MISSILE GUIDANCE SYSTEMS

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BY

KRUNAL SATHAVARA

DEPT: ELECT & COMM

YIT-JAIPUR

AIM

To discuss about different types of missile guidance system

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SEQUENCE

• Missile

• Guided Missile

• Missile components

• Working of guidance system

• Types of guidance system

• Q & A

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MISSILE

• Latin word ‘Mittere’ means “To send”

• A self propelled projectile used as a weapon

• Typically propelled by rocket or jet engines

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GUIDED MISSILESSelf-propelled aerial projectiles containing

explosivesGuided either by remote control or internal

mechanisms  5 categories – surface to surface, surface to

air, air to surface, air to ground & air to airBased on area of operation – tactical,

support & strategic Based on flight characteristics –

aerodynamic & ballistic

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MISSILE COMPONENTSGuidance, control, armament & propulsion

sectionsGuidance – brain of the missile, directs its

maneuversControl – executes the maneuversArmament – carries the explosive charge

and the fusing & firing sectionsPropulsion – propels the missileGuidance orders are initiated by electronic

sensing systems

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WORKING OF A GUIDANCE SYSTEM Consists of 2 separate systems – altitude

control & flight path control Altitude control – maintains the missile in

the desired altitude by controlling it in pitch, roll & yaw

Flight path control – guides the missile to its designated target; done by determining flight path errors & generating orders for error correction

Orders then sent to missile control sub-system which exercises control to maintain flight path

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Categories of guidance systemsGuidance systems are divided into

different categories according to what type of target they are designed for - either fixed targets or moving targets.

The weapons can be divided into two broad categories,

1.Go-Onto-Target(GOT) 2. Go-Onto-Location-in-

Space (GOLIS)

GOT/GOLIS• A GOT missile can target either a moving or fixed target.• A GOLIS weapon is limited to a stationary or near-

stationary target.• The trajectory that a missile takes while attacking a

moving target is dependent upon the movement of the target. Also, a moving target can be an immediate threat to the sender of the missile.

• The target needs to be eliminated in a timely fashion in order to preserve the integrity of the sender. In GOLIS systems the problem is simpler because the target is not moving.

GOT systemsIn every GOT system there are three subsystems:

•Target tracker

• Missile tracker

• Guidance computer

The way these three subsystems are distributed between the missile and the launcher result in two different categories:

• Remote Control Guidance: The guidance computer is on the launcher. The target tracker is also placed on the launching platform.

• Homing Guidance: The guidance computers are in the missile and in the target tracker.

TYPES OF GUIDANCE SYSTEMSInertial guidanceCommand guidanceBeam-rider guidanceHoming guidance – active, semi-active, passiveLASER GUIDANCEWIRE GUIDED MISSILEINFRARED GUIDED MISSILE

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INERTIAL GUIDANCEMissiles controlled by self-contained

accelerometersAccelerometers measure vertical, lateral &

longitudinal accelerations During flight outside forces cause changes in

speed commands which are transmitted to missile by-radio uplink transmitter or by varying characteristics of missile guidance beam

This data is taken by onboard computers & converted to precise position of missile

Lately inertial systems have been combined with GPS – used in ICBMs

Suffer from drift – chances of missing target are higher

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COMMAND GUIDANCETracking and guidance are ground basedUses two radars, one to track the target and the other to

track the missileThe bearing and elevation of the radar trackers is

monitored by a computer which directs the control system to alter the missile trajectory until it reaches the target

This system uses a human operator to observe the trajectory of the missile, and direct its control system by remote control radio link

This system is broadly similar to radio command, but is less susceptible to electronic counter measures. The command signals are passed along a wire (or wires) dispensed from the missile after launch

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Three accelerometers, mounted on a platform space-stabilized by gyros, measure accelerations alongthree mutually perpendicular axes; these accelerations are then integrated twice, the first integration giving velocity and the second giving position. The system then directs the control system to preserve the pre-programmed trajectory

