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Advantages and Limitations of Supersonic Planes 2015
SEMINAR REPORT
ADVANTAGES AND LIMITATIONS OF SUPERSONIC
AIRCRAFTS
Submitted by:
Sana Syed(153106004)
M.Tech (Design)
153106004 Page 1
Advantages and Limitations of Supersonic Planes 2015
Mech. Engg. Dept.
IIT BOMBAY
ADVANTAGES AND
DISADVANTAGES OF
SUPERSONIC AIRCRAFTS
ABSTRACT:
A detailed study of the operational and
ergonomic requirements of a supersonic
aircraft for various applications, either
military or commercial passenger flights
is essential to understand the nuances of
supersonic flight. Further, the control of
various factors that affect supersonic
flights and its mitigation techniques is
essential to reduce sonic boom, achieve
low supersonic wave drag, and offer
high subsonic performance. This report
discusses the various advantages and
limitations of a supersonic aircraft.
Further, it introduces a new innovative
concept of a supersonic bi-directional
(SBiDir) flying wing (FW) concept,
which has the potential to overcome the
major limitations of supersonic aircraft,
i.e. sonic boom and efficiency.
According to the case study for the
SiBiDir FW, it is possible to reduce or
completely eliminate sonic boom and
achieve low supersonic wave drag.
INTRODUCTION :
Supersonic flights have been a popular
choice for military applications since
common enemy surveillance radars are
unable or find it quite difficult to detect
objects flying at supersonic speeds [1].
In addition, the commercial sector has
been interested in these flights due to its
great potential to reduce the inter-
continental travel time [2].
However, various disadvantages are
associated with Supersonic flight, the
major factors of these being the sonic
boom, supersonic wave drag and low
efficiency during supersonic flight. The
Concorde, which was the only
153106004 Page 2
Advantages and Limitations of Supersonic Planes 2015
commercialized civil Supersonic
aircraft, was discontinued from service
in 2003 due to high operating costs and
infeasibility constraints. Since that time,
various efforts have been made to make
supersonic commercial flights
economically and environmentally
feasible for passenger flights. The
introduction of the concept of SBiDir is
one such effort in this direction, which
has the potential to overcome and
possibly eliminate the drawbacks of a
conventional supersonic flight.
SUPERSONIC FLIGHT : A BASIC
INTRODUCTION
A bullet fired from a gun travels at supersonic
speeds. This picture shows a bullet and the air
flowing around it. The bullet is traveling at 1.5
times the speed of sound.
Credits: Andrew Davidhazy/Rochester
Institute of Technology
An F/A-18 Hornet aircraft speeds up to
supersonic speed. The Hornet is flying through
an unusual cloud. This kind of cloud sometimes
forms as aircraft break the sound barrier.
Credits: Ensign John Gay, USS
Constellation, U.S. Navy
The aerodynamics of supersonic flight
is called compressible flow because
of the compression
(physics) associated with the shock
wavesor "sonic boom" created by any
object travelling faster than sound.
Supersonic aircraft are the
aircraft that travels with the
speed more than mach 1. Mach
1 is the speed of sound. The
aircraft travelling with the speed
very large than the speed of
sound is known as hypersonic
aircraft (above mach 5). In the
current global economy, where
individual companies as well as
business partnerships, transcend
national boundaries, and
mandate collaborations across
the globe, the required time for
travel has become a valuable
resource, prompting interest in
high speed transportation.
Compared to today’s typical
transport aircraft mission
profiles with cruise flight speeds
of Mach M=0.8 and design
ranges of 4000 nautical miles
(nm), up to a 55% time savings
can be achieved by increasing
the cruise speed to M=1.8 [1].
However, a successful
153106004 Page 3
Advantages and Limitations of Supersonic Planes 2015
supersonic aircraft design has to
overcome numerous challenges
to meet opposing requirements.
1. History:
60 years ago Chuck
Yeager, captain of United States
air force, broke the sound barrier
while flying his bell X-1 aircraft.
That was the beginning of the
supersonic flight era. Since then,
numerous advances have been
made, from the introduction and
design improvements of military
supersonic jets to the innovation
aimed at passenger supersonic
flight. Concorde was the first
supersonic aircraft used for
passenger travel [2].
