Sandia Lab News
December 5, 1997

Labs developing means to sniff out mines chemically and electronically

Menace of land mines almost an insurmountable problem

Chris Miller

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Sandia has joined the effort to rid the world of what Ron Woodfin (2522) describes as "the worst form of pollution mankind has ever come up with" - land mines.
MINE SNIFFER - Phil Rodacy (1552) demonstrates a mock chemical sensing detector on an antitank mine in the makeshift minefield in Tech Area 3. The final field-ready sensor probably will look similar to the mock detector and will be easy to use. (Photo by Randy Montoya)

Ron oversees much of Sandia's exploratory work in land-mine detection and demining, which ranges from chemical sensing to laying down a quick-hardening foam to clear a path for military vehicles. Sandia also is developing robotic vehicles and backscattered X-ray technologies that can be used to support the demining effort.

The Sandia team focuses its efforts on three types, or levels, of demining activities.

The first is standard military demining used for clearing a path for soldiers and vehicles during war. Speed counts, and some casualties are expected.

The second level, also connected with military operations, deals with an army's need to clear greater numbers of mines in an occupied country. This is similar to the case of the United Nations' occupying forces in Bosnia-Herzegovina.

The third level is humanitarian demining and involves trying to remove all mines and restoring an area to productive use.

'No silver bullet'

Ron, who has represented Sandia at several international conferences on demining, says the general consensus is that there is no "silver bullet," or one technology that can unfailingly detect all types of mines under all types of conditions.

Current state-of-the-art demining technologies are mostly various forms of anomaly detectors - they detect things not expected in their environments. The detectors use passive infrared, microwave, electrical conductivity, and ground-penetrating radar, but they so far have been very expensive and low in accuracy and have high false-alarm rates.

Metal detectors are the most prevalent form of electronic mine detection but are largely

ineffective for some of today's plastic mines. And like all anomaly detectors, metal detectors give high rates of false alarms in battle zones filled with bullet casings and other metal debris.

Brute force methods using plows, rakes, and explosive breaching are sometimes used to clear a path for soldiers and vehicles but almost always fail to find or detonate all mines. The most reliable method of mine clearing, but also the slowest and most dangerous, is manually probing the soil with a rod.

Worldwide, there are an estimated 100 million land mines in 68 countries. Those with the worst problems are Angola, Afghanistan, Cambodia, Iraq, Laos, and Bosnia-Herzegovina.

Each year an estimated 100,000 mines worldwide are cleared, but 2 million are laid. An average of 2,000 people each month are killed or maimed by land mines.

"Even if everyone stopped laying mines today, it still would take 1,000 years to clear those now in the ground throughout the world," Ron says. "In my mind, it's the worst form of pollution mankind has ever come up with, bar none."

Chemical sensing

One of the most promising technologies under development at Sandia to identify sea mines, land mines, and unexploded ordnance is chemical sensing.

All mines emit molecules of the explosive chemicals contained inside them. Sandia is helping to develop a portable system incorporating ion mobility spectrometry (IMS) - the same technology developed for the explosives-detection portal to check airline passengers (Lab News, Sept. 12) - that will be capable of quickly detecting and classifying minute quantities of explosives molecules.

The system is not an anomaly detector - it looks for the explosives molecules themselves rather than a container holding the explosives. It incorporates a new Sandia-developed concentration technology, which potentially can chemically amplify the source strength thousands of times.

The project originally was directed at detecting sea mines and unexploded ordnance in shallow water and is sponsored jointly by DOE and the Department of Defense, Office of Munitions. Many land mines are placed in shallow water such as rice paddies, fords, domestic water sources, laundry areas, and irrigation canals.

That work, which is ongoing, has since been expanded to include land-mine detection with the help of Defense Advanced Research Projects Agency (DARPA) and Laboratory Directed Research and Development funding.

"We are the world leader by a nose in the area of chemical sensing for explosives classification, and we will be able to demonstrate that soundly in the next six months," says Ron, who has worked closely on the project with numerous Sandians in a cross-section of disciplines. They include Joe Simonson (2422), Phil Rodacy (1552), Bill Chambers (1824), Greg Frye (1315), Jim Phelan (6131), Steve Webb (6524), Ed Jones (2522), Bernie Gomez (2522), Pam Leslie (1552), Chuck Rhykerd (5848), Steve Reber (1552), and David Faucett (2522).

Explosives in soil, air, and water

Jim and Steve Webb are supporting the development of the land mine chemical sensing technology by modeling the environmental fate and transport (EF&T) of explosives signature molecules. They are analyzing how environmental conditions such as temperature and precipitation influence the movement of explosives molecules through soil, air, and water.

"What this work will emphasize is the significant influence of environmental conditions, such as temperature, soil type, precipitation, and evaporation on the movement of chemical signature molecules to locations that can be detected by the chemical detector," Jim says.

"For instance, the amount of explosives signature molecules emitted from a mine in Bosnia may show a much different concentration at the ground surface than a mine in Iraq or Afghanistan. We'll also evaluate such things as whether it's better to look for mines in the afternoon when soil is warmer rather than during the morning, and how rainfall affects detection."

DARPA is co-funding the effort through a DoD/DOE/EPA program called SERDP, or Strategic Environmental Research and Development Program.

Mock minefield in Area 3

Phil and Bill have been doing much of the field work related to the development of the chemical sensor technology. They periodically take soil samples from a small mock minefield inside a fenced area at the south end of Tech Area 3. The minefield contains six unfuzed antitank mines and several surrogate mines made of plastic or consisting of metal boxes painted with explosive compounds. They also plan to conduct field tests on small antipersonnel mines.