COMMAND GUIDANCE

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Missile Target

CommandTransmitter

Computer MissileTracker #2

TargetTracker #1

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BEAM-RIDER GUIDANCEMissile seeks out centre of controlled directional

energy beam – radar beamBeam provides information regarding position of

missile to guidance systemSystem interprets this information & generates its

own correction signals to keep missile at centre of beam

Fire control radar points beam at target and the missile "rides" the beam to the target

As beam spreads out – more difficult for missile to remain at centre of beam

As range increases, accuracy of beam-rider decreasesEffective only against short & medium range targets

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NarrowGuidance Beam

Tracking Beam

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HOMING GUIDANCEControls path of missile by means of a

device in missile that detects and reacts to some signal from target

Signal may be light, radio, sound, heat waves or magnetic field

System tracks energy reflected off targetMissile derives guidance error signals

based on its position relative to targetMost accurate type of guidance 3 types – active , semi-active & passive

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ACTIVE HOMINGTarget illuminated by component

within missile – radar transmitter

Radar signals transmitted by missile, reflected off the target & received back by receiver

This gives information – target’s distance & speed

Missile sends electronic commands to control section

Control section Controls angle of attack

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SEMI-ACTIVE HOMINGTarget illuminated by

external source – transmitter carried in launching aircraft

Receiver in missile receives reflected signals , computes information & sends electronic commands to control section

Hawk anti-aircraft systems

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PASSIVE HOMINGDirecting intelligence is

received from target itself

This may be a source of infrared rays (such as the hot exhaust of jet aircraft) or radar signals (such as those transmitted by ground radar installations)

Missile receiver receives signals generated by the target and then the missile control section functions in the same manner

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LASER GUIDANCE

Laser guidance is a technique of guiding a missile or other projectile or vehicle to a target by means of a laser beam.

WIRE-GUIDED MISSILE A wire-guided

missile is a missile guided by signals sent to it via thin wires reeled out during flight.

INFRARED HOMING

Infra-red homing refers to a guidance system which uses the infra-red light emissions of a target to track it. Missiles which use infra-red seeking are often referred to as "heat-seekers". Infra-red is just below the visible spectrum of light and is radiated mostly by hot bodies.

MAJOR GUIDANCE TECHNIQUE Long Range Navigation (LORAN)Global Positioning System (GPS) Laser designation Optical guidance

Long Range Navigation (LORAN)

This was the predecessor of GPS and was (and to an extent still is) used primarily in commercial sea transportation. The system works by triangulating the ship's position based on directional reference to known transmitters.

Global Positioning System (GPS) This system of satellites provides

extremely accurate position information. The receiver's position is triangulated using satellites in known orbits. Commercial receivers are limited in how accurately they may provide position data, as well as the maximum velocity at which they may operate. This is to prevent their use in manufacturing weapons.

Optical guidance Guided missiles use stored images of

the terrain they are to fly over and an external sensor to track their current position. This guidance system was extremely expensive and not suitable for use in small payload operations. These were used on cruise missiles before the advent of GPS, which is both cheaper and more accurate. Devices that implement optical guidance incur high costs because of the high on-board processing requirements needed to check the current location against the course data

FIRE & FORGET Fire and forget is the military term for a

type of missile which does not require further guidance after launch such as illumination of the target, and can hit its target without the launcher being in line of sight of the target.

CONCLUSIONGuidance System is a complex system which

involves several systems working in tandemDevelopment of missile involve huge

expenditures – essential that guidance system is properly designed for accurate interception of targets

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REFERENCES 1) GPS Theory and Practice. B. Hofmann - Wellenhof, H.

Lichtenegger, and J. Collins. Springer-Verlag Wien. NewYork. 1997. Pg [1-17, 76].

2) ttp://www.navcen.uscg.gov/pubs/gps/Icd200/icd200cw1234.pdf 3) E.D. Kaplan, Understanding GPS:Principles and Applications. 4)http://www.aero.org/news/current/gpsorbit. html. 5) http://www.trimble.com/gps/ 6)http://wikipedia.com

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