Fig.1 The Concord Jet
Concorde ceased to fly from
2003 because of following
reasons.
1. Sonic boom, a very loud
shockwave that sounds a lot
like an explosion when
aircraft breaks the sound
barrier.
2. Fall in number of passengers
travel because of high cost.
3. Large amount of fuel used to
propel the aircraft.
4. High maintenance cost.
5. Air pollution (exhaust
emission).
2. Functional requirements:
1. The aerodynamics of
supersonic flight are
dramatically different
from those of subsonic
flight (i.e., flight at
speeds slower than
that of sound). In
particular,
aerodynamic drag
rises sharply as the
aircraft passes the
transonic regime,
requiring much greater
engine power and
more streamlined
airframes.
2. To keep drag low, wing
span must be limited,
which also reduces the
aerodynamic efficiency
when flying slowly.
153106004 Page 4
Advantages and Limitations of Supersonic Planes 2015
Since a supersonic
aircraft must take off
and land at a relatively
slow speed, its
aerodynamic design
must be a compromise
between the
requirements for both
ends of the speed
range.
3. The structural sizing needs
to balance minimum weight
with adequate safety margin
to support high loads at high
speed.
4. Engine must be
compact and should
consume less fuel.
5. The need for efficient
fuels is tied to the
need to reduce the
fuel contribution to the
weight of the aircraft,
both in terms of fuel
weight and the weight
of the rest of the
aircraft using this fuel
for propulsion,
because the weight is
a major contributor to
the sonic boom and
the drag. The fuel and
propulsion system also
affects the emission
levels of NOx at high
altitudes as well as the
cruise efficiency,
leading to changes in
aircraft
configuration[2].
6. Environmental
constraints are
becoming more and
more stringent. The
high altitude emission
should be as low as
possible. Again the
sound produce by
supersonic aircraft
while taking and
landing should be
within the limit, so that
it is not harmful to
human beings. The
sound produce by
sonic boom should also
be less[3].
7. The heat generated by
friction as the air flows
over the aircraft is
very high therefore the
material should have
the capacity to
withstand the high
temperature.
8. The ticket price should
be low.
3. Advantages of supersonic
aircraft:
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Advantages and Limitations of Supersonic Planes 2015
1. The value of time has been
growing, resulting in a
premium being placed on the
ability to get to the
destination faster.
a. Supersonic aircraft
reduces travel time for
business leading to
increased productivity. It
also shortens travel time
for leisure.
b. It has the ability to
provide rapid response in
disaster situations and
faster delivery of time-
critical goods[2].
2. Supersonic aircraft quickly
delivers the time-critical
cargo which could save
lives, as in the case of organ
transplants[2].
3. It is also useful for defence
in military.
a. Supersonic speed with
manoeuvrability
provides amazing dog
fighting ability to fighter
aircraft.
b. Supersonic aircraft can
quickly and safely attack
enemy targets.
c. Supersonic speed allows
fighter jets to intercept
enemy airplanes.
Supersonic interceptors
can quickly reach their
target if the target is
slow, in a matter of
minutes if they are close
by. (The hijacked
airplanes of 9/11 should
have been intercepted.)
4. Disadvantages:
1. Sonic boom:
A major problem, which all
supersonic aircrafts face, is
sonic boom. The term sonic
boom is used to refer to the
shocks caused by the
supersonic flight of an
aircraft. Sonic booms
generate enormous amounts
of sound energy, sounding
much like an explosion[4].
Sonic boom is the reason
why supersonic flights are
not allowed over populated
areas.
Fig.2 Propagation of sound waves produced by
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Advantages and Limitations of Supersonic Planes 2015
aircrafts at different speeds
When aircraft travels at the
speed less than sound, the
sound it creates will
propagate in all the
directions ahead of the plane
as shown in fig.2 when it
travels with mach 1 the wave
propagation is also shown in
fig.2. Now when it travels
with the speed greater than
sound, it travels faster than
the sound wave it creates and
it breaks the sound barrier
and it forms the cone like
structure behind the aircraft
as shown in fig.2. The visual
impact of the sonic boom is
shown in fig.3. It is because
of the speed with which
aircraft is travelling causing
the pressure to drop
significantly which in turn
reduces the temperature
causing condensation in the
air.
