Underwater Detection and Tracking Systems

1. Underwater Detection and Tracking Systems Naval Weapons Systems

2. Transducer Theory • Transducer: Device for converting one form of energy to another • Electrical energy into acoustic (oscillation of water molecules through which sound travels) Acoustic Signals Electric Signals TRANSDUCER

3. Transducer Power • Pressure of sound wave is limited by: • Hydrostatic pressure • Cavitation pressure • Water vaporizes! • Increasing power normally means increased transducer array size • How can we increase power from an array of fixed size?

4. Types of Transducers • Crystal • Piezoelectric effect – converts pressure changes into electrical form • Ceramic (Electrostrictive) • An electric field is applied to polarize the transducer causing a slight change in shape (mechanical deformation) • Magnetostrictive • Magnetic field can cause materials to expand or contract (change shape) • Nickel rods placed in a magnetic field vibrate

5. Basic Sonar Systems • Active • Echo Ranging Systems • Acoustic energy is transmitted, and the received signal is the echo from the target • “Ping” • Passive • Listening Systems • Dependant on receiving signals radiated from the target

6. Advantages & Disadvantages • Limitations of sonar due to physical properties of sound travel in water • Active vs Passive sonar in detection • Active vs Passive sonar in tracking

7. Questions?

8. Hydrophones • Lighter than transducers • Designed for reception only • Bearing information only, no range • Much like a transducer • Electrostrictive • Magnetostrictive

9. Other Sonar Equipment • Tactical Towed Array Sonar (TACTAS) • Passive system • Linearly spaced hydrophones • Heading, Temp, depth sensors

10. Other Sonar • Sonobouys • Passive • Active • Special Purpose • Dipping Sonar • Sound Surveillance System (SOSUS) • VISUAL!

11. Magnetic Anomaly Detection(MAD) • Principle: A metallic submarine disturbs the magnetic lines of force of the earth • The magnetic distortion or anomaly caused by a submarine below surface can be detected from above submarine • P-3C, SH-60B

12. Underwater Communications • ELF TO UHF satellite • What is the disadvantage • Relatively Short Range • Water conditions, noise, reverberation • Sound Channels • Ideal conditions • 12,000 meters

13. Introduction (Platforms) • Surface Ships (DDG, CG, DD, FFG) • Advantages: • more available manpower • greater time on station • variety of detection equipment • variety of available weapons and better fire control systems • ability to operate in foul weather • embarked LAMPS aircraft

14. Introduction (Platforms) • Surface Ships • Disadvantages: • NOT “in” the submarine’s environment • Relatively Slow • Noisy • ASW prosecution is protracted

15. Introduction (Platforms) • Aircraft Carriers • Advantages: • Same as for Surface Ships • Disadvantages: • Same as for Surface Ships • Aircraft Carrier is a High Value Unit • Its importance to naval operations requires many assets to be employed to protect it

16. Introduction (Platforms) • Aircraft (S-3, P-3, SH-60B) • Advantages: • Speed • Ability to deploy sensors over a large area • Surprise through use of passive detection • Not in submarine’s environment • Altitude increases radar horizon

17. Introduction (Platforms) • Aircraft • Disadvantages: • Low time on station • Limited weapons capacity • Limited range • Vulnerable to weather • Not in submarine’s environment

18. Introduction (Platforms) • Submarines • Advantages: • Shares the advantages of the target • passive detection • concealment • less distracted by sound properties of water • Nuke subs can stay submerged for months • What is the limiting factor?

19. Introduction (Platforms) • Submarines • Disadvantages: • To detect targets, subs must run deep • To communicate, subs must be shallow • Capable of high speed, but at higher noise level • Diesel subs must snorkel to recharge batteries

20. Questions?