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An Exclusive Publication from Students of Department of Aeronautical Engineering, F G Institute of Engineering & Technology
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PRAKSHEP
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PRAKSHEP
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P R A K S H E P An Exclusive Publication from Students of Department of Aeronautical Engineering,
FGIET
THE FIRST SUMMER SEMESTER EDITION
2013
PRAKSHEP
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Prakshep An Exclusive Magazine from Department of Aeronautical Engineering, F G
Institute of Engineering & Technology
Year 1, Volume 1
Published on May 30, 2013
Chief Editors
Yajur Kumar
Megha Marwari
Technical Editors
Pankaj Mishra
Pankaj K Kushwaha
Creative Editor
Pushpa Kumari
Cover, Finance, Layout and Typesetting
Yajur Kumar
PUBLISHED BY
Students of Department of Aeronautical Engineering
F G Institute of Engineering & Technology, Rae Bareli 229001
ISBN 978-1-304-01467-2
Prakshep by Students of Department of Aeronautical Engineering, FGIET is
licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0
Unported License.
PRAKSHEP
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A FEW WORDS FROM THE EDITOR
When the idea of regular magazine was suggested, I was in slight doubt if we will be able to
make it in time and in an interesting flavor. From telling the students to accepting the entries,
everything was a new experience, its being our first time handling a departmental publication
and my first time handling the overall editing.
Really big things starts from small things, I learnt it from somewhere, I exactly dont know,
but the words worth immense motivation in themselves. In my years at the college, I faced
several good things, several bad things too. Most of the times I planned starting a new
project, but everything went beyond my controls, either because of financial inabilities or
because I spent too much time in planning only. But, now when I look behind, I found there
were many reasons, the most important was working alone. A really big thing also needs a
really good team. So, in this project, which is however, a small step, we started with a good
team, who have, frankly speaking, no previous experience in this field of publication. But,
what we see later, that after a lot of clashes in views and opinions, we finally made it.
The magazine is intended at demonstrating the thoughts, creativity and imagination
capabilities of the students of the aeronautical engineering in the college. We have included
different sections for the purpose like concepts-which presents some of the hard concepts of
the aeronautical engineering, technology-a section on the latest technologies being
exploited in the aerospace field, curiosity-for those who likes to think out of the box, and
writing sections-a cluster of thoughts that came out on paper by the students, poetry and
other imaginative work. In addition, several other sections of importance are added.
However, I and we tried our best to present the things, it may be possible that we may
otherwise lack on a particular point. I personally ensures the reader that there is a good team
of coming fresher, sophomores and seniors, and they will present the publication in a more
interesting and curious ways in the future editions.
We warmly welcome any further ideas or suggestions to improve the quality of the
publication, for which you may write to Prakshep Magazine Publication Board, Department
of Aeronautical Engineering, F G Institute of Engineering and Technology, Rae Bareli.
Yajur Kumar
(Chief Editor)
PRAKSHEP
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AKNOWLEDGEMENTS
I would like to thank the contributors for
contributing such smart articles and essays in a
very limited period of time, which made the
publication of the magazine possible on time. The
supporting editors deserves a special place,
Pankaj Kumar Kushwaha, Pushpa Kumari and
Pankaj Mishra, who helped us editing the technical
and creative work. Joint chief editor Megha
Marwari, who also worked hard late night like me,
deciding the flavor of the magazine and also
collaging the photo stuff, deserves a warm thanks.
Finally, thanks to our teacher, assist. Prof. N.
Srivastava the man behind the idea of the
magazine.
From my desk at 5 PM of May 1, 2013
YAJUR KUMAR
CHIEF EDITOR
PRAKSHEP
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ONTENTS
Message from the Institutes Director
Message from the Head of the Department
A Few Words from the Editor
Acknowledgements
Concepts 1. The Rocket Principle 10 Yajur Kumar
2. Surface Control Devices 20 Megha Marwari
3. Thrust Vectoring 24 Nripendra K Singh
4. The Pulse Jet 26 Praveen K Singh
5. The Smart Materials 29 Akshay Gupta
6. Gliding Flight 32 Pankaj Mishra
7. Use of Blunt Shape in Reentry
Vehicles 33 Akshay Malik
8. Aircraft Propellers 35 Shraddha Singh
C
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9. Aircraft Flaps 38 Archana
10. NACA Airfoil Series 41 Pushpa Kumari
11. Do You Know? 44 Prof. R K Singh
12. All about Mach
number 47 Dimple Varshney
Technology 1. How a Satellite Works? 51 Yajur Kumar
2. What are Solar Flares? 56 P K Kushwaha
3. Electronic Warfare 58 Prof. A K Pandey
4. Green Aviation 60 P K Kushwaha
5. Introducing Stealth
Technology 63 Mayank Verma
6. The Traffic Collision
Avoidance System 68 Mayank Verma
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Curiosity 1. How to Find Them? 72 Yajur Kumar
2. Are We Alone in this
Universe? 77 Shiv Om
3. Boeing 787 Dreamliner 79 Megha Marwari
4. Flying High 83 Apoorva Mehrotra & Devanand Yadav
Poet among us 1. 87 Akshay Malik 2. 89 Archana
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Writer among us 1. Set Your Goals 92 Pushpa Kumari
2. Who is Responsible? 94 Namrata Saini
3. Brief History of Aviation 97 Pankaj Mishra
4. The Paper Airplane 100 Rateesh & Abhishek
AVIATION CAREERS 105 Megha Marwari | Yajur Kumar
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Concepts
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Chief Editor Yajur Kumar Final Year
Thanks to my three person smart team who assist me in the
designing of the whole magazine layout and also, thanks to the
random photographers whose contribution makes this magazine
colorful.
Connect with Yajur at fb.com/YajurK
___________________________________________________________________________
From flying a small rocket firework to
launching a giant cargo rocket to Mars, the
principles of how rockets work
are exactly the same. Understanding and
applying these principles means mission
success. Isaac Newton, born the year Galileo
died, advanced Galileos discoveries and
those of others by proposing three basic laws
of motion. These laws are the foundation of
all rocket science. This law simply points out
that an object at rest, such as a rocket on a
launch pad, needs the exertion of an
unbalanced force to cause it to lift off. The
amount of the thrust produced by the rocket
engines has to be greater than the force of
gravity holding it down. As long as the thrust
of the engines continues, the rocket
accelerates. When the rocket runs out of
propellant, the forces become unbalanced
again. This time, gravity takes over and causes
the rocket to fall back to Earth. Following its
landing, the rocket is at rest again, and the
forces are in balance.
1. Delta IV Medium Rocket
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There is one very interesting part of this law
that has enormous implications for
spaceflight. When a rocket reaches space,
atmospheric drag is greatly reduced or
eliminated. Within the atmosphere, drag is an
important unbalancing force. That force is
virtually absent in space. A rocket traveling
away from Earth at a speed greater than
11.186 kilometers per second will eventually
escape Earths gravity. It will slow down, but
Earths gravity will never slow it down enough
to cause it to fall back to Earth. Ultimately,
the rocket (actually its payload) will travel to
the stars. No additional rocket thrust will be
needed. Its inertia will cause it to continue to
travel outward. Four spacecraft are actually
doing that as you read this. Pioneers 10 and
11 and Voyagers 1 and 2 are on journeys to
the stars!
I am now going to explain the rocket
principle, in the easiest possible way. People
are usually very familiar with Newtons third
law. It is the principle of action and reaction.
In the case of rockets, the action is the force
produced by the expulsion of gas, smoke, and
flames from the nozzle end of a rocket
engine. The reaction force propels the rocket
in the opposite direction. When a rocket lifts
off, the combustion products from the
burning propellants accelerate rapidly out of
the engine. The rocket, on the other hand,
slowly accelerates skyward. It would appear
that something is wrong here if the action
and reaction are supposed to be equal. They
are equal, but the mass of the gas, smoke,
and flames being propelled by the engine is
much less than the mass of the rocket being
propelled in the opposite direction. Even
though the force is equal on both, the effects
are different. Newtons first law, the law of
inertia, explains why. The law states that it
takes a force to change the motion of an
object. The greater the mass, the greater the
force required to move it.
