Guidance and Control Principles Naval Weapons Systems

Missiles Unguided Guided No course corrections Elevation, ballistics, gravity, etc Guided Control system Change direction We will talk about Aerodynamic Guided Missiles, but these principles apply to other types of weapons, for example torpedoes!

Three Phases of Guidance There are three Phases of missile guidance: 1. BOOST Phase: - Get the missile up to SPEED! - Missile leaves the launcher until Booster burned out - Places the missile at a high altitude - see the target - receive target information. 2. Midcourse Guidance Phase: - Missile closes the target - Generally the longest phase - General corrections to course and altitude 3. Terminal Phase - Last phase; missile guidance is critical - Final corrections, close the target, detonate warhead. Boost Mid-Course Terminal

3 Main Categories of Guidance Control 1. Control Guidance Command Beam rider 2. Homing (reacts to target features) Active Semi-Active Passive 3. Self Contained – “Smart Weapon” Three categories of missile guidance control. 1. Controlled guidance - the shooter (WCO, TAO, etc) actively controls the weapon, for a time. - examples: Mk 48 wire guided, TOW 2. Homing guidance - Distinguishing feature of the target to zero in on - Active - Harpoon, Phoenix, AMRAAM, Mk 46 and 48 (after wire breaks) - Semi-active - NATO Sea Sparrow, SM-2, SM-1P - Passive - Mk – 46 and 48 (magnetic influence, acoustic), HARM, SLAM, Sidewinder 3. Self-contained guidance - Most sophisticated - All detection, error generation and guidance corrections determined by the missile - examples: - TLAM, Trident

Beam Rider Control Guidance Older method of guidance control. Tracking Beam Narrow Guidance Beam Beam Rider Control is older method a. Guidance is performed by keeping the missile inside a radar or laser beam cone. b. The beam comes from a friendly source. c. If beam remains on target, then the missile will follow the beam to the target. d. Point and shoot type of control. NOT FIRE AND FORGET! Disadvantage: - Missile is always LAGGING behind the target! - Must keep target illuminated the WHOLE TIME!

Homing Guidance Control Reflected Waves Reflected Waves Target Characteristic Radar Radar MOST ACCURATE! TARGET GIVES THE DATA! 1. Homing Guidance Systems react to a target feature. Could be radio EM, Light, Heat, Acoustic 2. For consistency we will talk EM (RADAR) Three types of homing guidance controls: 1. Active: Missile uses own radar to transmit and receive information about target to make changes in flight profile. 2. Semi Active: The target is illuminated by a friendly platform. Missile receives the reflection and uses that information to alter flight profile. 3. Passive: Target is the source of energy. There are hybrid systems which combine command guidance with some active homing. Guidance systems are combined and use other systems for backup. 1. Active 2. Semi-Active 3. Passive

Self-Contained Guidance Systems Consists of two parts: Preset Updating

Self-Contained Guidance Systems Preset Path is predetermined, inside the weapon Preset guidance: Flight path profile is inserted in weapon before launch. Preset: Uploaded to the missile before flight. Details about where to fly and when. TLAM – midcourse Mk 46 & 48 – can follow a preset search pattern Harpoon – midcourse It might help to discuss the concept of Simultaneous Time on Top for Harpoon. Also this is applied to TLAM in that the launch times are staggered in order for the missiles to arrive at the same time.

Self-Contained Guidance Systems Updating – 3 kinds: 1. Inertial Senses weapon’s movement and make adjustments. 2. Terrestrial Compares actual terrain with predicted and adjusts. 3. GPS Updating: Various ways. The missile receives an update to its position so it can correct itself. 1. Inertial: Use accelerometers to sense weapons movement/deviation from the intended flight path. Make corrections based on what motion it senses. Terrestrial: Compares photo or electronic map of actual terrain seen by the missile with what it would see if on correct path. Makes adjustments so actual track coincides with desired track. DSMAC / TERCOM – Tomahawk Celestial Navigation – Trident D5 / C4 GPS: The missile receives an update on its position and adjusts the internal computer. TLAM Blk III

Guided Flight Paths Preset Variable Constant Programmed Pursuit Constant Bearing Proportional Navigation Line-of-Sight (being phased out) Preset Constant: Fixed before launch. Once launched, profile can not be changed Programmed Programmed phases (torpedo search) Variable Pursuit: ‘Chases’ the target Constant Bearing: Predict target bearing, fire at intercept point Proportional Navigation: Rate of change information Line-of-Sight (being phased out): Beam rider!

Pursuit Path Points the target at all times. Pursuit Guided flight path 1. The weapon will remain pointed at the target at all times. 2. The weapon constantly heads along the line of sight from the weapon to the target. Disadvantage: Weapon needs lots of gas!!

Constant Bearing Path X Initial Target Path Intercept Point New Path Constant Bearing Guided Flight Path Weapons anticipates where the target will be. As a result: 1. Weapon is aimed ahead of the target and will intercept the target at a point in space further down the track. 2. Weapon will alter course to maintain this constant bearing Constant Bearing Path

Proportional Navigation Initial Range Proportional Navigation. 1. A receiver measures the rate of change of the line of sight to the target, new steering commands are generated. The weapon 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. Very similar to Constant Bearing

Line of Sight Initial Range Line-of-sight. 1. This is being phased out. (The old beam rider) 2. This is different than the other because the line-of-sight is from the launch platform to the target and the weapons stays in the line of sight.

Putting It All Together Target Reflection ANTENNA BEAM LAUNCH CYCLE Air Example: 1. Point out boost, mid-course and terminal phases. 2. For Self Control Guidance a. Uses preset initially to get out of beam. b. Uses Inertial while flying towards the target c. Uses pursuit when in close (terminal phase) 3. For Homing a. Uses semi-active for mid-course guidance b. Uses active when get into terminal phase If time for more review Use Tomahawk to go over its path. Use CNET 12-5 to talk about phases of torpedo BOOST MIDCOURSE GUIDANCE TERMINAL GUIDANCE PRESS “LAUNCH” SEPARATE INITIATE SEMIACTIVE MODE INITIATE ACTIVE MODE IMPACT

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