Phil and Bill periodically analyze soil samples to determine the concentration of explosives molecules that can be found at various distances from the mines. They also have taken samples in shallow water for the chemical detection of unexploded ordnance (UXO).

Water and soil pose different challenges, they say. Explosives dissolve easily in water, making it difficult to extract the explosives molecules. Water also is often a dirty environment, with salts, organic materials, and pollution interfering with the detection process. Soil also has interfering chemicals, and environmental factors such as moisture and temperature can affect the performance of the technology.

The IMS technology already has successfully analyzed both water and soil field samples in the laboratory at the Explosive Components Facility. The technology also was successfully demonstrated in the field on San Clemente Island as part of a two-year program with the Office of Naval Research.

Portability the goal

The goal now is to reduce the technology to the portable stage, which has been aided by a new IMS designed and developed by Electronic Research Group in Las Cruces, based on work done at New Mexico State University.

Ron estimates a portable system weighing no more than 20 pounds will be ready to field test for sea mines by next spring. The system probably will have a sensing tube that extends from a box and will be simple to use: A green light will indicate the unit is sampling but has found no explosives; a yellow light will mean a small concentration of explosives has been found and that further sampling is required; and a red light will indicate that a significant concentration of explosive has been detected.

Phil said if the water field tests go well in the spring, the technology should be in use by the military and available for licensing within another year. The soil IMS system probably will be ready for field use a year or two after that.

"We want to get this down to what one person can carry reasonably comfortably, and which ultimately could be put on some robotic crawler of some sort," says Bill. "The push is really to scale this down to a rugged, lightweight package for the field."

DARPA is also funding a parallel three-year project by Sandia and an industry partner, Nomadics Inc., of Stillwater, Okla., directed at efficient chemical sensing of land mines. This project will use results of Jim Phelan and Steve Webb's EF&T model, as well as the analysis results of Phil Rodacy and Bill Chambers. Joe is managing the project, which is part of a large DARPA chemical sensor development program involving multiple universities, industrial researchers, and national labs.

The program seeks to develop artificial sensors that can successfully mimic the extreme sensitivity and specificity of trained dogs. The Sandia/ Nomadics responsibility in this program is to design a "front end" prototype that can quickly and efficiently gather traces of explosive materials in the field and deliver them in usable form to the various chemical sensors.

Development of a miniaturized mine detector is one of the applications of a wider Grand Challenge LDRD Proposal to develop an autonomous microscale chemical laboratory, more commonly called "ÁChemLab."

Greg Frye says Sandia's microfabrication capabilities are being used to develop chemical sensing modules the size of a postage stamp that will be used to make microchemical-analysis systems the size of current palm top computers.

The systems will have unprecedented capabilities for sensitively detecting and deciphering detailed chemical signatures. They will have a wide variety of uses in areas such as covert sensing for nonproliferation, contraband and land-mine detection, medical diagnostics, and environmental and process monitoring.

Backscattered X-rays

Sandia also is receiving funding from the US Army as well as through a DoD/DOE Memorandum of Understanding managed by Tom Hitchcock (2521) to help develop a mobile, continuously scanning X-ray machine that can detect mines. Steven Shope (9521), project manager of the backscattered X-ray project, says in September the technology successfully imaged antitank mines buried in sand and rocky New Mexico soil. The image showed enough detail to ascertain the type of mine and the location of its fuze, which is important for unearthing it.

"This was the first time this technique had been demonstrated in the field," says Steven, who has worked on the project with Grant Lockwood (9311) and Joe Wehlburg (9521). "It's the only process that gives a real-time image of a buried mine."

Development of a field-ready prototype, however, is still about a year away, and it could be another year after that until the backscattered X-ray mine detector is in actual use.

The continuously scanning X-ray machine itself was designed and fabricated by Imatron Inc. under contract to the US Army's Night Vision and Electromagnetic Sensors Directorate (NVESD) at Fort Belvoir, Va. Sandia was contracted by NVESD to prepare the X-ray unit for field tests, to integrate Sandia-developed detector technology, and to integrate imaging algorithms developed by the University of Florida into a fieldable land-mine detector.

The technique relies on the absorption and scattering of energetic photons. A detector system located above the soil intercepts backscattered photons. A higher detector response is recorded when the beam strikes a plastic land mine than when it strikes only soil.

For the recent field test, the experimental backscatter X-ray imaging system was suspended from a gantry that rolled on small, movable tracks above a small field in which several antitank and antipersonnel mines had been buried. The information was sent to a computer situated in a van near the field.

"The system can image land mines down to about four inches through water and snow and all types of debris such as rocks, logs, and leaves," Steve says. "It can image one square meter in about five minutes."

Steve says now that the technology has been successfully demonstrated in a field test, the next step is to produce a prototype system that probably will go into a redesigned Humvee. An ideal platform for the detector system itself, Steve says, probably would be Sandia's Remote Telerobotic Vehicle for Intelligent Remediation (RETRVIR), an all-terrain vehicle that has a robotic arm that can dig and pick up objects weighing up to 250 pounds.

Foam countermine development

Ron also is project manager and principal investigator for another MOU-sponsored project to determine the effectiveness of rigid polyurethane foam to neutralize mines and barriers.

Several field tests have been conducted to determine the effectiveness of quick-hardening foam to serve as a cushion against land- and water-mine explosions for vehicles and soldiers. The foam has successfully withstood the weight of trucks and tanks.

Although the field tests so far have shown that the foam is adequate from the standpoints of wear and strength, further work and tests are continuing, including explosives experiments in air, soil, and water, Ron says.

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