assembly. The hydrostatic piston acts to open and close
electrical switches. The explosive piston aligns the
explosive train when the hydrostatic piston and the
explosive piston are forced in by water pressure after the
mine is laid. These pistons are held in the retracted or
safe position by safety pins during ground handling.
The safety pins are replaced by arming wire assemblies
after the mines are loaded aboard the aircraft.
After planting, a clock-delay mechanism prevents
firing until the mine has been submerged for a
predetermined period of time, A switch in the detonator
circuit of the mine controls the firing mechanism. This
switch remains open until the clock-delay device has run
its predetermined time. This time could vary from 8
minutes to 10 days, depending upon the type of clock
installed. Sometimes another clock is also used to
sterilize the mine after a preselected period of armed
life.
Firing Components
Firing components include elements that detect the
target, analyze target information, and act to fire the
mine. In simple systems, these functions are done by a
single device, However, in most systems, these
functions are performed by two or more components.
The types of firing mechanisms used in mines vary
widely in appearance and configuration. In older mines,
the firing mechanism might be a circuit arrangement. In
newer mines, the firing mechanism might be a
color-coded rectangular box.
Since influence-actuated mechanisms are the only
type of firing mechanisms currently used in aircraft
mines, they are discussed in the following paragraphs.
Influence-actuated firing mechanisms may be
subdivided into three general categories-acoustic,
pressure, and magnetic.
ACOUSTIC.— An acoustic mine is fired by the
initiation of an enclosed microphone. The microphone
picks up the sound waves generated by a nearby ship’s
rotating screws or other operating machinery. These
mines are equipped with an anticountermine device that
prevents detonation of the mine from explosions set off
during minesweeping operations.
PRESSURE.— The pressure mine firing
mechanism is actuated by a decrease in water pressure
immediately surrounding the mine. Normally, this
occurs only when a large ship passes over it. The
pressure mine firing mechanism is used in conjunction
with a magnetic-influence mechanism.
The
combination of these two mechanisms makes effective
minesweeping operations nearly impossible.
MAGNETIC TYPE.— Magnetic mines are
induction mines actuated by changes in the earth’s
magnetic field. Their actuation depends primarily on
the rate at which the field changes rather than the amount
of change. A change in the magnetic field induces an
electromagnetic field in the winding of a coil. This
electromagnetic field and the resulting current are
proportional to the rate of change of the magnetic field.
When the magnetic field increases to a predetermined
level, a relay actuates and closes the firing circuit.
Parachute Packs
Some mines laid from aircraft use parachutes to
prevent them from building up too much speed before
REVIEW NUMBER 2 ANSWERS TO QUESTIONS Q1. THROUGH Q6.
A1.
A2.
A3.
A4.
A5.
A6.
Mines classified by their intended use are classified as service, exercise
(recoverable), and training mines.
Service mines are fully loaded with explosives and designated for use in wartime.
Moored or bottom mines are classified by the position they take in the water after
being laid.
The effective depth of a bottom mine is controlled by the amount of charge
contained in the mine relative to the depth to which the mine is planted.
Moored mines are stabilized by a cable connected to an anchor resting on the
ocean floor.
Influence-actuated mines are classified as magnetic, acoustic, and pressure.
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