The second law relates force, acceleration,
and mass. The law is often written force
equals mass times acceleration. The force or
thrust produced by a rocket engine is directly
proportional to the mass of the gas and
particles produced by burning rocket
propellant times the acceleration of those
combustion products out the back of the
engine. This law only applies to what is
actually traveling out of the engine at the
moment and not the mass of the rocket
propellant contained in the rocket that will be
consumed later. The implication of this law
for rocketry is that the more propellant you
consume at any moment and the greater the
acceleration of the combustion products out
of the nozzle, the greater the thrust.
2. The Pioneer 10
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So far, so good. But, launching
rockets into space is more
complicated than Newtons laws
of motion imply. Designing
rockets that can actually lift off
Earth and reach orbital velocities
or interplanetary space is an
extremely complicated process.
Newtons laws are the
beginning, but many other
things come into play. For
example, air pressure plays an
important role while the rocket
is still in the atmosphere. The
internal pressure produced by
burning rocket propellants
inside the rocket engine
combustion chamber has to be
greater than the outside
pressure to escape through the
engine nozzle. In a sense, the
outside air is like a cork in the
engine. It takes some of the
pressure generated inside the
engine just to exceed the
ambient outside pressure.
Consequently, the velocity of
combustion products passing
through the opening or throat of
the nozzle is reduced. The good
news is that as the rocket climbs
into space, the ambient
pressure becomes less and less
as the atmosphere thins and the
engine thrust increases. Another
important factor is the changing
mass of the rocket. As the rocket
is gaining thrust as it accelerates
upward due to outside pressure
changes, it is also getting a boost
3. An engineering concept shows NASA's new heavy lift and crew launch vehicles.
PRAKSHEP
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due to its changing mass. Every bit of rocket
propellant burned has mass. As the
combustion products are ejected by the
engine, the total mass of the vehicle lessens.
As it does its inertia, or resistance to change
in motion, becomes less. As a result, upward
acceleration of the rocket increases.
In real rocket science, many other things also
come into play. Even with a low acceleration,
the rocket will gain speed over time because
acceleration accumulates. And, not all rocket
propellants are alike. Some produce much
greater thrust than others because of their
burning rate and mass. It would seem obvious
that rocket scientists would always choose
the more energetic propellants. Not so. Each
choice a rocket scientist makes comes with a
cost. Liquid hydrogen and liquid oxygen are
very energetic when burned, but they both
have to be kept chilled to very low
temperatures. Furthermore, their mass is
low, and very big tanks are needed to contain
enough propellant to do the job.
Rocket science is a subject of immense
interest for aerospace engineers, and if you
are comfortable with getting crazy about
launching these real fireworks, there is a
rocket waiting to be launched at some place
by you in the very near future.
A Boeing 737 weighing 150,000 pounds (68,000 kg) must deflect about 88,000 pounds
(40,000 kg) of air - over a million cubic feet
(31,500 cubic meters) down by 55 feet (16.75
m) each second while in flight.
FACT FILE.
PRAKSHEP
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Joint Chief Editor Megha Marwari Final Year
I find it very enjoyable to edit the different sections of the
magazine. Although it was a new task for us, but thanks to our
chief editor who helped organizing things in a delightful way.
Connect with Megha at fb.com/Megha.Marwari
Many of you like to solve crossword puzzles. So heres the one, all you have to do is to find the seven surface control and high lift devices. So lets begin!
Now let us have a brief knowledge about these control surface devices and high lift devices.
T R A I G Z S L O T S
E E X O F C Y T R S P
D L N T S E B I W A Y
U I E W F Q M R Z D N
V O X V L T V U O J O
W P D M A T J D K I R
N S F B P T F D U P E
K F S R S V O E L Y L
C O X L T G W R J R I
E M Z K A I M O Q T A
W A X J B T F L C Z R
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Ailerons are the control surfaces which are used to roll the aircraft. Two aileron control surfaces on each wing at the trailing edge and move opposite to each other generating the rolling moment and rolling the aircraft. A roll is positive if the aircraft rolls towards the pilots right. A roll is negative or negative roll when the aircraft rolls towards the pilots left.
Elevators are the control surfaces which are used for the pitching moment of the aircraft and are present at the trailing edge of the Horizontal tail or
horizontal stabilizer. An elevator role is to pitch the aircraft
i.e. (nose up or nose down). When elevator moves up, the aircraft nose moves up. When elevator moves down, the aircraft nose moves down.
Rudders are control surfaces which are used to yaw the aircraft. The rudders are present on the vertical tail or stabilizer and used to the yaw the aircraft in the required direction.
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Flaps are hinged surfaces mounted on the trailing edges of the wings of a fixed-wing aircraft to reduce the speed at which an aircraft can be safely flown and to increase the angle of descent for landing. They shorten takeoff and landing distances. Flaps do this by lowering the stall speed and increasing the drag.
Trim tabs are small surfaces connected to the trailing edge of a larger control surface on a boat or aircraft, used to control the trim of the controls, i.e. to counteract hydro- or aerodynamic forces and stabilize the boat or aircraft in a particular desired attitude without the need for the operator to constantly apply a control force. This is done by adjusting the angle of the tab relative to the larger surface.
Slats are aerodynamic surfaces on the leading edge of the wings of fixed-wing aircraft which, when deployed, allow the wing to operate at a higher angle of attack. A higher coefficient of lift is produced as a result of angle of attack and speed, so by deploying slats an aircraft can fly at slower speeds, or take off and land in shorter distances. They are usually used while landing or performing maneuvers which take the aircraft close to the stall, but are usually retracted in normal flight to minimize drag.
A leading edge slot is a fixed aerodynamic feature of the wing of some aircraft to reduce the stall speed and promote good low-speed handling qualities. A leading edge slot is a span-wise gap in each wing, allowing air to flow from below the wing to its upper surface. In this manner they allow flight at higher angles of attack and thus reduce the stall speed.
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ANSWERS
T R A I G Z S L O T S
E E X O F C Y T R S P
D L N T S E B I W A Y
U I E W F Q M R Z D N
V O X V L T V U O J O
W P D M A T J D K I R
N S F B P T F D U P E
K F S R S V O E L Y L
C O X L T G W R J R I
E M Z K A I M O Q T A
W A X J B T F L C Z R
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Nripendra K Singh Final Year I worked on my final year project of wind tunnel designing with my
team and find out that there is much more to explore in the field of
aviation than we know presently. Thanks to the editors for
presenting this magazine at its best. Connect with Nripendra at fb.com/Nripendra.Kr.Singh
You all must have
heard it or learned
this fact in your
course, that an
aircraft is controlled
and maneuvered by
using the Surface
controls viz.
Elevators, Ailerons,
Rudder and Trim
tabs. But these
controls are good
until we are talking
about general
purpose aircrafts
(such as
Passenger/Cargo
aircrafts), while
taking Fighter
aircrafts and
STOL/VSTOL
aircrafts under
considerations we
need some other
tool to control and
maneuver the
aircraft more faster and tightly during crucial
turns. This tool comes in the form of the
power produced by the Engine i.e. Thrust of
the Aircraft.
Thus, Thrust vectoring can be defined as the
technique of using the Engine thrust for the
purpose of controlling the Attitude of the
aircraft
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For applying the above mentioned
technique we use the movable nozzles.
These nozzles are specially designed, so as
to deviate the thrust producing hot mass of
gas from the turbine outlet in the desired
line of action. Nowadays, almost all of the
fighter aircrafts are using the technique of
Thrust vectoring. This is because when you
are operating under the situation of war or in
the battlefield(during Dog-Fights) then very
high maneuverability is required, as under
these conditions the pilot having less control
over its aircraft will be having a great
disadvantage.
A famous example of thrust vectoring is the
Lockheed Martin F-22 Raptor fifth-
generation jet fighter, with its afterburning,
thrust-vectoring Pratt & Whitney F119
turbofan.
Earlier, usage of this technology can be seen
in the Rolls-Royce Pegasus
engine used in the Hawker
Siddeley Harrier, as well as
in the AV-8B Harrier II
variant.
In India, The Sukhoi Su-30
MKI, produced under
license at Hindustan
Aeronautics Limited
employs 2 -Dimensional
thrust vectoring. The 2 -
Dimensional thrust
vectoring makes the
aircraft highly
maneuverable and capable
it to make high angles of
attack without stalling.
Thus, making Sukhoi Su-30
MKI as one of the best
fighter aircraft in active
service with the Indian Air
Force.
