Missiles & its classifications

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:

1. 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.
2. 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.