1 MISSILE GUIDANCE SYSTEMS
Presented By:
2 GUIDED MISSILES Self-propelled aerial projectiles containing explosives Guided either by remote control or internal mechanisms 5 categories – surface to surface, surface to air, air to surface,air to ground & air to air Based on area of operation – tactical,support & strategic Based on flight characteristics – aerodynamic & ballistic
3 MISSILE COMPONENTS Guidance, control, armament & propulsion sections
Guidance – brain of the missile, directs its manoeuvres Control – executes the manoeuvres Armament – carries the explosive charge and the fusing & firing sections Propulsion – propels the missile Guidance orders are initiated by electronic sensing systems
4 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
5 PHASES OF GUIDANCE 3 phases – boost, midcourse, terminal
6 BOOST PHASE Missiles are boosted to flight speed by booster component of propulsion system Lasts from the time missile is launched until booster burns up its fuel Missiles aimed in specific direction on orders from fire control computer This establishes line of fire along which missile must fly during boosted period At the end of boost , missile must be at pre-calculated point Essential that it provides stability to missile
7 MID-COURSE PHASE Not always present; but when present it is the longest in time & distance Changes may be needed to bring missile onto desired course & to keep it on course Puts missile near target, from where terminal phase takes over control
8 TERMINAL PHASE Highly important phase
Must have high degree of accuracy, fast response to guidance signals to ensure an intercept Missile may need to manoeuvre to its max capability to make sharp turns to overtake & hit a fast moving & evasive target In some missile manoeuvres are limited during the early part & becomes more responsive to error signals during later stages
9 TYPES OF GUIDANCE SYSTEMS
Inertial guidance Command guidance Beam-rider guidance Homing guidance – active, semi-active, passive Optronic guidance TERCOM guidance system
10 INERTIAL GUIDANCE Missiles controlled by self-contained accelerometers
Accelerometers 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
11 COMMAND GUIDANCE Missile Target Command Transmitter Missile Target
Tracker #2 Target Tracker #1 Computer
12 BEAM-RIDER GUIDANCE Missile seeks out centre of controlled directional energy beam – radar beam Beam provides information regarding position of missile to guidance system System 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 decreases Effective only against short & medium range targets
13 Beam Rider Guidance Tracking Beam Narrow Guidance Beam
14 HOMING GUIDANCE Controls 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 target Missile derives guidance error signals based on its position relative to target Most accurate type of guidance 3 types – active , semi-active & passive
15 ACTIVE HOMING Target 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
16 SEMI-ACTIVE HOMING Target illuminated by external source – transmitter carried in launching aircraft Receiver in missile receives reflected signals , computes information & sends electronic commands to control section Hawk antiaircraft systems
17 PASSIVE HOMING Directing 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
18 OPTRONIC MISSILE GUIDANCE
Advantages such as high resolution , no signal emission compact size and low weight of the onboard equipment Includes highly-sensitive small-size sensors and ground-based information systems for receiving and processing images, generating target designation and reference data and to promptly transmit the data to the missile launch sites More efficient in overcoming anti-missile defense zones and do not deviate from their target by more than a few meters Used in Tomahawk cruise missiles
19 Optronic guidance system
20 CELESTIAL GUIDANCE SYSTEM
First used in american poseidon missile Uses star positioning to fine-tune the accuracy of inertial guidance system Potentially very effective means of improving accuracy
21 TERCOM GUIDANCE SYSTEM
TERCOM (Terrain Contour Matching) is used to solve the problem of drift Radar used to scan the ground/terrain that the missile is passing over. The terrain data is compared to the digital maps stored in the computer on the missile If a drift is noticed, the inertial navigation system is corrected and a course correction is made to put the missile back on path .This is repeated a number of times Advantages are that missiles fly very low - coupled with their small size and radar cross-section, low infrared signature, they become virtually undetectable by enemy radar GPS can be used to complement data computed by inertial system
22 TERCOM guidance system
23 POLYPHEM FIBRE-OPTIC GUIDED MISSILE SYSTEM
Uses infra-red imaging for high precision targeting Transmissions through fibre-optic cables System uses advanced image processing algorithms,electro-optical converters and radio links Main part of the guidance system is the infrared imager Fibre-optic links provide high data transmission rate,immunity to active jamming and electro-magnectic interference
24 ADVANCED GUIDANCE CONCEPTS
Boeing has developed a Laser JDAM (LJDAM) to provide both types of guidance in a single kit Raytheon has developed the Enhanced Paveway family , which adds GPS/INS guidance
25 Guided Flight Paths Preset Variable Constant: Programmed Pursuit
Fixed before launch. Once launched, profile cannot be changed Programmed Weapons has several programmed phases Variable Pursuit Constant Bearing Proportional Navigation Line-of-Sight (being phased out)
26 Pursuit Path Points the target at all times.
27 Constant Bearing Path X Initial Target Path Intercept Point New Path
28 Proportional Navigation
A receiver measures the rate of change of the line of sight to the target and new steering commands are generated The weapons chooses a course in which the rate of change of the weapons heading is directly proportion to the rate of rotation of the line-of-sight from the weapon to the target Initial Range
29 Line of sight This is being phased out
This is different from the others because the line-of-sight is from the launch platform to the target and the weapons stays in the line of sight.
30 Putting It All Together
REFLECTION FROM THE TARGET ANTENNA BEAM LAUNCH CYCLE OR LAUNCH TO EJECT CYCLE (LTE) PRESS “LAUNCH” SEPARATE INITIATE SEMIACTIVE MODE ACTIVE MODE IMPACT PROGRAMMED FLIGHT OR MAINBEAM AVOIDANCE MANEUVER (MBAM) SEMIACTIVE MIDCOURSE GUIDANCE SEMIACTIVE (SA) ACTIVE TERMINAL GUIDANCE ACTIVE (A)
31 Conclusion Guidance System is a complex system which involves several systems working in tandem Development of missile involve huge expenditures – essential that guidance system is properly designed for accurate interception of targets