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4. F22 Raptor Thrust Vectoring
Praveen K Singh Final Year
I have been researching on various areas of Aircraft
Propulsion. I hope you will enjoy reading this article on
Pulsejet engines. Also, a warm thanks to my friend and Chief
Editor Yajur Kumar for presenting this magazine at its best. Connect with Praveen at fb.com/Praveen.Singh.100
The idea that the simplest engine an
engineer can make is a jet engine will sound
strange to most people -- we perceive jet
engines as big complex contraptions
pushing multi-million dollar aircraft through
the skies. Yet, this is completely true. In its
most basic form the pulsejet -- the jet
engine can be just an empty metal tube
shaped in a proper way.
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FACTS
The pulsejet engine was first invented in the early 1900 by a Swedish inventor Martin Wiberg.
Paul Schmidt, who engineered the first production pulsejet during the Second World
War with his flying bomb, the Argus V1.
Nicknamed the buzz bomb because of the low hum it admitted during flight.
Used by the Germans to bomb London from 1944-1945.
Over 9,000 V-1 were fired on England during WW2.
The pulsejet took a backseat in the engineering world when the turbofan jet engine was invented.
Has returned to the engineering scene as of late because of the interest in Pulse Detonation Engines.
WORKING PRINCIPLE
A pulsejet engine is a very simple jet engine
consisting of very little to no moving parts.
The combustion cycle comprises five or six
phases: Induction, Compression, (in some
engines) Fuel Injection, Ignition,
Combustion, and Exhaust.
The rapidly expanding gasses exit out of the
engine and as this happens a vacuum is
created in the combustion chamber which
pulls in a fresh new air charge from the
atmosphere, and then the whole cycle
repeats itself.
ADVANTAGE OF PULSE JET
The pulsejet is the only jet engine combustor
that shows a net pressure gain between the
intake and the exhaust. All the others have
to have their highest pressure created at the
intake end of the chamber. From that
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station on, the pressure falls off. Such a
decreasing pressure gradient serves to
prevent the hot gas generated in the
combustor from forcing its way out through
the intake. This way, the gas moves only
towards the exhaust nozzle in which
pressure is converted to speed. The great
intake pressure is usually provided by some
kind of compressor, which is a complex and
expensive bit of machinery and consumes a
great amount of power. Much of the energy
generated in the turbojet engine goes to
drive a compressor and only the remainder
provides thrust. The pulsejet is different.
Here, the exhaust pressure is higher than the
intake pressure. There is pressure gain
across the combustor, rather than loss.
Moreover, the pulsejet does it without
wasting the power generated by
combustion. This is very important.
WHY LOOK AT PULSEJETS NOW?
All the piston engines currently used in ultra-
light flying are relatively heavy and
cumbersome, even in their simplest form.
They also require much ancillary equipment,
like Redactors, prop shafts, propellers etc.
etc. Having all that gear mounted on a
lightweight flying machine almost defeats
the original purpose. A simple lightweight
pulsejet seems much more appropriate. The
enormous advances in computing power
over the past few decades have made
modelling of pulsating combustion more
realistic, too. It is still not easy even for the
supercomputers, but it can now be done.
This can cut down development time
drastically and make it much more
straightforward.
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Akshay Gupta Final Year
I have been researching over properties of smart materials.
Smart materials can enhance the entire aviation field, if
used suitably, so as I am presenting in this short article.
Thanks to the team of smart editors for presenting this
magazine in the best and most beautiful way. Connect with Akshay at fb.com/Aks.Gpt
Basically, there is no standard definition for
smart materials, and the term smart
material is generally defined as a material
that can change one or more of its properties
in response to an external stimulus. For
example, the shape of the material will
change in response to different temperature
or application of electrical charge or
presence of magnetic field. In general, it can
be catalogued to three main groups, which
are thermo to-mechanical, electrical-to-
mechanical and magnetic-to-mechanical. In
the other hand, there are some materials
which termed as smart material do not
have the properties stated above, like the
material with self-healing property is also
termed as smart material.
Therefore, smart material can also be
expressed as a material that can perform a
special action in response to some specific
condition such as very high/low
temperature, high stress, very high/low pH
value, even material failure, etc.
How are they significant in Aeronautical
applications?
Materials have a strong relationship with
aeronautical industry, as it always
determines the weight, strength, efficiency,
cost and difficulty of maintenance of an
aircraft.
Therefore, the discovery of new material
usually makes a breakthrough in
performance of an aircraft. Especially the
findings of smart materials, it makes an
innovation in aircraft because it can provide
a special function or property. Accordingly,
the smart materials receive a great attention
in order to improve the performance of
aircraft.
Categorization
Piezoelectric Materials
Figure 5: Monocrystal [Left] and Polycrystal [Right].
PRAKSHEP
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Conducting Polymers
Shape Memory Alloys (SMAs)
Electrostrictive Ceramics
Magnetic Smart Materials
Fire Resistant Composites
Piezoelectric Materials
Basically, piezoelectric materials are
transducers between electricity and
mechanical stress. The piezoelectric
material has this effect because of its
crystallized structure. For the crystal, each
molecule has a polarization; it means one
end is more negatively charged while the
other end is more positively charged, and it
is called dipole. Furthermore, it directly
affects how the atoms make up the
molecule and how the molecules are
shaped. Therefore, the basic concept of
piezoelectricity is to change the orientation
of polarization of the molecules.
A Piezoelectric Material:
PZT [Lead Zironate Titanate]
Material Youngs Modulus, Gpa
Max actuator strain, m/m
Density, gm/cm3
PZT 50-70 0.12-0.18
7.6
Regarding the orientation of polar axis, the
crystal can be divided into two types which
are monocrystal and polycrystal.
The monocrystal means that all the
molecules polar axes are oriented in the
same direction, and the polycrystal means
that the polar axes of the molecules are
randomly oriented.
Application of Piezoelectric Material
Regarding the application of piezoelectric
material, there are two main functions
which are shape control and vibration
control.
Aerodynamic Feature
In term of shape changing, it means the
changing of aerodynamic feature.
Conventionally, the aircrafts control surface
is still controlled indirectly and lack of
flexibility. However, the piezoelectric
actuator can perform an innovative
mechanism of control system; it greatly
increases the performance and
maneuverability due to flexible, efficient
and thin actuator.
Vibration Control
Regarding vibration, it is an unwanted effect
in aircraft because it can contribute to stress
concentration, material fatigue, shortening
service life, efficiency reduction and noise.
Obviously, these problems influence the
safety and maintenance cost sharply.
Besides, the noise problem is always
considered, especially the passengers
aircraft, as the noise is a great annoyance.
Therefore, the engineers always want to
minimize the vibration. Conventionally, it is
difficult to provide a precise active damping
which produces a vibration with anti-
resonance frequency. By the piezoelectric
material, it can be used as sensor and
actuator at the same time, so it has a fast
enough response to produce the anti-
resonance vibration. Furthermore, it is
flexible, small and thin to be applied in many
parts of aircraft.
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Adaptive Smart Wing
Conventionally, the flap, rudder and
elevator are adjusted by electronic motor or
mechanical control system like cable or
hydraulic system. By applying piezoelectric
actuator, no discrete surfaces are required
because the control surface can be change
the sharp itself in order to change the
aerodynamic feature.
Therefore, it creates a continuous surface
which will not cause early airflow separation
hence to reduce the drag, but also the lift is
increased due to the delay airflow
separation. Accordingly, it increases the
efficiency significantly.
Basically, the concept of smart wing is to
construct a continuous control surface
embedded by a series of piezoelectric
actuator. Furthermore, it is required to have
a high strength-to-weight ratio; it means the
actuator has to be placed strategically for
optimizing a light weight design. Finally, it
should have an ability to change the shape
response to different flight condition, hence
the performance of cruise flight can be
improved that the conventional aircraft
cannot achieve. In fact, this concept has
started to be investigated since 2000.
However, the smart wing system is mainly
focus on military aircraft performance and
maneuver improvement. Since 2004, this
smart wing project has been started by
many industries and research centers such
as US Air
Force, NASA, Northrop Grumman and
Lockheed Martin. They constructed a 30%
scale Unmanned Combat Air Vehicle (UCAV)
at NASA Langley Research Centre. By two
wind tunnel testing, it showed that the
system had a high rate, large deflection,
conformal trailing edge control at realistic
flight conditions.
