The U.S. military has evolved so fast in the post-September 11th era that much of its technology would be nearly unrecognizable to commanders, soldiers, airmen, marines and sailors only a few decades ago. Some of the biggest advances over the past decade have come with the development, application and integration of sophisticated information technology and robotics in daily operations.

The September 11, 2001 attacks created both motive and opportunity for military technology to advance rapidly. New types of weapons and equipment to fight a new type of war were in demand as the U.S. military and its allies deployed to the Middle East in late 2001, and the fighting has not stopped since. The U.S. Congress has approved nearly $1.3 trillion for military spending in support of Operation Enduring Freedom in Afghanistan, Operation Iraqi Freedom and Operation Noble Eagle, a program to improve security at military bases (pdf). About $2 billion has been spent on military construction as well as the research, development, testing and evaluation of new and improved technology to provide U.S. troops with better weapons, logistical capabilities and defenses against persistent threats such as roadside bombs.

This emerging technology ranges from the military's workhorse remotely piloted aircraft (more generically known as "drones") to futuristic soldier-supporting exoskeletons and laser cannons. Scientific American takes a look at some of the more significant developments in military technology occurring in the wake of September 11, 2001. [View a slide show of different military technologies whose development was spurred by the past decade of combat.]

Directed energy
Some of the military's research seems to come straight from the pages of science fiction. Lasers that attack enemy targets and disrupt missile guidance systems are closer than ever to seeing combat, as are "active denial systems" that emit 95 GHz millimeter-wave directed energy as a form of crowd control.

In April, the U.S. Navy and Northrop Grumman Corp. successfully demonstrated high-energy, solid-state laser defenses at sea by completing a test of the Maritime Laser Demonstrator (MLD) against small remotely piloted boats. In a 2010 demonstration Raytheon's Phalanx Close-In Weapon System and a Navy solid-state laser shot down four unmanned aerial vehicle (UAV) targets flying over water near the Navy's weapons and training facility on San Nicolas Island in California's Santa Barbara Channel.

Raytheon is also developing an active denial system that emits a focused beam of millimeter wave energy that travels at the speed of light, heating the water in a person's outer layers of skin and producing an intense burning sensation designed to stop crowds or combatants in their tracks without killing them. In another approach to directed energy, microwaves can also be used as a weapon by stimulating portions of the ear around the cochlea, creating extremely high and uncomfortable noise levels in the skulls of targeted individuals.

The high-powered millimeter wave systems "make you feel like you're getting a sunburn," says U.S. Air Force chief scientist Mark Maybury. "If you're trying to defend against or clear a way through an unruly crowd, you don't want to shoot into that crowd. This is an example of how, as we move to very low and eventually zero tolerance for collateral damage, we're going to see more and more of these tools."

The military has yet to use active-denial technology; one such system was sent to Afghanistan but later recalled. The Defense Department did not provide specifics about its reason for not using the system.

Body armor and exoskeletons
Far more of the Western military operating in Afghanistan and Iraq survive improvised explosive devices (IEDs) and direct-fire/small-arms engagements because of improved body armor made from ceramic, composites and other materials, says Kristian Gustafson, deputy director of the Brunel Center for Intelligence and Security Studies at West London's Brunel University. British Armed Forces use body armor rigs such as the Osprey, whereas U.S. Army soldiers favor Interceptor bullet-proof vests. Defense contractor BAE has developed a battery-powered body armor (weighing just over 7 kilograms) with its own GPS and night-vision goggles.

Raytheon, Lockheed Martin and other defense contractors are developing hydraulic-powered exoskeletons that soldiers will be able to wear to ease heavy loads while increasing strength and endurance. The Army is testing Lockheed's Human Universal Load Carrier (HULC) exoskeleton at the Army's Natick Soldier Research, Development and Engineering Center in Natick, Mass. Lockheed designed HULC as an untethered, battery-powered, hydraulic-actuated anthropomorphic exoskeleton to provide soldiers the ability to carry loads up to 90 kilograms for up to 20 kilometers on a single battery charge.

Raytheon's second-generation Exoskeleton—XOS 2—is a 95-kilogram support system that enables the wearer to effortlessly lift about 23 kilograms with each arm. The company expects its exoskeletons to become available to the military in 2015. Those suits will likely be tethered by power cables, followed three to five years later by untethered versions. The exoskeletons are expected to be used initially to help soldiers carry heavier loads farther, whether they are performing combat or logistical operations.

Robot pack mule

U.S. soldiers wearing exoskeletons will not be burdened with the entire weight of their supplies if Boston Dynamics's Legged Squad Support System (LS3) comes to fruition. The LS3 would be the first step in fulfilling the military's call for an autonomous, legged robot.

