The obvious way to protect Humvees from roadside bombs is to add armor, but the military is looking at a new design that protects them with chimneys:
The chimney was designed by a small Maryland firm, Hardwire L.L.C., which is working with AM General, an Indiana company that has built 270,000 Humvees since the mid-1980s. Hardwire is run by a colorful group of aeronautical engineers who say they took a fresh approach to evaluating how to make the vehicles safer.
George Tunis, the company’s chief executive, likened the chimney to an exhaust vent on a rocket.
He said that rather than just piling on more armor to absorb the blasts, as has been typical in the past, the idea was to disperse as much of the explosive energy as possible.
Tests show that the explosive gas from a roadside bomb can accelerate to speeds as high as Mach 4 in less than a millisecond, Mr. Tunis said, or far less time than it takes to blink an eye.
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Mr. Tunis said the chimney, which is hidden next to a gunner’s turret atop the Humvee, is the biggest change. But like the mine-resistant vehicles, the Humvee prototypes have V-shaped steel bottoms to deflect parts of the blasts.