Fig.3 Sonic Boom
2. Emission:
Atmospheric effects of
supersonic aircraft depend
on the number of aircraft, the
altitude of operation, the
exhaust emissions, and the
background chlorine and
aerosol loading. Emissions
from the engines are
functions of engine
technology and the operation
of the aircraft on which the
engines are installed.
Primary engine exhaust
products are C02 and H20,
which are directly related to
the burned fuel, with minor
variations due to the precise
carbon-hydrogen ratio of the
fuel. Secondary products
include NOx (=NO + N02),
CO, unburned and partially
153106004 Page 7
Advantages and Limitations of Supersonic Planes 2015
burnt fuel hydrocarbons
(HC), soot
particulates/smoke, and SOx.
NOx is a consequence of the
high temperature in the
engine combustor; the
incomplete combustion
products (CO, HC, and
soot/smoke) are functions of
the engine design and
operation and may vary
widely between engines.
SOx is directly related to
fuel composition.
Rough estimates of the
impact of future supersonic
operations (assuming 500
aircraft flying at Mach 2.4 in
the stratosphere and emitting
15 grams of nitrogen oxides
per kilogram of fuel)
indicate an increase of the
North Atlantic flight corridor
concentrations of NOx up to
about 250%, water vapour
up to about 40%, S Ox up to
about 40% , H2S04 up to
about 200%, soot up to about
1 00%, and CO up to about
20%[5].
Since supersonic aircraft
engines may emit significant
amounts of NOx, the fear is
that large fleets of
supersonic aircraft flying at
stratospheric levels, where
maximum ozone
concentrations exist, might
seriously deplete the
stratospheric ozone layer,
leading to increased
ultraviolet radiation flux on
the biosphere. Also, climate
sensitivity studies have
shown that ozone changes in
the upper troposphere and
lower stratosphere will have
greater radiative effects on
changing surface and lower
tropospheric temperatures
than would ozone changes at
other levels[5].
3. Climatic Effects:
Supersonic aircraft
emissions include
constituents with the
potential to alter the local
and global climate. Species
important in this respect
include water vapor, NOx
(through its impact on 03),
sulfur, soot, cloud
condensation nuclei, and
C02 .
Increases of C02 and water
vapor, and alterations of
ozone and cirrus clouds have
the potential to alter in situ
153106004 Page 8
Advantages and Limitations of Supersonic Planes 2015
and global climate by
changing the infrared
(greenhouse) opacity of the
atmosphere and solar
forcing[5].
Sulfuric acid:
Sulfuric acid, which results
from SOx emissions, may
cool the climate through
producing aerosols that give
increased scattering of
incoming solar radiation.
Effect of ozone depletion:
The impact of ozone changes
on the radiation balance of
the surface troposphere
system depends on the
vertical distribution of the
ozone changes. Reduction in
tropospheric and lower
stratospheric ozone tends to
cool the climate, by reducing
the atmospheric greenhouse
effect. Reduction in middle
and upper stratospheric
ozone tends to warm the
climate, by allowing more
shortwave radiation to reach
the surface.
Water Vapour:
Water vapour is the primary
atmospheric greenhouse gas.
Increases in water vapor
associated with aircraft
emissions have the potential
to warm the climate at low
tropospheric levels, while
cooling at altitudes of
release, due to greater
thermal emission. The
effects are largest when
water vapor perturbations
occur near the tropopause as
is likely to be the case[5].
4. Some supersonic fighter jets
use afterburners to gain
speed, which can reveal
there position on enemy
radar due to heat signatures.
5. The heat generated by
friction as the air flows
over the aircraft limits
the speed of aircraft to
around mach 2.2. It
implies that new
material should be
developed such that it
should withstand the
heat[6].
6. High Wave Drag, high fuel
consumption/cost[7].
7. Low Subsonic performance,
long takeoff/landing
distance[7].