The U.S. Defense Advanced Research Projects Agency's Tactical Technology Office and the U.S. Marine Corps awarded Boston Dynamics a 30-month, $32-million contract last year to deliver a prototype LS3. At the end of the contract the company is expected to deliver two prototype LS3s that can carry the required weight (181 kilograms) a required distance (at least 32 kilometers) without refueling across a relatively flat surface. The LS3s will also have to be able to run up to 16 kilometers per hour and feature at least a rudimentary version of the systems it will need to operate autonomously. [See a Scientific American video featuring military robots.]

Electronic warfare
What really separates combat post 9/11 from anything that came before it is the use of information technology. "Iraq and Afghanistan have been the first wars of the Internet age," says Chris Bronk, an information technology policy research fellow at Rice University's James A. Baker III Institute for Public Policy in Houston and a former U.S. State Department diplomat.

*Correction (9/9/11): This sentence was edited after posting. It originally referred to Raytheon's active denial system as using microwave energy. The system employs millimeter waves.

Whereas the disruption of an enemy's communications systems and other technology is not a novel concept, the Defense Department is searching for new ways to do this. "If I'm flying against an air defense system trying to track me, if I can suppress or block that signal and send back a false one, that's an example of electronic warfare," Maybury says. "This is particularly important as we get into the advanced information age; more and more aircraft are being run by software."

Boeing's $67 million EA-18G Growler is an example of an electronic warfare weapon. It has been used by the U.S. Navy as a communications jammer aircraft since 2009. The Growler is now or will likely soon be able to transmit malicious software code via its array of sensors, Bronk says.

"The whole field of cyber has exploded since 9/11," Maybury says. "In the last year alone, we have created two brand-new career fields in the Air Force—one for remotely piloted aircraft operators and one for cyber operators."

Applying traditional military strategy to the cyber world, "you want to outmaneuver your attacker or change the battlefield dynamically," Maybury says. One idea the Air Force has been pursuing is dynamically changing the signature of its information technology (IT) systems to prevent hackers from targeting Defense Department computers. This could mean moving information around on virtual servers within a physical server or, potentially, switching a server's operating system without disrupting operations. "We're talking about saving the state of your data and then quickly converting to a different OS or application using the same data," he adds.

Cyberconflict is already a reality, although it is debatable whether it has ever escalated to the level of a "cyberwar," where one nation uses IT systems to attack the computers and networks of another nation. "For me, the biggest IT weapon innovation is Stuxnet, a piece of malware that reputedly knocked perhaps as many as one-third of Iran's centrifuges at Natanz offline—that's a major piece of engineering," Bronk says. "Regardless of who made it we must see this as an enormous change in how covert-action, low-intensity battle is waged," he adds. "This will likely not be an isolated case."

Missile guidance systems
Combat zones in Afghanistan and Iraq often exist right in the middle of civilian areas, placing even greater demands on precision use of explosive weaponry. Guided Multiple Launch Rocket Systems (GMLRS) have been in development for much longer than a decade, but they have matured since 9/11 to the point where the U.S. and its allies can "destroy a particular corner or room of a house with a rocket fired from 70 kilometers away, something that is both ludicrous and outstanding," Gustafson says.

Guided missile systems have become accurate to within a square meter, according to Gustafson. "In fact, we are now so accurate that we are downgrading the warheads," he says. "Why do we need to cause all the extra destruction when all we want to do is kill the baddies in [a particular] room?"

Smart grenade launcher
The shoulder-fired XM25 Counter Defilade Target Engagement (CDTE) System, about the size of a regular rifle, has been in the hands of U.S. soldiers in Afghanistan since late 2010. The CDTE uses thermal sensors and a laser range finder to spot its target, after which microchipped, radio-controlled 25-millimeter ammunition can destroy that target, even when hidden behind a wall or other cover. Called "the Punisher," the CDTE weighs about 6 kilograms and is 75 centimeters in length.

Satellite-guided parachutes
Joint Precision Airdrop Systems (JPADS) use global positioning systems, maneuverable parachutes and an onboard computer to increase airdrop precision when delivering pallets of supplies to precise targets, something that is a particular challenge in the mountainous regions of Afghanistan. The Air Force first tested JPADS in Afghanistan in August 2006, dropping containers with food, water, ammunition and other supplies, weighing 230 to 1,000 kilograms, to troops on the ground. The U.S. Marine Corps have been using similar technology in Iraq since 2004 to drop 900-kilogram loads within 70 meters of their designated target points.

The Air Force has increased its precision airdrops significantly, says Maybury, adding that "this is particularly a challenge in places like Afghanistan, where there are lots of hills and you want to make sure that you drop things in particular locations so they don't fall into enemy hands."