Theory and Design Principles Flashcards
Why are magnetics important wrt to torpedos?
Ferrous metals contain iron molecules. Groups of molecules called domains each have their own magnetic orientation and field.
As the metal is worked, energy is added, allowing the domains to align, magnetizing the metal.
This magnetic field distorts earth’s magnetic fields, which can be detected.
Does the magnetic field distortion around a ship change?
Yes, it changes with loading stress on the hull, work stresses, water temperature, and different areas of the worl dhave different field strengths.
Warmer water - higher magnetization rate.
Describe Degaussing
Decreasing or eliminating a remnant magnetic field by inducing a counter-magnetic field to cancel it out.
This is temporary and only works when power is applied to the internal coils.
Describe a degaussing range
Undersea magnetometers arranged in different orientations to the earths magnetic field. As the ship travels over the range, its magnetic bias is recorded.
Describe Deperming
Large coils are wrapped around a ship and high electric currents are used to cancel the permanent magnetism of the ship.
This is permanent and uses external coils.
Torpedo Danger Zone (TDZ)
Area in which an enemy torpedo would have a high probability of hitting the ship.
Describe the SLL’s.
Submarine Limiting Lines define the arcs where a submarine is capable of intercepting the ship. Due to the ship’s speed, the submarine must be in an area forward of the ships direction of travel since the ship moves faster than the submarine.
How would a single ship use its sensors to detect submarines?
Inorganic sensors (spitpointers), helicopters (ponies and dippers), and maritime patrol aircraft (pelicans)
Describe how a task group would detect submarine threats.
What are sensor methods to detect submarine threats?
Visual
Sonar
Magnetic Anomaly Detection
Describe MAD
Magnetic Anomaly Detection
Detects variance in earth’s magnetic field. Magnetic fields are not refracted or attenuated at the air/water interface so they can be used from aircraft.
What is the CANTASS problem?
CANTASS determines direction by analyzing the time of arriva (TOA)
It cannot tell which side of the array the sound arrives from.
This is solved by changing the ship’s heading. The false target will move at a nonsensical rate.
What is TMA?
Target Motion Analysis monitors the direction and movement of the contact and the listening platform to determine the target range. Used to determine range with passive sonar sensors.
How is the Kill Assessment performed?
Sound profile of the explosion
Secondary explosions
Bulkhead collapses
Dirt and oil may be spotted on teh surface
A sub may be forced to surface
Describe Run-out (Cobra) search pattern
Used to strike a target which is far away. Used as counter-fire.
Note the torpedo snakes in order to maximize the area it is listening to.
Describe the No Run-out search pattern.
Used to strike close targets, ideally within the search radius of the torpedo.
Describe the bubble jet effect
The shockwave strikes the hull, lifting the ship
The expanding bubble collapses, and the hull sinks into the void.
As the bubble collapses from the highest point of pressure (the bottom), a jet of water towards the top of the bubble is created which impacts the bottom of the hull, often splitting it in half.
If the explosion is too deep, a bubble may not form at all due to the pressure.