5. Mitigation techniques:
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Advantages and Limitations of Supersonic Planes 2015
1. Sonic boom:
The following are some
factors affecting sonic boom
strength[6]:
a. Aircraft weight, shape
and length:
The bigger the aircraft is,
the more air molecules
push aside. Thus a big
aircraft will produce a
stronger sonic boom.
b. Aircraft altitude:
The altitude of the
aircraft and the strength
of the sonic boom are
reciprocal. As the
altitude increases, the
strength of the sonic
boom decreases.
c. Aircraft maneuvers:
Maneuvers such as
pushovers, S-turns and
accelerating can amplify
the intensity of the shock
wave. Hills, valleys and
other topographic
features can create
multiple reflections of
shock waves thus
affecting intensity.
d. Location in sonic boom
carpet [8]:
Special topographic
features in each area
such as mountains, hills
and valleys can create
multiple reflections of
shock waves thus
affecting intensity.
e. Attitude: orientation of
the aircraft’s axes
relative to its direction of
motion[9].
Quiet Spike project [10] showed
that by extending the length of
the nose, and by changing the
position of the wings, sonic
boom would be reduce to about
55 dB[11]. But the capacity of
Quiet Supersonic Jet suggested
by Gulfstream is about 8-11
passengers. Extended and
shaped nose of the aircraft will
propagate the shock waves. The
nose will break up the initial
shock into a series of very weak
shocks.
2. Emission:
Hydrogen fuel can be
used to reduce the
emission and it is also
very light. If more
efficient propulsion
systems are created
then smaller amounts
of hydrogen fuel could
be used for the same
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Advantages and Limitations of Supersonic Planes 2015
flight distance.
Hydrogen fuels do not
eliminate pollution, but
their use significantly
reduces its level.
Development of new
synthetic fuels that are
highly efficient,
produce less
pollutants, and are
inexpensive appears to
be very promising[2].
3. The lift/drag ratio of a
supersonic jet is much
lower than that of a
subsonic aircraft.
Reducing the drag
could in part be
accomplished by
reducing the weight of
the aircraft. The new
light weight,
innovative composite
materials, in particular
those that can
withstand high
temperatures could be
a part of solution. It is
one of the ways to
reduce fuel needed per
passenger-mile[2].
References:
[1] Deremaux, Y., 2009, “Why a
Small Size Supersonic Transport
Aircraft? Objectives and Trade-
Offs,” HISAC 2009 Conference,
Paris.
[2] Making the Small Supersonic
Airliner
a Reality: Obstacles and Solutions.
Gail M. Krutov, Bard High School,
New York, NY.
NASA Fundamental Aeronautics
Student Competition 2008-2009
Academic Year.
[3] Joel brezillon, Gerald carrier and
Martin laban, “Multidisciplinary
optimization of supersonic aircraft
including low-boom considerations,”
journal of mechanical design, ASME,
October 2011,vol.133/105001.
[4] Wikipedia, Sonic Boom,
Available at:
http://en.wikipedia.org/wiki/Sonic_
boom.
[5] Scientific Assessment of ozone
depletion:1994. World
Metrological Organisation Global
Ozone Research And Monitoring
Project-Report No:37( US
department of commence/National
Oceanic And Atmosphereic
Administration/NOAA Research).
Chapter 11, book by A.Wahner and
M.A.Geller.
153106004 Page 11
Advantages and Limitations of Supersonic Planes 2015
[6] NASA Fundamental
Aeronautics Student Competition,
Supersonic flight project by
Emmanuel Vasileios and Dimitrios
Tsounis, high school of Kareas
(Greece).
[7]Toward Zero Sonic-Boom and
High Efficiency Supersonic Flight: A
Novel Concept of
Supersonic Bi-Directional Flying
Wing. Gecheng Zha, Hongsik Im ,
Daniel Espinal,
University of Miami, Dept. of
Mechanical and Aerospace
Engineering,AIAA Paper 2010-1013.
