WAUSAU, Wis. — A team of mechanical engineers funded by the Pentagon has an idea for saving the lives of troops in Iraq: an airless tire that won't go flat if shot or hit by shrapnel from a roadside bomb.

The tires, which are still under development at Resilient Technologies, are filled with compressed polymers, or plastic, instead of compressed air. The tension of the plastic provides strength, allowing them to work just like air-filled tires, said Ali Manesh, the company's chief technology officer.

The idea isn't entirely new, but Manesh is convinced he's found ways to overcome problems that have plagued other airless tires — such as dissipating the heat buildup that occurs when they're driven. A handmade prototype has already been built, he said.

A flat tire on a vehicle like the Army's Humvee, especially in urban warfare, makes it vulnerable to an ambush, said Manesh, a mechanical engineer who spent five years developing his idea before the $11 million government contract was awarded.

"You can have all the armor in the world you want on a vehicle, but if the tire is vulnerable, it is going to stop the vehicle. What the military hopes to do is develop the next generation of tire to help alleviate that problem," said Jim Dobbs, a Resilient Technologies spokesman.

The goal is to have an airless tire survive what Chief Executive Officer Robert Lange calls the damage of "something shy of a land mine" so the vehicle can still drive away from the danger.

Capt. Jason Stebbins, commander of the Wisconsin National Guard's 1158th Transportation Company, spent a year hauling equipment between Kuwait and Iraq. His big trucks traveled a combined 4.6 million miles, and his crews changed hundreds of flat tires because of punctures and blowouts.

The soldier had never heard of airless tires but likes the idea.

"I would like to have a set on my truck," Stebbins said.

Charles Pergantis, a mechanical engineer for the Army Research Laboratory in Maryland, said the Army uses what are called "run-flat" tires on some vehicles. They allow a vehicle some mobility even if the tires are flat. An airless tire is the next step, he said.

In 2005, Michelin, one of the world's largest tire makers, unveiled an airless tire, calling it a "tweel" — flexible spokes fused with a flexible wheel surrounded by a tread of rubber and no air pressure.

The tweel was described as the most radical change in the industry since the radial tire was invented nearly 60 years ago. Time magazine named the tweel as one of the most amazing inventions of 2005, but no products are being sold yet.

All Manesh will say is the series of web-like cavities on his airless tire make it different than Michelin's tweel.

The Army uses up to 200,000 tires for Humvees a year, said Lt. Col. William Wiggins, an Army spokesman at the Pentagon.

Pergantis said airless tires must provide comfort, no vibrations and little noise, in part because of the sophisticated electronics used in military vehicles.