Stopping intruders can be a sticky mess: Joint non-lethal program office funds development of Mobility Denial System.

In the future, U.S. military peacekeepers and law enforcement authorities may use a novel sticky gel to prevent trespassers or troublemakers from entering a building or to stop a run-away vehicle without having to use lethal force.

The gel is part of a crowd-control anti-traction technology currently in development, known as the Mobility Denial System.

MDS is supposed to serve as a deterrent to intruders who may be trying to break into an embassy or any restricted facility, said Marine Capt. Joseph Kloppel, a spokesman for the Joint Non-Lethal Weapons Directorate, in Quantico, Va. "The whole purpose of a system like this is to see what the person's intentions are.

"It gives the commander on the ground options other than tear gas and more of a flexible response," he said.

The Mobility Denial System consists of three parts, explained Bill Mallow, one of the inventors of MDS at the Southwest Institute, in San Antonio, Texas. One component is a liquid polymer emulsion, the other component is a polymeric powder that produces a slurry, which then is pumped into a nozzle where it meets a stream of water.

"When it hits the water it turns into a viscous, elastic, sticky, slimy, slippery gel," he said. "The resulting gel is 95 percent water, and the other 5 percent is a polymer pretty much used in soft contact lenses and baby diapers as an absorbent."

The gel remains slippery for many hours. "When it dries, it can be swept away or be reactivated with water," Mallow said. The anti-traction substance is effective at surface temperatures ranging from 32 to 125 degrees Fahrenheit and lasts for six to 12 hours.

The substance sticks to grass, asphalt, concrete, wood, metal, walls and most other surfaces, Mallow said. "On walls, it prevents people from bringing ladders. ... The ladder will slip and the person will fall."

The gel also can be sprayed on people, in which case, "it would make them extremely miserable and distract them from any intentions they had," Mallow said. "It makes door knobs and windows totally inaccessible."

What makes MDS work is the powder that is mixed with water to create the gel.

Trying to walk on the slurry substance can cause injuries, explained Mallow. "People can't control the way they fall," he said. "The fall can be traumatic." Once the substance comes in contact with water, it reacts instantaneously.

Mallow said that there are serious concerns about the psychological and physical dangers of the Mobility Denial System. "I don't know who is going to account for the broken legs," he said. "Also, [people] will be a slimy mess of worms."

"It is non-lethal, but it can be lethal," he added. When they fall, people can break their backs and even fracture their skulls.

He said the Marines worry about the potential consequences of deploying MDS and are considering putting up barricades and barbed wire in addition to the sticky gel. That assumes they would have time to do that, which often is not the case in military operations.

Two methods are used to dispense the MDS gel. A vehicle-mounted system provides wide-area coverage and a self-contained, man-portable dispenser that can focus on specific targets. A man-portable system weighs about 55 pounds when loaded and carries enough material to cover a 2,000 square-foot area. It is hand-pumped and has a two-gallon reservoir of water and a quart of the polymer.

The vehicle-mounted system fits in the cargo compartment of a Humvee truck and provides about 100,000 square feet of coverage. "That can cover a couple of football fields and can be pumped at a very rapid rate," Mallow explained. "The vehicle can cover a road, bridge, parking lots in just seconds." The polymers are carried in five-gallon pails that can be pumped into a reservoir, which then can be pumped into the nozzle to come in contact with the water.

The institute received a two-year $200,000 contract to develop the MDS. The Non-Lethal Directorate is investing $950,000 overall on mobility denial systems. There is still work to be done on the dispensing equipment and quality control, said Mallow. So far, the institute used makeshift devices to test the product. The most expensive items will be the dispensing equipment and the environmental and toxicity studies, he said. "The Marines are concerned about that."

But Mallow contends that the MDS is nontoxic and biodegradable. The formula needs to be optimized, he noted. "It could be improved. ... We are looking at, materials from the same general class to see if they are better to remove."

Disposing of the material is still an unsolved problem. "A group of Marines that successfully kept a crowd at bay may have to doss that area too," Mallow said. "We have to come up with a countermeasure to deactivate the product."

According to Mallow, though, the system could be ready for deployment by 2003 or 2004.

The system could be used by any peacekeepers, police, civil defense and United Nations forces. But the patent belongs to the U.S. Marine Corps.

RELATED ARTICLE: Acoustic-Energy research hits sour note

Acoustic-energy weapons have intrigued military scientists ever since the Germans boasted about them during World War II. But after decades of research, such weapons have yet to be fielded.

The Joint Non-Lethal Weapons Directorate stopped funding acoustic-energy research, a program it has inherited from the Army. Nevertheless, there is some ongoing work on acoustic weapons at the Army's Picatinny arsenal, in New Jersey. A company named American Technology Corporation (ATC), based in San Diego, currently is working with scientists from the arsenal on a new type of acoustic weapon.

ATC has been developing the directed stick radiator, a weapon that fires high-intensity sonic bullets, said the company's chairman Elwood Norris. The device could be used to inflict pain and disorient. The directed stick radiator is encased in a polymer composite tube about one meter long and four centimeters in diameter. The company acquired the patent from a German scientist.