Helicopter Blade Application
For the improvement of helicopter, most of
engineers focus on the eliminating acoustic
problem because it is the major problem and
disadvantage. From the theoretical and
experimental work both in Europe and USA,
it shows that the BVI (Blade Vortex
Interaction, shown in Figure) is the main
source of noise, fortunately it can be
dramatically reduced, 8 to 10dB, by an
appropriate control of blades.
In order to solve this problem, there are two
possible solutions. The first solution is to
construct the blade that can perform a
continuous twisting. The second solution is
the servo-aerodynamic control surface like
flap, tab, or blade-tip is installed on the
blade
to generate aerodynamic force. Practically,
it is difficult to install any conventional
actuator in the blades of helicopter.
However, the piezoelectric actuator seems
to be suitable for the blades, so it receives an
extensive attention.
PRAKSHEP
26
Editor Pankaj Mishra Final Year
We worked really hard for presenting this magazine at its
best and I hope aero-students will surely enjoy exploring it.
Gliding Flight is
heavier than air
flight without use
of thrust. Gliders means sailplanes. Take an
airplane in a power off glide. The forces act
on this aircraft are lift drag and weight;
Thrust is zero due to power off. Glide flight
path makes angle below horizontal (means
without engine power).
For an equilibrium un-accelerated glide,
sum of the forces must be zero. Sum of
these forces along flight path
D = W Sin .. (i)
Perpendicular to flight path
L = W Cos (ii)
From (i)/ (ii)
Sin/cos = D/L
tan= 1/ (L/D)
Clearly, glide angle is a function of lift to
drag ratio. Higher the L/D, shallower the
glide angle. Smallest equilibrium glide
angle occurs at (L/D) max, which corresponds
to maximum range for glide.
Most common human application of gliding
flight is in sport and re-create using aircraft
design.
Gliding can be achieved with a flat (un-
cambered) wing as with simple paper plane.
IMPORTANCE OF GLIDE RATIO IN GLIDING
FLIGHT
Best Glide ratio is important to measuring
performance of gliding aircraft. Sometimes
fly aircrafts best L/D by controlling airspeed
and smooth operate to reduce drag. To
achieve higher speed, gliders loaded with
water ballast to increase airspeed which has
little effect on glide angle but increase rate
of shrink (speed over ground in proportion)
because the heavier aircraft achieve optimal
L/D at high airspeed.
BALLAST
Used in sailboats to provide moment to
resist lateral forces on sail.
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6. Glider.
Akshay Malik Pre-Final Year
Connect with Akshay at fb.com/Akshay.Malik.718
At the time of
reentry, near outer
edge of atmosphere, the reentry vehicle has
high velocity and as it is at high altitude, it
has large amount of potential energy. But
when the vehicle reaches to surface of earth,
it has relatively small velocity and nearly
zero potential energy. This large amount of
energy is lost due to following two reasons:
1. Heating the body of vehicle.
2. Heating the airflow around
vehicle.
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The shock wave formed at the nose of
vehicle heats the airflow around the vehicle
and at same time the vehicle is heated within
the boundary layer region due to intense
skin friction.
The temperature generated by such skin
friction is very high. We are required to make
less heating of the space craft. Because such
high temperature can damage the space
craft. The heat generated in this phenomena
will either heat vehicle body or air flow
around the body. If somehow we are able to
dissipate more heat into airflow than on
vehicle body, then our aim can be fulfilled.
This can be achieved by creating a stronger
shock wave at the nose of the reentry
vehicle.
If a slender body is used for reentry purposes
then weaker shock wave will be formed at
the nose of vehicle. It is shown by following
figure-Due to creation of weaker shock
waves the vehicle body will be heated more
than the surrounding airflow.
But if we use a blunt shape body then
stronger shock waves will be generated at
the nose of vehicle. As it can be seen clearly
with the help of following figure-
Thus by using the blunt shape body reentry
vehicle large heating of vehicle surface is
avoided.
This concept was first uncovered by Harvey
Allen in 1951.
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Shraddha Singh Pre-Final Year Connect with Shraddha at fb.com/ShraddhaSingh3014
Propeller is the
word which comes from the word propel
which means drive forward. Propeller is
used for providing thrust only. The engine
supplies brake horsepower through a
rotating shaft & the propeller converts it into
thrust horsepower.
=
Blade angle is the angle between the propellers plane of rotation, and the chord line of the propeller airfoil. Blade station is a reference position on a blade that is a specified distance from the center of the hub. Pitch is the distance (in inches or millimeters) that a propeller section will move forward in one revolution. Pitch distribution is the gradual twist in the propeller blade from shank to tip.
PROPELLER SLIP The distance this particular element would move forward in one revolution along a helix, or spiral, equal to its blade angle, is called Geometrical pitch. The Effective pitch is the actual distance a propeller advances through the air in one revolution. This cannot be determined by the pitch angle alone because it is affected by the forward velocity of the airplane. The difference between geometric and effective pitch is called propeller slip. Example- If a propeller has a pitch of 50 inches, in theory it should move forward 50 inches in one revolution. But if the aircraft actually moves forward only 35 inches in one revolution the effective pitch is 35 inches and the propeller efficiency is 70%.
Blade Angle & Angle of Attack
Blade angle is the angle between the propellers plane of rotation, and the chord line of the propeller airfoil.
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Angle of Attack is the angle between the chord line of an airfoil and the relative wind. When the airplane is at rest on the ground with the engine operating, or moving slowly at the beginning of takeoff, the propeller efficiency is very low because the propeller is restrained from advancing with sufficient speed to permit its fixed pitch blades to reach their full efficiency. In this situation, each propeller blade is turning through the air at an angle of attack which produces relatively little thrust for the amount of power required to turn it. To understand the action of a propeller, consider first its motion, which is both rotational and forward. Thus, as shown by the vectors of propeller forces, each section of a propeller blade moves downward and forward. The angle at which this air (relative wind) strikes the propeller blade is its angle of attack. The air deflection produced by this angle causes
the dynamic pressure at the engine side of the propeller blade to be greater than atmospheric, thus creating thrust. The shape of the blade also creates thrust, because it is cambered like the airfoil shape of a wing. Consequently, as the air flows past the propeller, the pressure on one side is less than that on the other. As in a wing, this produces a reaction force in the direction of the lesser pressure. In the case of a wing, the air flow over the wing has less pressure, and the force (lift) is upward. In the case of the propeller, which is mounted in a vertical
instead of a horizontal plane, the area of decreased pressure is in front of the propeller, and the force (thrust) is in a forward direction. Aerodynamically, then,
thrust is the result of the propeller shape and the angle of attack of the blade. Another way to consider thrust is in terms of the mass of air handled by the propeller. In these terms, thrust is equal to the mass of air handled, times the slipstream velocity, minus the velocity of the airplane. The power expended in producing thrust depends on the rate of air mass movement. On the average, thrust constitutes approximately 80% of the torque (total horsepower absorbed by the propeller). The other 20% is lost in friction and slippage. For any speed of rotation, the horsepower absorbed by the propeller balances the horsepower delivered by the engine. For any single revolution of the propeller, the amount of air handled depends on the blade angle, which determines how big a "bite" of air the propeller takes. Thus, the blade angle is an excellent means of adjusting the load on the propeller to control the engine RPM. The blade angle is also an excellent method of adjusting the angle of attack of the propeller. On constant speed propellers, the blade angle must be adjusted to provide the most efficient angle of attack at all engine
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and airplane speeds. Lift versus drag curves, which are drawn for propellers as well as wings, indicate that the most efficient angle of attack is a small one varying from 2 to 4 degrees positive. The actual blade angle necessary to maintain this small angle of attack varies with the forward speed of the airplane.
When relative airflow increases and airspeed remains constant then angle of attack also increases. When air speed increases and relative
airflow remains constant then angle of
attack decreases.
7. Hercules
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Archana Pre-Final Year
Flaps are hinged portion at trailing edge of
aircraft wing .Flaps are used to increase lift,
drag or both when deflected and used
principally for landing and take-off. The
higher the deflection of the flap is, the
greater the drag. It is like when your palm is
flat against the wind flow as you stretch your
hand out in a moving car. As you reduce the
angle against the airflow, the drag reduces
and you get better lift and your hand moves
up.
Flaps are used when the aircraft is slowing
down in preparation for a landing. In a plane,
flaps are usually used for both takeoff and
landing. They are partially extended before
takeoff to increase lift and reduce the
runway distance required to leave the
ground. They are fully extended during the
landing phase to allow the aircraft to safely
approach the runway at the lowest possible
speed.
