In the movies, they go by many names: death ray, ray gun, laser beam, phaser, blaster and, of course, lightsaber. These weapons are science fiction icons. Remember Han Solo blasting Greedo the bounty hunter in "Star Wars"? The alien invaders annihilating the White House in "Independence Day"? Classic science fiction films like "War of the Worlds" feature equally fearsome aliens with death-ray-equipped UFOs. "Ghost Busters" taught us never to cross the streams of our super-cool, though equally fanciful, "proton packs."

In reality, they're collectively known as directed-energy weapons, and they channel lasers, heat, or particles into targeted beams. The military has made several attempts in recent years to create viable, field-ready directed-energy weapons, primarily for missile defense, but most of these projects have been abandoned. Starting in 2000, a joint U.S.-Israeli prototype called the Tactical High-Energy Laser (THEL) took down 25 Katyusha rockets during a demonstration program and a mobile version destroyed multiple mortar rounds. The project was discontinued in 2005.

The U.S. Air Force's Airborne Laser Test Bed successfully took out a ballistic test missile in February of 2010, but funding for the device was later suspended, as the test revealed that it was difficult to maintain the laser's precise alignment. The device also had a tendency to overheat and malfunction during adverse weather conditions.

While they may come up short in missile defense, directed-energy weapons like the ZEUS-HLONS system, commonly known as ZEUS, have been successfully deployed on Humvees on the battlefield to burn out land mines and unexploded munitions, preventing a larger explosion. The ZEUS heats up and defuses explosives up to 300 meters away using a laser beam.

As for targeting individual soldiers, it looks like we'll be setting our phasers to stun--at least for now--with devices that incapacitate people rather than eliminate them, like the military's Active Denial System (ADS). The ADS is essentially a ray gun, but it doesn't cause instant death or, like the "District 9" version, turn its targets into Jell-O. Instead, it uses a very precise frequency of microwaves to agitate fat molecules in the top layer of the skin. The skin heats up, causing a sensation which CBS News correspondent David Martin likened to scalding water.

It's also been described as similar to the blast of heat you feel upon opening a very hot oven. Most people find this unpleasant enough to send them running out of the beam's path within a few seconds--and once they do, the pain instantly subsides. These devices won't actually fit in your pocket, and you can't see or hear the beam. The beam projects from a large reflector plate usually mounted on top of a vehicle and controlled by an operator with a joystick. ADS could be used to repel a large group of people at a range of over 700 meters. The United States Marines and police are working on portable versions.

There is one kind of hand-held "laser gun," known as a dazzler, which is used to disorient or temporarily blind its targets. The Personnel Halting and Stimulation Response rifle (PHASR) is one of the most recent prototypes. Laser weapons that cause permanent blindness are banned by the UN, but DoD representatives say they're developing extra safety features like an "eye-safe ranger finder" which would adjust the power of the laser based on the distance to the target to prevent permanent damage.

If there's one beam weapon which avid fans--many scientists and engineers themselves--would love to see become a reality, it's the lightsaber. In the first "Star Wars" film, Obi-Wan Kenobi describes the lightsaber to Luke Skywalker: "This is the weapon of a Jedi Knight. Not as clumsy or random as a blaster: an elegant weapon for a more civilized age." Many "Star Wars" enthusiasts have built replicas of this renowned device, but these are far from functional. For obvious reasons, the military is not developing any kind of ray beam, sword-like weapons.

Theoretical physicist (and Secret Lifer!) Dr. Michio Kaku, like most scientists who have considered this, believes that the most plausible candidate for a real-life lightsaber would be a large, superheated plasma torch. Plasma, sometimes called the fourth state of matter, is an electrically conductive ionized gas and the main component of stars. Dr. Kaku believes we could steer the plasma into a beam using a magnetic field. But this would require enough electricity to power a small town. There is no power-source strong enough and small enough to fit into the base of the hand-held device. But Dr. Kaku seems confident that his design, which he presented to fans on the show "Sci Fi Science," will work once we've created nanobatteries. Nanobatteries would use tiny carbon nanotubes to produce a vast amount of electricity. These atom-thick batteries would have 10 times the power density of traditional batteries. Dr. Kaku believes this technology will be available within the next 50 years. Who knows, maybe this could one day modernize the sport of fencing--assuming we also invent impenetrable protective gear.

Military leaders and scientists haven't given up on directed-energy weapons yet. While many costly endeavors have been put on indefinite hold, new projects are always on the horizon. It may take decades for the technology to improve enough for these applications, but researchers seem to determine to make the ray gun a reality. Bring it on, Boba Fett.

Samantha Johnston is currently studying broadcast and print journalism at UCLA Extension. She has traveled through Greece, Ecuador and Peru studying anthropology and archaeology, and earned her BA from the University of California, Santa Barbara, in 2007. On clear, moonless nights, you'll find her stargazing on Southern California's Mount Pinos.

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