sonar & undersea warfare Flashcards
undersea warfare defensive
stealth
undersea warfare offensive
employ acoustic sensors and weapons
speed of sound (ocean)
speed of sound varies from point to point in the ocean
factors affecting speed
temperature (T), pressure (P), Salinity
speed of sound increases with
warmer water, higher pressure, higher salinity
shadow zone
region beyond where sound rays travel and sound intensity is negligible
surface layer
daily weather, time of day. 150 meters
seasonal thermocline
seasons about 1000m
permanent thermocline
slightly seasons about 1000m
deep isothermal layer
pressure 1000m+
deep sound channel (DSC)
axis of minimum sound speed within deep sound channel. 1000m+
expendable bathythermograph (XBT)
measures water temp, probe sinks at a known rate, produces a sound velocity profile of immediate area
direct propagation path
simplest propagation path. sound ray travels in approx straight linepath between the source and the receiver
surface duct
sound waves trapped in the surface layer, surface layer is deep enough to trap sound waves
bottom bounce (BB)
sound beam is directed at an angle toward the bottom, the sound beam reflects back toward the surface, path is dependent on the depth, and absorption of sound by the ocean bottom
convergence zone
occurs in deep isothermal layer, if depth is great enough, sound rays bend back toward surface
self noise
machinery noise, flow noise, cavitation
sonar
sound navigation and ranging, consists of source, medium and receiver
active sonar system
transducer emits a ping, short burst of energy transmitted thru the water. range is measured, time interval between transmission and return. closely resembles the operation of radar system
passive sonar system
ONLY listens, thru hydrophones. displays frequency and bearing, range calculated thru target motion analysis
light airborne multi-purpose system (LAMPS)
consists of helicpoter & assets utilized for antisub warfare. dipping sonar, sonobuoys, forward looking infrared (FLIR), magnetic anomaly detector (MAD)
sonobuoys
expendable piece of equip. detect underwater sounds and transmit the data back to the search vessel
towed array sonar system
multi function towed array (MFTA), PASSIVE sonar receiver, long 3 inch diameter array towed behind surface ships
fathometer
acousit system that determines water depth
WQC-2 (Gertrude)
two-way voice communications
WQC-6
one way coded pulse, sent thru surface ships sonar dome to subs