Flap deflection of up to 15 primarily
produces lift with minimal drag. Deflection
beyond 15 produces a large increase in
drag. Drag from flap deflection is parasite
drag, and as such is proportional to the
square of the speed. Also, deflection beyond
15 produces a significant nose-up pitching
moment in most high wing airplanes
because the resulting downwash increases
the airflow over the horizontal tail.
Up/Down position of flaps during take off
It depends on the type of aircraft and the
circumstances of the takeoff. Aircraft
designed to cruise at high speedsincluding
most jet-powered aircraftmay extend
flaps slightly for takeoff because their low-
speed performance is limited by a design
that favors high-speed flight. A wing design
that provides a lot of lift at low speeds isn't
likely to be suitable for high speeds because
it will generate too much lift and too much
drag, but a wing design that works well at
high speeds may not generate a lot of lift at
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low speeds. So flaps are used to increase lift
for takeoff.
Low-speed aircraft, including small private
propeller-drive aircraft, can usually take off
without flaps, since they never fly at high
speed and their wings are designed to
generate plenty of lift at low speeds.
Flaps may also be extended (or extended
further) for takeoff from short runways,
again depending on the aircraft and the
exact circumstances. In any case, full
extension of the flaps is rare, as that often
generates more drag than it's worth.
Flaps during take-off position
Depending on the aircraft type, flaps may be
partially extended for takeoff. When used
during takeoff, flaps cover runway distance
for climb rateusing flaps reduces ground
roll and the climb rate. The amount of flap
used on takeoff is specific to each type of
aircraft.
Flaps during landing position
Flaps may be fully extended for landing to
give the aircraft a lower stalling speed so the
approach to landing can be made more
slowly or at low speed, which also allows the
aircraft to land in a shorter distance.
Types of flaps
There are basically main four types of flaps:
plain, split, fowler and slotted type
Plain flap: when this flap is deflected, it
changes (increases) both upper & lower
chamber of wing airfoil .This increase in
chamber leads to more lift at low speed and
low angle of attack. If flap is moved down
sufficiently, the drag increases significantly
and the lower surface become an effective
air-break.
Split edge flap: This type of flap is used
mostly in case of air beak where high drag is
required .when this flap is deflected upper
chamber remains same but lower chamber
increases which leads to more drag
.Deflected flap acts much like a spoiler,
producing lots of drag and little or no lift.
Fowler flap: Split flap slides backwards flat,
before deflecting downwards, thereby
increasing first chord, than camber. The flap
may act both like plain and split flap but it
must slide rearward before lowering.
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Slotted flap: In this type of flap there is
a gap between wing and flap which is
called slot and allows air from the
bottom of the wing to flow to the upper
portion of flap and downwards at
trailing edge of the wing .This delays
airflow separation and creates
downwards flow of air which produces
lift to the wing.
FACT FILE. A commercial aircraft door will not open in flight because it is actually bigger than the window
frame itself, and the door opens inwards towards the cabin. To open, it must be opened
inwards, rotated, and then slipped sideways out of the frame. Even if the door could somehow
be opened, it would be like lifting a 2,200 pound weight.
PRAKSHEP
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Editor Pushpa Kumari Final Year
To consider the creative editing was a very enjoyable experience. It
gives me a feeling that I am connected with the nature in an amazing
way. Thanks to our chief editors for presenting this magazine on time
and such a beautiful way.
Connect with Pushpa at fb.com/Pushpa.Kumari.96343
Airfoil structure is the basic of our
aeronautical world, but many times we are
not able to understand its dimensions to
know more about its parameter regarding
dimensions let see the AIRFOIL NACA
SERIES FAMILY.
NACA 4 DIGIT SERIES
The first digit specifies the maximum
camber (m) in percentage of the chord
(airfoil length). The second indicates the
position of the maximum camber (p) in
tenths of chord. The last two numbers
provide the maximum thickness (t) of the
airfoil in percentage of chord, e.g., NACA
2412
Maximum camber= .002c , position of
max camber = 0.04c, max thickness = .12c
NACA 5 DIGIT SERIES
The first digit, when multiplied by 3/2, yields
the design lift coefficient (cl) in tenths. The
next two digits, when divided by 2, give the
position of the maximum camber (p) in
tenths of chord. The final two digits again
indicate the maximum thickness (t) in
percentage of chord, e.g., NACA 23012
Lift coefficient = 0.3,
position of max camber = .15c,
max thickness = 0.12c
NACA 6 DIGIT SERIES
The first digit denotes the series and
indicates that this family is designed for
greater laminar flow than the Four- or Five-
Digit Series. The second digit is the location
of the minimum pressure in tenths of chord.
The subscript 1 indicates that low drag is
maintained at lift coefficients 0.1 above and
below the design lift coefficient (0.2)
specified by the first digit after the dash in
tenths. The final two digits specify the
thickness in percentage of chord, e.g., NACA
641-212,
The 6 denotes the series and indicates that
this family is designed for greater laminar
flow than the Four- or Five-Digit Series. The
second digit, 4, is the location of the
minimum pressure in tenths of chord (0.4c).
The subscript 1 indicates that low drag is
maintained at lift coefficients 0.1 above and
below the design lift coefficient (0.2)
specified by the first digit after the dash in
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tenths. The final two digits specify the
thickness in percentage of chord, 12%.
NACA 7 DIGIT SERIES
The 7-Series was a further attempt to
maximize the regions of laminar flow over
an airfoil differentiating the locations of the
minimum pressure on the
upper and lower surfaces, e.g., NACA
747A315.
The 7 denotes the series. The 4 provides the
location of the minimum pressure on the
upper surface in tenths of chord (40%). The
7 provides the location of the minimum
pressure on the lower surface in tenths of
chord (70%). The fourth character, a letter,
indicates the thickness distribution and
means line forms used. The fifth digit
indicates the design lift coefficient in tenths
(0.3). The final two integers are the airfoil
thickness in percentage of chord (15%).
NACA 8 DIGIT SERIES
A final variation on the 6- and 7-Series
methodology was the NACA 8-Series
designed for flight at supercritical speeds.
Like the earlier airfoils, the goal was to
maximize the extent of laminar flow on the
upper and lower surfaces independently.
The naming convention is very similar to the
7-Series, e.g., NACA 835A216.
The 8 designates the series. The 3 is the
location of minimum pressure on the upper
surface in tenths of chord (0.3c). The 5 is the
location of minimum pressure on the lower
surface in tenths of chord (50%). The letter A
distinguishes airfoils having different
camber or thickness forms, the 2 denotes
the design lift coefficient in tenths (0.2). The
16 provides the airfoil thickness in
percentage of chord (16%). Now we have a
brief description about all the NACA series.
We study above
FAMILY ADVANTAGE DISADVANTAGE APPLICATION
4- DIGIT 1. Good stall characteristics 2. Small center of pressure movement across large speed range 3. Roughness has little effect
1. Low maximum lift coefficient 2. Relatively high drag 3. High pitching moment
1. General aviation 2. Horizontal tails Symmetrical: 3. Supersonic jets 4. Helicopter blades 5. Shrouds 6. Missile/rocket fins
5-DIGIT 1. Higher maximum lift coefficient 2. Low pitching moment 3. Roughness has little effect
1. Poor stall behavior 2. Relatively high drag
1. General aviation 2. Piston-powered bombers, transports 3. Commuters 4. Business jets
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6-DIGIT 1. High maximum lift coefficient 2. Very low drag over a small range of operating conditions 3. Optimized for high speed
1. High drag outside of the optimum range of operating conditions 2. High pitching moment 3. Poor stall behavior 4. Very susceptible to roughness
1. Piston-powered fighters 2. Business jets 3. Jet trainers 4. Supersonic jets
7-DIGIT 1. Very low drag over a small range of operating conditions 2. Low pitching moment
1. Reduced maximum lift coefficient 2. High drag outside of the optimum range of operating conditions 3. Poor stall behavior 4. Very susceptible to roughness
Seldom used
8-DIGIT Unknown Unknown Very seldom used
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Assist. Prof. R K Singh Faculty Member
No one
knows who
discovered
the Jet
Propulsion
Principle, but
the favor is
sometimes
given to a
man named
Hero, who
lived in
Alexandria, Egypt, about 150 B.C.
One of the largest piston engine ever built, the R4360, 28 cylinder radial,
which develops 4,000 SHP, and the JT9D engine powering the Boeing 747.
