET PROPELLANT
2. TYPES OF PROPELLANTS
• SOLID PROPELLANT
• LIQUID PROPELLANT
• GAS PROPELLANT
• HYBRID PROPELLANT
3. CONCLUSION
4. REFERENCES

4. INTRODUCTION
Rocket propellant
Rocket propellant is a material used by a rocket as, or to produce in a
chemical reaction, the reaction mass (propulsive mass) that is ejected,
typically with very high speed, from a rocket engine to produce thrust,
and thus provide spacecraft propulsion. In a chemical rocket, propellants
undergo exothermic chemical reactions to produce hot gas. There may
be a single propellant or multiple propellants. In the case of multiple
propellants, one can distinguish fuel and oxidizer. The gases produced
expand and push on a nozzle, which accelerates them until they rush out
of the back of the rocket at extremely high speed. For smaller attitude
control thrusters, a compressed gas escapes the spacecraft through a
propelling nozzle.

5. Types of propellants
There are four main types of chemical rocket propellants: solid, liquid,
gas and hybrid.
1. Solid propellants
Solid propellants are either "composites" composed mostly of large,
distinct macroscopic particles or single, double, or triple-bases which are
homogeneous mixtures of one or more primary ingredients. Composites

6. typically consist of a mixture of granules of solid oxidizer
(examples: ammonium nitrate, ammonium per chlorate, potassium
nitrate) in a polymer binder with flakes or powders of: energetic
compounds (examples: RDX, HMX), metallic additives (examples:
Aluminum, Beryllium), plasticizers, stabilizers, and/or burn rate
modifiers (iron oxide, copper oxide).
Advantages of solid propellants
• Solid propellant rockets are much easier to store and handle than
liquid propellant rockets.
• High propellant density makes for compact size as well.
• These features plus simplicity and low cost make solid propellant
rockets ideal for military applications.
• Their simplicity also makes solid rockets a good choice whenever
large amounts of thrust are needed and cost is an issue.
Disadvantages of solid propellants
• Relative to liquid fuel rockets, solid fuel rockets have lower
specific impulse.
• The propellant mass ratios of solid propellant upper stages is
usually in the .91 to .93 range which is as good as or better than

7. that of most liquid propellant upper stages but overall performance
is less than for liquid stages because of the solids' lower exhaust
velocities.
• The high mass ratios possible with (unsegmented) solids are a
result of high propellant density and very high strength-to-weight
ratio filament-wound motor casings.
• A drawback to solid rockets is that they cannot be throttled in real
time.
• Solid rockets can be vented to extinguish combustion or reverse
thrust as a means of controlling range or accommodating warhead
separation.
• Casting large amounts of propellant requires consistency and
repeatability which is assured by computer control.
• Solid fuel rockets are intolerant to cracks and voids and often
require post-processing such as x-ray scans to identify faults.

8. 2. Liquid propellants
In a liquid propellant rocket, the fuel and oxidizer are stored in separate
tanks, and are fed through a system of pipes, valves, and turbo pumps to
a combustion chamber where they are combined and burned to produce
thrust. A good liquid propellant is one with a high specific impulse or,
stated another way, one with a high speed of exhaust gas ejection. This
implies a high combustion temperature and exhaust gases with small
molecular weights. However, there is another important factor which
must be taken into consideration: the density of the propellant. Storage
temperature is also important.

9. Advantages of liquid propellants
• Liquid-fueled rockets have higher specific impulse than solid
rockets.
• They are capable of being throttled, shut down, and restarted.
• On vehicles employing turbo pumps, the propellant tanks are at
very much less pressure than the combustion chamber. For these
reasons, most orbital launch vehicles use liquid propellants.
• The primary performance advantage of liquid propellants is due to
the oxidizer. Several practical liquid oxidizers (liquid oxygen,
nitrogen tetroxide, and hydrogen peroxide) are available which
have better specific impulse than the ammonium per chlorate used
in most solid rockets, when paired with comparable fuels.
• While liquid propellants are cheaper than solid propellants. Some
propellants, notably Oxygen and Nitrogen, may be able to
be collected from the upper atmosphere, and transferred up to low-
Earth orbit for use in propellant depots at substantially reduced
cost.

10. Disadvantages of liquid propellants
• These are generally least moderately difficult to store and handle
due to their low reactivity with common materials.
• Several exotic oxidizers have been proposed which are unstable,
energetic, and toxic.
• Liquid-fueled rockets also require potentially troublesome valves
and seals and thermally stressed combustion chambers, which
increase the cost of the rocket.
3. Gas propellants
A gas propellant usually involves some sort of compressed gas.
However, due to the low density and high weight of the pressure vessel,

11. gases see little current use, but are sometimes used for vernier engines,
particularly with inert propellants.
Advantages of gas propellants
• They do not burn (although other liquids in the aerosol
may burn).
• They are readily available and cheap.
• Gaseous fuels lack density.
• Long term storage is possible.
Disadvantage of gas propellants
• The pressure in the can reduces over the lifetime of the
aerosol.

12. 4. Hybrid propellants
A hybrid rocket usually has a solid fuel and a liquid or gas oxidizer. The
fluid oxidizer can make it possible to throttle and restart the motor just
like a liquid-fueled rocket. Hybrid rockets can also be environmentally
safer than solid rockets since some high-performance solid-phase
oxidizers contain chlorine (specifically composites with ammonium per
chlorate), versus the more benign liquid oxygen or nitrous oxide often
used in hybrids. This is only true for specific hybrid systems.

13. Advantages of hybrid propellants
• These are much cheaper.
• Can be shut down easily.
• Throttle control.
• Much safer to handle.
• Higher theoretical specific impulse.
Disadvantages of hybrid propellants
• Slightly more complex than solids.
• Difficult to make use of hybrid propellants for very large thrusts.
• Less researched.

14. CONCLUSION
The knowledge that has been obtained through the research of rocket
technology has brought the promise of the eventual commercialization
of space ever closer. If more research and development is invested into
solid-fuel and liquid-fuel technology, the dream of commercializing the
space industry can be can be realized. Perhaps prior to that realization,
whole new technologies for design and construction of spacecraft and
different fuels may be required. However, it is a good bet that further
research and development, cost effectiveness and overall improvement
with the current workhorses of space exploration will be around for
some time.

15. REFERENCES
• www.wikipedia.com
• www.angelfire.com
• Google images
• www.ph.utexas.edu
• www.braeunig,us
• history.nasa.gov.in
• www.scientificamerican.in