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Improving Creep and Probe

We believe three currently available technologies, when used together, could offer a 10- to 20-fold improvement over today’s demining rate within the next two years. These technologies include detection by a variant of the electronic metal detector (called the meandering winding magnetometer); safe and swift excavation by a device called an air knife; and detonation by a cheap and easily deployed foam-like explosive. All three of these improved demining technologies still require field testing and refinement, but the development tasks look modest.

The basic operating principle of the new meandering winding magnetometer (MWM) detector is the same as that of conventional metal detectors that use a pulsed-electromagnetic induction sensor. But whereas conventional detectors generate an electromagnetic field and sense if it is disturbed by conducting material in their path, MWM detectors generate a varying magnetic field that excites currents in metallic objects that align primarily in one direction and can be read by the detector. An MWM detector slightly larger than a conventional metal detector can thus obtain a crude hint of the size and shape of a buried metallic object by combining readouts of these so-called eddy currents. The MWM detector now being developed by Jentek Sensors Inc., of Brighton, Mass., can reportedly determine the rough size, shape, depth of burial, and type of material of the outer shell of a buried metal object. Laboratory evidence indicates that the device can provide enough information for an experienced operator to discern whether a buried object is mere clutter, a mine, or a larger piece of unexploded ordnance.

Field tests of a first-generation MWM prototype indicate that it can lower the false-alarm rate by a factor of 5 to 10 below that of a conventional metal detector. Given such discriminating power, a refined version of such an MWM device could reduce the time spent examining a square meter of scrap-rich ground from 10 to 20 minutes to a fraction of a minute.

Once a mine is detected, the air knife, now commercially available although not in field-ready form, offers a significant improvement in efficiency and safety over the stick commonly used in today’s demining efforts. The air knife blows high-pressure air through a small hand-held probe and can blow away most dirt to expose mines without disturbing them enough to detonate them. Existing air knives are powered by a 3-horsepower gasoline engine, like those that run power lawnmowers, and cost a few thousand dollars. A version adapted for demining could replace the simplest manual probes, greatly speeding up a searcher’s ability to expose a mine while improving safety at the same time by obviating the need to dig in the ground with a stick.

The use of the product Lexfoam will also aid demining efforts. The product, much like shaving cream in appearance, is a dilute dispersion of an explosive contained within a foaming plastic substance. Lexfoam is safe and simple to apply and can be set off by an ordinary detonation cap, removing the delicate and hazardous task of wiring a charge onto an unearthed mine. We estimate the use of such a product to blow up the exposed mine would considerably speed up the overall demining process, perhaps by as much as a factor of 2 to 5.

The air knife would require an air compressor (or compressed air supply) carried on a hand-drawn wheeled cart, packaged into a backpack-like portable unit, or built into a small motorized vehicle that carries the MWM metal detector, air knife, and Lexfoam dispenser. In a small, relatively new humanitarian demining unit at Fort Belvoir in Virginia, the U.S. Army is now assembling such a vehicle that combines an MWM detector, compressor, air knife, an operator’s plastic shield to protect against explosion, an air-operated weed-cutter, and a Lexfoam dispenser. Col. Harry (Hap) Hambric, who directs development and testing in this unit, estimates that the combined use of these relatively simple technologies where terrain is suitable could speed up demining by a factor of 10 within a year or two, and another factor of 10 with refinements to come.

Just as creep-and-probe methods can find quick technological improvements, though, the brute force demining of open spaces, like field and paddy, can also profit almost at once by the adoption of simple technical improvements. One promising approach proposes to use a small-sized tined roller with hinged spring-loaded prods that can set off anti-personnel mines as it passes over them. The rope-towed (or winched) roller is simple, inexpensive, and easy to repair. It contains hundreds of closely spaced, stiff, spring-mounted fingers able to penetrate up to 25 centimeters into the ground; the roller is towed back and forth across the target area using power supplied by animals or motor vehicles kept at a safe distance.

Tests under controlled conditions performed by the U.S. Army at Fort Belvoir in 1995 proved that the roller was capable of exploding or otherwise destroying small anti-personnel mines even in the mud bottom of rice paddies and other soft floored terrain. A footpath-sized version of the roller also proved to be easily repaired using simple hand tools and hardware. The roller was effective against mines in soft ground and mud. With some design modifications it could be configured to operate on harder surfaces, including areas bearing light foliage.

Thus in certain terrain this technology will allow the welcome option of clearing anti-personnel mines without detecting them first. The Fort Belvoir experts estimate the cost of this multi-pronged roller to be under $20,000, adding that it could drop to as low as $5,000 if the device were mass-produced. The group hopes to field test the system shortly. Taking tools of this sort into the field-even these initial aids imply further improvements-will make a large difference at whatever scale they are put to work. The whole job cannot be finished soon; indeed, a long-lasting culture of understanding and vigilance in the whole countryside, and a reliable source of technical aid from beyond the village-including personnel, equipment, and training-will have to be established in the most affected countries. Determination to keep up and extend the good work will thrive if visible progress comes soon in one or two places.

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