If we use the
generally
accepted
conversion of
2.5 pounds of
thrust per SHP,
propeller static
thrust of R4360
would be
approximately
10000 lbs.,
neglecting
propeller
efficiency
losses. The
Boeing 747
8. The Jet Engine
9. R4360 Piston Engine
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would need 23 such engines to give the 230, 000 lbs. static thrust, currently
produced by its four JT9D turbofan engines.
The Pulsejet engine is fitted with inlet
shutters (flapper valves) to open and
close the air entering the engine. These
inlet shutters blew open and close
approximately 40 times per second to
allow and stop the air entering into the
engine.
Wright brothers incorporated first time
fuel injection system into a spark ignition
engine.
In a high by-pass ratio, turbofan engine
which has a by-pass ratio of 5:1, the by-
pass air produces 80% of the thrust and
10. JT9D Turbofan Engine of Boeing 747
11. The Pulse Jet Engine
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the core engine produces only 20% of the thrust. (By-pass ratio is the ratio
between the amount of air not entering the core engine (compressor,
combustion chamber, and turbine) or by passing the core engine and
amount of air entering the core engine.)
Assist. Prof. R. K. Singh, is a premier faculty member of
Department of Aeronautical Engineering. He served Indian
Navy as Chief Aircraft Maintenance Engineer for 15 years. He
teaches Aircraft Propulsion, maintenance and advanced
subjects like Rockets and Missiles at the institute.
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Dimple Varshney Final Year
The Mach number is commonly used
both with objects traveling at high
speed in a fluid, and with high-speed
fluid flows inside channels such
as nozzles, diffusers or wind tunnels. As
it is defined as a ratio of two speeds, it is
a dimensionless number. At Standard
Sea Level conditions (corresponding to
a temperature of 15 degrees Celsius),
the speed of sound is 340.3 m/s (1225
km/h, or 761.2 mph, or 661.5 knots, or
1116 ft./s) in the Earth's atmosphere.
The speed represented by Mach 1 is not
a constant; for example, it is mostly
dependent on temperature and
atmospheric composition and largely
independent of pressure. Since the
speed of sound increases as the
temperature increases, the actual speed
of an object traveling at Mach 1 will
depend on the fluid temperature
around it. Mach number is useful
because the fluid behaves in a similar
way at the same Mach number. So, an
aircraft traveling at Mach 1 at 20C or
68F, at sea level, will experience shock
waves in much the same manner as
when it is traveling at Mach 1 at 11,000
m (36,000 ft.) at 50C or 58F, even
though it is traveling at only 86% of its
speed at higher temperature like 20C
or 68F.
Classification of Mach regimes
While the terms "subsonic" and
"supersonic" in the purest verbal sense
refer to speeds below and above the
local speed of sound respectively,
aerodynamicists often use the same
terms to talk about particular ranges of
Mach values. This occurs because of the
presence of a "transonic regime" around
M=1 where approximations of
the Navier-Stokes equations used for
subsonic design actually no longer
apply, the simplest of many reasons
being that the flow locally begins to
exceed M=1 even when the free stream
Mach number is below this value.
Meanwhile, the "supersonic regime" is
usually used to talk about the set of
Mach numbers for which linearized
Regime Mach Mph km/h m/s
Subsonic 8,465
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theory may be used, where for example
the (air) flow is not chemically reacting,
and where heat-transfer between air
and vehicle may be reasonably
neglected in calculations.
In the following table, the "regimes" or
"ranges of Mach values" are referred to,
and not the "pure" meanings of the
words "subsonic" and "supersonic".
Generally, NASA defines "high"
hypersonic as any Mach number from
10 to 25, and re-entry speeds as
anything greater than Mach 25. Aircraft
operating in this regime include
the Space Shuttle and various space
planes in development.
High-speed flow around objects
Flight can be roughly classified in six
categories:
Regime
Subsonic
Transonic
Sonic
Supersonic
Hypersonic
High-hypersonic
Mach
10.0
For comparison: the required speed
for low Earth orbit is approximately 7.5
km/s = Mach 25.4 in air at high altitudes.
The speed of light in a vacuum
corresponds to a Mach number of
approximately 881,000 (relative to air at
sea level).
At transonic speeds, the flow field
around the object includes both sub-
and supersonic parts. The transonic
period begins when first zones of M>1
flow appear around the object. In case
of an airfoil (such as an aircraft's wing),
this typically happens above the wing.
Supersonic flow can decelerate back to
subsonic only in a normal shock; this
typically happens before the trailing
edge. (Fig.1a)
As the speed increases, the zone of M>1
flow increases towards both leading and
trailing edges. As M=1 is reached and
passed, the normal shock reaches the
trailing edge and becomes a weak
oblique shock: the flow decelerates over
the shock, but remains supersonic. A
normal shock is created ahead of the
object, and the only subsonic zone in
the flow field is a small area around the
object's leading edge. (Fig.1b)
(a)
(b)
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Fig. 1. Mach number in transonic
airflow around an airfoil; M1 (b).
When an aircraft exceeds Mach 1 (i.e.
the sound barrier) a large pressure
difference is created just in front of
the aircraft. This abrupt pressure
difference, called a shock wave, spreads
backward and outward from the aircraft
in a cone shape (a so-called Mach cone).
It is this shock wave that causes
the sonic boom heard as a fast moving
aircraft travels overhead. A person
inside the aircraft will not hear this. The
higher the speed, the more narrow the
cone; at just over M=1 it is hardly a cone
at all, but closer to a slightly concave
plane.
At fully supersonic speed, the shock
wave starts to take its cone shape and
flow is either completely supersonic, or
(in case of a blunt object), only a very
small subsonic flow area remains
between the object's nose and the
shock wave it creates ahead of itself. (In
the case of a sharp object, there is no air
between the nose and the shock wave:
the shock wave starts from the nose.)
As the Mach number increases, so does
the strength of the shock wave and the
Mach cone become increasingly
narrow. As the fluid flow crosses the
shock wave, its speed is reduced and
temperature, pressure, and density
increase. The stronger the shock,
greater the changes. At high enough
Mach numbers the temperature
increases so much over the shock that
ionization and dissociation of gas
molecules behind the shock wave
begin. Such flows are called hypersonic.
It is clear that any object traveling at
hypersonic speeds will likewise be
exposed to the same extreme
temperatures as the gas behind the
nose shock wave, and hence choice of
heat-resistant materials becomes
important.
FACT FILE... Most planes flying internationally have their home country's flag painted on or around
their tails. Generally, the flag is facing the proper way round on the left (port) side of
the aircraft, and backward on the starboard side. Why? Because that's how it would
look if a real flag were hoisted on a pole above the airplane during flight.
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Technology
PRAKSHEP
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Yajur Kumar Final Year
As per definition, satellite is basically
any object that revolves around a planet
in a circular or elliptical path. Well, in
this article, we are talking about
artificial or man-made satellites.
Satellites are an essential part of our
daily lives, from their use in weather
reports, television transmission and
everyday telephone calls. In many other
instances, satellites play a background
role that escapes our notice, such as
some newspapers and magazines are
timelier because they transmit their text
and images to multiple printing sites via
satellite to speed local distribution.
Your cellphones GPS device is also
functioning by the virtue of satellites.
Emergency radio beacons from downed
aircraft and distressed ships may reach
search-and-rescue teams when
satellites relay the signal.
The Soviet Sputnik
satellite was the first to
orbit Earth, launched
on Oct. 4, 1957.
Because of Soviet
government secrecy at
the time, no
photographs were
taken of this famous
launch. Sputnik was a
58 cm and 83 kg metal
ball. On the outside of
Sputnik, four whip
antennas transmitted
on short-wave
frequencies above and below what is
today's Citizens Band (27 MHz). After 92
days, gravity took over and Sputnik
burned in Earth's atmosphere. Thirty
days after the Sputnik launch, the dog
Laika orbited in a half-ton Sputnik
satellite with an air supply for the dog. It
burned in the atmosphere in April 1958.
Sputnik is a good example of just how
simple a satellite can be. As we will see
later, today's satellites are generally far
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more complicated, but the basic idea is
a straightforward one.
The path a satellite follows is an
orbit. In the orbit, the farthest
point from Earth is the apogee,
and the nearest point is the
perigee. All satellites today get
into orbit by riding on a rocket.
