There's one for every 50 U.S. troops in Afghanistan. Typically they get the most dangerous assignments -- they're sent to inspect roadside bombs, enter suspicious buildings before others, and search for Taliban fighters in remote and hostile areas.
They're robots, and their numbers are expanding rapidly. During the next two years, the number of robots is expected to nearly double to one for every 30 troops in combat, said Robert Moses, who heads the government and industrial robots division of Boston-based iRobot.
The machines are quickly becoming more sophisticated, and as they do, they will take on more chores that humans would rather not do, Moses said. Already, small remotely piloted helicopters are delivering supplies to troops in hostile areas. Expect to see robot trucks in convoys delivering supplies by road soon, he said.
"We've got some technology that we're putting on our robots that map where the robot has been" so an operator can safely explore the interior of a suspicious building. If communication is lost, the robot will automatically head back to its base to re-establish communication. And a "self-righting capability" enables robots to sense when they have tipped over and get back upright, he said.
There are an estimated 2,000 robots in Afghanistan today. They're mainly used for explosive ordnance disposal, but they're branching out. Equipped with wire cutters, spades, rakes and cameras, iRobot's bomb-inspecting PackBots also are used for clearing supply routes and inspecting vehicles at checkpoints.
"That's not what we originally designed it for," Moses said. But the Army likes its performance enough to have bought 350 during 2010. Four have been destroyed in explosions, others have come back in pieces for repairs, he said.
The robots, which weigh 60 pounds and move on treads like miniature tanks, can be equipped with chemical and biological weapons sensors and an assortment of cameras for reconnaissance.
iRobot is developing a smaller 30-pound robot and a tiny 5-pounder that infantry troops can carry in their backpacks. The infantry "is a much larger market than explosive ordnance disposal," Moses said.
And the market extends well beyond the U.S. military. iRobot sells its machines to 23 countries, mainly for military use, he said.
Worldwide, as many as 80 countries already are using or are acquiring robots for military use, according to ABI Research, a New York-based market research firm.
"The market for military robots will remain healthy," growing from $5.8 billion in 2010 to $8 billion in 2016, ABI said in a mid February report.
Unmanned aerial, ground and underwater vehicles "all have in common the purpose of taking the place of or supplementing humans in battlefield situations," ABI said. Although robots can improve efficiency, accuracy and operational performance, their chief attraction is they reduce injuries and deaths, the ABI report said.
The U.S. robot inventory in Afghanistan includes vehicle-size robots that detonate mines and a variety of remotely piloted aircraft, from hand-launched reconnaissance systems such as Ravens and Pumas, to large missile-firing Predators and Reapers.
Cost is another compelling reason to use robots, Moses said. For the military, "the most expensive thing is manpower," and robots that enable the services to operate with fewer troops, can help cut costs.
Today, one soldier typically operates one robot, but with improvements in robots' ability to operate autonomously, "we'd like to get to where one operator can operate five to 10 robots," Moses said.
With the cost of deploying troops to Afghanistan estimated to be $390,000 per soldier, according to one Congressional Research Service study, robots begin to look like a bargain. Moses said PackBots cost $100,000 to $200,000 apiece depending on their sensor packages.