The military - increasing its reliance on robots in war - soon will use explosive-sniffing versions made by a Massachusetts company to better detect roadside bombs accounting for more than 70 percent of the U.S. casualties in Iraq.

Fido is the first robot with an explosives sensor integrated into its body. iRobot Corp., of Burlington, Mass., is filling the military's first order of 100 in this southwest Ohio city and will begin shipping the robots over the next few months.

There are nearly 5,000 robots in Iraq and Afghanistan, up from about 150 in 2004. Soldiers use them to search caves and buildings for insurgents, detect mines and ferret out roadside and car bombs.

As the war in Iraq enters its fifth year, the federal government is spending more money on military robots and the two major U.S. robot-makers have increased production.

Foster-Miller Inc., of Waltham, Mass., just delivered 1,000 new robots to the military. iRobot cranked out 385 robots in 2006, up from 252 in 2005.

The government will spend about $1.7 billion on ground-based military robots between fiscal 2006 and 2012, according to Bill Thomasmeyer, head of the National Center for Defense Robotics, a congressionally funded consortium of 160 companies, universities and government labs. That's up from $100 million in fiscal 2004.

Fido, produced at a GEM City Manufacturing and Engineering plant, represents an improvement in bomb-detecting military robots, said Col. Terry Griffin, project manager of the Army/Marine Corps Robotic Systems Joint Project Office at Redstone Arsenal, Ala.

The bomb-sniffing sensor is part of the robot, with its readings displayed on the controller along with camera images.

Otherwise, a soldier would have to approach the suspect object with a sensor or try to attach it to a robot. The new robot also has a 7-foot manipulator arm so it can use the sensor to scan the inside and undercarriages of vehicles for bombs.

Officials would not release details of how the sensors work because of security concerns.

"The sniffer robot is a very good idea because we need some way of understanding ambiguous situations like abandoned cars or suspicious trash piles without putting soldiers' lives on the line," said Loren Thompson, defense analyst with the Washington, D.C.-based Lexington Institute.

Philip Coyle, senior adviser to the Center for Defense Information in Washington, said the robots could be helpful if they are used in cases where soldiers already suspect a bomb. But he said explosive-sniffing sensors are susceptible to false positives triggered by explosive residues elsewhere in the area, smoke and other contaminants.

"The soldiers can begin to lose faith in them, and they become more trouble than they're worth," he said. "It can slow down things."

Thompson said all military robots have limitations. Their every move must be dictated by an operator, they can be stopped by barriers or steep grades, they are not highly agile, and they can break down or be damaged, he said.

Robots range in size from tiny - 1.5 pounds - to brute - 110-pound versions that move rubble and lift debris. Fido is an upgrade of PackBot, a 52-pound robot with rubber treads, lights, video cameras that zoom and swivel, obstacle-hurdling flippers and jointed manipulator arms with hand-like grippers designed to disable or destroy bombs. Each costs $165,000.

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