Post-1991

 

♦ Mk 69

Training shape for California sea lions used for ordnance recovery.

♦ Mk70

Exercise and training mine for Mine Mk 52.

♦ Mk71

Training device to duplicate the trajectory of Destructor Mk 40.

♦ Mk72

Training device for Mine Mk 56.

♦ Mk73

Training device for Mine Mk 55.

♦ Versatile Exercise Mine (VEM) MK 74

The VEM Mk 74 is a specially constructed interactive mine simulator training device that represents a typical bottom mine. Cylindrical in shape, it is 9 feet long, 21 inches in diameter, and weighs a little over 1,200 pounds. It is used to assess the effectiveness of mine countermeasures (MCM) operations as well as providing realistic training for MCM forces. The VEM Mk 74 is designed to be representative of foreign threat mines and does not possess a U.S. Navy Service mine counterpart.

The VEM Mk 74 contains multiple sensors and programmable electronics housed in a mine case that presents a realistic sonar profile of a bottom mine. Each VEM Mk 74 can be programmed to emulate the target detection capabilities of various known bottom mines by emulating their mine-fire logic. In addition to emulating the logic, each VEM Mk 74 collects data from its sensors and provides it to exercise participants in either real-time or as stored data for later analysis. By exercising against such a device, mine hunting and sweeping forces can obtain a quantitative assessment of their effectiveness and vulnerability.

The VEM Mk 74 comprises two subassemblies: a three-foot buoy section is connected in line with a six-foot ballast section. The buoy section is watertight and houses the VEM’s sensors and microprocessor-based electronics. The sensors include three passive acoustic sensors located along the buoy section’s circumference at the 4, 8, and 12 O’clock positions. A triple-axis magnetometer, a seismic sensor, and a pressure sensor are also permanently installed. The buoy section is painted orange and the ballast section is painted white.

Other buoy section components include three active communication transducers interspersed between the passive sensors for the acoustic link. An inclinometer determines the VEM’s roll angle on the bottom. A pressure transducer measures the depth and adjusts the communication transducer’s output power accordingly. Two depth switches awaken the VEM upon water entry and also activate safety and security features that (1) prevent inadvertent release of the buoy assembly near the surface when an unseparated VEM Mk 74 is being recovered, and (2) erase the emulation programming (but not the recorded data) during recovery to prevent unauthorized access to classified mine emulations.

The ballast section anchors the VEM Mk 74 via a free-flooding case weighted with lead along its bottom to orient the VEM upright as it lands and to stabilize itself on the seabed. A release mechanism in the ballast section uses a cable cutter driven by pressurized air stored in a tank. Upon command via acoustic link or at a preprogrammed time, the cutter severs an internal wire rope, freeing the buoy section to surface.

 

♦ Versatile Exercise Mine (VEM) MK 75

Originally conceived as the Universal Laying Mine, the Mk 75 is a mine development project. Procurement was 3500 in FY86, at a total cost of $3.7 million. None were bought in FY87, but late in 1986 the navy hoped for 2400 in FY88 and 3600 in FY89. Engineering evaluation was completed during FY86, and approval for full production was expected late in FY87. Details have not been published, but presumably the universal laying mine is a new moored mine to replace Mk 56/57. The new mine is included in. the same pro-gram element as the Quickstrike series of new bottom mines. No Mark number has been announced.

The VEM Mk 75 is a specially constructed interactive mine simulator training device that represents a stealth type of shallow water mine. Shaped like a truncated cone, it is 18 inches tall, 38 inches in diameter, and weighs a little over 800 pounds. It is used to assess the effectiveness of mine countermeasures (MCM) operations as well as providing realistic training for MCM forces. The shape, in combination with an anechoic coating, results in a low target strength and a realistically small sonar shadow. The VEM Mk 75 is designed to be representative of foreign threat mines and does not possess a U.S. Navy Service mine counterpart.

The VEM Mk 75 contains multiple sensors and programmable electronics. Each VEM Mk 75 can be programmed to emulate the target detection capabilities of various known bottom mines by emulating their mine-fire logic. In addition to emulating the logic, each VEM Mk 75 collects data from its sensors and provides it to exercise participants in either real-time or as stored data for later analysis. By exercising against such a device, mine hunting and sweeping forces can obtain a quantitative assessment of their effectiveness and vulnerability.

The VEM Mk 75 comprises two subassemblies: a buoy assembly (with the truncated cone shape) sits atop a flat sinker assembly. The buoy assembly is watertight and houses the VEM’s sensors and microprocessor-based electronics. Both of these subassemblies are painted orange. The sensors include a passive acoustic sensor located atop the buoy assembly and a triple-axis magnetometer housed within it.

Other buoy assembly components include an active communication transducer, also facing upward atop the VEM. An inclinometer determines the VEM’s roll angle on the bottom. A pressure transducer measures depth and adjusts the communication transducer’s output power accordingly. Two depth switches awaken the VEM upon water entry and also activate safety and security features that (1) prevent inadvertent release of the buoy assembly near the surface when an unseparated VEM Mk 75 is being recovered, and (2) erase the emulation programming (but not the recorded data) during recovery to prevent unauthorized access to classified mine emulations.

The buoy assembly also houses a pair of spring-loaded release mechanisms. Upon command by acoustic link or at a preprogrammed time, they release their grip on a corresponding pair of sinker assembly attachments, freeing the buoy assembly to surface. The lead-weighted sinker assembly attaches underneath the buoy assembly to orient the VEM Mk 75 upright as it lands. It has a flat bottom to stabilize itself on the seabed.

This mine may be associated with a new parachute flight-gear Mk 16 for 500-lb mines.

♦ MOWAM

EDO's private-venture mobile mine project is designed for use principally against amphibious vehicles in shallow water. MOWAM would be deployed from helicopters or small patrol craft. MOWAM would appear to be a bottom-laid rising mine, triggered acoustically, that would use a rocket motor and a magnetic proximity fuze. These data were published in 1986.



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Derick S. Hartshorn - 2009-present
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