[8]Martin K. Chan, “Supersonic
Aircraft Optimization for
Minimizing Drag and Sonic
Boom”, Available at:
http://aero.stanford.edu/Reports/Ma
rtinFinalThesis.pdf, 2003
[9] David Gallo, AP Physics project
on propagation of sonic boom,
Available at:
http://library.thinkquest.org/
12228/page6.html
[10] NASA, Supersonic Jousting,
Available at:
http://www.nasa.gov/vision/earth/
improvingflight/
supersonic_jousting.html Accessed
10 April 2004.
[11] Preston A. Henne, Sr VP
Programs, Engineering, & Test
Gulfstream Aerospace Corp
Available at:
http://www.aiaa.org/events/aners/Pr
esentations/ANERS-Henne.pdf,
Accessed May 2005.
ake supersonic co, Supersonic flight is
one of the four speeds of flight.
Objects moving at supersonic speeds
are going faster than the speed of
sound. Supersonic includes speeds up
to five times faster than the speed of
sound. When the aircrafts exceed the
speed of sound, the pressure wave’s
mix and form shock waves that travel
forward from where they were
153106004 Page 12
Advantages and Limitations of Supersonic Planes 2015
released. As the plane flies at
supersonic speed, it continuously
generates shock waves, dropping
sonic boom along the flight path. The
sonic boom is swept backwards as it
travels way from the plane. This
boom later hits the ground in front of
it. The aerodynamics of supersonic
flight is called compressible
flow because of the compression
associated with the shock wavesor
"sonic boom" created by any object
travelling faster than sound.
ADVANTAGES :
- With the use of delta-wing design, it
can attain a high angle of attack at low
speeds, which generates a vortex on
the upper surface which greatly
increases lift and gives a lower
landing speed.
-Supersonic speed with
maneuverability provides amazing
dog fighting ability to fighter aircraft.
- The major advantage of a modern
supersonic commercial aircraft over
the commercial subsonic aircraft is
more passengers carried on overseas
flights per day per aircraft
- With the use of a variable-geometry
wing, commonly known as the
"swing-wing," which spreads wide for
low-speed flight and then sweeps
sharply, supersonic aircraft able to
take off and land at a relatively slow
speed.
- Most supersonic designs use
aluminum alloys such as Duralumin,
which are cheap and easy to work.
DISADVANTAGES :
- Expensive flights (passenger use)
- Supersonic flights cause sonic boom
and noise pollution.
-Some supersonic fighter jets use
afterburners to gain speed, which can
reveal their position on enemy radar
153106004 Page 13
Advantages and Limitations of Supersonic Planes 2015
due to heat signatures
- Supersonic flights uses aluminum
alloys which loses their strength
quickly at high temperatures.
FUNCTIONAL REQUIREMENT :
1) Supersonic airfoils : -
A supersonic airfoil is a cross-section
geometry designed to
generate lift efficiently at supersonic
speeds. The need for such a design
arises when an aircraft is required to
operate consistently in the supersonic
flight regime. Supersonic airfoils
generally have a thin section formed
of either angled planes or opposed
arcs, with very sharp leading and
trailing edges. The sharp edges
prevent the formation of a detached
bow shock in front of the airfoil as it
moves through the air.This shape is in
contrast to subsonic airfoils, which
often have rounded leading edges to
reduce flow separation over a wide
range of angle of attack. A rounded
edge would behave as a blunt body in
supersonic flight and thus would form
a bow shock, which greatly
increases wave drag. The airfoils'
thickness, camber, and angle of attack
are varied to achieve a design that will
cause a slight deviation in the
direction of the surrounding airflow.
2) Propelling Nozzle :
Propelling nozzles accelerate the
available gas to subsonic, transonic,
or supersonic velocities depending on
the power setting of the engine, their
internal shape and the pressures at
entry to, and exit from, the nozzle.
The internal shape may be convergent
or convergent-divergent (C-D).C-D
nozzles can accelerate the jet to
supersonic velocities within the
divergent section, whereas a
convergent nozzle cannot accelerate
the jet beyond sonic speed. Propelling
nozzles may have fixed geometry, or
they may have variable geometry to
153106004 Page 14
Advantages and Limitations of Supersonic Planes 2015
give different exit areas to control the
operation of the engine when
equipped with an afterburner or a
reheat system. When afterburning
engines are equipped with a C-D
nozzle the throat area is variable.