Many used to hitch a ride in the
cargo bay of the space shuttle.
Several countries and
businesses have rocket launch
capabilities, and satellites as
large as several tons make it
safely into orbit regularly.
For most satellite launches, the
scheduled launch rocket is
aimed straight up at first. This
gets the rocket through the thickest
part of the atmosphere most quickly
and best minimizes fuel consumption.
After a rocket launches straight up,
the rocket control mechanism uses
the inertial guidance system to
calculate necessary adjustments to
the rocket's nozzles to tilt the
rocket to the course described in
the flight plan. In most cases, the
flight plan calls for the rocket to
head east because Earth rotates to
the east, giving the launch vehicle a
free boost. The strength of this
boost depends on the rotational
velocity of Earth at the launch
location. The boost is greatest at
the equator, where the distance 12. The GPS Network
13. A drawing of the orbital path for the TRMM (Tropical Rainfall Measuring Mission) satellite
PRAKSHEP
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around Earth is greatest and so rotation
is fastest.
To make a rough estimate of boost from
an equatorial launch, we can determine
Earth's circumference by multiplying its
diameter by pi which gives, 40,065 Kms.
To travel around this circumference in
24 hours, a point on
Earth's surface has to
move at 1,669 Kmph.
A launch from Cape
Canaveral, Florida,
doesn't get as big a
boost from Earth's
rotational speed. The
Kennedy Space
Center's Launch
Complex 39-A, one of
its launch facilities, is
located at 28 degrees
36 minutes 29.7014
seconds north
latitude. The Earth's
rotational speed
there is about 1,440
Kmph. The difference
in Earth's surface
speed between the
equator and Kennedy
Space Center, then, is
about 229 Kmph.
Well, considering that
rockets can go
thousands of miles
per hour, you may
wonder why a
difference of only 229
Kmph would even
matter. The answer is that rockets,
together with their fuel and their
payloads, are very heavy. For example,
14. STS 11 Launching from Kennedy Space Center
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the Feb. 11, 2000, lift-off of the space
shuttle Endeavour with the Shuttle
Radar Topography Mission required
launching a total weight of 2,050,447
Kgs. It takes a huge amount of energy to
accelerate such a mass to 229 Kmph,
and therefore a significant amount of
fuel. Launching from the equator makes
a real difference.
Once the rocket reaches extremely thin
air, at about 193 Kms up, the rocket's
navigational system fires small rockets,
just enough to turn the launch vehicle
into a horizontal position. The satellite
is then released. At that point, rockets
are fired again to ensure some
separation between the launch vehicle
and the satellite itself.
A rocket must accelerate to at least
40,320 Kmph to completely escape
Earth's gravity and fly off into space.
Earth's escape velocity is much greater
than what's required to place an Earth
satellite in orbit. With satellites, the
object is not to
escape Earth's
gravity, but to
balance it.
Orbital velocity
is the velocity
needed to
achieve balance
between
gravity's pull on
the satellite and
the inertia of
the satellite's
motion -- the
satellite's
tendency to
keep going.
This is
approximately
27,359 Kmph at
an altitude of 242 Kms. Without gravity,
the satellite's inertia would carry it off
into space. Even with gravity, if the
intended satellite goes too fast, it will
eventually fly away. On the other hand,
if the satellite goes too slowly, gravity
will pull it back to Earth. At the correct
15. Schematic of a Rocket Motor
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orbital velocity, gravity exactly balances
the satellite's inertia, pulling down
toward Earth's center just enough to
keep the path of the satellite curving
like Earth's curved surface, rather than
flying off in a straight line.
Despite the significant differences
between the various kinds of satellites,
they have several things in common.
Such as:
all of them have a metal or
composite frame and body,
usually known as the bus. The
bus holds everything together
in space and provides enough
strength to survive the launch.
all of them have a source of
power (usually solar cells) and
batteries for storage. Arrays of
solar cells provide power to
charge rechargeable batteries.
Newer designs include the use
of fuel cells. Power on most
satellites is precious and very
limited. Nuclear power has
been used on space probes to
other planets (read this page
for details). Power systems are
constantly monitored, and
data on power and all other
onboard systems is sent to
Earth stations in the form of
telemetry signals.
all of them have an onboard
computer to control and
monitor the different systems.
all of them have a radio system
and antenna. At the very least,
most satellites have a radio
transmitter/receiver so that
the ground-control crew can
request status information
from the satellite and monitor
its health. Many satellites can
be controlled in various ways
from the ground to do
anything from change the orbit
to reprogram the computer
system.
all of them have an attitude
control system. The ACS keeps
the satellite pointed in the
right direction.
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Editor Pankaj K Kushwaha Final Year
Designing a whole new scientific publication needs hard work
and days of planning. I am heartily thankful to our chief editor
for managing things in such a precise way. Connect with Pankaj at fb.com/Pankaj.K.Kushwaha.9
A flare is defined as a sudden, rapid, and
intense variation in brightness. A solar flare
occurs when magnetic energy that has built
up in the solar atmosphere is suddenly
released. Radiation is emitted across the
entire electromagnetic spectrum, ranging
from radio waves to gamma rays. The
amount of energy released is the equivalent
of millions of 100-megaton hydrogen bombs
exploding at the same time! The first solar
flare recorded in writing was on September
1, 1859. Two scientists, Richard C.
Carrington and Richard Hodgson, were
independently observing sunspots at the
time, when they viewed a large flare in white
light.
As the magnetic energy is being released,
particles, including electrons, protons, and
heavy nuclei, are heated and accelerated in
the solar atmosphere. The energy released
during a flare is typically on the order of
10^14
Mega
joules per
second.
Large
flares can
emit up to
10^19
Mega
joules of
energy.
This
energy is
ten million
times
greater
than the
energy released from a volcanic explosion.
On the other hand, it is less than one-tenth
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of the total energy emitted by the Sun every
second.
There are typically three stages to a solar
flare. First is the precursor stage, where the
release of magnetic energy is triggered. Soft
x-ray emission is detected in this stage. In
the second or impulsive stage, protons and
electrons are accelerated to energies
exceeding 1 MeV. During the impulsive
stage, radio waves, hard x-rays, and gamma
rays are emitted. The gradual build up and
decay of soft x-rays can be detected in the
third, decay stage. The duration of these
stages can be as short as a few seconds or as
long as an hour.
Solar flares extend out to the layer of the
Sun called the corona. The corona is the
outermost atmosphere of the Sun,
consisting of highly rarefied gas. This gas
normally has a temperature of a few million
degrees Kelvin. Inside a flare, the
temperature typically reaches 10 or 20
million degrees Kelvin, and can be as high as
100 million degrees Kelvin. The corona is
visible in soft x-rays, as in the above image.
Notice that the corona is not uniformly
bright, but is concentrated around the solar
equator in loop-shaped features. These
bright loops are located within and connect
areas of strong magnetic field called active
regions. Sunspots are located within these
active regions. Solar flares occur in active
regions.
The frequency of flares coincides with the
Sun's eleven year cycle. When the solar cycle
is at a minimum, active regions are small and
rare and few solar flares are detected. These
increase in number as the Sun approaches
the maximum part of its cycle.
A person cannot view a solar flare by simply
staring at the Sun. Flares are in fact difficult
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to see against the bright emission from the
photosphere. Instead, specialized scientific
instruments are used to detect the radiation
signatures emitted during a flare. The radio
and optical emissions from flares can be
observed with telescopes on the Earth.
Energetic emissions such as x-rays and
gamma rays require telescopes located in
space, since these emissions do not
penetrate the Earth's atmosphere
Assist. Prof. A. K. Pandey Faculty Member
In the present age the electronics plays a
great role in our life, without it the globe is
devoid. The electronic warfare utilizes
electromagnetic spectrum from the low
frequencies to the high frequencies. Mainly
it is used in military operation which includes
electronic attacks, electronic support and
electronic fortification. By this this, we can
obtain tactical intelligence and surveillance
to achieve the war goal.
As the threats received from the intruder, it
reconfigures itself to counter threats. In
doing this, higher data bit rate technique are
incorporated to track the communication
system, also to intercept, identify and locate
the source of electromagnetic wave for the
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purpose of targeting enemy resources and
planning for the future war techniques.
Electronic warfare provides electronic
protection, which is used to protect man and
material from the intentional or
unintentional circumstances.
