From Chapter 9 - THE QUEST FOR THE ULTIMATE WEAPON In the years of the incredible laser, the potential of the new device seemed unlimited. It could be the ultimate weapon that Roy Johnson and ARPA had sought to overcome the threat of Soviet ballistic missiles. To doctors the laser could conquer cancer. To physicists it could be the key to understanding atomic physics. To communications engineers it promised a way to transmit almost unlimited amounts of information. All those wonders seemed to be on the horizon, like the exploration of space, which would, inside of a decade, land men on the moon. Sixty years after Gordon Gould walked into ARPA with the idea of the laser, we''ve learned nothing is that simple, that good, and that fast. Lasers have enabled a revolution in telecommunications.

Pulses of laser light traveling through hair-thin fibers of glass carry words, pictures, voices, video, and vast amounts of computer-generated information around the globe. It''s an amazing triumph, but it took forty years, and tremendous advances in electronics and computing as well as in lasers and fiber optics. Developing laser death rays has proven much more difficult. The only part of the body that laser beams can damage easily is the eye, and doing so deliberately is rightly considered inhumane. Over a hundred countries have ratified the Protocol on Blinding Laser Weapons that bans them. However, the electronic vision systems used by smart bombs and guided missiles are considered fair targets, and laser weapons can target them. The emerging new generation of solid-state laser weapons can go beyond blinding sensors to damaging, disabling, or destroying enemy weapons. So far they have only been used on test ranges, but the day is coming when they will be taking out drones, rockets, artillery shells, or small boats wielded by insurgents or enemy troops in combat.

APPEALS OF LASER WEAPONS What attracted ARPA to Gould''s proposal in 1959 was the laser''s potential to become an ultimate weapon that could deliver energy precisely to a target at the speed of light. In military jargon, lasers are directed-energy weapons, a term that specifies their precision and the fact that they focus energy rather than fire bullets or detonate explosives. Today, what Janet Fender, as chief scientist for the Air Combat Command, and her military colleagues find the most important attraction of laser weapons is their persistence. Why persistence? "Lasers can stay in the fight longer than expendables," she explains. Modern electrically powered laser weapons run on power from diesel generators that hum constantly on the modern battleground. Bullets, rockets, and bombs can run out, but the laser keeps on firing as long as the diesel holds out and logistics specialists make sure field troops have ample supplies. No commander wants to run out of diesel before the enemy runs out of fight. "We''re not going to junk all our two-thousand-pound bombs," says Fender.

The weapons needed depend on the mission. But lasers have the sustained firepower to create a defensive shield to protect an aircraft or a ship, allowing it to stay in the fray longer. That''s what field commanders want. "Persistence is the first attribute that everyone agrees on." Precision lethality is high on the list. "You don''t want to be dropping two-thousand-pound bombs on everything," she said. Laser precision minimizes collateral damage and civilian casualties, key concerns in modern counterinsurgency. Laser beams also can be retargeted quickly.

Zap one quadcopter drone with a small but menacing payload, and the beam can reach out at the speed of light to zap another target. The precision laser beams also give commanders new options. When he headed the Air Force Special Operations Command, General Bradley Heithold praised the benefits of covert laser operations like reaching out to quietly slice key communications lines without putting troops in harm''s way. Underlying all that is what Fender calls "reversing the cost equation." A sophisticated Patriot missile costs a couple of million dollars. A dollar''s worth of diesel fed into a generator will provide enough power for a modern electric laser to zap an insurgent rocket or drone. Today we use expensive weapons to defend against attacks by inexpensive rockets, drones, and small boats. "If we had the low cost per shot capability that lasers offer, then we would be fighting inexpensive threats with inexpensive shots," she says.

If enemies attack with more expensive threats, "we would really be reversing the cost equation in our favor, not just equalizing it." The air force research timetable does not include any laser ultimate weapons. For the near term, the air force is focusing on ground-based applications that seem the most feasible and don''t pose technical challenges as severe as trying to squeeze a high-energy laser into a fighter jet. Looking to the longer term, the Missile Defense Agency is studying prospects for nonchemical megawatt lasers that could be installed into super drones for the ballistic missile defense mission once seen for the Airborne Laser. Fender has seen an important shift recently in how interest grows in laser weapon systems. Historically, developers of laser systems have pushed their new technology to potential military users. Now she sees a pull from users who want new laser technology once they see what lasers can do when tested in an operational environment. For example, the army took demonstration laser systems down to Fort Sill in Oklahoma and put a general officer into the driver''s seat along with the weapons officer for laser target shots at drones.

"When the quadcopter went up in flames, the general officer said, ''We want a hundred of these,''" Fender says. A consensus is emerging that laser weapons are now ready to begin moving into operations, she says. "Don''t get me wrong. The research is not done, but it''s done enough for a first generation." Lasers and other directed-energy weapons do have important limitations. They can hit their target at the speed of light, but the beam has to dwell for a while to deliver a lethal dose of energy. An interceptor moves like a tortoise compared to a laser beam, but if it hits the target, it can kill it instantly. Watch a laser zap a rocket, and it''s not the instant blast you expect from watching science fiction ray guns.

Instead, the laser spot glows before it blows. Lock a laser weapon onto a rocket, and the rocket continues moving, with the focal spot getting hotter and brighter, and only after a matter of seconds does the explosive payload reach the detonation point and explode. It''s like heating a teakettle of water on an electric stove. Turn on the burner and it warms almost instantly, but it takes time to heat the water to boiling. That means the laser must keep its killer beam focused on the moving target until it explodes or loses control and crashes. Don''t be fooled either by videos showing high-powered laser beams slicing sheet metal almost like butter. That beam is focused across a matter of inches so it can be concentrated on a tiny spot. Laser weapons are hundreds of meters or more from their targets, so the beam can''t be focused that tightly onto a spot.

It works by heating an area inches across. That can burn a hole through the hood of a stopped truck, but it''s better at heating a thin-skinned fuel tank until the pressure blows out the softened metal, or heating an explosive to the detonation point. A laser weapon can ignite gasoline fumes from the tank of an outboard motor, but it won''t slice through the heavy armor of an enemy tank on the battlefield. In any case, lasers do have a special mystique. Dr. Evil in the movie Austin Powers didn''t just want sharks; he wanted "sharks with frickin'' laser beams." US troops overseas now warn off people approaching checkpoints with bright green laser dazzlers, essentially superpowered laser pointers that are so bright that people instinctively turn away from their glare. Using the green lasers is said to have reduced deaths at checkpoints.