Nozzles for supersonic flight speeds,
at which high nozzle pressure ratios
are generated,also have variable area
divergent sections
3) Scramjet :
-A scramjet (supersonic combusting r
amjet) is a variant of a ramjet air
breathing jet engine in which
combustion takes place in
supersonic airflow.
- As in ramjets, a scramjet relies on
high vehicle speed to forcefully
compress the incoming air before
combustion (hence ramjet), but a
ramjet decelerates the air
to subsonic velocities before
combustion, while airflow in a
scramjet is supersonic throughout the
entire engine. This allows the scramjet
to operate efficiently at extremely
high speeds: theoretical projections
place the top speed of a scramjet
between Mach 12 (8,400 mph;
14,000 km/h) and Mach 24
(16,000 mph; 25,000 km/h).
MITIGATION TECHNIQUES:
1)JET NOISE REDUCTION :
Jet aircraft noise is a combined effect
of aircraft noise and the jet engine.
And this can be reduced by
Controlling The Source i.e. Reduce
exhaust velocity and Enhance jet
mixing (like chevrons). And one of
the other possible ways to reduce jet
noise and aircraft noise is to make use
of bypass turbofan engines instead of
turbojet engines as the noise created
by turbofan engines is lesser than that
generated by turbojet engines.
2)SONIC BOOM REDUCTION:
When an aircraft passes through the
air it creates a series of pressure
153106004 Page 15
Advantages and Limitations of Supersonic Planes 2015
waves in front of it and behind it,
similar to the bow and stern
waves created by a boat. These waves
travel at the speed of sound, and as
the speed of the object increases, the
waves are forced together, or
compressed, because they cannot get
out of the way of each other.
Eventually they merge into a single
shock wave, which travels at the
speed of sound.For sonic-boom
mitigation can be achieved by
increasing the wing dihedral angle—
the angle between the left wing and
right wing—on the ground sonic-
boom noise
3)SHOCK WAVE MITIGATION:
To modify the shock structure and to
move the shock wave upstream, the
flow perturbations have to move
upstream beyond the original shock
front. Shock wave appears in the form
of a steep pressure gradient. It
introduces a discontinuity in the flow
properties. plasma spike serves the
same purpose, which encounters the
flow in the region upstream of the
location of the original shock front20.
The induced flow perturbations from
the plasma spike coalesce with the
flow perturbations from the object
into a new shock front, which replaces
the original one located behind it.
4) REDUCTION IN DRAG:
drag reductions allow lower fuel
requirements and can lead to reduced
operating costs and reduced sonic
boom and noise effects. The drag on
supersonic vehicles can be classified
into three different categories: 1) skin-
friction drag, 2) drag caused by lift,
and 3) zero-lift bluntness (thickness-
wave) drag. Linearised supersonic
theory indicates that for an airfoil of a
given thickness the shape that gives
minimum zero-lift bluntness drag is
the sharp diamond airfoil. However,
153106004 Page 16
Advantages and Limitations of Supersonic Planes 2015
very sharp leading edges are not
practical. During takeoff, landing,
climb and maneuvering light, blunted
leading edges are desirable so that
flow separation is prevented .this is
required because at higher speed there
are chances that due to higher heating
the sharp edge would melt.
REFERANCES :
1) Bill Gonston, "The
Development of Jet and Turbine
Aero Engines", 2006, 4th
edition, pp. 160.
2)
http://www.brown.edu/research/p
rojects/scientific-computing/sites/
brown.edu.research.projects.scien
tific-computing/files/uploads/
Demonstrating%20Shock
%20Mitigation%20and%20Drag
%20Reduced%20Pulsed
%20Energy%20Lines.pdf
3) http://eeweb.poly.edu/faculty/
kuo/publications/Mitigation-
review.pdf
4) http://web.stanford.edu/group/
frg/publications/recent/sonic-
boom3.pdf
5) http://
www.langleyflyingschool.com/
Pages/
CPGS+4+Aerodynamics+and+T
heory+of+Flight+Part+1.html
6) http://
digitalcommons.calpoly.edu/cgi/
viewcontent.cgi?
article=1081&context=aero_fac
153106004 Page 17