Electromagnetic radiation can be used to
degrade the combat capabilities, such as
misleading the weapon with the help of IR
rays emission, changing the transmission
frequency randomly which is known to our
forces, to deceive the enemy. The electronic
attack to devastate the enemy forces is
commonly used. In this process intense
electromagnetic waves are emitted which
can be used to block the wireless
communication which controls the radio
combat devices of the enemy.
Assist. Prof. A. K. Pandey, is a premier faculty member of
Department of Aeronautical Engineering. He served
different organizations in his brilliant career of serving the
nation. He teaches the Aircraft Instrumentation, Aircraft
Rules and advanced subjects like Avionics at the institute.
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Pankaj K Kushwaha Final Year
People around the world are switching to
skies in large numbers. In 2009, for the first
time in aviation history, Asia recorded more
air travelers than U.S., while U.S. airplanes
flew 704 million passengers, a number
forecast to reach 1.21 billion by 2020.
Catering such a humungous growth in
number of air travelers will require new
flights, more runways and airports .But
increment in all these will also have
repercussions which manifest it in the form
of engine emissions, unprecedented air
traffic, and nonstop noise and not to
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mention the unhappy citizens concerned
about their health and quality of life.
In order to reduce potential harm to the
environment and have a pleasant and
economical flight, NASA and other space
agencies are working in collaboration with
universities and industries to develop
environmentally beneficial, or "green,
aviation technologies. Green aviation means
aviation so in such a way to create least
possible disturbance in the environmental
balance.
GOALS FOR GREEN AVIATION
* to reduce aircraft fuel consumption.
* To reduce aircraft emissions.
* To reduce aircraft noise.
* To achieve the above three economically.
SOLUTIONS FOR GREEN AVIATION
Some of the above mentioned problem
could be dealt with improvement in
technologies and some with completely
revolutionary, innovative technologies.
1. The solution to reduction in fuel
consumption can be achieved by allowing
pilots to directly climb to their cruising
altitude or descend down at the touchdown
without levelling off frequently in order to
check for the traffic at the airport
2. A revolutionary satellite based air
transport communication system could be
installed with other avionics equipment to
allow fliers fly directly to their destination,
reducing 200 gallons of fuel every year.
3. Use of advanced lightweight composites
for aircraft body construction (e.g. Boeing
787 dream liner), increment of laminar flow
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over aircraft body which increases the lift is
to drag ratio.
4. Changes in engine design or operation
might include ultra-high bypass turbofans,
open rotor engines, use of alternative fuels
or locating engines on the body of the
aircraft in such a way that deflects engine
noise upward to keep it from reaching the
ground.
5. The last but not the least point to ponder
upon is research on development of
alternate fuel for the jet airliners. Amongst
all the available fuel alternatives algae
biomass has bagged the topmost position.
IT is not a food stock, scalable, has high
calorific value, easy to manufacture, works
well with existing infrastructure and meets
the fuel standard. Currently Boeing, GE,
P&W Airbus all are working on developing
biomass as an alternative fuel.
If the above mentioned points are
implemented then the earth would be a
better place to live in for sure with distances
which could be fathomed within a couple of
hours.
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Mayank Verma Pre-Final Year Connect with Mayank at fb.com/Er.Mayank2013
Stealth technology
also known as LOT
(Low Observability Technology) is a
technology which covers a range of
techniques used with aircraft, ships and
missiles, in order to make them less visible
(ideally invisible) to radar, infrared and other
detection methods.
In simple terms, stealth technology allows an
aircraft to be partially invisible to Radar or any
other means of detection. This doesn't allow
the aircraft to be fully invisible on radar.
Stealth technology cannot make the aircraft
invisible to enemy or friendly radar. All it can
do is to reduce the detection range or an
aircraft. This is similar to the camouflage
tactics used by soldiers in jungle warfare.
Unless the soldier comes near you, you can't
see him. Though this gives a clear and safe
striking distance for the aircraft, there is still
a threat from radar systems, which can detect
stealth aircraft.
STEALTH PRINCIPLE
The concept behind the stealth technology is
very simple. As a matter of fact it is totally the
principle of reflection and absorption that
makes aircraft "stealthy". Deflecting the
incoming radar waves into another direction
and thus reducing the number of waves does
this, which returns to the radar. Another
concept that is followed is to absorb the
incoming radar waves totally and to redirect
the absorbed electromagnetic energy in
another direction. Whatever may be the
method used, the level of stealth an aircraft
can achieve depends totally on the design
and the substance with which it is made of.
THE KEY FEATURES OF STEALTH
-Unusual Design
-Outer Paint
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-Reduce Heat Exhaust Signatures
-Eliminate High Altitude Contrails
-Eliminate Brown Exhaust
METHODS OF AVOIDING DETECTION
Design for stealth requires the integration of
many techniques and materials. The types of
stealth that a maximally stealthy aircraft &
ships seeks to achieve can be categorized as
visual, infrared, acoustic, and Radar.
VISUAL STEALTH
Low visibility is desirable for all military
aircraft and is essential for stealth aircraft. It
is achieved by coloring the aircraft so that it
tends to blend in with its environment. For
instance, reconnaissance planes designed to
operate at very high altitudes, where the sky
is black, are painted black. (Black is also a low
visibility color at night, at any altitude.)
Conventional daytime fighter aircraft are
painted a shade of blue known as "air-
superiority blue-gray," to blend in with the
sky. Stealth aircraft are flown at night for
maximum visual stealth, and so are painted
black or dark gray. Chameleon or "smart skin"
technology that would enable an aircraft to
change its appearance to mimic its
background is being researched
INFRARED STEALTH
Another important factor that influences the
stealth capability of an aircraft is the IR (i.e.
Infrared, electromagnetic waves in the. 72
1000 micron range of the spectrum)
signature given out by the plane. Usually
planes are visible in thermal imaging systems
because of the high temperature exhaust
they give out. This is a great disadvantage to
stealth aircraft as missiles also have IR
guidance system. The IR signatures of stealth
aircraft are minute when compared to the
signature of a conventional fighter or any
other Military aircraft.
Engines for stealth aircraft are specifically
built to have a very low IR signature. Another
main aspect that reduces the IR signature of
a stealth aircraft is to place the engines deep
into the fuselage. This is done in stealth
aircraft like the B-2, F-22 and the JSF. The IR
reduction scheme used in F-117 is very much
different from the others. The engines are
placed deep within the aircraft like any
Figure 17VISUAL STEALTH PLANE-HAWK
Figure 16 Thermal infrared image - US Military F117 Stealth
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stealth aircraft and at the outlet; a section of
the fuselage deflects the exhaust to another
direction. This is useful for deflecting the hot
exhaust gases in another direction.
Infrared radiation are emitted by all matter
above absolute zero; hot materials, such as
engine exhaust gases or wing surfaces heated
by friction with the air, emit more infrared
radiation than cooler materials. Heat-seeking
missiles and other weapons zero in on the
infrared glow of hot aircraft parts. Infrared
stealth, therefore, requires that aircraft parts
and emissions, particularly those associated
with engines, be kept as cool as possible.
ACOUSTIC STEALTH
Figure 18 Acoustic Stealth Aircraft
Although sound moves too slowly to be an
effective locating signal for antiaircraft
weapons, for low-altitude flying it is still best
to be inaudible to ground observers. Several
ultra-quiet, low-altitude reconnaissance
aircraft, such as Lockheed's QT-2 and YO-3A,
have been developed since the 1960s.
Aircraft of this type are ultra-light, run on
small internal combustion engines quieted by
silencer-suppressor mufflers, and are driven
by large, often wooden propellers. They make
about as much sound as gliders and have very
low infrared emissions as well because of
their low energy consumption. The U.S. F-117
stealth fighter, which is designed to fly at high
speed at very low altitudes, also incorporates
acoustic-stealth measures, including sound-
absorbent linings inside its engine intake and
exhaust cowlings.
RADAR STEALTH
Radar stealth or invisibility requires that a
craft absorbs incident radar pulses, actively
cancel them by emitting inverse waveforms,
deflect them away from receiving antennas,
or all of the above. Absorption and deflection
treated below are the most important
prerequisites of radar stealth.
AB SORPTION
Metallic surfaces reflect RADAR; therefore,
stealth aircraft parts must either be coated
with RADAR-absorbing materials or made out
of them to begin with. The latter is preferable
because an aircraft whose parts are
intrinsically RADAR-absorbing derives
aerodynamic as well as stealth function from
the