Custom Search
|
|
  |
|
|
The components used in a mine vary, depending on the type of mine and its specific use. In addition to the mine case and explosive system, mine components provide mine arming, target sensing, actuation, laying control, countermeasure resistance, firing power, and sterilization. Exercise components are used in exercise (recoverable) mines. Mine Case The mine case is the main element of the mine. It contains or carries all other components. The mine case is normally made of sheet steel, but aluminum, spun glass, or various plastics are used in some types of mine cases. The case is watertight and strong to resist water pressure. Mine case openings are carefully sealed with suitable gaskets. The explosive system of a mine includes the main charge, the booster, the initiating system, and auxiliary explosive devices. MAIN CHARGE.- The main charge is the mine's payload. It is a high explosive cast directly into the mine case, or into an explosive section attached to the mine case when the mine is assembled. The amount of explosives used in air-laid mines ranges from 160 pounds to 1,300 pounds. Types of explosives used include Comp B, TNT, H6, or HBX mixtures. The HBX mixtures are commonly used explosives. BOOSTER.- The booster varies from a few ounces to several pounds of explosive. Generally, the smaller boosters contain tetryl, and the larger boosters contain granular grade A TNT. The intermediate size booster contains Comp B. In some cases, the booster consists of a subbooster. The booster is housed in either a brass, terneplate, plastic, or fiber container. When assembled in the mine case, the booster is in intimate contact with the main charge explosive, INITIATING SYSTEM.- An electric primer in an explosive fitting is used to set off a flash detonator. This initiates the leads to the booster or subbooster, causing the mine to detonate. Explosive fittings may contain a primer or a detonator, depending on their design function. AUXILIARY EXPLOSIVE DEVICES.- Auxiliary devices are usually small explosives that blow or open a hole in the mine case to sink it. A small explosive device, such as the explosive driver, is used during the mine planting or operating sequence. For example, it is used to close or open electrical switches, unlock mechanical linkages, open gas bottles, and jam cables from further payout. Other types of auxiliary explosive devices are used to cut cables and to release pyrotechnic signals from exercise and training mines. Arming Components An arming device (fig. 5-10) is a combination of a hydrostatic switch piston and an explosive aligning piston. They are internally mounted in a single
Figure 5-10.-Arming device. 5-9 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 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. 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 armed. The parachute pack currently used is the 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 parachute release gear consists of a metal ring that attaches the parachute to the mine during air travel. It is released from the mine upon water impact by inertia weights, wipe-off plates, or hydrostatic mechanisms. The control device opens the parachute during the mine's descent. It is usually controlled by an adjustable fixed-delay device. Since the parachute is deployed by firing an explosive fitting, parachute pack control devices contain explosive components. |
 
|
|
|
