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 5. GENERAL MINE INFORMATION

Today’s mines are designed for deployment against many different classes or types of ships to achieve a variety of results.  To meet the challenges of the missions that they may be called upon to perform, mines are becoming increasingly complex.  Moreover, the number and types of these missions is so large that no one mine can serve all purposes.  This is why the Navy’s stockpile contains several different kinds of mines with the necessary built-in versatilities that provide the options needed for a wide variety of missions.

PHOTO OF A NAVY F/A-18 HORNET PLANTING MK62 QUICKSTRIKE MINES

Navy F/A-18 Hornet Planting QUICKSTRIKE Mines Mk 62

It should be noted that all mines discussed herein refer to sea mines, i.e. those mines which are emplaced in deep or shallow waters, coastal areas, harbor entrances, rivers, canals, and estuaries.

Although it has been said that mines are becoming increasingly complex, it is largely because of the “intelligence” that is built into their firing systems.  Conversely, the same technology that made mines more complex in some ways has made them simpler in others.  The newer mines, for example, have features that make assembly, testing, and stowing much easier and safer than was possible with older mines.  Further, mines are eliminated as a threat to shipping at the end of their underwater life by automatic sterilization or self-destruction.  This occurs after a preset period of time or at the end of battery life, whichever comes first. 

Offensive and Defensive Mining Roles

As offensive weapons, mines may be planted in the enemy’s waterways, harbors, anchorages, and channels to menace his military and commercial shipping.  It should be noted that just a threat of such mines is frequently of equal importance as the actual sinking or damaging of ships, since the presence of mines requires costly/lengthy countermeasures to sweep or neutralize them.  Consequently, this causes delays in shipping schedules that may require ships to use alternate routes and port areas.  As defensive weapons, mines may be planted in our own friendly ports, harbors, channels, anchorages (perimeter defenses), bays, estuaries, or open waters to protect against enemy offensive seaborne attacks into these areas.

PHOTO OF THE DAMAGE DONE TO A DESTROYER RESULTING FROM AND UNDERWATER BLAST.

Damage From a Submerged Mine Can Be Quite Lethal!

Anatomy of a Typical Mine

The typical major components of a Naval mine are the flight gear (only if air-delivered), explosive‑loaded case, the arming device, the Target Detecting Device (TDD), a battery, an electric detonator, an explosive relay, and a booster.  The last three items may be considered as the explosive train.  These components, and how they interact, are highlighted in the illustration of a QUICKSTRIKE Mine Mk 63 on the next page and discussed in the following text: 

·         Flight gear (a bomb fin or tail section) is used to stabilize the mine in flight and retard its falling velocity following release from the aircraft, thus lessening the impact shock as the mine strikes the surface of the water.  A bomb fin extends four fin blades to slow the mine, while a tail section deploys a parachute.  Generally, fins are designed to break away from the mine’s case upon water entry.  Tail sections normally remain with the mine to the bottom. 

·         The explosive‑loaded case contains the main explosive charge of the mine.  It also contains internal conduits for electrical wiring and wells (cavities) at both ends of the case that house the arming device, TDD, and booster. 

·         The arming device provides for safety in the firing train by providing a mechanical interrupt until such time as the mine is safely separated from its delivery vehicle and within its operating underwater environment.  In the safe position, fixed and rotated explosive leads are kept out of physical alignment within the arming device.  A window on the device provides the mineman with a visual indication that it is safe, usually a white “S” on a green background.  A black “A” on a red background would indicate the device is armed.  Finding an arming device in such a state during mine assembly or disassembly would require an immediate area evacuation and summon for EOD personnel.  The safety wire seen in the illustration below provides an additional measure of safety.  It is only removed during mine assembly, replaced by a safety clip attached to an arming wire.  In our QUICKSTRIKE Mine Mk 63 scenario, vanes on the front of the arming device are freed by the pull of the arming wire upon mine release from the aircraft, allowing them to rotate in the air stream a set number of turns.  This rotation provides one of two necessary inputs that allow alignment of the arming device’s two internal explosive leads.  The second input to the arming device comes from the mine’s hard impact (shock) upon entering the water.  At this point, the fixed and rotated explosive leads inside the arming device are aligned and are able to transfer the explosive wave from the explosive relay to the booster should the TDD command a detonation.  These actions complete the arming sequence.

The TDD detects a combination of magnetic, seismic, and pressure stimuli generated by enemy vessels.  The mix of sensors depends on the type of TDD used.  There are a few exercise and training (E&T) mines that also detect underwater acoustic stimuli, which will be covered in Section 8 of this publication.  The TDD is electrically connected to the detonator mounted at the other end of the case via a cable routed through the mine’s internal conduit.  Note the tagged safety pin below that is only removed during mine assembly to provide an added measure of safety during storage and handling.

HIGH RESOLUTION DRAWING OF THE MK62 QUICKSTRIKE MINE'S, FIRING TRAIN  COMPONENTS

Location of Firing Train Components in a QUICKSTRIKE Mine Mk 63

·         The TDD’s battery provides electrical energy to power the TDD as it senses underwater stimuli from vessels in the vicinity following a safety time delay.  The battery also provides the energy to charge the TDD’s firing capacitors.  A new generation of lithium batteries is being fielded soon which will provide higher energy densities, increased reliability, and extraordinarily long shelf life.

·         The electric detonator is located within the closed end of the mine’s booster.  It typically consists of fine nichrome heating wire surrounded by a small quantity of very sensitive explosive material.  When the TDD initiates a mine explosion, the TDD’s capacitors discharge and the resulting current heats the wire to the point of exploding the detonator.  This electric detonator is much too small to ignite the mine’s main charge directly.  A simple analogy would be trying to light a log on fire with a common match, which would be difficult at best.  But, by lighting some newspapers with the match, the newspapers ignite some kindling, which is then able to ignite the log because of the kindling’s increased burn intensity and longevity.  In a mine, the electric detonator serves as the match, an explosive relay and fixed/rotated explosive leads in the arming device serve as the newspapers, a booster serves as the kindling, and the mine’s main charge signifies the log.  Utilizing a chain such as this is also important to ensuring ordnance insensitivity and safety.

·         The explosive relay fits into a cavity in the base of the arming device.  When the electric detonator in the booster fires, it sympathetically detonates the explosive relay, which serves to amplify the available explosive energy.  This increased energy is then passed to the fixed explosive lead within the arming device.  The fixed explosive lead then ignites the rotated lead, made possible only because these two leads have been pre-aligned via the arming sequence 

·         The booster accepts the explosive wave from the rotated lead, greatly amplifies its intensity, and transfers this increased explosive energy directly to the mine’s main charge.

The QUICKSTRIKE Mine Mk 63’s stairstep ignition sequence is illustrated in the simplified flow chart below.  Of course, this entire process is almost instantaneous in actual practice within the mine.  Most important, mine detonation cannot occur if the arming device is in the “safe” position, which keeps its internal explosive leads out of alignment.  This provides for enhanced safety for both minemen and aircrew alike throughout the mine’s stockpile-to-target sequence.

DRAWING DEPICTING THE MK63 STAIRSTEP IGNITION SEQUENCE

Firing Train Sequence of Events for QUICKSTRIKE Mine Mk 63

There are small variations to the above explanation, but the basic idea is sound for all mines. Bottom line: the functions, locations, and nomenclatures for the various components mentioned in the preceding paragraphs may change somewhat from mine to mine, but their safety interrupts, operation, and relevance in the firing train remain very similar.

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