Use of
modern weapon systems has revolutionized the concept of warfare. The technology
of guided missiles ell compasses the multiple streams of engineering. A number
of factors are responsible for the successful launching of missiles. 'These
involve coordination of a variety of subsystems.
Missiles
are attractive to many nations because they can be used effectively against an
adversary with a formidable air defense system, where an attack with manned
aircraft would be impractical or too costly. In addition, missiles can be used
as a preventive or an instrument of coercion. Missiles also have the advantage
of fewer maintenance, training, and logistic requirements than manned aircraft.
Even limited use of these weapons could be devastating, because missiles can be
armed with chemical, biological, or nuclear warheads.
PEDIGREE
In the
history of missiles began during the World War I1 with the use of V1 and V2
missiles by Germany. Since then there has been a tremendous and rapid global
advancement in this field. It spawned the growth and pushed the frontiers of
many new technologies in the areas of materials science, aeronautics,
communications, radars and computers. Huge amounts of prime resources have been
channelized into this field resulting in the development of sophisticated
missiles.
WHAT IS A MISSILE
Any
object thrown at a target with the aim of hitting it is a missile. Thus, a
stone thrown at a bird is a missile. The bird, by using its power of reasoning
may evade the missile (the stone) by moving either to the Left, right, top or
bottom with respect to the flight path (trajectory) of the missile. Thus, the
missile in this case has been ineffective in its objective of hitting the bird
(the target) . Now, if the stone too is imparted with some intelligence and
quick response to move with respect to the bird, to overcome aiming errors and
the bird's evasive actions and hit it accurately, the stone now becomes a
guided missile
The
incorporation of energy source in a missile to provide the required force for
its movement (propulsion), intelligence to go in the correct direction
(guidance) and effective maneuvering (control) are mainly the technologies of
guided missiles. They help in making a missile specific to a target, that is,
they determine the size, range and state of motion of a missile.
TYPES OF GUIDED MISSILES
Presently,
there are many types of guided missiles. They can be broadly classified on the
basis of their features such as type of target; range; mode of launching;
system adopted for control, propulsion or guidance; aerodynamics; etc. They are
also termed in a broad sense as strategic or tactical, defensive or offensive.
On the basis
of target they could be called
·
Anti-tan/anti-amour,
·
Anti-personnel,
·
Anti-aircraft
/helicopter,
·
Anti-ship/anti-submarine,
·
Anti-satellite,
or
·
Anti-missile
Surface-to-surface-missiles (SSM)
SSMs are
common ground-to-ground ones though these may also be launched from a ship to
another ship. Underwater weapons which are launched from a submarine also come
under this class of missiles
Surface-to-air missiles (SAM)
SAMs are
essential complement of modern air defense systems along with anti-aircraft
guns which are used against hostile aircraft
Air-to-air missiles (AAM)
AAMs are
for airbarne battle among fighter/ bomber aircraft. These are usually mounted
under the wings or fuselage of the aircraft and are fired at enemy airborne
targets by the pilot through the press of a button. In his decision to launch a
missile at a particular moment, the pilot is aided by a computer and radar
network onboard as well as from ground- based data link.
Air-to-surface missiles (ASM)
Air-to-surface
missiles are guided missiles designed to be carried and
launched by aircraft
and helicopters
against ground targets. Generally these targets are land-based, but can also
include targets at sea such as ships.
On the basis
of range,
·
missiles
can be broadly classified as Short-range missiles (50 to 100 km);
·
Medium-range
ballistic missiles (MRBM) (100 to 1500 km);
·
Intermediatelrange
ballistic missiles(1RBM) (5000 km);
·
Intercontinental
or long-range ballistic missiles (1CBM) (12000 km).
On the basis
of launch platform, missiles can be termed as
·
Shoulder
firedltripod launched,
·
Landmobile
(wheeled vehicle or tracked vehicle),
·
Aircraft/helicopter-borne,
·
Space-based
(Star Wars concept).
Based
on guidance, missiles
are broadly classified as
·
Command
guidance,
·
Homing
guidance,
·
Beam
rider guidance, and
·
Inertial
navigation guidance.
Depending
on the aerodynamic control adopted, a missile is called
·
Wing
controlled.
·
Tail
controlled, or
·
Canard
controlled.
One more
classification is based on the type of trajectory and a missile is
called a ballistic missile or a cruise
missile. It covers a major part of its range outside the atmosphere where
the only external force acting on the missile is the gravitational force of
Earth
Cruise missile is the one which travels its
entire range in the atmosphere at a nearly constant height and speed. However,
a missile could have a combination of the two also where a missile could cover
part of the flight in ballistic mode and later a terminal portion in cruise
mode.
another
classification is based on the propulsion system provided in the
missile. In rocket propulsion, we have:
·
Solid
propulsion,
·
Liquid
propulsion, and
·
Hybrid
propulsion.
·
In
air-breathing propulsion, we have: Gas turbine engine jet or propeller Ramjets
or ram-rockets
MISSILE SYSTEM
CONTROL SECTION OF
MISSLES
·
The control
actuator maneuvers
the missile during flight and provides internal electrical power. It consists
of four fins, four thrust vector control and a thermal battery.
·
Thermal battery provides internal electrical
power for the missile during flight. It is sealed in the body of missile.
Missile Propulsion
Propulsion
is the means of providing power to accelerate the missile body and sustain, if
necessary, to reach the required target. The basis for the working of missile
propulsion systems are the well-known Newton's laws of motion.
The
propulsion of a missile is achieved with the help of a rocket engine. It
produces thrust by ejecting very hot gaseous matter, called propellant. The hot
gases are produced in the combustion chamber of the rocket engine by chemical
reactions. The propellant is exhausted through a nozzle at a high speed. This
exhaust causes the rocket to move in the opposite direction (Newton's third
law).