The weapon is directional, explained Norris, and is only effective at distances of no more than 15 feet. "It works in the range of hearing and it is so intense that it is painful," said Norris. However, "for crowd-control [this weapon] wouldn't be enough," because it wouldn't cover a large enough area.

The directed stick radiator is light-weight, battery-powered and could be clipped to an M-16 rifle.

According to Kevin Stul, an engineer at the Non-Lethal Weapons Directorate, any sound between 125-150 decibels is considered effective. "It is difficult to reach that level of acoustics beyond several meters," he said.

"There is not a repeatable universal bio effect that we can take advantage of with acoustics," said Stul. This is one of the main reasons why his office dropped the program. "We set up an executive criteria for the Army to demonstrate that you can achieve a repeatable bio-effect in an animal," Stul told National Defense.

"You'd expose a surrogate to whatever frequencies of acoustic energy and that animal would display some sort of adverse effect and that would be a repeatable event if you exposed any animal to that set of frequency."

But the Army could not demonstrate that effect he said. "Even if you are able to achieve incapacitation, it is very difficult to propagate acoustic energy."

"The responses are not universal," said John Kenny an acoustics engineer at the Applied Research Lab at Penn State University. "Most non-lethal weapons rely on pain to get people to comply." Kenny said the use of acoustic weapons was based on the same idea of inflicting pain.

"Pain aversion is related to [people's] motivation," Kenny said. "You are in Washington and you are in some kind of demonstration and the police asks you to disperse--you get out of there. But if you are in Palestine and if they had bombed your house already, killed your family there isn't any non-lethal weapon that is going to stop you."

David Swanson works at the advanced sensors and control department of the laboratory. "Sound in the air is essentially harmless physically," he said. But short bursts of sounds can cause some damage. "Very high amplitude sounds with sharp pressure rises can tear cell structures and damage nerves," he said during a presentation at Quantico, Va. "Damage to the cochlea and auditory nerve sensor cells are considered permanent, while the middle and outer ear can be surgically repaired."

The severe ringing which accompanies deafness can sometimes lead to insanity, Swanson said. In Third World countries, where illiteracy is fairly high, the loss of hearing could be a worse handicap than amputation. In the United States and other NATO countries, hearing aids and hearing loss disability are the most costly health claims, said Swanson. Ultimately, if hearing loss occurs, an acoustic non-lethal weapon is no longer effective. For a non-lethal acoustic weapon to be effective it must be disruptive to the neural pathways to the brain, said Swanson. Also, it must not cause any hearing loss.

According to Swanson, acoustic energy weapons would be effective in water. "The sound that passes through water can destroy cells," he said. "You can be seriously injured or killed, depending on the frequency and range." However, they can stay non-lethal at a certain range.

Air Force Major Noel Montgomery, chief of health effects assessment at the Non-Lethal Directorate, explained that there are two types of acoustics: audible-such as flash bangs and loud music-and a field called infrasound.

Infrasound is too low in frequency to be heard by human ears. Montgomery explained that anything below 20 hz is considered infrasound. But that effort was discontinued, because the military users wanted a quieter, stealthy weapon, he said.

Infrasound in the air, additionally, does not couple well with the human body. "It just bounces off," he said. "In order for it to cause an effect you have to have a huge amount ... We could not generate as much." The effect of powerful infrasound would be pain, resonance in the body organs and even liquefaction of the bowels, said Montgomery. But he added that only 10 percent of the people exposed to infrasound get nauseous.

Operator safety is a critical consideration, said Stul. The people using the weapons could have been just as adversely affected as the people targeted. He pointed out that special application of acoustics cannot be ruled out For example, it could be used for security applications, in combination with other weapons.

A multi-sensory grenade is being developed under a Marine Corps contract at Science and Research Associates in San Diego. "They have been playing with all sorts of different irritants," said Stul. The grenade would combine audible sound, flaring light and smell.

A SARA official refused to comment on the development citing company policy and government confidentiality. Jim Wes, a business development executive at the company, said that acoustic weapons and other sorts of non-lethal weapons will not necessarily defeat an attacker, but are useful tools to assess the intentions of potential criminals.

Meanwhile, General Dynamics Bath Iron Works, in Bath, Maine, is developing an acoustic-energy weapon that potentially could have applications in ship self-defense, said Vince Quintana, a company engineer.

During the Surface Navy Association Symposium, in Arlington, Va., Quintana told National Defense that the Navy is considering testing this technology as an alternative means of defending a ship when the commander may not want to fire lethal rounds against an approaching vessel.

The acoustic energy weapon, if it works, could disable a suspected enemy ship's crew. However, Quintana cautioned that the technology is not fully mature.

The system in development at Bath Iron Works would be based on commercial technologies. The hardware includes a high-end, medium-range wireless communications system, wearable computers for the ship sentries, a notebook computer for the commander in charge of the ship and up to five acoustic projectors that would be installed around the ship.

These types of non-lethal weapons, said Quintana, would give ship commanders flexibility to deal with potential aggressors "without getting mired in the seriousness of consequences" associated with the use of lethal fire.