Underwater Detection Underwater Detection and Tracking Systemsand Tracking Systems

Naval Weapons SystemsNaval Weapons Systems

Transducer TheoryTransducer Theory

TransducerTransducer: Device for converting one : Device for converting one form of energy to anotherform of energy to another Electrical energy into acoustic (oscillation of Electrical energy into acoustic (oscillation of

water molecules through which sound travels)water molecules through which sound travels)

TRANSDUCERAcoustic Signals

Electric Signals

Transducer PowerTransducer Power

Pressure of sound wave is limited by:Pressure of sound wave is limited by: Hydrostatic pressureHydrostatic pressure Cavitation pressureCavitation pressure

• Water vaporizes!Water vaporizes!

Increasing power normally means Increasing power normally means increased transducer array sizeincreased transducer array size How can we increase power from an array of How can we increase power from an array of

fixed size? fixed size?

Types of TransducersTypes of Transducers

CrystalCrystal Piezoelectric effect – converts pressure changes into Piezoelectric effect – converts pressure changes into

electrical formelectrical form Ceramic (Electrostrictive)Ceramic (Electrostrictive)

An electric field is applied to polarize the transducer An electric field is applied to polarize the transducer causing a slight change in shape (mechanical causing a slight change in shape (mechanical deformation)deformation)

MagnetostrictiveMagnetostrictive Magnetic field can cause materials to expand or Magnetic field can cause materials to expand or

contract (change shape)contract (change shape) Nickel rods placed in a magnetic field vibrateNickel rods placed in a magnetic field vibrate

Basic Sonar SystemsBasic Sonar Systems

ActiveActive Echo Ranging SystemsEcho Ranging Systems

• Acoustic energy is transmitted, and the Acoustic energy is transmitted, and the received signal is the echo from the targetreceived signal is the echo from the target

““Ping”Ping” PassivePassive

Listening SystemsListening Systems• Dependant on receiving signals radiated Dependant on receiving signals radiated

from the targetfrom the target

Advantages & Disadvantages Advantages & Disadvantages

Limitations of sonar due to physical Limitations of sonar due to physical properties of sound travel in waterproperties of sound travel in water

Active vs Passive sonar in detectionActive vs Passive sonar in detection Active vs Passive sonar in trackingActive vs Passive sonar in tracking

Questions?Questions?

HydrophonesHydrophones

Lighter than transducersLighter than transducers Designed for reception onlyDesigned for reception only Bearing information only, no rangeBearing information only, no range Much like a transducerMuch like a transducer

Electrostrictive Electrostrictive MagnetostrictiveMagnetostrictive

Other Sonar EquipmentOther Sonar Equipment

Tactical Towed Array Sonar (TACTAS)Tactical Towed Array Sonar (TACTAS) Passive systemPassive system Linearly spaced hydrophonesLinearly spaced hydrophones

• Heading, Temp, depth sensorsHeading, Temp, depth sensors

Other SonarOther Sonar

SonobouysSonobouys PassivePassive ActiveActive Special PurposeSpecial Purpose

Dipping SonarDipping Sonar Sound Surveillance System Sound Surveillance System

(SOSUS)(SOSUS) VISUAL!VISUAL!

Magnetic Anomaly DetectionMagnetic Anomaly Detection(MAD)(MAD)

Principle: A metallic submarine disturbs Principle: A metallic submarine disturbs the magnetic lines of force of the earththe magnetic lines of force of the earth

The magnetic distortion or anomaly The magnetic distortion or anomaly caused by a submarine below surface can caused by a submarine below surface can be detected from above submarinebe detected from above submarine

P-3C, SH-60BP-3C, SH-60B

Underwater CommunicationsUnderwater Communications

ELF TO UHF satelliteELF TO UHF satellite What is the disadvantageWhat is the disadvantage

Relatively Short RangeRelatively Short Range Water conditions, noise, reverberationWater conditions, noise, reverberation Sound ChannelsSound Channels

Ideal conditionsIdeal conditions 12,000 meters12,000 meters

Introduction (Platforms)Introduction (Platforms)

Surface Ships (DDG, CG, DD, FFG)Surface Ships (DDG, CG, DD, FFG) Advantages:Advantages:

• more available manpowermore available manpower• greater time on stationgreater time on station• variety of detection equipmentvariety of detection equipment• variety of available weapons and better fire control variety of available weapons and better fire control

systemssystems• ability to operate in foul weatherability to operate in foul weather• embarked LAMPS aircraftembarked LAMPS aircraft

Introduction (Platforms)Introduction (Platforms)

Surface ShipsSurface Ships Disadvantages:Disadvantages:

• NOT “in” the submarine’s environmentNOT “in” the submarine’s environment• Relatively Slow Relatively Slow • Noisy Noisy • ASW prosecution is protractedASW prosecution is protracted

Introduction (Platforms)Introduction (Platforms)

Aircraft CarriersAircraft Carriers Advantages:Advantages:

• Same as for Surface Ships Same as for Surface Ships Disadvantages:Disadvantages:

• Same as for Surface ShipsSame as for Surface Ships• Aircraft Carrier is a High Value UnitAircraft Carrier is a High Value Unit• Its importance to naval operations requires many Its importance to naval operations requires many

assets to be employed to protect itassets to be employed to protect it

Introduction (Platforms)Introduction (Platforms)

Aircraft (Aircraft (S-3S-3, P-3, SH-60B), P-3, SH-60B) Advantages:Advantages:

• SpeedSpeed• Ability to deploy sensors over a large areaAbility to deploy sensors over a large area• Surprise through use of passive detectionSurprise through use of passive detection• Not in submarine’s environmentNot in submarine’s environment• Altitude increases radar horizonAltitude increases radar horizon

Introduction (Platforms)Introduction (Platforms)

AircraftAircraft Disadvantages:Disadvantages:

• Low time on stationLow time on station• Limited weapons capacityLimited weapons capacity• Limited rangeLimited range• Vulnerable to weatherVulnerable to weather• Not in submarine’s environmentNot in submarine’s environment

Introduction (Platforms)Introduction (Platforms)

SubmarinesSubmarines Advantages:Advantages:

• Shares the advantages of the targetShares the advantages of the target passive detectionpassive detection concealmentconcealment less distracted by sound properties of waterless distracted by sound properties of water

• Nuke subs can stay submerged for monthsNuke subs can stay submerged for months What is the limiting factor?What is the limiting factor?

Introduction (Platforms)Introduction (Platforms)

SubmarinesSubmarines Disadvantages:Disadvantages:

• To detect targets, subs must run deepTo detect targets, subs must run deep• To communicate, subs must be shallowTo communicate, subs must be shallow• Capable of high speed, but at higher noise levelCapable of high speed, but at higher noise level• Diesel subs must snorkel to recharge batteriesDiesel subs must snorkel to recharge batteries

Questions?Questions?