As per
the second law also called the law of momentum, the change in momentum of the
missile body including the rocket motor casing, the nozzle and other systems
due to the ejected matter creates a force leading to the propulsive action on
the missile body.
The missiles,
propelled into air, would continue to move if there were no other forces acting
on it. However, resistance to its forward movement due to air (commonly called
the aerodynamic drag) and the force of gravity acting downwards towards the center
of the earth are to be taken into account. By using Newton's first law, also
called the law of inertia, compensative forces are imparted to the missile to
overcome these negative forces.
PARTS OF PROPULSION
SYSTEM
All
types of rocket propulsion engines contain a chamber, a nozzle, and an igniter.There
are certain propellant combinations which do not need an igniter and they are
called hypergolic. These propellants burn spontaneously when they come in
contact in a certain proportion.
TYPES OF PROPULSION SYSTEMS
Missile
propulsion will be mainly of the following two types:
Air
breathing, and
Non-air
breathing.
the air
breathing rocket engines use the surrounding medium of air for the support of
their oxidizer. Thus. They can be used only within the Earth's atmosphere whereas
in the case of non-air breathing engines the rocket engine itself' carries its
fuel and oxidizer on board and hence can be used in space above the Earth's
atmosphere also and is thus independent of the air medium.
WARHEADS AND
TARGETS
Ballistic
and cruise missiles can be armed with conventional or non conventional warheads.
Conventional warheads are filled
with a chemical explosive, such as TNT, and rely on the detonation of the
explosive and the resulting metal casing fragmentation as kill mechanisms.
Non conventional warheads include weapons of mass
destruction (nuclear, biological, and chemical weapons), as well as nonlethal
warheads, a relatively new class of warhead designed to disable equipment
rather than harm personnel. Conventional, biological, and chemical weapons can
be packaged in unitary (single) warheads and in sub munitions (multiple small
bombs that are released at altitude to disperse over a wide area).
Purpose
The only
purpose of the missile is to deliver a warhead to the target. The function of
the warhead is to damage the target. The warhead is located in the missile. In
most of the tactical missiles, the warhead is based on conventional chemical
explosives called high explosive. They
are meant for large-scale destruction of areas. The smaller ones carry nuclear
material equivalent of 10-15,000 tons of TNT (a high explosive) while the larger
ones are in terms of tens of million tons of TNT. Most of the advanced versions
of ballistic missiles carry multiple nuclear bombs in each missile and these
are called MIRVs (Multiple Independently-targetEd Re-entry Vehicles.
TYPES OF WARHEAD
Shaped charge warhead (anti-tank or anti-Armour) and kinetic energy rod penetrator (against armour), Fragment type (anti-aircraft, anti-personnel), Blast-cum-earth shock (for damaging built up structures), and
Incendiary type (against fuel and ammunition dumps, etc.)
COMPONENTS OF WARHEAD
PAYLOAD.—The payload is the element of
the missile that does what a particular missile is launched to do. The payload
is usually considered the explosive charge, and is carried in the warhead of
the missile. High-explosive warheads used in air-to-air guided missiles contain
a rather small explosive charge
FUZING.—The fuzzing and firing system is
normally located in or next to the missile's warhead section. It includes those
devices and arrangements that cause the missile's payload to function in proper
relation to the target. The system consists of a fuze, a safety and arming
(S&A) device, a target-detecting device (TDD), or a combination of these
devices
Guidance and
Control Section
The
guidance section is the brain of the missile. It directs its maneuvers and
causes the maneuvers to be executed by the control section. The guidance section is the brain
of the missile. It directs its maneuvers and causes the maneuvers to be
executed by the control section.
Inertial
guidance systems make possible the precision delivery of long-range ballistic
missiles for which the target is, for example, a known set of Earth
coordinates. However, these systems are not suitable for guiding missiles
against unpredictable targets like maneuvering aircraft or anti-ship cruise
missiles or against a target whose location is not known precisely when the
missile is launched .
As mentioned
earlier guidance missiles are broadly classified as
·
Command
guidance,
·
Homing
guidance,
·
Beam
rider guidance, and
·
Inertial
navigation guidance
A homing
guidance system is one in which the missile seeks out the target, guided by
some physical indication from the target itself. Radar reflections or thermal
characteristics of targets are possible physical influences on which homing
systems are based. Homing systems are classified as active, semi active, and
passive.the figure below explains it all.
ADVANTAGES OF
MISSILES
·
Missile
combat employment is completely autonomous
·
Missile
flexible flight trajectory
·
High
supersonic speed at a whole trajectory
·
High
effectiveness in case of strong electronic and fire counter measure
·
High
level of mobility
·
Minimal
crew
DISADVANTAGES
·
Missile
can be destroyed while during the flight
·
Missile
have to rely on ground radar for navigation
·
Nuclear
missile make atmosphere radioactive.
REFERENCES:
- T V Karthikeyan A K Kapoor . (). Guided Missiles . Available:
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB0QFjAA&url=http%3A%2F%2Fdrdo.res.in%3A8080%2Falpha%2Fdrdo%2Fdata%2FGuided%2520Missiles.pdf&ei=Mlw0VdS3Oo2PaIXJgUg&usg=AFQjCNFza30J.
Last accessed 20th april2015.
- Neil F. Palumbo. (2010). Guest Editor’s Introduction: Homing Missile Guidance and Control. In: N. F. PALUMBO JOHNS HOPKINS APL TECHNICAL DIGEST,. england: palumbo guest. P1-32.
