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guided missile
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MISSILE GUIDANCE SYSTEMS
•1
BY
KRUNAL SATHAVARA
DEPT: ELECT & COMM
YIT-JAIPUR
AIM
To discuss about different types of missile guidance system
•2
SEQUENCE
• Missile
• Guided Missile
• Missile components
• Working of guidance system
• Types of guidance system
• Q & A
•3
MISSILE
• Latin word ‘Mittere’ means “To send”
• A self propelled projectile used as a weapon
• Typically propelled by rocket or jet engines
•4
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
•6
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
•13
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
•14
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
•16
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
•18
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
•19
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
•20
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
•21
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
•22
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
•31
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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