CH 8: Radar Missile Guidance Techniques

Question 1

The 3 basic. Requirements for successful missile guidance

Answer 1

1. Precise target tracking by s TYR go provide target parameters (range, azimuth, elevation, velocity etc)
2. A method to track the position of the missile compared with the target
3. A fire control computer to generate missile guidance commands based on target and missile position.

Question 2

3 distinct phases in any missile intercept

Answer 2

Boost, mid-course, and terminal

Question 3

Boost phase def

Answer 3

Nearly all missiles are unguided during the initial boost phase. During the boost phase, the missile electrical and hydraulic systems are activated and are coming up to operating parameters. The missile is gathering speed and normally will be in an unguided mode of flight.

Question 4

Mid course phase definition

Answer 4

During mid course phase, the missile is actively being guided to the target using some type of guidance signal. Guidance signals deflect the control vanes of the missile to change its direction. These canes change roll, pitch, and yaw in some combination to control the missile flight path.

Question 5

Terminal phase def

Answer 5

During this phase, the missile attempts to pass close enough to the target to detonate the fuse while the target is within the lethal radius of the warhead. Modern middles employ both a contact fuse and some type of proximity fuse.

Question 6

Command guidance def

Used by which systems?

Answer 6

Command guidance uses a fire control computer to constantly send course correction commands to the middle throughout its flight.

Guidance commands are passed to the middle by specialized antennas on the TTR and an antenna installed on the missile, called a missile beacon. This beacon is usually masked until missile booster separation. This type of delay is one of the reasons that all command guidance missile systems have a min launch range.

Command guidance is used by the SA2, SA-3, SA-4, and SA-8.

Question 7

Rectified flight profile def

Answer 7

Command guided missiles will generally fly a rectified (full of half) or three point pursuit geometry during the mid course portion of the intercept. However, a command guided missile may transition to a pure pursuit geometry during the terminal phase of the intercept. Rectified geometry involves the prediction of where the target and the missile will be at some point in the future.

Question 8

Three point pursuit geometry def

Answer 8

Three point pursuit geometry is often used when there is incomplete range tracking data on the target. In this case, it’s impossible to predict where the target will be in the future. So the TTR constantly tracks the target, the missile beacon relays missile location, and fire control computer will direct missile to fly directly down the tracking radar beam towards the target.

Point 1- target tracking radar
Point 2-the missile itself
Point 3-the target

By keeping all three points always in a line, the missile will intercept the target at some point, but the range of the target is unknown.

Question 9

Advantages of command guidance

Answer 9

1. Command guided missiles can adjust their flight profile throughout an intercept profile.
2. Missiles are uncomplicated since they don’t carry onboard computers or target tracking equipment
3. Primary intercept profile, a full of half rectified intercept, is the fastest and most fuel efficient intercept.
4. Command guidance is diffuse to jam since the middle beacon antenna is at he rear of the missile and can be relatively high powered.
5. An intercept is possible even without accurate range info by using a 3 point profile

Question 10

Command guidance disadvantages

Answer 10

1. The use of a missile beacon delays the capture of the missile by the tracking radar, equating to a larger minimum engagement range.
2. The accuracy of the intercept geometry is only as good as the tracking information provided by the TTR. Jamming, interference, or loss of signal will adversely affect the intercept accuracy.
3. With insufficient range info, the 3 point profile is very slow and could result in the missile running out of energy before it gets to the target.
4. Command guidance is reactive and so the missile maneuvering lags behind target maneuvers.

Question 11

Semi active guidance def

Answer 11

Semi active guidance has the TTR Maintain a solid target track, with the tracking data being supplied to the fire control computer. The fire control computer then directs a target illumination antenna to point at the target and illuminate it with CW energy. The missile then passively homes on the reflected CW energy.

Question 12

Semi active guided missile characteristics

Answer 12

The missile that homes on CW energy must be equipped with a seeker section composed of an antenna and an internal receiver. The seeker section processes and computed the necessary course corrections as it flies towards the target.

When the error between the antenna position and the boresight position is zero, the missile is pointed directly at the target.

Missile systems that use semi active guidance normally use velocity as the primary target discriminator during the intercept. The missile seeker locks onto a reference Doppler signal provided by the fire control computer before launch. After the missile is launched, it initially compares the reference Doppler to the target Doppler signal.

Question 13

Mid course phase for a semi active missile

Answer 13

A semi active guided missile follows the reflected CW energy during the mid course phase of the intercept and normally attempts to fly a lead pursuit profile to the target. A semi active guided missile does not use a missile beacon.

Semi active guidance is the primary mode of guidance for many SAMs and almost all radar guided AAMs.

Question 14

Semi active guidance for terminal phase

Answer 14

As the middle enters the terminal phase of the intercept, there is no change in the guidance mode used by a CA homing missile. The middle may complete the terminal phase of the intercept geometry by going to a pure pursuit flight path, if needed. The missile continues to home in on the reflected CW signal until it passes close enough for the fuse to function.

