by David Axe

The new generation of military robots can hover silently overhead, swarm undetected around enemies, and disable bombs—all without sweating a drop.

Silent Assassins

Predator: The Remote Executioner
The father of the modern war 'bot, the Predator can orbit overhead—unseen and unheard—for nearly 12 hours before needing to refuel. Until 10 years ago, the planes were used only for spying, but then the CIA and the U.S. Air Force equipped them with Hellfire anti-tank missiles. Fortunately, Predators can't open fire on their own; they still require a human operator (or "man-in-the-loop"), who tells them when to shoot via a high-speed satellite link. As a result, soldiers can avoid the line of fire. Recently, a version of the Predator controlled by a secret task force reportedly killed more than 1,000 insurgents in Iraq.

Reaper: Warding Off Aliens

Reaper is like the Predator's brawny, muscle-bound cousin. Weighing in at 5 tons, Reaper can carry 5,000 lbs. of bombs and missiles, yet it's still quiet enough to evade detection. In Iraq and Afghanistan, Reapers have specialized in rescuing cornered ground troops. More recently, however, the American government has been using them for a different purpose—to catch illegal immigrants. In 2005, the U.S. Customs and Border Patrol started flying weaponless versions of the hulking drones to monitor the Mexican border. They're expected to head for the Canadian border later this year.

Lords of the Flies

X-47 Bombers: 'Bots that Can Swarm

Engineers are working to build the first prototypes of the X-47 bombers—unmanned fighter planes that will be able to swarm around the enemy like giant locusts. According to defense-industry engineer Pat Johnson, the goal is to "get the drones to communicate with each other so they can work as a team." They'll be able to "see" each other using radars and cameras and "talk" to each other using radios. They'll also be able to make split-second decisions about maneuvering in the air—all while keeping in constant contact with military planners back at headquarters. Combining all of those features is a tall order for engineers, and it may be another 15 years before the X-47s are ready for action.

fire-scout.jpgFire Scout: The Looming Menace
Fire Scout is an armed drone helicopter that acts like a massive dragonfly. It can hover silently for hours, hiding behind treetops and hillsides, waiting patiently to open fire on its target. But it can also chase down fleeing cars and shoot laser-guided rockets up their tailpipes. Basically, it's a lightweight civilian chopper with its cockpit sliced out and replaced with sensors, computers, and weapons stations. With so much versatility, it's at the top of the wish list for the Army, Navy, and law-enforcement agencies everywhere.

Creepy Crawlies

MULE: Ahead of the Pack
MULES can roll around the battlefield using infrared cameras to find bad guys and fire rockets at them. About the size of Jeeps, MULES obey simple orders, such as "Go over there," from human commanders working off-site. Although the ground robots aren't in use andros.jpgyet, military officials believe they will be invaluable on the front lines. In fact, the Army is spending billions of dollars to deploy hundreds of MULES to war zones.

ANDROS: The New Bomb Squad
To dismantle bombs, the Israeli army uses a horse-size robot called ANDROS (at left). It can shoot apart booby traps with a shotgun, or it can simply crush bombs with its weight. In February 2008, a terrorist tried to detonate a bomb in the town of Dimona, Israel.

After police shot and killed the bomber, an ANDROS rolled over to inspect and destroy any bombs that might have been strapped to his chest.

This article originally appeared in mental_floss magazine. Want a free six-month subscription? Get the details here.