piston. They are internally mounted in a single
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
Firing components include elements that detect the
target, analyze target information, and act to fire the
mine. In simple systems, a single device does these
functions. 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.
subdivided into three general categoriesacoustic,
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.
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 com-
bination of these two mechanisms makes effective
minesweeping operations nearly impossible.
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
REVIEW NUMBER 2 ANSWERS
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
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.
A cable connected to an anchor resting on the
ocean floor stabilizes moored mines.
Influence-actuated mines are classified as
magnetic, acoustic, and pressure.
Some mines laid from aircraft use parachutes to
prevent them from building up too much speed before
entering the water. The parachute reduces the impact
velocity and protects the mine components from
damage. The use of parachute packs permits the mines
to be released from an aircraft at high altitudes, which
may be required when ports or sea passages are heavily
delayed-opening type. In this type of parachute pack, a
control mechanism is used to open the parachute at
some point in the air trajectory of the mine. A typical
delayed-opening parachute pack contains a drogue-
type parachute, release gear, and a control device. The