Question 15

Semi active missile guidance advantages

Answer 15

1. Semi active guided missile is resistant to electronic jamming that may be used to deny range info
2. Semi active missile can be guided almost immediately after launch, equaling a small mi out range since it can maneuver almost as soon as it clears the launch rail.
3. It computed its own course corrections as necessary, allowing for suicide reaction to target maneuvers.
4. During long range intercept, a CE missile can be more accurate than a command guided missile since the TTR only has to keep the target illuminated so it can point the CW antenna at the target.

Question 16

Semi active missile guidance disadvantages

Answer 16

1. Semi active guided missiles normally requires reference Doppler values to be entered into the missile Computer before launch. Without this reference, a semiactive missile can’t be launched.
2. A semi active homing missile must maintain a lock onto the target Doppler. The use of chaff and beam maneuvers, which result in a near zero target Doppler, may cause a missile or radar to break lock.
3. If a break-lock occurs, a CW homing missile normally cannot regain target track and complete the intercept.

Question 17

Active Guidance def

Answer 17

Active guidance is an improvement that has been included in several new long range missiles. This specialized guidance mode is only active during the terminal phase of flight. The mid course phase usually employs semi active or command guidance.

The range at which the middle goes ‘active’ is dependent on the intercept geometry. Missiles that employ active guidance carry a complete miniature radar system and fire control computer within the missile. As the middle nears the target, its internal radar system turns on and locks onto the target. The internal fire control computer directs control inputs to complete the intercept.

Question 18

Active guided missile advantages

Answer 18

1. Active guided missiles are very accurate at long ranges because they do not rely on the TTT once their internal radar takes over the intercept.
2. An active missile is very difficult to jam since It uses a narrow beam and its relative power is constantly increasing as it nears the target.
3. An active guided missile is a fire and forget weapon, meaning the interceptor can turn around and maneuver defensively after missile launch.

Question 19

Active guided missile disadvantages

Answer 19

1. Active homing missiles are complex missiles integrating both command and active guidance modes.
2. Missiles may still be susceptible to electronic jamming during the mid course phase of flight, where the middle relies on command or semi active guidance. Jamming the TTR may affect the missiles ability to see the target near the terminal phase.

Question 20

Seeker-aided ground guidance/track-via/missile guidance def

Answer 20

In seeker aided ground guidance (SAGG) and track-vis-missile (TVM) guidance, the target is illuminated by the ground based radar and the missile receives reflected energy from the target. The middle does not generate its own guidance commands. Instead the middle transmits raw engagement data to the ground based fire control system (FCS) in order to generate uplink guidance commands.

TVM is similar to SAGG, however additional processing is done on board the missile prior to transmitting the engagement data to the ground based FCS.

Question 21

SAGG and TVM advantages

Answer 21

1. They are extremely accurate at long ranges where the inherent radar tracking errors may be large enough to cause a miss.
2. They can respond very quickly to actions taken by the target since the missile seeker can track these changes and transmit the new position to the TTD fire control computer.
3. TVM and SAGG can be used with a large and capable fire control computer since most computations are accomplished by the TTR.
4. The integration of a phased array radar and the powerful TTR fire control computer allows the missile system to engage multiple targets.

Question 22

SAGG and TVM disadvantages

Answer 22

1. They are the most complex forms of middle guidance and require the use of sophisticated computers to combine radar tracking data and data received from the missile. this required hardware is expensive and demands greater MX and logistical support. The missile also needs to be large enough to store the appropriate hardware for computations and data transfer.

Question 23

Anti aircraft artillery (AAA) def

2 types of AAA systems

Answer 23

Classic role of AAA is point defense. AAA systems provide close in defense for HVTs (cities, C2 centers, SAM sites etc). There are two types of AAA systems: towed and mobile.

Towed AAA: deployed in fixed sites around key targets

Mobile AAA: deployed to provide air defense for army units and to protect mobile SAM sites.

Effectiveness of AAA systems is dependent on ability to predict an aircrafts future position to fire its unguided ballistic projectile to intercept the aircraft and destroy it.

Question 24

Aimed AAA fire tactics def

Answer 24

Aimed AAA fire requires very accurate aircraft position info and an accurate prediction of fire positions. This info is derived by using an optical sighting system on the gun or by employing a radar system coupled with a fire control computer.

Smaller caliber guns rely on optical target acquisition and firing

Larger caliber AAA systems generally use a TT and fire control computer

Question 25

Sector or barrage fire tactics def

Answer 25

Sector of barrage fire tactics are employed when the aircraft cannot be accurately tracked. Acquisition info suggests an aircraft will traverse a volume of airspace or a specified sector. The fire director instructs the gunners to fire randomly into this sector in an effort to hit the aircraft with the barrage of AAA fire or have the aircraft fly into a curtain of AAA fire.

Sector/barrage fire can be directed to cover the expected attack directs and altitudes.