For a while, the U.S. military worked and worked to develop a sticky foam that could stop rioters in their tracks. The goop never quite panned out (despite some rather hilarious pictures, like this one to the right). But that isn't stopping the Army from trying again. This time, it's hostile vehicles, not angry individuals, who are going to get slimed.

There was some initial excitement over sticky foam during the Marine deployment to Somalia in 1995; troops used it to help cover a retreat. But there were problems with the weapon, too. For example, "people could move their feet faster than the sticky foam could be applied," according to one account. "Although ... if you hit a person's thighs his legs sometimes stuck together." Not surprisingly, interest in the anti-personnel foam faded pretty quickly from there.

Perhaps encasing a car or truck in goop will prove less problematic, however. The Army recently awarded a small business contract to Adherent Technologies of Albuquerque, New Mexico, to develop the "foam-based vehicle arresting system," which could stop a car or a truck before it gets close enough to do real damage. According to the contract description, the system would consist of "low-profile containers, each containing enough foam base to generate several cubic meters of high-strength foam."

In theory, the foam would "instantly disable" the oncoming vehicle by clogging up the engine intakes and blocking the steering mechanism. The foam would absorb the vehicle's kinetic energy, bringing it to a stop. "Lastly," the company says, it "will leave the driver trapped inside an encapsulated vehicle, with no means of orientation." The system could be tripped automatically (through pressure sensors or light barriers) or by remote control. It's one of a bunch of new technologies being floated for stopping a runaway (or suicide) truck.

Sliming an enemy vehicle is an idea that's been around for a while. In 1993, one Moishe Garflinkle of Philadelphia patented a method of stopping armored vehicles "with a rigid polymeric foam within which is dispersed metallic flakes."

Maybe this time, the idea will, er, um, stick around.

– Noah Shachtman and Nathan Hodge

*[Photo: (c) Corbis, used with permision] ***